Thursday, April 16, 2020

Thursday Night - Cloudy, with rain. Low: 34-38

Friday - Cloudy with AM rain. High: 44-48

Friday Night - Decreasing clouds. Low: 28-32

Saturday  - Mostly sunny. High: 58-62

Sunday - Cloudy, rain possible. High: 62-66

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Thursday night will be cloudy with rain, accompanied with southerly winds. Rain is expected to taper off Friday morning as the wind direction switches to the north. Colder air will move in causing Friday nights low to be at freezing or slightly below freezing. High pressure will move into the area Saturday causing skies to be mostly sunny and warmer temperatures. A small disturbance is expected to bring cloudy skies and a chance of rain Sunday morning with near average temperatures. (CD)

Forecasters: Dowell, Lieberman, Ritter
Issued:  5pm: April 16, 2020
Technical Discussion (The nerdy stuff we are discussing in class)

We used the GFS and NAM supplemented with SREF and GEFS. The model diagnosis from the WPC recommends a general model blend for this forecast. (CD)
From the top down and beginning with 250MB, there is a jet max stretching from the central-Mississippi River valley into the western Atlantic Ocean. This leaves Columbia in the convergence entrance region. The subtropical and polar jet couple together on the east coast. At 500MB, a positively tilted trough is currently located upstream of Missouri extending into the northwest United States. There are several shortwaves scattered across the eastern half of the country. At 700MB, there is a decent amount of moisture to be found over Columbia with the greatest values over northern Missouri stretching upstream into Wyoming. Finally, at the surface, the stationary front is situated across mid-Missouri. (CD)
At 500MB, the positively tilted trough is making its way across the midwest. Circulation ahead of it will reach mid Missouri today around 21Z. At 700MB, UVM is seen across central Mssouri from 21Z today until 18Z tomorrow. RH maps from the GFS and NAM at the same level show moisture saturation in the area for roughly the same time period with the NAM showing dry air from the west setting in a few hours earlier. At 850MB, wind speed maps show a very strong LLJ max over central Missouri from 03Z until 15Z Friday with wind max wind speeds in excess of 60 knots. At the surface, frontogenesis across Missouri will result in the aforementioned stationary front becoming effectively a cold front. RH, winds, and pressure at 300K show isentropic upglide of saturated parcels is likely from 0Z to 12Z Friday. Soundings for throughout the period support the possibility for rain during this time. However, despite saturation increasing after that time, lift deteriorates significantly. SREF plumes indicate about ⅔” of rain during that time. The cold front will result in northerly winds shortly after 12Z. There was previous consideration for snow but this seems basically impossible given surface temperatures and soundings showing a significant layer above freezing. CL
Friday night being mostly clear shortly after cold FROPA will result in unseasonably cold temperatures. Minimum temperatures will reach just below freezing. Saturday, zonal flow and dry air from the west will bring seasonal temperatures back. Thermal advection and surface winds will be minimal. CL
Another shortwave trough will move across the midwest Saturday and begin to effect our weather that night. Despite not being as deep as the Friday’s, the circulation associated with this disturbance is stronger than the first. This circulation at 500MB will reach Missouri around 6Z on Sunday and clear out by 18Z. Associated with it at 700MB is UVM that will be present from about 6Z to 12Z. Saturation at this level is somewhat limited however. At 850MB, vertical velocities and RH are more limited than the previous system and than this one at 700MB on GFS and NAM maps. Soundings are also not encouraging for precip as there is limited moisture and lift. Despite this, SREF members are in disagreement with outputs ranging from no precip to about half an inch. At this time, rain looks possible but leaning toward unlikely. Future forecasters should monitor that possibility. CL

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