Thursday, February 28, 2019

Tonight - Cloudy. Low: 24-28.

 Friday - Mostly cloudy  High: 42-46.

 Friday Night - Cloudy. Low: 22-26

Saturday - Cloudy. High: 34-38.

Sunday- Cloudy with snow through the afternoon. Total accumulation: 4-6 inches     High: 32-34.

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Hope you haven't packed away those snow shoes just yet! Tonight will be a continuation of today keeping temperatures well below freezing and skies remaining covered with clouds. Tomorrow we will see warmer temps giving us just a slight tease of incoming spring as well as minor breaks in cloud cover. Unfortunately this will be short lived as a cold front moves through Columbia Friday evening bringing cold air from the north and clouds remaining overhead into Saturday. Saturday keeps the clouds looming overhead and brings us snow beginnning later Saturday evening that will continue and worsen later in the night. Sunday keeps the snow rolling until noon with a total accumulation of 4-6 inches.

Forecasters: Doll, Myers, and Bongard
Issued: 4:35 p.m., February 28, 2019

Technical Discussion (The nerdy stuff we are discussing in class!)
Overnight tonight we are expecting our flow to stay zonal across the region.  We do have a polar jet setting to our north across southern Minnesota. We have moist air near the surface which will keep cloud cover overnight, but we are relavitely dry at 700 mb.  Our winds are staying out of the west which paired with the expected cloud cover will keep our temperatures warmer than previously predicted.  The high pressure that will be moving into our area tomorrow will help kick off a dry start to the day.  We do moisten up slightly but we don't expect to see any precipitation for Friday due to the high pressure system providing divergence at the surface. Upper level flow remains zonal throughout the day with model agreement for the NAM and the GFS.  Low level southwesterly winds will help our temperatures stay warmer than today. The models start to disagree for Friday evening in regard to the timing of a frontal passage.  Looking at the 12Z model soundings, the NAM is keeping us a lot more moist with a low level southwesterly wind direction while the GFS swings winds out of the northwest sooner as a result of the cold front moving in a lot earlier with temperatures cooling off and the atmosphere drying out quicker. After the frontal passage Friday night, a zonal ridge will come through at 250 mb and bring with is a jet max that will sweep through Missouri. Low level northerly winds bring in much colder temperatures overnight. We do have some vorticity associated with the large system over central Canada staying to our north overnight. 

For Saturday, we wake up to a low level dry layer in the morning. Both models agree on the fact that we will stay zonal in our upper atmosphere as a ridge moves over the central Plains. During the mid morning we are seeing some convergence forming in the mid layer but we still are seeing divergence at the surface. Around noon the GFS has winds at 850 mb veer to the southwest which will start to bring in Gulf moisture. In general, the GFS has us mositening quickly during the afternoon. In contrast, the NAM is taking its time with this and has us slowly moistening over the course of the day. We have slight vorticity at 500mb but in general we aren't seeing a whole lot of vorticity with this system. One thing to note is that our moisture at 700mb is building in from the northwest while our moisture at 850 mb is coming from the Gulf which may aid in precipitation development overhead.  The GFS has a light dusting of snowfall around midnight whereas the NAM has no precipitation reaching the surface for Saturday evening.  

Sunday starts off with the GFS snowfall consistent throughout the morning into the early afternoon.  Our max vorticity aligns with our heaviest snowfall amounts around 6 am with a gain of around 3 inches in 6 hours. The GFS also has a low pressure system developing over Arkansas at daybreak. The NAM is showing us very different outcomes. The low pressure system forms over western Missouri but then treks east quickly. Snowfall will start early Sunday morning and continuing into the early afternoon. NAM is taking a more southerly track with the bulk of the snowfall over the southern part of the state and pushing this system through a lot faster than the GFS. Both models have snowfall stopping in the early afternoon and drying out quickly.  The GFS is having us receive close to 4-6 inches of snowfall while the NAM has us getting under 2 inches.  

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