WKU Meteorology

Temperatures are beginning to become more fall like after a strong cold front and canadian air mass moved through Kentucky over the weekend. Surface high pressure has built in behind with winds remaining out of the north allowing the colder temperatures to continue to be advected into Kentucky.

Another area of low pressure has begun to develop over the Canadian border. A trough continues to deepen to the west over the Canadian border and propagate to the east into the week brining more cold temperatures and chance of showers by Tuesday night as another cold front develops and moves east over Kentucky. As with the last Canadian air mass, this one will also be dry which will inhibit precipitation chances. Both NAM and GFS models paint a line of precipitation moving through Wednesday ahead of the front. With a tight band of moisture out ahead of the front, this looks bleak. A few stray showers/sprinkles cannot be ruled out Tuesday night into Wednesday. Frost advisories are likely to remain into the week as cold overnight lows and dew points in the 30’s combine.

Forecast Overview:
Monday 10/8: High, 62. Low, 39 . 10% chance of precipitation, morning frost likely. Winds chilly out of the north.

Tuesday 10/9: High, 68. Low, 43. 20% chance of precipitation, morning frost likely. Front approaching overnight Tuesday with colder temperatures filtering in behind. Winds will remain northerly.

Wednesday 10/10: High, 63. Low, 39 . Front passes through with colder temperatures in behind. Morning frost likely. Temperatures drop further with passage of front. Winds chilly and out of the north.

FORECASTER: Emily Yates
NEXT UPDATE: 8/10/12

While areas from Paducah to Louisville have received several rounds of rain this week, south central Kentucky has stayed relatively dry.  A slow moving surface front has been located through the Ohio River Valley with several rounds of showers and storms moving along the front.  Some location in Kentucky picked up 2 to 3 inches of rain in the last 3 days, while others picked up very little if any at all.

3 Day Rainfall Totals:

Meade County Mesonet (near Brandenburg)- 3.71 inches
Fulton County Mesonet (near Hickman)- 2.20 inches
Louisville Bowman Field- 1.57 inches
Bowling Green/Warren Co Regional- 0.15 inches
Allen County Mesonet (near Scottsville)- 0.00 inches

As of this morning (Thursday) the front responsible for this rainfall extended from the mid-Atlantic states, through the Ohio River Valley and down to Oklahoma.  This front will finally be getting a push to the south today however, which will bring better rain chances for southern KY today through midday Friday, before the front pushes south of the state.  Rainfall amounts should generally be light with totals ranging between 0.1 and 0.5 inch.

HPC forecast surface map for Friday. The front will be pushing south of Kentucky and thus bringing any rainfall to an end.

Behind the front, a trough will deepen into the area which will bring a return to cooler temperatures.  An upper-level low centered over the Great Lakes associated with the trough will bring some clouds in for Saturday and a light shower can’t be ruled out early.  This trough will continue to spin over the Great Lakes into Sunday before pulling out by Monday.  Overall however the weather should make for a nice early fall weekend with temperatures in the mid 70s for highs while lows will return to the low 50s.  Our next weather maker looks to be in the form of a cold front which will impact us on Tuesday.

Daily Forecasts:

Thursday: 60% chance rain and thunderstorms, especially into the evening, with a high near 78.  Winds will be from 5-10 mph switching from the southwest to the west-northwest.

Friday: 40% chance of rain coming to an end by the afternoon.  Morning lows will be around 61 and afternoon highs will be near 74.  Winds will be out of the west to northwest from 3-7 mph.

Saturday: Mostly cloudy skies will become partly cloudy with a stray shower possible.  Temperatures will be cooler with a low around 52 and a day time high around 74.  Winds will be from north between 4-8 mph.

Sunday: Mostly sunny skies with a low near 50 and a high around 75.

The first weekend of fall brought with it fall like weather.  Saturday and Sunday brought beautifully sunny skies with temperatures falling from high near 80 on Saturday to a high of only 68 on Sunday behind the cold front.  Overnight lows took a dive as well falling to 37 this morning at the Warren Co mesonet site as a result of clear skies and calm winds.  Temperatures will be rebounding throughout the first part of this week however.  The trough that has brought the cool temperatures will be retreating to the north which will allow temperatures to begin warming back up throughout the week.  After a very nice day in the low 70s today, 80s will return to south-central Kentucky for highs by Tuesday.

The NAM surface pressure/winds/temperature forecast for 4 pm Tuesday with analyzed fronts. Green arrows indicate moist air coming to the Ohio Valley from the Gulf of Mexico.

