WKU Meteorology

The low pressure system that brought the cold front through our area is now located over New York, and both the NAM and the GFS are expecting it to slowly drift over New England for the next couple days, dropping several inches of rain throughout the region as the first Nor’easter of the season.

Meanwhile, the Ohio River Valley remains in the same drought conditions that have been affecting it for the past few months, with no sign of a drought-busting precipitation event anytime soon. Over the past few days, a large ridge has built up over much of the western half of North America, bringing predominantly dry conditions to much of the country. This will translate to mostly sunny skies over the weekend, with temperatures rising into the mid 70’s…still slightly above average for this time of year, but still a remarkably pleasant weekend.

NAM 24HR Precip, 15 October 2010

Yesterday brought the first rainfall of October for Bowling Green, with 0.08 inches recorded at the airport and 0.14 inches at the Mesonet station south of town. Today will feature another good shot at precipitation as a shortwave trough digs through the Ohio Valley, bringing a surface cold front through the area. However, moisture will be limited with this system as precipitable water values will only be around 1.2 inches, and no more than a quarter of an inch of rainfall is expected. This will not be the type of drought-busting rain that most of the state needs.

After the frontal passage, a deep upper-level trough and associated northwest flow aloft will move over the area. This will result in cooler conditions and more dry weather, with highs in the upper 60s and nighttime lows dipping into the lower 40s over the next few days. By Saturday, the axis of the trough will have moved to our east, resulting in beautiful weather for the weekend. On Saturday and Sunday, highs are expected to be in the mid 70s under sunny skies.

With a low pressure system sitting over Missouri and Kansas and moving southeast, the Mid-South is going to see some isolated to scattered showers, today. The main reasons for the lack of rain with this system are mainly the lack of overall moisture in the area, and the lack of soil moisture does not help the situation much, either.  The system that is moving toward Dixie has also become occluded, and is going to follow the southern branch of the split jet stream that is over Dixie. That being said, today will not be as warm as yesterday due to clouds being ever prevalent, today.  Any rain that is received today should be no more than 0.1 in., maybe some totals will approach 0.25 in., but that would be in some isolated extreme cases. In general this low is going to mark the beginning of a change in the overall pattern back to a ridge in the west and a trough axis right over the Great Lakes and extending down into Dixie, thereby setting the east coast up for the potential for more rain, and very likely exacerbating the already dry conditions the Mid-South and Ohio Valley alike are facing.

The latest 250mb Velocity plots show a very clear split flow in the jet stream as of late, with the Mid-South caught in the middle of it, which usually leaves the area high and dry, and that is not the best of news considering the hydrological situation in the Commonwealth, especially along the Ohio River.

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After this morning’s patchy frost, temperatures should moderated quickly. The pesky upper level low that has been dominating the east coasts weather is finally being moved via a 500mb shortwave. High pressure will be the dominating factor for the next few days as heights rise and surface ridging takes ahold.

Today Bowling Green should top out at a much warmer 74 degrees and tonights low will also be much warmer at 44 degrees. Expect the warming trend to continue into the weekend with weekend highs busting the 80 degree mark.

Last night frost was widely scattered but was reported at some locations, especially low lying areas. Here is a graphic of last nights temperatures that reflect this idea.

Graphic taken from NWS Louisville

Tonight will be a similar story as last night with low temperatures approaching 35 as surface high pressure takes hold. Expect a few more areas to receive frost tonight as radiational cooling is maximized under high pressure with light winds. Otherwise, todays high temperatures will be on the increase with a high of 69. As ridging takes place temperatures will rebound this week, and conditions will remain abnormally dry.

Currently, upper level low is still situated over the West Virginia and Ohio border and is still dominating our weather as it has for the last few days. Temperatures have remained below normal for much of SE kentucky as cloud cover has kept temps in the 60’s. Today should be similar to yesterday with light northerly winds and temperatures topping out at about 63 with mostly cloudy conditions in the afternoon. Tonight, skies will begin to clear from western to eastern KY as the Upper level low translates east slightly and surface high pressure takes over.

Areas more to the west with the clearest skies and maximized radiational cooling could approach the freezing mark at the surface. Also valley areas where cold air drainage takes place are frost prone tonight. One limiting factor for any frost chances could be light winds tonight, so any areas sheltered from the wind are frost prone.

