WKU Meteorology

After a brief lull in forecasts here on the blog last week during WKU final’s week, we are back and will continue providing you up-to-date weather information here on the WKU meteorology blog throughout WKU’s winter break.

The sun has now returned to south-central KY after several cloudy and rainy days.  Even thunderstorms impacted the area with small hail reported near Morgantown (see pic) with other isolated reports of small hail in Logan and Warren Counties.  Most of the hail reports in the state yesterday occurred near near the Louisville area (check out the Louisville NWS recap).

Hail from just south of Morgantown on 12/17/12. Image courtesy of Landon Hampton (@BeechTreeWx) on twitter.

The storms have of course since pushed east and the low clouds from this morning have now pushed east as well giving way to mostly sunny skies.  Clear skies will continue throughout today as high pressure builds in at the surface at least for a couple of days before our next system moves in.  We are currently in a very active pattern with several disturbances or shortwaves moving across the US.  A disturbance and associated low pressure system in Iowa along with the high pressure over the Gulf of Mexico is allowing a warm SSW wind to set up over the mid-South.  This will allow highs to continue to be above average for this time of year with highs in the mid-50s today to low 60s tomorrow.  Our next weather maker is currently associated with an upper-level trough near the California coast.  This system will progress east in the coming days and could bring stormy and rainy weather to Kentucky by late Wednesday night and primarily Thursday morning.  Rain will likely move in after 2 am Thursday.  As you can see in the image below (at 9am Thurs) a surface low will be located near Chicago with a cold front extending to the south.  This will bring rain which could be heavy at times.  A few rumbles of thunder are possible though instability will be very weak due to the time of day.  Meanwhile heavy snow with near blizzard like conditions will be occuring from Iowa to Wisconsin.  Back here at home rainfall is expected to be greater than a quarter of an inch and could be as high as a half an inch.  Temperatures

NAM Mean Sea-Level Pressure, 850 temperatures & 6 hour precipitation at 15Z (9 am CST).

will then cool quickly behind the front which will pass through during the morning; temperatures will get colder throughout most of the day.  Temperatures should start out in the mid-50s on Thursday however temperatures are expected to drop to around 40 by 6 pm Thursday.  The colder temperatures will be ushered in by strong northwest winds Thursday afternoon.  Winds will be blowing between 20 and 30 mph with gusts up to 35 mph+ so hold onto your hats.  Those winds will make if feel much cooler than actually will be Thursday afternoon.  Friday should be cool as well with an upper-level trough over the Ohio Valley and northwest winds at the surface.

Daily Forecast:

Today: High near 56.  Clouds this morning will clear making for a mostly sunny day.  Winds will be from the south-southwest at 6-12 mph.

Tonight: Low near 38.  Mostly clear skies with light SSW winds up to 5 mph.

Wednesday: High near 64.  Warm with mostly sunny skies.  SSW wind becoming more southerly from 5-10 mph.

Wednesday Night: Low around 55.  Increasing clouds with 70% chance of rain after 2 am; thunder possible.  Winds from the south at 8-16 mph.

Thursday: 90% chance of rain especially before noon.  A rumble of thunder will be possible early.  Temperatures will warm to near 57 early with temperatures then falling throughout the day.  Noon near 50; near 40 by 6 pm.  Windy with winds from the northwest from 20-30 mph with gusts 35 mph+.  Total rainfall from 0.3 to 0.6 inches of rain.

Friday: Much cooler with a morning low in the mid 20s and a high near 41.  Sunny skies with continued blustery northwest winds.

Rain today, rain tomorrow will be the general theme of this weekend.  This is due to several disturbances passing through our area between now and Monday when a strong cold front will finally pass through.  Until that time we’ll have a cold front approaching from the northwest will which begin to stall out near the Ohio River Valley.  Because the front will begin to stall to our north we’ll see continued rain chances along with warm temperatures.

A cold front near the Ohio River Valley will be the focus of scattered areas of rainfall the next couple of days. Surface forecast from the HPC for Saturday.

