Friday, March 22, 2019

Friday Night - Clouds start to increase. Low: 36-40.

Saturday - Cloudy with scattered showers possible in the evening. High: 57-61.

Saturday Night - Cloudy with scattered showers. Low: 48-52.

Sunday- Showers likely. High: 60-64.

Monday - Mostly Cloudy. High 48-52.

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The sun and clear skies move out overnight allowing clouds to dominate this weekend. Rain possibility starts Saturday evening through this weekend. Warmer conditions this weekend will take a turn Sunday night to below average temperatures to start the work week.

Forecasters: Johnston, Rojas, Bongard, and Hirsch
Issued: 4:3 p.m.March 22, 2019

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

Model Diagnostics: The WPC has averaged preference on the blend of 12Z GFS and 12Z ECMWF/UKMET for the closed low moving from the Central Plains on Saturday to the East. 

Concern of our forecast: Timing of showers this weekend and much cooler temperatures to start the work week.

This evening a ridge will move southward putting us under high pressure. A longwave trough with a closed low imbedded will move toward us eroding the high pressure over us as the ridge moves toward the eastern CONUS. SPC Day 2 and Day 3 outlook has us in the non-severe showers and thunderstorms region. However we don’t think we will get any thunderstorms. Sunday we will experience quasi-zonal flow over Missouri and Kansas with the jet core with 95 – 110 kts to our south in Texas, Oklahoma, and Arkansas. The mean and spread ensemble product for CAPE values at 18 Z on Sunday show a contour of 300 J/kg +-200J/kg , so highly uncertainty for this value, the next time step the values decreases until disappear at 00Z. Although this values in this range of time 18Z-00Z are the most optimum for CAPE, there are not enough unstable conditions to support thunderstorms. Because for the 18Z at 500 mb we are out of the maximum vorticity, at 700mb a drier tongue is advancing to our area, the omega values are still positive. The following 3 hours, a filament of higher vorticity cross the area at 500mb but drier and no vertical motion at 700 mb will cancel conditions for more activity. The NAM and GFS soundings for the 18Z on Sunday disagree in the upper level saturation, NAM shows drier conditions and GFS indicates saturation above 600 mb. After that hour both soundings dry out the column, keeping saturation at the lower level. GFS compare with the ECMWF model tends to accelerate the advancement of the low pressure system which support the idea of not enough unstable condition at the moment of the system bring the maximum vorticity. Cold front moves through Sunday evening at 0Z to 3Z on 3/25 when the winds start shifting to the north on soundings. This will bring below average temperature to start the work week. Possible drizzle early Monday morning with soundings only moist near surface and dry above 800 mb. Total precipitation we expect through Monday is between 0.15 - 0.30 in.