WKU Meteorology

The SPC has placed us under a slight risk for severe weather Thursday

The temperature tonight will only drop to the low 60s with southern winds bringing in warm temperatures.  Thursday morning and day will see temperatures only climb to 70 under cloudy skies.  Scattered rain showers and storms chances will persist throughout the day; however, the main focus is tomorrow evening/night as a strengthening mid-latitude cyclone settles into the Great Lakes Region.  The associated cold front will bring heavy rain and potentially severe weather as it advances through our region late tomorrow evening.    High amounts of moisture and strong winds are  factors playing into the strength of this cold front.

High amounts of moisture will provide fuel for the strong cold front as it approaches our region

Southern 850mb winds are already busy pumping moisture into the area which will push precipitable water values over 2.0” by the time the front pushes through.   This will result in heavy downpours and potential flash flooding.A steep pressure gradient will result in steady winds of 10-20mph throughout the day climbing to the upper 20s by evening.  Stronger gusts are expected with the advancement of the cold front, should these gusts break 65+mph will determine whether or not “Severe Weather Warnings” get issued.

A band of slight instability will develop ahead of the front

The only instability with this system will occur just ahead of the front as a slender strand of CAPE values over 1000 J/kg will contain the best chance to see any thunderstorms.  Although a linear band of storms may develop, low instability will limit the strength of these storms.  A tornado or two along the front will also be possible with strong low-level helicity.  However,  strong winds and flash flooding are the main threats with this front as weak instability will limit thunderstorm coverage and intensity.

Looking past Thursday, a sunny and dry weekend awaits.  However, jackets will be needed as temperatures will  drop.

Friday: Mostly sunny. High in the mid 60s. Low  in the mid 40s.

Saturday:  Mostly sunny. High in the mid 50s. Low in the mid 30s.

Sunday:  Mostly sunny. High in the mid to upper 50s. Low in the mid 30s.

Forecast Discussion:

Somebody turn up the heat because its cold outside! The coldest air so far this season has arrived to south-central Kentucky after three pushes of cold air have moved in this past week. The cold air along with a weak disturbance moving over the Ohio Valley allowed some locations across northern Kentucky to see some sleet and snow this morning. There will be no snow here in south-central Kentucky but the ground may be solid white by morning. With an upper-level trough and a surface high pressure in place, creating a couple of calm clear nights, you can bet that the temperature is going to drop. A Freeze Warning has been posted for the entire state of Kentucky for Thursday night as temperatures plummet to the mid 20s. Be sure to grab the jacket or maybe even the coat before heading out the door Friday morning.

A surface high pressure system will create calm winds and clear skies allowing for a cold night with temperatures dropping to the mid 20s. RUC forecast temperatures for 7 am Friday morning.

Temperatures will not warm much Friday despite sunny skies; the high will be around 50. Temperatures will again drop into the upper 20s Friday night/Saturday morning under clear skies. By Saturday winds will switch from the southwest ahead of a very weak disturbance. The southwest winds and sunny skies will allow temperatures to moderate into the low 60s. The weak disturbance will bring a few clouds to the sky by Saturday evening but they should clear by Sunday morning and thus a sunny Sunday with a high near 60 is expected. This is the result of another surface high pressure system moving in behind the weak disturbance.

Looking longer range and into early next week, a warm front should start the week off right allow temperatures to warm to the mid to upper 60s by Monday. Data suggests that 70s will return by Tuesday. The next major storm system is expected around during the midweek time frame.

Daily Forecasts:

Friday: A cold start after a morning low near 25. Skies will be sunny but it will be a cool day with a high near 49. Light northwest winds up to 8 mph.

Friday Night: Cold, clear with nearly calm winds and a low around 27.

Saturday: Sunny to start the day with increasing clouds though the afternoon becoming mostly cloudy by evening. Warmer with a high near 62. Southwest winds from 5-15 mph.

Saturday Night: Mostly to partly cloudy skies with some clearing by morning. Low around 39. West winds up to 8 mph.

Sunday: Sunshine with a high near 60. West to northwest winds from 5-10 mph.