Today and Saturday by no means look to be wash outs.  For today, the majority of the rain will be focused north of south-central Kentucky near the Ohio River which is closer to the front but at least a few scattered showers are likely in our area.  On Saturday rain seems more likely in our area as a band of rainfall should set-up in south-central Kentucky along the front which will slowly drift closer to our area and even pass through during the evening hours.  Rain chances will be highest into the afternoon but this rainfall shouldn’t be terribly heavy with generally less than a quarter of an inch of rainfall possible.

Total rainfall forecast from the HPC through Wednesday morning.  Rainfall totals in Kentucky/Tennessee are expected to be between 1.50-2.00 inches of rainfall.

By the time we move into Sunday another cold front will be approaching from the west ahead of a deep trough in the upper-levels which will be moving east.  As this system approaches the front which had stalled near our area will begin to lift back the north as a warm front.  This should enhance rainfall chances with the front near our area especially Sunday morning as the front pushes back through our area.  Sunday should be a warm day as we once again challenge record highs in Bowling Green.  Highs should be near 70 and could reach the record high of 71 set in 1952.  The warm weather will break into early next week however as the aforementioned strong cold front pushes through bringing much colder temperatures to our area.  Furthermore as the cold front moves through Sunday night/Monday morning rain will be likely.  Rainfall is expected to fall steadily for several hours and thus the area could pick up as much as an inch of rainfall by midday Monday.  Some of the models disagree with the timing of when the rainfall will move out Monday and thus this will be monitored to see how forecast models can come into agreement.  Meanwhile temperatures will fall throughout the day on Monday with temperatures expected to be in the 30s by the afternoon.

Daily Forecast:

Today: High: 66  Cloudy with a 70% of a few scattered showers through the day with around a tenth of an inch of rainfall possible.  Winds from the south-southwest from 10-15 mph.

Saturday: Low: 58  High: 67  Cloudy skies with and an 80% chance of showers especially in the afternoon.  Rainfall should be less than a quarter of an inch.  Winds from the southwest switching to the northeast late at 5-10 mph.

Sunday: Low: 54  High: 71  Cloudy skies with an 80% chance of rainfall especially before noon.  Rainfall around a quarter of an inch.  Winds out the south-southwest from 10-15 mph.  More rainfall moving in overnight Sunday night; overnight/Monday morning rainfall totals could approach one inch.

Yes, you read your calendar correctly, though it may not feel like it outside, it is indeed December.  Highs of 68 (Rec: 71) on Saturday and and high of 72 (Rec: 76) on Sunday challenged daily records for Bowling Green.  On average we should be in the low 50s for highs this time of year and thus we are 20-25 degrees above average.  The warmth looks to continue as temperatures will climb even with Bowling Green situated on the warm side of a surface high pressure system off the southeast coast.  It looks as though we will once again fall short of the record high of 78 set in 1982 as highs are only expected to be around 75.  Meanwhile skies will be mostly sunny and thus making for a phenomenal day for December.  The only drawback to the weather is that it will be blustery with winds between 12 and 18 mph out of the south/south-southwest.  Temperatures will reach the maximum for the week today however as a cold front is set to bring in cooler temperatures and likely rainfall by Tuesday afternoon.  Their could even be enough instability for a rumble of thunder.  The cold front will not be a very powerful front as it is far from the surface low pressure centered well into Canada; this will allow the front to be somewhat slow moving.  Due to this rain could fall for several hours Tuesday afternoon and thus rainfall totals could be as high as a half an inch in some places with even higher totals further south and east of Bowling Green.  The best chances of rain will be between noon to just after 6 pm when the front pushes through.

The Hydrometeorological Prediction Center’s 1-2 Day QPF (Total Rainfall) Forecast.  Notice forecast rainfall totals around a half an inch in south-central Kentucky.

Behind the front on Wednesday, skies look to clear out for a sunny day as another high pressure system will work its way in from the northwest.  While temperatures will be cooler, highs near 60 will still mean that we’ll be about 10 degrees warmer than average.  Thursday looks to be the coolest day with morning lows reaching the upper 20s and highs only in the mid to upper 50s due to cool winds coming in around the high pressure.  Looking longer term into the end of the week temperatures will remain above average and rain looks to enter the forecast again for the weekend as front stalls out in the Ohio Valley.