The high pressure system that is currently centered directly over Kentucky will be sliding southeastward.  The position of the high pressure system by Tuesday and a weak cold front from the Great Lakes to the Midwest will create a strong low-level jet which will bring in warm moist air from the Gulf of Mexico.  Winds could be quite blustery Tuesday, blowing out of the south-southwest from 15 to 20 mph.  As far as any precipitation is concerned, forecast models generally agree that an axis of rainfall will setup just to the south of the cold front.  For us here in southern Kentucky current thinking is that heaviest of the rainfall will remain along and north of the Ohio River.  Still yet, increased clouds and the chance of rain does enter the forecast for Tuesday and Wednesday.  Our best chance of rain comes Wednesday afternoon as the washed out front comes ever closer.

The Hydrometeorological Prediction Center’s 1-3 Day QPF or quantitative precipitation forecast.

A glance into the late week pattern reveals more of an east-to-west flow which generally spells quite weather for our area; however, a few small disturbances may pass just to our north which will mean slight rain chances through late week.

Daily Forecast:

Monday: Another gorgeous sunny fall day with temperatures warming to a high near 73.  Light southeast to southerly winds from 3 to 8 mph.

Tuesday: After a morning low around 54 temperatures will warm to a high near 83.  Skies will be partly to mostly cloudy at times with a 30% chance of rain.  Winds will be blustery out of the south-southwest from 15 to 20 mph.

Wednesday: Partly cloudy skies early becoming mostly cloudy in the afternoon with a 40% chance of rain.  Lows will be near 63 with an afternoon high around 85.  Southwest winds from 8 to 14 mph.

Thursday: A 20% chance of a shower in the morning before giving way to a partly cloudy day.  Low near 64 and a high around 84.

The surface high pressure system that entered the area yesterday has mostly migrated to the New England states, but is still exhibiting control over our area into the lower Mississippi River valley. A cold front is extending from a surface low pressure center situated just north of Minnesota. The front extends with a SW orientation from Michigan’s Upper Peninsula into central Kansas. Overall, the upper level support is not very prevalent. For one, the 300mb trough has a neutral orientation with the jet max misaligned to the south of the center of surface low pressure. This will inhibit intensification and forward movement of the weather system. Also, there appears to be little positive vorticity advection, which in abundance stimulates lift and support for the surface low and front. The surface high pressure is important because it is preventing any chance of significant moisture advection into our area ahead of the cold front.

Above is the NWS Storm Prediction Center’s Short Range Ensemble Forecast Model valid for 7 AM this Saturday. It is showing probabilities for precipitation of .01 inches during a three hour span. Percentage values are almost nonexistent for our area.

Into Sunday, the upper level trough is shown to remain in its neutral orientation and deepening with the presence of a jet streak. As the jet max goes around the bottom of the trough, it will begin to shallow it out and move it eastward at the start of next week. The surface cold front presently draped across the midwest will likely fizzle out into Friday because of the stationary high pressure and lack of upper level support. The residual high pressure will resume control until being swept out by a cold front on Saturday. This front bearing low will have more support from the jet stream with the cold front looking to impact our area on Saturday afternoon. Because of the high pressure over our the region, the availability of moisture will be a concern and will determine the severity and even occurrence of precipitation associated with the frontal passage. Warm air advection will also be inhibited, which will put in question the strength of the front because of the diminished temperature gradient. Models are currently behind these assumptions with almost no indication of measurable precipitation associated with the frontal passage. With it being three days out, there is still room for error. Behind the front into Sunday, expect cooler temperatures again with a high pressure settling into the region.

Days at a glance:

Thursday: High 75 Low 48

Friday:      High 81 Low 54

Saturday:  High 77 Low 52

Sunday:     High 67 Low 37

Currently, we are situated in the southerly, return flow of an eastward tracking surface high pressure system. There is also a center of surface low pressure in the Gulf of Mexico due south of Louisiana pumping moist, Gulf air straight north into our area. This is creating moderate values of moisture for the lower Mississippi and lower Ohio River valleys. A significant short wave situated in the lower Mississippi River valley is aiding in the moisture advection and providing lift, giving us the current showers. Periods of rain today are more widespread and prolonged, with less severe implications. To our west exists a cold front extending from Michigan’s Upper Peninsula with a southwest orientation across Iowa and into the Texas panhandle, with the center of low pressure in the northern extent of Quebec.

This is the Hydrometeorological Prediction Center’s qualitative precipitation forecast for today into tomorrow morning.

