Welcoming December on a Mild Note

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

More Cold Weather This Week

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

Thanksgiving Forecast....

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.

Unseasonably warm temperatures to stick around....

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

End of the Week and Weekend Forecast

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.

Forecast Overview:

Thursday: Low, 28. High, 52. Mostly clear with morning temperatures below freezing.

Friday: Low, 32.  High, 54. Clouds increasing in the morning with periods of clearing throughout the day. Morning temperature below freezing.

Saturday: Low, 34. High, 55. Warming up with clear skies.

Sunday: Low, 40. High, 55. Mostly clear skies.

Severe Weather Potential for Monday and Beginning of the Week Forecast

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 ,66. Low, 28. 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.

FORECASTER: Emily Yates
NEXT UPDATE: 11/14/12

Showers, Major Cool Down to Start the Work Week

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.

Rainy, Cool Election Night, Warming Trend Starts Thursday

Tuesday has been overcast and cool thus far, with afternoon temperatures in the lower 50s.  A shortwave trough (Figure 1) is currently affecting Bowling Green’s weather, and it is expected to continue to dig southeast to further affect the forecast for Tuesday night into early Wednesday morning.  Before the clouds set in from the northwest Tuesday morning, the temperature did fall to 34 °F.  Current enhanced infrared satellite imagery (Figure 2) shows the heavier cloud cover over Illinois, Indiana, and western Kentucky.

Figure 1

Rain showers over these same areas will move southeast this evening into tonight, so expect a wet and chilly evening as you watch election results roll in.  Cloudy skies will remain through the night and through half of Wednesday.  Overnight lows will be in the lower 40s.

Figure 2

The clouds will persist until Wednesday afternoon, so expect highs only around 50 degrees.  A ridge of high pressure begins building into the region Wednesday night into Thursday, and this feature will produce warming each day into the weekend.  The NAM (Figure 3) shows surface temperatures rising back into the mid 60s by Friday.  

Figure 3

Bowling Green, KY Forecast:

Tuesday Night: Rain.  Cloudy, with a low around 42.

Wednesday: Cloudy in the morning, partly sunny in the afternoon and evening. High 50.

Wednesday Night: Clear. Low 32.

Thursday: Sunny. High 58. 

Forecaster: Evan Webb

Time Falls Back this Weekend... Will Temperatures Fall Too?

What a nice week to end October and move into November.  Skies have been generally sunny all week despite temperatures that have been slightly below average.  Temperatures should be in the mid-60s for this time of year in Bowling Green but highs have been in the 50s to near 60 this week.  As for overnight lows, Bowling Green fell to 30 degrees Thursday morning which is one of the coldest nights we’ve had thus far this fall.  There has been a gradual warm up in temperatures this week and this slow warm up should continue into this Saturday before yet another trough dips down to encompass southern Kentucky by Sunday.  As the trough and the jet stream dips to our south, slightly cooler air will once again filter into our area.  Until then however we will be on the southern edge of a trough but very near the southern edge of the jet stream as a ridge tries to build in. Generally when this jet moves to our north we warm, and when it moves to our south we cool down, thus this week with the jet stream virtually speeding by directly above us temperatures have been fairly consistent and neither warm nor cold.  

NAM 300 mb heights/winds forecast for Saturday afternoon. Temperatures will gradually warm thanks to being on the south side of jet stream but overall temperatures will be relatively neither warm or cold.

Thus until the trough dips in on Sunday expect temperatures to be warming ever so slightly. A shortwave is expected to move through Saturday afternoon ahead of the trough which could bring enough lift to create a few showers.  Rain chances Saturday afternoon are about 40% though any rain that does fall should be very light with a 0.1 of an inch of rain at the very most.  The system lacks a strong forcing mechanism as warm thermal advections and positive vorticiy advections will be very weak if present at all.

NAM forecast vertical velocity (rising air) at 7 pm Saturday. Increased vertical velocity here in southern Kentucky at this time just ahead of the shortwave (yellow dashed lines) indicates rising air and thus a chance of rainfall.

In summary, expect a very slow warm up through Saturday followed by increased cloudiness as rain chances enter the picture Saturday afternoon.  Cooler air will once again try to spill its way in by Sunday.  Looking longer term into early next week, models somewhat disagree to the strength of another trough axis moving through, nevertheless, more troughing is expected and thus cool weather will likely continue.

Daily Forecast:

Friday: Low: 40  High: 63  Mostly sunny skies with increasing high clouds late in the day.  Northwest winds will become more northerly; speeds from 4-9 mph.

Saturday: Low: 35 High: 64  Mostly cloudy skies will become overcast with a 40% chance of rain after noon.  Rain will be light with up to a 0.1 of an inch possible.  Winds from the north-northeast turning to the north at 5-10 mph.

Sunday (Daylight Savings Time Ends: Fall Back): Low: 41  High: 57  Partly to mostly sunny with light north winds between 3-8 mph.

Forecaster: Ryan Difani