Once again, stiff
southerly winds prevented it from getting below 70F last night (record warm low
again), and then full sunshine initially led to a quick warmup, but then it slowed
a lot with a bit more low-level clouds than expected in the afternoon, with a high
of 84F, slightly cooler than yesterday. Maximum wind is 24 kt. Day 3 will be
very different from days 1 and 2. The high for day 3 will be achieved tonight
with strong south-southwesterly winds and compressional warming right ahead of
a cold front keeping temperatures elevated, a classic case of temperatures
staying warmer than modeled, especially compared to the HRRR, RAP, and NAM 3-km
which seems to keep an unrealistically cool surface layer given the strong
winds that should mix out any inversion. While skies will be clear initially, thickening
low-level clouds between 06z and 09z tonight right ahead of the cold front will
likely lead to a slight temperature boost (1-2F) then due to the elimination of any weak
radiational cooling, like the GFS and some other models show.
The cold front will bring a short period of likely heavy rain and/or thunderstorms,
with potentially slightly stronger winds (perhaps 25+ kt) with any stronger
thunderstorms able to mix down stronger winds from aloft enhanced by cool downdrafts.
The Storm Prediction Center even gives a marginal risk of severe thunderstorms
mainly for wind threat, though isolated hail and tornadoes are not out of the question.
It will turn much cooler afterward with winds shifting to northwesterly, and it
stays cloudy through early afternoon. Some breaks in the clouds will lead to a
slight warmup later tomorrow afternoon, but it won’t be anywhere near as warm
as overnight tonight. With clearing skies and lighter winds tomorrow night as surface high pressure moves in, the low will
occur at the end (Friday 06z), with winds possibly lightening just enough for good
radiational cooling then, though KSTL isn’t known for particularly rapid
radiational cooling.
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