Sunday Night: Clear skies with clouds increasing by morning however. Low near 39.

Monday: Partly cloudy skies and becoming warmer with a high in the mid to upper 60s.

After a rainy start to the weekend on Saturday morning, weather conditions certainly cleared up for a gorgeous Sunday. The day got off to the chilliest start of the fall season thus far though. The low was 34 at the BGWC Regional Airport while the low dropped to the freezing mark at the Warren County mesonet site just outside of BG. The wall-to-wall sunshine helped to warm us into the low 60s by this afternoon, however that is several degrees below our average high for the date of 70. With such cool temperatures there were some areas of frost along with areas of fog to start Sunday.

Our cool weather is thanks to a cold front which passed through Saturday and also an upper-level trough located over the upper-Midwest which has setup a fairly zonal flow over the Ohio Valley. Associated with this trough is the next weather system poised to impact Kentucky. There is an associated low pressure system which is currently over the Great Lakes and a cold front extends from the system through Illinois and into Texas. Ahead of the system southerly winds and mostly sunny skies will allow for temperatures to rise into the upper 60s. It should be a phenomenal fall Monday but clouds will begin to increase into the afternoon hours, with cloudy skies likely by sunset thanks to the approaching system. The low pressure system itself will pass well to our north but the cold front will slide through the Commonwealth on Monday night. The frontal passage marks the first of several weak fronts to pass through this week which will usher in much cooler air. There is a slight chance of a few showers with the front, though any showers will likely be in the early morning hours Tuesday morning and thus go unnoticed by most. Rainfall will very light totaling no more than a tenth of an inch.

This NAM model forecast indicates light rain along the cold front valid for 4 am on Tuesday. Behind the front cooler air will move in, and after another system moves by on Tuesday night, more cool air will spill in for mid-week.

Clouds will move out temporarily on the day Tuesday though yet another weaker system will approach by Tuesday evening bringing with it more cloudiness. Due to the very dry air which will already be in place, showers are unlikely with this system. However cool air will come crashing in. By Wednesday, mostly sunny skies will dominate but temperatures will struggle to climb. After starting out Wednesday morning near 40 highs will only reach the low 50s. Yet another weak disturbance will move toward the Ohio Valley by Wednesday night/Thursday morning and depending on its exact timing (which the models currently disagree on) will determine just how chilly it is to start Thursday. Either way it will likely be in the 30s. This very weak disturbance will again bring in more cool air in for the end of the week and it looks quite likely that our first real freeze of the season will occur Friday morning as temperatures are expected to drop to near 30. Cool below average temperatures are expected to continue right into next week as you can see predicted by the Climate Prediction Center’s 6-10 day temperature outlook. They are giving at least a 70% chance of below average temperatures through next Wednesday.

At least a 70% probability of below average temperatures is predicted by the Climate Prediction Center for this weekend into early next week. Thus cool temperatures are here to stay for a while.

Daily Forecasts:

Monday: Mostly sunny to start the day though clouds will increase after 3 pm, becoming cloudy by 7 pm. Highs will warm to near 68. Southwesterly winds at 5-12 mph.

Monday Night: Cloudy skies with a 60% chance of showers primarily after midnight. Showers will remain light with rainfall totals less than 0.10”. Low around 44. Light winds from the northwest.

Tuesday: Clouds will clear early becoming mostly sunny during midday. High near 61. Clouds will again increase by the evening. 5-12 mph winds turning back from the southwest.

Tuesday Night: Cloudy skies with a low near 39 with westerly winds at 4-10 mph.

Wednesday: Clouds will clear early for a mostly sunny day but cool with a high only around 52. Northwesterly winds from 5-10 mph.

Wednesday Night: Low near 37 with increasing clouds.

Thursday: Mostly cloudy to start the day with skies becoming mostly sunny by the afternoon. High in the low to mid 50s.

Days at a Glance:

Friday: Begin at a chilly 38! Scattered fog is possible in the early morning hours and should dissipate quickly after daybreak. High of 65 under sunny skies with scattered clouds increasing into the evening. Winds light and variable.