Models are depicting the upper level support for the front to increase as the 250mb trough over the upper Midwest is deepening positively with a jet max on the down stream side over the Great Lakes. This, coupled with increasing vorticity and vertical velocity values extending at the surface frontal vicinity will help to provide substantial support for the front. Moisture advection from the Gulf is shown to continue before the expected frontal passage shown by both the NAM and GFS models as early Tuesday morning around 7 AM.  Moderate to heavy rain and strong winds should be presumed as the main threat for the frontal passage. Periods of rain related to the front should be relatively brief, but intense. Models are showing a majority of the precipitation to be experienced to our east in eastern Kentucky and central Tennessee along the Cumberland Plateau with high probabilities of 3-hour accumulations around a quarter of an inch for the period of the next day.  The HPC’s forecast for precipitation accumulations agree with the models showing over 4 inches for the same geographic area through tomorrow morning. I think this is a little exaggerated depending on the speed of the cold front and will keep precipitation amounts lower for our area. We are also along the projected precipitation gradient, so precipitation amounts for our area look to be one inch to an inch and a half in total. A flood watch has been issued for areas to our east because of the duo of soaking rains today with the frontal passage tomorrow morning. Behind the front, dry, cool air will look to bring a hint of fall as a surface high pressure situates over the area. A light jacket will be advisable.

Days at a glance:

Today:         High 74     Low 65

Tomorrow:  High 70     Low 44

Wednesday: High 67     Low 40

The weekend kicked off fairly nice across the area with partly to mostly cloudy conditions for much of your Saturday.  The ridge that hovered over the Ohio Valley region much of the week moved into the New England region and is now situated well off the eastern coast.  A weak, but dry front tracked through the area by Friday morning bringing a few isolated showers across parts of the state.  In behind the front cooler and drier air filtered in throughout the state bringing pleasant conditions for many.  Temperatures on Saturday struggled to hit the 80 degree mark as most of the area dealt with partly to mostly cloudy skies.

As we head into the overnight hours, generally calm conditions should be expected as high pressure and light northwest winds will keep drier, cooler air over the area.  Saturday nights lows will be chilly with temperatures expected to drop into the upper 50’s as clouds will continue to thicken through the overnight hours.

850 mb showing heights and cloud cover valid for Sunday 13z. By Sunday morning, as mentioned above, clouds will thicken and continue to hang tough around our area. Much of the state should see partly to mostly cloudy conditions. Image produced by IDV.

The light rains currently over southern Missouri will weaken pretty quickly as they move southeast across western Kentucky during the early morning hours.  Sunday morning will bring mostly cloudy skies with an isolated chance for a shower, especially across parts of Southwestern KY.  Highs for your Sunday will be very comfortable with temperatures reaching 77 degrees.

High pressure aloft has continued to bring in very nice, but pleasant conditions across the area as high temperatures topped out in the low 80’s under mostly sunny skies. The ridge was once situated over the Ohio Valley region has now progressed further eastward into the New England Region.  Return flow has helped gradual warming across the region as temperatures have jumped a degree or two higher since Monday.

700mb heights and winds map showing the ridge just to our east over parts of Pennsylvania with a projected north-east path. Red arrows indicate return flow which explains the gradual climb in temperatures for highs since Monday.

The ridge will continue its track off the east coast as a mainly dry front sets to move through the region Thursday night. Normally with a front we would see showers and storms develop just ahead of it. Significant dry air above the lower level and precipitable water values around normal or just above will lead to relatively low chances for any development for pop up showers and storms.  We should continue to see partly cloudy conditions over the next couple of days as the weak frontal passage works through the region. Highs look to be a tad bit warmer for your Thursday with temperatures topping out in the mid 80’s across the Commonwealth. Thursday night should bring partly cloudy skies with a SLIGHT chance for an isolated shower over the area. Look for lows to be a bit cooler  as temperatures are expected to bottom out around 60 degrees.

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Friday: Expect slightly cooler conditions with a high of 79 degrees. Partly cloudy skies should stick around into the evening and overnight hours. Low: 56, Light winds from the north around 5 mph.

Saturday: Expect mostly sunny conditions with a comfortable high around 76 degrees. Low: 56, Light winds from the north around 3 mph.

A strong frontal boundry moved through the region this past weekend bringing showers and storms for many across the state.  As the front tracked through the region, cooler and drier air filtered across the Commonwealth bringing very comfortable conditions for many. Monday morning brought an Autumn like feel about it as lows dipped down in the upper 50’s under clear skies. Temperatures rebounded nicely as highs topped out in the mid to upper 70’s as a few fair weather cumulus clous began to build by the early afternoon hours.