Daily Forecast:

Today: Low: 57  High: 75  A few clouds especially in the morning but otherwise mostly sunny and warm.  Blustery with S/SSW winds at 12-18 mph.

Tuesday: Low: 59  High: 68  Cloudy skies with rain moving in mainly after noon.  Rainfall totals between 0.3-0.6 in.  Chance of rain 90%.  S/SSW winds between 8-14 mph becoming NW/N in the evening between  5-10 mph.

Wednesday: Low: 39  High: 60  Sunny skies with light north winds 3-8 mph.

Thursday: Low: 28  High: 58  Mostly sunny with winds from 5-12 mph switching from the east to the SSE/S.

For the past couple of days, we have been under a dominant surface high pressure system. Currently, the upper level flow is zonal and the models show this pattern persisting into Sunday. Thus, we are going to be stuck under this stationary high pressure to close out the week. As it moves eastward, our area will begin to experience a return flow, bringing in warmer, more moist, Gulf air. With this said, expect a warming trend into the weekend with beautiful weather. Get ready to welcome in December with mid-60 temperatures!

Days at a glance:

Friday: High – 60; Low – 32
Saturday: High – 65; Low – 42
Sunday: High – 67; Low – 48

Forecaster: Austin Boys

We are currently in the return flow of a surface high pressure system with a weak cold front draped diagonally across central Illinois and Missouri. The strengthening upper level support will help to push the boundary through our area early Tuesday morning. The inflow of moisture is apparent, but not very significant. There is a nose of moisture extending into western Kentucky from the Gulf of Mexico.

NAM 11/25 18Z run valid for Tuesday 11/27 03Z (9PM 11/26) showing 850mb dew points greater than 0 Deg C, heights, and winds. The nose of moisture is clearly visible as well as the frontal boundary across the Ohio River valley.

The question is whether this precipitation will be of the frozen kind, and how much.

GFS 11/26 00Z run valid for Tuesday 11/27 12Z (6AM) showing mean SLP, 1000-500mb thickness, and 6 hour precipitation in inches. The boundary between red and blue thickness lines marks the freezing line bisecting Kentucky.

The GFS run above is showing the line of critical thickness (estimated freezing line) horizontally dividing Kentucky. Being situated near the freezing line makes determining the type of precipitation very tricky. Concerning the amount, both the NAM and GFS are concluding the precipitation at 12Z Tuesday, with the GFS calling for up to .09 inches and the NAM calling for up to .24 inches. I will stick to the lower end, since the frontal lifting and moisture inflow are moderate at best. The temperature difference on either side of the front is lacking, thus further reducing its chance of strengthening, especially at night. Right now, precipitation received is looking like rain, but I will continue to monitor and provide updates to precipitation type up to the frontal passage if needed.

After the frontal passage early Tuesday morning, a surface high pressure will settle into the region for the middle of the week bringing more of a return flow into Thursday.

Days at a glance:

Monday: High of 56, Low of 34, no precipitation

Tuesday: High of 43, Low of 22, .11 inches of rain

Wednesday: High of 49, Low of 25, no precipitation

Thursday: High of 55, Low of 32, no precipitation

Forecaster: Austin Boys

One more warm and sunny day is expected across the area for the Thanksgiving Holiday before a cold front brings a big temperature change for the Ohio Valley region. For today, high pressure currently stretching across the region will slowly shift eastward leaving the area the last full day of sunny and warm conditions.  Highs are expected to reach the mid to upper 60’s with light and variable winds from the southwest making the holiday an absolute gorgeous one.

SPC Mesoanalysis Map 500mb heights, temps, and winds valid Thursday 14Z. Ridge building over the south with the short wave trough to our north and west.

Looking ahead, a cold front will move into parts of southern Indiana late tonight while advancing southeastward near the Ohio River by tomorrow morning.  The cold front will bring  showers into the forecast as the highest coverage of precipitation looks to be just to our west.  Shower activity will become more scattered in nature as the front progresses eastward over our area.   The HPC’s  latest QPF map shows a light to moderate rainfall event over the Midwest with heaviest rainfall falling in parts of Missouri and southern Illinois.

