WKU Meteorology

On Wednesday, an overachieving storm system brought a surprise dose of rainfall to the Bowling Green area. This precipitation was associated with an upper level low and frontal boundary over the Gulf states that pumped overrunning moisture into our region, and it was not anticipated well by the models. The Mesonet station at the WKU farm measured a total of 0.35 inches of precipitation from 6:00 AM to 7:30 PM Wednesday with this event, while the NWS observing station at the airport measured 0.32 inches.

Currently, the entire eastern half of the U.S. is under the influence of a deep upper-level trough that reaches all the way down into the Gulf of Mexico. A ripple of shortwave energy embedded in this trough brought us a few light showers this morning. Over the next few days, the trough should slowly progress to the east, with an upper-level ridge moving in to take its place. This will lead to moderating temperatures, with highs near 70 expected by Monday and Tuesday.

Current 250 mb heights and wind, showing the highly meridional flow across the U.S.

With the current jet stream pattern the way it is and the expected evolution of the jet stream as projected by the NAM and GFS, cooler temperatures can be expected throughout the week, with a more winter like feel to the weather as we head toward the weekend where highs might even struggle to reach the 50s.  The expected evolution of the pattern at 250mb is for a continued high amplitude meridional pattern with a trough digging very deep over the Midwest and producing a cutoff upper level system that will progress into the Gulf of Mexico by mid week and be picked back up by the main flow heading toward the end of the week. What does that mean for us?

Continue reading →

This weekend should be excellent weather for fall festivities. The surface high pressure that was responsible for many of SE KY’s freezing temperatures has translated east toward the carolinas, and return flow out of the south has allowed for some warm air advection and moderating temperatures. Temperatures should top out in the lower 60’s while dipping i8n to the upper 30’s at night. So, enjoy your fall activities, and have a safe and happy Halloween.

Today should be a nice fall day, with weak cold air advection still taking place from yesterdays frontal passage. Temperatures today should see a high of 59 with light winds out of the WNW topping out about 7 mph. Tonight, however, things will really begin to cool off as surface high pressure dominates the area. The cumberland river area has the best chance of a hard freeze as they will be under the high pressure maximum at sunrise, and radiational cooling will be maximized. For Bowling Green, expect widespread frost under light to no winds tonight,with a low of 32. Again, frost and possible freezes are possible in the more prone sheltered and low lying areas.

Sunny skies are deceiving as temperatures have begun to fall in Southern KY. A reinforcing shot off cold air from Tuesday system has arrived in the form of a cold front as Cold air advection is currently taking place. It will be wind with winds 10-15mph, and continuing to get colder as today’s maximum temperature has already been reached today.
For tonight, frost is once again possible as temperatures fall, the skies clear, and high pressure settles in. Most areas will approach freezing with Bowling Green specifically reaching 33 under light winds. Otherwise any other low lying areas or sheltered areas are prone for a patchy frost. Otherwise the rest of the week seems climatologically seasonal, or just a tad bit cooler. More to come..

Tomorrow there is a good chance that the storms rolling through around midday will be severe, straight line wind damages will be the main threat as winds will be sustained at around 20 mph.  Gusts could be over 40 mph.  Winds will pick up overnight and by early morning hours we will see the effects of the tight pressure gradient and the approaching cold front.  The cold front will be through the area by 3:00-4:00 pm. But expect the heaviest winds ahead of the cold front.  An embedded tornado can’t be ruled out though, tornadic supercells will be favorable near the southern end of the squall line.  So depending on how far the squall line reaches southward, that southern tip will be favorable for tornadoes.  In the main line, the main threat is straight line winds.

Otherwise expect a high temperature around 75 and a low around 50.  Winds being the main factor starting overnight tonight.  Keep an outlook on weather throughout the day.  If frontal timing is later, that will give the atmosphere more time to heat up and destabilize which could up the severe potential.  If that is the case, an update will be posted as soon as it becomes eminent.

Wednesday we will be under mostly sunny skies with a high in the mid to upper 70s.  Still on the windy side with winds ranging from 7-13 mph and gusts over 20 mph.  A low Wednesday night around 45.  Winds calming down Wednesday night as well.

An upper level tough exists over the region and will allow for some convection to our west through the morning hours, allowing for rain chances before noon.  However most of the heavy precipitation has pushed its way on out of the area.  Highs today will reach near 80, which is not normal for late October.  Tonight temps will stay unseasonably warm as well as we remain in the warm sector of system to our north.  A cold front will approach early Tuesday morning with a few scattered showers out ahead of the front.  However, Tuesday is when things get real interesting.

Tuesday and Wednesday are setting up to be historic.  Maybe not for this area in particular but definitely for the northern Plains and the Great Lakes region.  A low is forming off the Rocky Mountains and is forecast to move northeast into Minnesota.  As it does so, will deepen to around 964 millibars, which is not typical in the U.S. at all.  A strong pressure gradient will exist through most of the eastern U.S., including our area.  Winds expected to be high today through Tuesday afternoon.  Stronger winds on Tuesday around 15 to 22 mph with gusts in the mid 30’s or higher.  Dynamics with this storm will be enough to suggest a strong line of storms rolling through the area Tuesday mid morning through Tuesday night.  A few embedded tornadoes can’t be ruled out from the strong line of storms to roll through Tuesday.  Rainfall amounts Tuesday through Wednesday are expected to be between 1 to 2 inches.  An update will come shortly as we gain more knowledge of what is to come.  Here is the look at NAM model output for Tuesday.

High pressure has settled in for the weekend along much of the country, making this weekend a perfect weekend to go out and view the autumn colors. Both the GFS and the NAM are forecasting the development of a moderate amplitude trough over our area in the middle of next week, with the National Weather Service forecasting rain showers throughout much of Tuesday, with temperatures dropping into the mid 60s next week, making it feel like fall just as much as it looks it. Still, with the exception of some rainfall over central California, there is not much to speak about today.

Here is a photograph of some of the autumn foliage in Bowling Green in a backyard on Nutwood Street under this weekend’s sunny skies.

Weather patterns across the country are fairly quiet for the moment. The shortwave trough moving out of the northwest has greatly decreased the amplitude of the ridge over the western US, helping to create a largely zonal flow pattern across the continent. Indeed, the only remaining storms of interest are dissipating: the Nor’easter affecting New England has now completely occluded, reducing precipitation to a few bands of scattered showers, and what used to be Hurricane Paula has now become nothing but a sheared apart area of weak convection between the Florida keys and Cuba.

Both the GFS and the NAM are forecasting a cut off low to pinch off from the jet-stream and build a ridge over the western half of the continent by the beginning of next week, as well as bring more rainy conditions to the southwest. Over the next week, this will likely help develop a fairly strong trough, which should bring cooler conditions, as well as a chance of rain in the middle of next week.