Even with clear skies and deep snow cover, the northerly wind off Lake Pontchartrain was just barely strong enough to prevent a rapid drop, with a low of 23F last night, while parts of inland Louisiana reached 0F, breaking all-time record lows! Maximum wind was only 11-12 kt at the start and in the morning. Sunny skies led to a gradual warmup to 33 or 34F, way below average, further chilled by the deep snow cover reflecting away the sunshine.
Calm winds and clear skies will lead to good radiational cooling for at least the first part of tonight before high-level clouds and a slight northerly wind off Lake Pontchartrain likely stops or slows the cool down. There is a small chance that it drops below 23F this evening before the end of day 2 (Thursday 06z) before any lake influence sets in (it was down to 15F in nearby areas without the lake influence last night, though with the cold air getting stale, it won't be that cold for most tonight). The high-level clouds will mostly clear out by sunrise tomorrow, leading to another sunny day with only light northerly winds. The lingering snow cover will still chill the air via reflecting sunlight away, though the snow becomes less reflective as it melts, and with the warmer air mass, it will become substantially warmer than today. Still, the snow cover adds uncertainty to both low and high temperatures, with even larger model uncertainty than yesterday given the light wind and steep nocturnal inversion and only shallow mixed boundary layer during the daytime. Once again, ECMWF, HRRR, GFS, and CMC are likely overdoing the effect of the snow cover, while the NAM 3-km and USL is underdoing it.
Calm winds and clear skies will lead to good radiational cooling for at least the first part of tonight before high-level clouds and a slight northerly wind off Lake Pontchartrain likely stops or slows the cool down. There is a small chance that it drops below 23F this evening before the end of day 2 (Thursday 06z) before any lake influence sets in (it was down to 15F in nearby areas without the lake influence last night, though with the cold air getting stale, it won't be that cold for most tonight). The high-level clouds will mostly clear out by sunrise tomorrow, leading to another sunny day with only light northerly winds. The lingering snow cover will still chill the air via reflecting sunlight away, though the snow becomes less reflective as it melts, and with the warmer air mass, it will become substantially warmer than today. Still, the snow cover adds uncertainty to both low and high temperatures, with even larger model uncertainty than yesterday given the light wind and steep nocturnal inversion and only shallow mixed boundary layer during the daytime. Once again, ECMWF, HRRR, GFS, and CMC are likely overdoing the effect of the snow cover, while the NAM 3-km and USL is underdoing it.
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| Source: PivotalWeather |
been reading your blog since I started the wx challenge last semester, and have been using the USL model in my forecast process in the past, however I can't seem to access the city forecasts at their normal spot (http://www.microclimates.org/forecast/KMSY/), it doesn't show any completed model runs. Do you have another site you use to access USL forecasts? thanks!
ReplyDeleteIt's there but not accessible via the main page -- apparently you have to hack the URL with the date: http://www.microclimates.org/forecast/KMSY/20250123_22.html
ReplyDeleteAnd thanks for reading the blog!
Thanks for the help! I don't think I would've ever figured that out
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