As expected, winds
prevented ideal radiational cooling last night, with a low of 54F. With mostly sunny
skies, a rapid warmup occurred, with a likely high of 83F and a maximum wind of
24 kt. The slowly-approaching cold front will bring showers and possibly thunderstorms
later tonight, with possibly a brief period of strong winds, though the setup
does not look favorable for severe thunderstorms. The high could occur at the
beginning (Saturday 06z), but it is very tricky, as it looks like the cold
front could be a little faster and arrive just before 06z, leading to a lower
high temperature. If the cold front is slower (perhaps less likely now), warm,
southerly flow right ahead of the cold front would lead to a high warmer than
model guidance (for the early Saturday 06z high). The slow-moving cold front
actually takes the form of an elongated area of low pressure, with one low
passing to the north tomorrow while weakening and another one forming and
strengthening to the southwest, over Missouri, tomorrow evening. This new low
pressure will pass just east of Des Moines late tomorrow night, leading to more
thick clouds and rain as the cold air pours in, unlike the usual clearing and
drying setup behind a cold front. The associated upper-level low will move
almost right over Des Moines late tomorrow night, and any pockets of heavier
precipitation will lead to dynamic cooling through evaporation, melting, and
bringing down of cold air from aloft. Therefore, the low will likely occur at
the end (Sunday 06z), and it could have dropped into the mid 30s by then, especially
if it changes to snow which is possible!
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