Surprisingly, it only dropped to 37F last night even with
seemingly good radiational cooling conditions. It quickly warmed up after
sunrise, with a high of 64-65F so far but still increasing a little, with a
maximum wind of 19 kt. Increasing southeasterly winds and clouds will prevent
much cooling down tonight, though a diffuse warm front and associated really
warm air mass will stay to the south until tomorrow. Also, some elevated showers
and thunderstorms likely will graze Des Moines late tonight ahead of the warm
front, which would cause evaporational cooling in the initially dry low-level
air mass, causing a dip in temperatures. Tomorrow’s high is quite tricky due to
competing effects of cloud cover, moderate southerly winds inducing warm
advection, and possibly showers forming on the northern edge of the warm air
mass that could prevent a full warmup. Although the diffuse warm front will be
tracking north of Des Moines, most indications are that the warmest air mass
will remain to the south or southwest, with low clouds hanging tough though perhaps
breaking somewhat in the afternoon at times over Des Moines. This differential
heating could serve as an effective secondary front, where showers and
thunderstormscould fire. A cold front or pre-frontal trough will initiate
thunderstorms in western Iowa border tomorrow evening and will push into Des
Moines overnight, likely leading to a brief period of heavy rain and strong
winds, with at least some of it likely occurring before 06z. With the rain all
falling as convection, the rainfall amount is especially uncertain!
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| Source: PivotalWeather |
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| Source: PivotalWeather |
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