Sunday Weather Blog: Drier Air Moves Back In

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

There are still some leftover stratus clouds over Southwest Georgia and parts of the western Florida Big Bend this morning. The Tallahassee balloon launch indicates that the remaining column of low-level moisture is very shallow (no more than 1500 feet thick). Daytime heating will act to mix down an otherwise very dry airmass, so skies will become sunny shortly. Highs will reach the lower and mid 60s, which is almost exactly average for late January.

A high pressure system centered over Northern Louisiana today will shift eastward and park itself right on top of us tonight and Monday morning. Under this pattern, the winds will become calm and nearly ideal radiational cooling conditions will be achieved. I still expect a widespread light freeze to last about 1 to 3 hours on average. The normally coldest locations (i.e. the sandy soil belt that lies from southern Leon county through northern Taylor county into the Suwannee Valley) could see freezing temperatures for 4 or more hours. Meanwhile, downtown Tallahassee and coastal locations are not expected to see a freeze at all. The air will be dry, but the ambient temperature should reach the dewpoint in many areas, so areas of frost are also likely.

The high is only slowly going to move eastward and a more pronounced southerly return flow probably won't set up until at least Tuesday. Even so, the airmass will modify and highs should recover into the middle and upper 60s Monday afternoon. Monday night's low temperature forecast is tricky. The high will still be close by, so the winds will be calm for a good portion of the night. The main question centers around the amount and opacity of mid and high-level clouds that can make it ahead of the next system. Most likely, lows will bottom out just above freezing, but we will have to watch this carefully. Tuesday will have the warmest temperatures we've seen around here in quite some time, as the mercury powers past the 70-degree mark.

We are still watching the progress of two weather-makers along the Pacific coast that will eventually affect us. The first one is bringing tremendous rains and snows from California all the way to Washington state. The models are forecasting the bulk of the energy from this vigorous system to stay just to our north, but the associated cold front should get this far south late Tuesday night and Wednesday morning. A band of showers is expected to move from west to east across our area at that time, but the heaviest rains should be in central Georgia and Alabama. The second storm system is the most worrisome one, but it's still located near the Bering Strait. The models forecast the middle and upper tropospheric energy to drop southeastward into the Four Corners region by midweek, then affect a large portion of the eastern and southern United States. The Canadian and European models (like yesterday) have the strongest solutions, while the American GFS is a bit weaker (but still strong enough for a severe weather threat). The UKMET offers a compromise between these models, but is leaning more toward the Canadian and European global models. The global ensemble forecast system (GEFS) mean and individual spaghetti models are clearly leaning toward the less-amplified solution of the GFS. The disagreement on the strength of the trough leaves important details unresolved, but strong ridging over the Gulf of Alaska (in the Pacific) and another one near the Davis Strait (in the North Atlantic) almost always favors deeper, more amplified troughs as forecast by the ECMWF, Canadian GEM and UKMET office models. Thus, there is a chance of light rain on Thursday as the cold front associated with the first system lifts back toward the north as a warm front. The highest threat of severe weather is expected to occur some time between Thursday night and Friday when the large-scale forcing from the upper trough coincides with the greatest instability and potentially very impressive wind fields. We will continue to monitor this threat and update you throughout the week as the model solutions converge.

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