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Sunday Weather Blog: Storm on track for Tuesday

By: Meteorologist Ray Hawthorne Email
By: Meteorologist Ray Hawthorne Email

A fine day is in store today thanks to a building deep-layer ridge over the Southeastern U.S. The surface high that has been dominating our weather this weekend is stretched out along the Atlantic Coastal Plain, but will slowly slide eastward this afternoon through Monday. This will cause our winds to turn from an easterly direction this morning to a southeasterly one this afternoon and tonight, and finally southerly on Monday. The thermometer should have few problems reaching the mid to upper 70s today and Monday, but immediate coastal areas may get stuck in the mid to upper 60s with the developing onshore flow.

Increasing low-level moisture from the Gulf could result in the formation of patchy stratus clouds early Monday morning, but temperatures ought to start in the milder 50s. The increasing pressure gradient between the departing high pressure and the strengthening low pressure to our west will create sustained south-southeasterly winds of 12 to 18 mph Monday afternoon. A few gusts could easily reach over 20 mph. Even though most areas will avoid rain on Monday, upper air observations depict a weak shortwave (separate from the bigger storm) over Southeast Texas early this morning. The models have picked up on this feature and bring it eastward across our area Monday afternoon. The last several runs of the operational and experimental NAM model are showing a narrow rain band developing from South-Central Georgia through the Suwannee Valley and toward the Tampa area either late Monday afternoon or evening. Meanwhile, the GFS keeps any rain from Tampa southward. There does appear to be a narrow warm/moist tongue of lower tropospheric air riding up the west coast of Florida into our eastern counties according to the diagnostic fields from our locally-run mesoscale models. As the shortwave in the middle atmosphere interacts with this moisture, showers may well develop closer to I-75. This is not a certainty, but folks in our eastern viewing area may get a little wet late in the day; however, nothing severe is anticipated.

The storm on Tuesday is still on track to affect our area, but there have been a couple of changes in the model guidance. That often happens when troughs over the Pacific Ocean move onto the West coast of the U.S. or Canada, when balloons can finally sample the different characteristics of these systems. The trough is going to take a little longer to arrive from the west and the track of the low pressure area will go a bit farther north and west of where we thought it would go yesterday. The surface low is now expected to move from Northern Louisiana early Monday evening to the West Virginia/Kentucky/Ohio line by early Tuesday evening. Its attendant cold front will criss cross our area from west to east on Tuesday afternoon. That means showers and thunderstorms will develop in the western part of our viewing area during the mid to late morning hours, then reaching the eastern areas by mid afternoon. Since the trough is now expected to track farther to the north and west, the deep-layer wind fields are not quite as impressive in today's model runs as they were in yesterday's, but are still more than adequate for severe weather. The greatest large-scale forcing and subsequent cooling in the middle part of the atmosphere is now expected to be over our South Georgia counties. Here, somewhat greater instability should be realized in the presence of strong vertical shear. There is where the highest threat of tornadoes will be realized, with supercells along or just ahead of an eastward-moving squall line. Damaging winds seem to be the greatest threat over North Florida, but an isolated tornado cannot be ruled out in the Sunshine State either.

The storms will exit stage right on Tuesday evening, but the air behind the front is not excessively cool. In fact, highs could reach 70 again on Wednesday under mostly sunny skies. Another trough is expected to approach from the west either late Thursday or Friday, but the global models do not agree on details that will ultimately determine whether we get rain. Since the trough will be interacting with an old front over the Florida Peninsula, the highest threat of rain (if it happens at all) will be in the Suwannee Valley.


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