Monday, February 18, 2019

Monday Night - Cloudy. Low: 20-24

Tuesday - Clouds remain. Snow beginning in the evening. High: 30-34

Tuesday Night - Clouds persist. Breezy. Snow transitioning to freezing rain overnight. Some sleet may mix in. 1-3" of snow possible. 0.10" of ice accumulation possible. Windy. Low: 28-32
Wednesday - Cloudy. Freezing drizzle changing over to drizzle ending by early afternoon. High: 36-40

Thursday - Mostly Sunny. High: 42-46

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Columbia is in store for yet another significant winter event this forecast period. We will see a brief period of calm and cold throughout Monday night. Despite the dry air in place over Missouri, clouds will continue to linger. Precipitation will begin as snow Tuesday evening and persist into the overnight hours until it is expected to transition to freezing rain after midnight. Columbia could see snow accumulations in the range of 1-3", and ice accumulations up to 0.10". Freezing drizzle is possible into Wednesday morning hours, but no additional accumulations are expected. Conditions Tuesday night into Wednesday morning will make for hazardous travel, so please exercises caution! On Thursday, temperatures will be slightly warmer with sunshine in the sky.

Forecasters: Danaher and Hirsch
Issued: 5:00 p.m., February 18, 2019

Technical Discussion (The nerdy stuff we are discussing in class!)

 The GFS is the preferred model according to the WPC. Cold and dreary conditions still continue through Monday night. As the Monday ends, high clouds will continue to linger in the atmosphere throughout the night indicated in the GFS 18Z model run. Entering into Tuesday morning, the 12Z sounding show backing winds from 850mb to 700mb indicating CAA. This becomes important because it will continue to keep the temperatures cooler and sets up the snow storm from Tuesday night into Wednesday morning. By 00Z Wednesday, Columbia will be sitting under the right-entrance region of a 110-kt 250 hPa jet with plenty of divergence aloft. At 500 hPa, several small vorticity maxima will move NE out of Arkansas and through mid-Missouri throughout the night. Also, at 850 hPa, a 40-kt LLJ will develop over Arkansas and push N/NE toward our area, leading to plenty of moisture advection. All this, combined with high omega values throughout the column, points to even more winter weather. The main question for this system is precipitation types and resulting amounts. Currently, all model guidance starts this system as snow between 21Z Tuesday and 00Z Wednesday, and continues as all snow through roughly 06Z Wednesday. After that, model guidance diverges, with all precipitation types being shown between the models used. With soundings showing veering winds in the column and a strong LLJ present, there will be WAA advection, likely beginning around 06Z Wednesday. Also, cloud ice will be rapidly lost between 06Z and 12Z Wednesday. With this being said, I have leaned toward a snow to freezing rain transition between 06Z and 12Z Wednesday, with some sleet mixing in. After 12Z Wednesday, the system will be mostly done impacting the area, although cannot rule out some drizzle or freezing drizzle before 18Z Wednesday. My conclusion leans more too 1-3" of snow and up to 0.1" of ice accretion is likely based on current information. As Thursday approaches, the wind profile will switch back to veering which means WAA. Temperatures will increase once again as we end this forecast period.