A strong ridge of High pressure situated just over the Ohio Valley region will continue to build and slide eastward over the next couple of days. This will allow temperatures to gradually warm by a couple degrees each day by mid-week.

700 mb map showing ridge location and intended movement over the next couple of days.

Looking ahead for your Monday evening, expect any fair weather cumulus clouds to subside by sunset as cool, clear, and calm conditions are expected. Many could see one of the cooler nights that we’ve had in a while with temperatures expected to bottom out in the low to mid 50’s statewide.  With the dominance of the high pressure aloft, Tuesday should be identical weather wise to your Monday.  Highs are expected to be a few degrees warmer with temperatures reaching the low 80’s.  Mostly sunny skies accompanied by a light northwest wind around 5 mph should make for another great weather day across the area.

Forecast Outlook:

Tuesday night: Cooler conditions expected once again with a low of 60 degrees. Expect mostly clear skies with a light southeast wind.

Wednesday: Another nice day with mostly sunny conditions.  A few fair weather cumulus clouds expected by early afternoon. High: 85 degrees, Low: 60 degrees. Winds from the south around 5 mph.

Friday has continued throughout the week to becoming more promising for a chance at severe weather for Bowling Green. The Storm Prediction Center has placed Bowling Green in a slight risk for storms for Friday. 

A surface boundary left over from a decaying MCS (Mesoscale Convective System) will be the focus for the first round of severe weather expected to move through Bowling Green in the early afternoon Friday. A line of storms is expected to move through the Bowling Green area between 1-2pm CST. The main threat with this first round of weather will be damaging winds and hail.

A second wave of severe weather is expected to move through in the later afternoon/night Friday. This wave will be associated with a larger potent low pressure system that has been evolving over the past few days to the west. A shortwave trough is expected to deepen and dig in from the east pushing along a strong cold front out ahead of it.

This system will have upper level support in the way of a potent trough axis with upper levels blasting around it in the 110 kts at 250 mb to 90 kts range around the 500 mb level. The 500 mb jet streak with peak winds around 90 kts will help provide support to a low level jet providing extra lift. A potent cold front will also provide added lift to this system as it sweeps through Friday evening/Saturday morning. In the low levels, moisture will be readily available with dew points across Kentucky in the 60’s and 70’s.  Bulk wind shear values spanning from 40 kts-60 kts will provide organization to any storms that develop. The main threat with this event will be damaging winds and large hail. Bowling line segments could develop within a greater squall line in  the event that the line is influence by a strong rear inflow jet.

After the passage of this system Saturday, a dry out is expected as the cold front moves out to the east. Due to the intense nature of this front, a major cool off is expected with almost fall like temperatures in the low to mid-70’s for highs and 50’s for lows on Saturday and Sunday.

Overlook:

Friday: Severe storms expected in rounds beginning in the early afternoon and concluding Saturday morning. High , 90. Low, 75.

Saturday: Major cool down after passage of cold front. Showers and storms continuing into the morning. High, 73. Low, 52.

Next Update: 9/8/12

Monday has brought us clearing from the remnants of Isaac with skies becoming partly cloudy by noon today and sunshine popping out around 2 pm. Rainfall totals over the weekend for Bowling Green ranged anywhere from 1 inch to 1.3 inches with the southern part of Warren County receiving the highest totals.

Moving onto the rest of the week, the precipitation should hold off until Wednesday. Until then, we will still be experiencing very humid conditions due to the abundance of moisture available from Isaac’s passage this weekend.  A frontal boundary will be making it’s way from the west into Kentucky overnight Wednesday bringing with it another chance at precipitation. The low pressure system associated with this front has already begun to occlude and weaken so it is expected the front will be substantially weakened when it arrives in our area Wednesday night.

This will lessen our chances for widespread precipitation as lifting with the front will be weakened as it continues to occlude. The precipitation will continue into Thursday with an eventual drying out Thursday night as the front moves to the east. The next influence should move in Friday as a more potent system looks to be in place.

Forecast At a Glance:

Tuesday Night: Partly cloudy with humid conditions. Stray showers possible in early night. Low 71 degrees.

Wednesday: Starting out dry with shower chances increasing into the night with approaching front. Partly cloudy conditions during the day. High, 90 degrees. Low, 73 degrees.

Next Update: 9/6/12