Saturday: Start the day with a low of 45. High of 58 under cloudy skies. A 60% chance of light to moderate showers in the early to mid-morning hours. Accumulations should remain under .10 of an inch. Clouds will stick around throughout the day before dissipating into the overnight hours. Winds will be mostly out of the west around 5-7 mph.

Sunday: Begin the day at a chilly 37! Sunny skies will dominate as temperatures top out at 65. Winds will be from the SSW at 10-12 mph.

Discussion:

The weather will remain fairly mundane as we head into the weekend despite the chance for light showers on Saturday. Tomorrow will start out in the upper 30’s so dust off the coat if you already haven’t since nighttime and morning temperatures will remain chilly throughout the weekend. The high tomorrow will reach the mid 60’s under sunny skies with clouds increasing into the evening hours. This will help to moderate the low somewhat and keep it in the mid 40’s. This is in association with a very weak and dissipating cold front projected to slide through the area midday Saturday. Due to the near absence of moisture, the greatest guarantee is overcast skies with light to moderate showers possible. Accumulations under .10 of an inch are expected in the morning hours after daybreak before dissipating around noon.

NAM 15Z (10am CDT) Saturday morning Composite Reflectivity showing scattered precipitation over the Ohio River Valley in association with the weak frontal boundary.

Clouds will hang around into the evening before dissipating overnight. Sunday will once again begin on a cold note, but will be absolutely beautiful under sunny skies with a high in the mid 60’s so get out and enjoy the great fall weather!

Days at a Glance:

Today: High of 80. Partly cloudy skies. North winds at 11-12 mph.

Monday: A chilly start to the day with a low of 48. High of 74. Mostly sunny skies. Northeast winds at 6-10 mph.

Tuesday: Start the day with a low of 55. High of 75. Clouds increasing to overcast into the afternoon and evening. A 80% chance of light to moderate rain showers possible into the evening and overnight hours. Accumulations will be under .05 of an inch area-wide with locally higher amounts possible. South winds at 11-12 mph.

Wednesday: High of 62 in the mid-morning before the cold frontal passage. 80% chance of light to moderate rain showers in the early morning before tapering off by noon. Total accumulations including Tuesday should remain below .25 of an inch with locally higher amounts possible. Winds will shift from 11-15 mph from the south to 11-15 mph from the northwest before noon. Clouds will begin to clear into the late afternoon and evening.

Thursday: Another chilly start with a low of 41. High of 60 with mostly clear skies. NW winds becoming W into the day at 5-6 mph.

Discussion:

After a week of very beautiful and benign weather, the possibility for rain will once again return to the area. A weakening and dry cold front has  passed our area this morning and dry air will filter into the area throughout the day. Therefore, will have two more pleasant days in the mid 70’s before clouds begin to increase throughout the day Tuesday in association with an approaching cold front. Light to moderate rain showers will accompany this into the evening and overnight hours. Locally heavy showers are possible with a few rumbles of thunder, but nothing severe is anticipated due to the lack of instability and the timing of the frontal passage. The cold front is projected to pass our area during the early to mid-morning hours on Wednesday. With this said, precipitation will quickly slack off before noon and clouds will begin to clear throughout the day.

NAM 12Z (7am CDT) Wednesday morning Mixing Ratio and 10m wind vectors representing atmospheric moisture and its transport or advection. Notice the drastic wind shift over our area denoting the cold front with much drier air projected to filter in throughout the day Wednesday.

With the drier and cooler air in place, a beautiful Thursday should be in store with temperatures barely cresting 60 degrees under sunny skies. A jacket is advised with morning temperatures starting in the lower 40’s.

You couldn’t ask for a more beautiful end to the week! High temperatures heading into our weekend will hover in the mid to upper 70s with no rain in sight. Morning lows will continue to be a bit chilly, but not as low as what we saw the past two mornings with lows dipping into the mid 40s. A large area of high pressure is sitting just to our southwest and will continue to give us sunny skies through the early weekend.