Bottom line, frost is possible, but it is widely scattered. Only sheltered low lying areas may recieve frost, most areas should stay frost free. If you had extremely tender vegetation one might want to take a precautionary measure of covering it tonight, especially if you lived in rural areas in SW kentucky. Bowling green should hit a low temp of 37 tonight with patchy frost.

Through the rest of the week, temperatures should continue to rise and we should remain dry, as surface ridging takes place.

If you have been keeping up with the blog the past two days, you’ve seen that the models have been disagreeing on the chance of showers making its way into the area for Sunday. Well we can disregard any of that because as mentioned last post, there simply isn’t moisture being fed in front of the approaching cold front. The ingredients just aren’t there. A cold front is stretched across the western portions of Kentucky and Tennessee and will be passing over tonight, there may be some clouds overhead as the front approaches, but the main thing to be aware of is the temperatures on the backside of the front. Lows will drop tonight into the low 40’s and a high tomorrow in the low 60’s. A huge negatively tilted trough is currently being dug out over the region today and tonight bringing with it arctic air. Cold air will remain in place over the next few days until the middle of next week.We may also even see our first frost of the year Monday morning. It will be patchy but with lows dipping into the mid to upper 30’s you can’t rule it out.

Fall is here folks, so enjoy the quiet, relaxing weather while it lasts! A blog update will come again on Monday.

Today is the same story as has been the past few days.  Clear skies with warm, comfortable temperatures in the low to mid 70’s.  A high pressure is parked out over the central plains and is bringing down northerly winds which will help cool us down for the remainder of the weekend.  Now yesterday I mentioned how the ECMWF, GFS and NAM were not in agreeing on the output for Sunday.  ECMWF had rain moving into the area late Saturday night and Sunday morning, where as GFS and NAM did not.  All three models are agreeing now that a little disturbance will swing by affecting the area of Cincinnati northward along the Ohio River into Pennsylvania.  Here is the latest 12z NAM run:

Valid: 10-03-2010 06Z

I am going to bump the chances of showers down to 20%, I feel it’s better to keep the chance in there due to previous runs not agreeing with each other.  It will be curious to see how the models agree in later runs.  I will update the blog again tomorrow and let you know what to expect for your Saturday evening and Sunday morning.

Here is the 850 hPa map from the same 12z NAM run valid for 10-03-2010.  You can see the tongue of cold air building its way down near the Ohio Valley. You can see the zero degree line for 850 hPa reaching down into central Indiana and Illinois.

Valid: 10-03-2010 06Z

Today expect the high to be in the low to mid 70’s with a low tonight in the low 40’s.  Saturday expect a high in the low 70’s along with a low of around 40.  I will keep checking the models and update you, I just don’t think enough moisture will be present to bring any showers to the area.  Enjoy your weekend!

A meridional flow is presently residing over the United States, a ridge axis in the west extending through Idaho and Nevada is allowing warm, dry air to make its way into the western portion of the U.S.  Whereas in the east, a neutrally tilted trough axis extends over the southeastern states bringing with it on the back side cool arctic air.  A cold front associated with an occluded low up in Canada will pass through the area overnight tonight bringing with it dry, cold air to help drop the temps going into the weekend.  A high pressure will be taking over the central  U.S. and bringing with it anti-cyclonic flow from the north.  Highs are expected to be only in the low to mid 70’s for Friday and Saturday due to the northerly flow.  Heading into Saturday night temperatures will really begin to fall as sinking air from the strong surface high will be influencing temperatures for Sunday and Monday.

Models are having trouble agreeing with Sunday’s weather.  The European model shows a decent amount of rain in the Ohio Valley region pushing through early Sunday morning and moving slowly out by Monday morning.  The GFS and NAM are not showing much in the way of any precipitation in the area.  The two show a small disturbance north of the area early Sunday morning and having it become more of a threat to the east of our area as it heads southeast.  The GFS and NAM however with the past run modeled the disturbance to be further west then previous runs and output some rain showers closer to the area.  Still not affecting us at the moment according the those, but will we see the GFS and NAM trend back even more and come to an agreement with the European model? I will post more on this Friday and Saturday.

Otherwise, enjoy the cool temperatures and clear skies as they will persist through Saturday night.  Once again expect highs in the low to mid 70’s for Friday and Saturday with lows in the mid 40’s at night.  Sunday will be much cooler with a high in the low to mid 60’s with a 30% chance of rain.  Low on Sunday around 40.  Will update rain chances tomorrow, enjoy your weekend!