HPC’s latest QPF map showing a light to moderate rainfall event over 24-36 hours.

As the front passes through Friday, some additional moisture swinging around the upper level trough may bring some scattered clouds in the north during the afternoon.  At this time, winds should begin to pick up out of the northwest behind the front with gusty conditions expected with winds up to 25 mph.  Colder air will filter in behind the front just in time for the weekend, as temperature will be noticeably cooler across the region.

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Friday: Showers likely. High: 54 Northwest winds around 10-15 mph.

Friday Night: Clearing skies and cold. Low: 28. Light Northwest winds around 5-10 mph.

Saturday: Sunny and cool. High: 41. Northwest wind around 5 mph.

Saturday night: Clear and cold. Low: 24.

Forecaster: Chris Johnson

As we start another week and head into the Thanksgiving holiday, conditions across the area are expected to be unseasonably warmer.  A fast zonal upper air flow continues across much of the eastern United States as the northern branch of the jet is located along the U.S./Canadian border, helping keep the cooler air to our north.  A weak 500 mb ridge will temporarily develop over the region today, followed by a weak trough that will slide through the Commonwealth by Monday.

HPC/NOAA short range forecast valid for Tuesday 12Z. Ridge of high pressure will build over the Tennessee Valley region as the weak trough to our west tracks eastward through the area by Monday night/early Tuesday morning.

As the low tracks through late Monday night, a slight chance for an isolated shower will exist although the main threat seems to be cloud cover.  Neither feature will have much effect on the the overall temperatures as a gradual warm up is expected through the Thanksgiving holiday.  The HPC’s QPF maps below seems to show agreement as any rainfall that does occur will be light and mainly to the north of the state.

HPC’s QPF precipitation forecast map valid for Tuesday 12Z. Showing areas of light precip. just to the north of the state in parts of southern Illinois and Indiana.

Highs for your Sunday will begin a nice stretch of comfortable fall time weather.  Temperatures are expected to reach the low to mid 60’s here in Bowling Green under mostly sunny skies, as identical days look to follow.  Skies will remain clear for your Sunday evening as temperatures drop to around 36 degrees with calm winds expected.

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Monday: Expect mostly sunny skies. High: 64.

Monday night: Expect increasing clouds with light and variable winds from the west. Low: 43

Tuesday: Another nice day with partly sunny conditions. High:65 Light winds from the southwest around 5mph.

Tuesday night: Partly to mostly cloudy skies expected. Low: 41

Forecaster: Chris Johnson

A calmer weather pattern looks to set in for the end of the week into the weekend here in Bowling Green. The biggest story will be the cooler temperatures with several mornings starting out below freezing. Conditions should remain dry Thursday into the weekend as our air remains very dry with dew points only in the 30’s throughout most of the period as winds remain out of the north advecting in dry cool air from Canada. Surface high pressure will dominate the forecast period.

NAM Forecast surface temperature for Thursday morning.

Some weak upper air disturbances in the form of shortwave troughs will move through Thursday into Friday. With moisture lacking, it is not likely that we will see showers. Thursday looks to be mostly clear and sunny. Cloud cover will likely increase into Friday with relative humidity forecast to be around 60% during the day. Saturday and Sunday we should see more clear sunny conditions.

NAM forecast relative humidity for Friday 7 am. Circle shows relative humidity values around 60-70% beginning to move into Bowling Green resulting in increased cloud cover.

Hi-Res radar courtesy of Noaa.gov

Showers and storms will be moving into the Bowling Green area into Monday morning and afternoon as a cold front sweeps across the southeast. Behind the front, we will see much colder temperatures which is change from the warm up we experienced this weekend. We see highs this Sunday as of 7:00 AM EST (6:00 AM CST) in and around 5-10 degrees above normal for this time in the month of November.

Photo courtesy of weather.com showing temperature departures from normal.