A small disturbance will push through the area Saturday night, but not much in the way of rainfall is expected due to the dry atmosphere. A 20% chance of thunderstorms will come into play on your Sunday, but don’t cancel any outdoor plans just yet as most people will see a good deal of sunshine and dry conditions. A more substantial chance for rain will arrive early next week ahead of a cold front which looks to push through during the day on Wednesday.

Short Term Outlook:

Temperatures will gradually cool down overnight and reach a low of 50 degrees by early tomorrow morning. WKU students will need that jacket for early morning classes. An absolutely perfect day is shaping up for your Thursday. The high temperature will be 75 degrees with mostly sunny skies and a light breeze at 5 mph. Tomorrow night will once again be on the chilly side with lows dropping into the low 50s.

Extended Forecast:

Friday: Sunny, with a high near 78. Light east wind.

Friday Night: Mostly clear, with a low around 53.

Saturday: Sunny, with a high near 77.

Saturday Night: Partly cloudy, with a low around 58.

Sunday: A 20 percent chance of showers and thunderstorms. Partly sunny, with a high near 78.

Sunday Night: Mostly cloudy, with a low around 58.

Columbus Day: A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 75.

Monday Night: Mostly cloudy, with a low around 57.

Tuesday: A 30 percent chance of showers and thunderstorms. Partly sunny, with a high near 71.

Heavy rain swept through the area this morning ahead of a cold front which is currently tracking through the region. Bowling Green picked up just over a half inch of rain last night through this morning with higher totals to the north and west. Flooding occurred in some of our far northern counties where torrential rain tracked over the same areas last night and early this morning. Over 6.5 inches of rain fell across Louisville within the past 24 hours. A few counties in far western Kentucky even saw a tornado warning issued with the round of storms that moved through yesterday evening. No damage has been reported with any of those storms.

The threat for severe weather will remain to the east of our area ahead of the cold front, but we will see only a few lingering showers for the rest of our Sunday. Clouds will persist through the evening.

The rain chances will continue to diminish as we head into the evening hours with clearing overnight.

After a warm start to October, a more seasonable pattern will begin to set in this week. Temperatures will find themselves on the chilly side as we head into our Monday morning. You won’t need that winter coat quite yet, but a jacket will be handy tomorrow, especially if your heading out before 10am. The sun will be out again tomorrow, but temperatures will only reach the mid 60s. Temperatures will again dip into the mid 40s for Tuesday morning and will climb to around 70 degrees by mid afternoon. Temperatures will remain fairly seasonable for the rest of the week with minimal chances for rain over the next five days.

It’s Fall and that means the leaves are changing! Here is a map from The Weather channel breaking down the time of peak foliage for the area. Bowling Green’s foliage peaks around late October.

So what causes the leaves to change color? Plants use glucose as a building block for growing. The plant turns water and carbon dioxide into oxygen and sugar through a process called photosynthesis which means (putting together with light). The chemical called chlorophyll is what gives the plants their green color. During the winter there is not enough daylight or water for photosynthesis. This means the trees must rest and live off the food stored up during the summer. They begin to shut down the food making process, which results in the disappearing of the chlorophyll. As the green color fades, we begin to see the yellow and orange colors (which have been in the leaves all along). The reason we can’t see these colors in the summer is because they are covered up by the vast amounts of green color.

Weekly outlook:

Monday: Mostly sunny, with a high near 65. Northwest wind 3 to 8 mph.

Monday Night: Mostly clear, with a low around 45. Northwest wind around 5 mph becoming calm in the evening.

Tuesday: Sunny, with a high near 69. Calm wind becoming northeast around 6 mph in the morning.

Tuesday Night: Mostly clear, with a low around 47.

Wednesday: Sunny, with a high near 74.

Wednesday Night: Mostly clear, with a low around 53.

Thursday: Sunny, with a high near 75.

Thursday Night: Mostly clear, with a low around 52.

Friday: Mostly sunny, with a high near 76.

Friday Night: Mostly clear, with a low around 53.

Saturday: Mostly sunny, with a high near 78.

