Current Conditions at Sanborn Field
Thursday Night: Cloudy with an isolated storm possible. Low: 62
Friday: Partly cloudy, seasonably warm. High: 84
Friday Night: A few clouds. Low: 65
Saturday: Cloudy and breezy. High: 83
Saturday Night: Showers and storms in the evening. Low: 58
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Discussion:
Forecasters: Splater, Noblitt, Vochatzer
Date Issued: 04/21/2022 5:00PM CDT
For our forecasting shift, both the GFS20 and NAM40’s MSLP were compared against 18Z surface analysis by the NWS. With both models being fairly accurate to the surface analysis as well as the SREF and GEFS plumes being very close to the temperatures recorded at Sanborn, both models were utilized in our forecast. Various combinations of NBM, soundings, and plumes were used in forecasting cloud cover, temperatures, and precipitation.
Starting with the 250mb plot of heights, winds, and divergence, an upper level ridge currently resides over the Great Plains, slowly traveling eastward. This ridge will eventually transition over the Mississippi Valley early Friday. Meanwhile, a LPS and its trough to the west of this ridge begins to deepen as it moves east throughout the day. This trough will begin to amplify, with the jet streak reaching a maximum around 120 knots. Divergence dominates the downstream side of the trough as it continues to the east Saturday, aided by the upper level LPS in the Northern Plains. This trend in divergence will continue as a jet streak begins to push into northwestern Missouri early Sunday morning.
Following this with the 500mb plot of heights, winds, and vorticity, the ridge continues to keep most of the Mississippi Valley fairly clear of any vorticity. There is an area of circulation identified sliding east across northern Missouri into central Illinois late tonight, however this will largely affect areas just north of Columbia. As the overhead ridge and the LPS in the Northern Plains both progress to the east, a band of circulation will slide across the upper half of the Mississippi Valley Saturday, followed quickly by the vorticity surrounding the LPS as it along the Dakotas Sunday.
Looking at the 700mb plot of heights, winds, RH, and omega, moisture fed by the LLJ rests over the eastern edge of the Central Plains late tonight. This will move east, allowing a slight chance of storm formation and precipitation given the corresponding location in vorticity. Moisture along the western edge of the Mississippi Valley begins to reform early Saturday, once again fed by the LLJ. This, combined with lift indicated in the omega values, will assist in storm development and precipitation throughout the day and into Saturday night.
Finishing with the 850mb plot of heights, winds, temperatures, and dewpoints, southerly winds will help increase surface temperatures. The LLJ’s south to north orientation will bring warm moist air throughout the forecasting period, reaching a maximum of 70 knots over central Kansas. A cold front formed from the LPS will slowly move across the Northern Plains into the Upper Mississippi Valley, advecting cold air into the northeast Central Plains late Saturday night. Looking at the MSLP and 1000mb-500mb thickness, we see very little advection over mid-Missouri throughout our forecasting period which indicates very little increases or decreases in our highs and lows. Given the slight chance of precipitation late tonight and the storm system moving in Saturday, our anticipated total precipitation is around 0.5”.
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