After a big warm-up through Friday, the weekend brings heavy rain and storm potential…especially on Sunday. Another frost or freeze is also possible next week!
The overall weather pattern will be trending towards a more amplified regime, and this typically brings about big changes as the atmosphere acts to “fix” itself.
As this pattern takes shape toward the end of the week, a subtropical ridge will extend from the Gulf into the eastern United States while a large trough of low pressure dives into the western states. This will set up a big warming trend for the western Carolinas as cooler air gets bottled up way to the north and west, over the Rockies. Highs could approach the low 80s in the Upstate Friday!
Amplified weather patterns tend to portend slower evolutions (beta effect) to the surface features such as cold fronts, low pressure centers, etc. As a result, confidence in the exact timing of Sunday’s storm potential remains low though overall confidence in rain and storms occurring is high.
Deep moisture return is expected in advance of this cold front, with some of this air emanating in the Bay of Campeche. Given days of antecedent warming, warm cloud depths will be quite favorable for tropical-type rains. This is confirmed by precipitable water values approaching 2” in many areas. Surface-400mb mean flow parallel to the frontal slope also suggests a slow eastward progression of the main moisture axis, bringing about some at least mild flooding concerns.
Of other concern is the potential for stronger storms accompanying this system. The aforementioned deep moisture column inherently limits instability due to latent heat release through condensation, but there is some potential of pockets of cooler/drier air in the mid-levels to locally increase areas of potential instability, according to the Euro especially.
One way or another, kinematic energy will be in plentiful supply as 60 knots of 0-6km shear overspreads the area as well as a 50kt+ low level jet. These are certainly sufficient for storm organization in the presence of enough instability, which has already been referenced to as a wild card.
BOTTOM LINE – heavy rain and strong storms are becoming a bit more possible on Sunday, but the timing and potential severity of this activity remain a bit murky. We’ll fine tune the forecast as the weekend draws nearer.
FROST/FREEZE NEXT WEEK? Indications are another surge of cooler air will arrive by Monday and Tuesday behind Sunday’s system. There’s a reason we always advise the general time of Tax Day before any meaningful planting is done – while increasingly unlikely and infrequent, freezing temperatures are possible through the month of April.
Copyright 2018 FOX Carolina (Meredith Corporation). All rights reserved.