We are keeping a close eye on an strong October mid-latititude cyclone that has been brewing in model forecasts for a few weeks now. This system is currently located over Nebraska bringing several inches of snow to Wyoming, and South Dakota. This system looks to arrive for us in central Kentucky late Saturday night into early Sunday morning brining a multi-cellular broken squall line across the eastern United States. The main threats appear to be damaging winds and an isolated hail chance. With the continued model consensus that the surface low will move to our north over the Great Lakes region, we can expected a much more dampened severe storm concern as the best ingredients will remain to the north along the warm front/surface low region. This does not rule out all chances for some storms to reach severe limits as instability looks to be more favorable than earlier this week with a strong cold front for ample forcing.

NAM forecast composite reflectivity (Left) and GFS  MSLP and precipitation (Left) comparison valid for 06 z (1 am CDT)  Sunday.

The NAM and GFS models agree fairly well on timing for this system entering around 1 am. They are also in good agreement about the mode being linear with the most intense sections of the line being to our north where better ingredients will be in play. The strong cold frontal boundary will pass through around lunchtime Sunday after the rain and storms move through brining a drop in temperature and a more October feel to the first part of next week.

NAM surface temperatures valid for 18z (1 pm) for Sunday showing sharp temperature gradient associated with cold frontal boundary.

Forecast Update:

Saturday: High, 82. Chance of precipitation increasing into the day. Some locally-strong storms possible.

Saturday Night: Low, 62. Chance of precipitation increasing into the night with a cool off after frontal passage.

Sunday: High, 68. Storms strong to severe in morning. Largest threat damaging winds and small hail.

Rain chances decreasing after front passes around lunchtime/early afternoon. 

Sunday Night: Low, 45. Cooling off with the passage of the front. Cloudy with lingering rain showers into the early morning Monday. 

Forecaster: Emily Thornton

Next Update: Sunday October 6th.

It has been a warm start to October with highs reaching into the 80’s for the first day of the month. According to a monthly summary from the Kentucky Mesonet for October 2012, the high temperature for October 1, 2012 was 66.4 F at the station located at the Western Kentucky agricultural farm. The following week, however, showed a climb back into the upper 70’s before a drop back into the 60’s with lows in the mid 30’s. This shows that though we are unseasonably warm, we are not far off from the October temperatures of last year.

As of now, a ridge of high pressure is dominating weather over the Commonwealth bringing in the oppressive October heat. A chance for precipitation exists Wednesday as an upper level low becomes a broad low pressure wave and moves over Kentucky. Any showers that develop will likely be in the morning hours and isolated in nature.  A pattern shift will occur  into the weekend when we will see a stronger system move in bringing a trough swinging through the eastern US and bringing the polar jet and cooler drier air behind a significant cold frontal boundary set to march across the eastern United States into Saturday. This cool down will provide us temperatures more favored to the mid-60’s with lows in the mid-40’s by Sunday after the front passes through.

NAM Surface Temperature and Winds Valid 12 z (7 am CDT) Saturday, October 5th.

With this system, we will also expect some rain/thunderstorm chances Saturday and Sunday as the front approaches. The highest chance for precipitation looks to be Saturday night as the models bring the frontal boundary through western/central Kentucky. With the surface low displaced to our northeast, the severe threat will be significantly higher to the northeast across  Illinois, Indiana, and Ohio and  diminished for us in south-central Kentucky. This will not rule out some locally strong storms with ample moisture and moderate pockets of instability depending on the frontal passage timing and thunderstorm development period. A further update on the severe weather potential will be given on Friday.

GFS Mean Sea Level Pressure and Precipitation valid 12 z (7 am CDT)  for Sunday, October 6th.

Daily Forecasts:

Wednesday: High, 80.  Partly cloudy with winds calm to 5 mph. Slight chance for isolated rain/thunderstorms around 30%.

Wednesday Night: Low, 69. Cloudy with light winds. Slight chance of precipitation around 20%.

Thursday: High, 81. Mostly sunny with light winds from 5-10 mph.

Thursday Night: Low, 68. Cloudy with light winds.

Friday: High, 83.  Sunny with few clouds.

Friday Night: Low, 70. Cloudy.

Saturday: High, 82. Chance of precipitation increasing into the day. Some locally strong storms possible.