As we examine the latest RUC model analysis of surface temperatures, you can clearly see the colder air mass in behind the front that will bring us the drop in temperatures for Monday and Tuesday. With the displacement of the surface low to the north west, we will see our chances of severe weather be cut down significantly. We do see a strengthened area of positive vorticity that will enhance upper level support into Monday. We also see pocket of elevated wind shear that will support lifting and provide a hail threat as upper level temperatures will be substantially cold. The main threats will be high winds and hail. The event will likely be in the nature of a squall line. Another inhibition will be the earlier in the day timing which will mean less daytime heating and energy for developing storms.  After the cold front passage, We will see our winds shift from the south to out of the north west as the front progresses through the area bringing much colder drier air into the Bowling Green area.

RUC surface temperature analysis for 23 UTC

We are seeing winds increase throughout the day here in Bowling Green. The Kentucky Mesonet shows peak wind gusts of up to 36 MPH in Warren County as of 6:50 CST. These winds are increasing in response to the tightening pressure gradient we are seeing across western Kentucky as the system is moving eastward.

Photo courtesy of kentuckymesonet.org

Looking into Tuesday, we will see a dry out with temperatures more normal to this time of year. Temperatures could drop below freezing Tuesday morning as that cold dry air continues to funnel in from the north west. Wednesday could also see below freezing temperatures in the morning hours and chilly temperatures remaining throughout the day. Wednesday our winds will shift to the north east as surface high pressure builds in behind the previous system. A weak upper level disturbance will move towards the area deepening somewhat as it approaches our area. We can expect some light showers to possibly develop with this system. Forcing will be lacking for any severe weather/thunderstorm potential.

Forecast Overview:

Monday: High 48,. Low, 43. Winds SSE, 5-15 knots. Rainy cloudy conditions to persist throughout the day. Slight chance of strong to severe thunderstorms.

Tuesday: High, 49. Low, 28. Winds NW, 5-10 knots. Clearing conditions with a cool down. Freezing temperatures possible in the morning hours.

Wednesday: High, 51. Low, 26. Winds NE, 5-10 knots Light showers possible. Partly cloudy conditions.

It is an absolutely beautiful Saturday in south-central Kentucky. A ridge of high pressure over Bowling Green (Figure 1) kept skies clear overnight, and fair weather will hang around until Sunday night. The Saturday morning low temperature was 42 degrees, and the afternoon high will be in the lower 70s. Sunday will be very similar to Saturday, with sunny skies and highs in the lower 70s. Get in your outdoor activities before the end of the weekend, folks, because Monday morning will be a return to dreary November weather.

Figure 1. 6 AM Saturday 500 mb Analysis.

A deep 500 mb trough (Figure 1) is located over the western United States and this feature will swing across the Plains today and into our area later on Sunday.  At the surface, the pressure gradient will tighten as the mid-latitude cyclone approaches, which will provide gusty winds on Sunday.  Sustained winds of 15-25 mph with gusts to 35 can be expected.  The surface low pressure center is expected to track northeast towards Lake Superior and then into Canada.  The system will feature a long cold front extending the full width of the U.S. (Figure 2) Current models have the front arriving Monday morning, so expect widespread showers and isolated storms overnight Sunday night into Monday morning.

Figure 2. Surface cold front at 6 AM CST Monday.

At this time, severe weather is not expected with the passage of the cold front.  The Hydrometeorological Prediction Center (HPC) is forecasting system rainfall totals in the 0.50″ – 0.75″ range through 6 AM Tuesday morning (Figure 3).

Figure 3. System total precipitation through Tuesday morning.

Polar air will flow into southcentral Kentucky on Monday behind the cold front, so expect the temperature to drop during the day on Monday from the mid 50s down to the upper 40s.  The clouds are expected to clear out to the east by Monday evening, so Monday night will be cold. The overnight low will be in the upper 20s, and Tuesday will be sunny with highs in the upper 40s.

Bowling Green, KY Forecast:

Saturday: Sunny. High 72.

Saturday Night: Clear. Low 46

Sunday: Sunny and windy. High 72.

Sunday Night: Showers and isolated storms. Overnight low in the mid 50s, dropping throughout the day Monday.

Monday: Cloudy. High 52, dropping into the upper 40s.

Monday Night: Clear. Low 29.