Saturday Night: Low, 62. Chance of precipitation increasing into the night with a cool off after frontal passage.

Forecaster: Emily Thortnon

Next Update: Friday, October 4th.

After a cool start to the week temperatures have gradually climbed and today’s high (Thursday) was actually a few degrees above average for this time of year. Temperatures were allowed to warm under generally sunny skies. The warmer temperatures and the mostly sunny skies are thanks in part to a high pressure system located over the eastern United States. Those sunny skies and warmer temperatures are about to change however as the high pressure system slides away from the Ohio Valley. Replacing the high will be a low pressure system and a cold front which is currently making its way across the Midwestern US. In fact there have been some areas of severe thunderstorms in parts of Missouri and Iowa. With the front bring severe storms to our area?

First of all, clouds will begin to move in during the overnight hours tonight and they will stick around likely for the majority of the day Friday. Slowly but surely rain will push from the west to the east across the state throughout the day. There could be some areas of showers and maybe a thunderstorm as early as noon but better chances for scattered showers and storms occur after 3 pm and especially after 6 pm. The heaviest and most consistent rainfall should be moving into south-central Kentucky around 8 pm. Several models indicate that the rain Friday evening will be a large shield of rainfall, with some embedded thunderstorms, lasting through the evening and into the overnight hours. Yes, this means it’s possible that Friday night football games will be soggy for south-central Kentucky; those east of I-65 will have a better chance at not having any rain problems however. So, about those storms, will any be severe you may ask? Due to Friday’s cloud cover across the region we will not have the same atmospheric instability (energy to make storms pop) as there was Thursday over the Midwest. Furthermore, the low-levels winds do not look overly favorable for severe thunderstorm development. Nevertheless, while severe storms appear unlikely at this time, there is still the potential for an isolated strong to severe storm with strong wind gusts being the main threat. The bigger story with the system will be the amount of rainfall possible. Indications are that the area will receive between 0.75 – 1.50 inches of rainfall through the course of the evening. This could lead to some ponding on the roads overnight. Rain will come to an end across the area by 6 am Saturday morning.

A cold front associated with a low pressure system in Canada will create a focal point for rain and thunderstorms Friday afternoon and especially overnight. Rainfall is expected to be between 0.75 – 1.50 inches. Behind the front cooler air (blue arrows) will filter in. Highs will only be in the 70s Saturday and Sunday and with sunny skies, it should make for a nice weekend weatherwise.

Behind the front weather conditions should clear up nicely with sunny skies for the afternoon hours. Temperatures will have cooled a bit as well, with a high only reaching the upper 70s. The weather should be ideal for those planning to attend the WKU vs. Morgan State football game. (Go Tops!) No major weather systems are expected for Sunday or even Monday for that matter, rather the weather will remain mostly sunny with highs in the 70s. Some fog development is likely during the morning hours both Sunday and Monday. Lows could again dip into the upper 40s by Monday morning. The warm weather is not completely done yet however, as was discussed in the early week post temperatures may warm to near 90 by mid-late week next week as another ridge moves over the Ohio Valley. Of course this is subject to change and updates will be posted on the blog next week detailing such.

Daily Forecasts:

Friday: Mostly cloudy to cloudy skies with a 30% change of rain after noon increasing to a 40% chance after 3 pm. Temperatures will be held down some what with the cloud cover and thus we’ll only see a high near 81. South to southwest winds at 6-14 mph.

Friday Night: 90% of rain and thunderstorms. Rain could be heavy at times. Total rainfall is expected to range between 0.75 – 1.50 inches. Low near 65. Winds from 5-10 out of the south switching to the west by morning.

Saturday: Clouds clearing early with a mostly sunny day in store. Cooler with a high around 77. Winds from the north-northwest at 6-12 mph.

Saturday Night: Fog may develop by morning. Otherwise clear skies, light winds with a low near 50.

Sunday: Sunny skies and cool with a high near 74. Northeast wind, generally between 2-8 mph.

Sunday Night: Patchy fog again possible. Cool and clear with a low around 47.

Monday: Sunny skies with a high in the mid 70s.