Friday, September 20, 2019

Current Conditions at Sanborn Field

Friday Night - Becoming Cloudy. Showers possible beginning after midnight. Windy. Low: 68-72

Saturday - Cloudy skies. Intermittent showers throughout the day. Windy. High: 78-82

Saturday Night - Cloudy. Showers ending in the evening. Windy. Low 70-74


Sunday - Cloudy. Rain beginning in the late morning hours. High: 72-76

Monday - Skies becoming clear. High: 72-76
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This weekend, if you like cooler temperatures, you will enjoy this Friday's night low of 68 to 72 degrees with the possibility of cloudy skies and showers.  Intermittent showers will persist through out this windy Saturday.  High probability of showers are given around noon of Sunday.  After the passage of a cold front, midnight on Sunday, we expect clearer skies and a high of 72-76 degrees on Monday. 

Forecasters: Balkissoon, Heaven, Munley, Travis 
Issued:  5:00 p.m. ; September 20,  2019

Technical Discussion (The nerdy stuff we are discussing in class!)
As the hot temperatures exit the region, the main issue for this forecast period is assessing the chances for precipitation throughout the weekend. Model disagreement was an unfortunate issue as WPC lowered forecast confidence as the NAM and CMC began to disagree with the GFS and Euro. Went with primarily GFS guidance with consult of SREF and GEFS for temperatures.

GOES East VIS satellite shows increasing cloudiness to the southwest of Columbia. These clouds will filter into the region as skies become overcast Friday night. This is all associated with a strong upper level disturbance. GFS 250-hPa heights and winds show the longwave trough over the western CONUS moving eastward breaking down the strong upper level ridge that has been stationary over the central US. Friday night into Saturday morning, Columbia will be sitting in the inflection point between the ridge to our east and trough to our west. GFS 500-hPa heights and vorticity favor an elongated area of circulation moving in from the southwest. Flow will remain out of the southwest in the lower levels of the atmosphere according to GFS 700 and 850 hPa. 700-hPa heights and RH show the remnants of Tropical Storm Imelda breaking apart, with ample moisture transport into mid-Missouri following the southwesterly flow.

Saturday, 850-hPa heights and winds show a strong LLJ maximizing off to our west eventually bringing strong winds over Columbia. GFS soundings show a 20 kt wind beginning Saturday morning and persisting into Sunday night until FROPA. Expect gusty winds for the course of the weekend. Seeing as these string winds will be out of the southwest, there exists the potential for strong moisture advection and WAA. GFS Skew Ts want a dry small dry layer in the lower levels of the atmosphere. If partial clearing can occur, current estimates of daytime highs may be an underestimate. Temperatures will remain relatively steady until Sunday night despite likely rain. This is due to the WAA offsetting evaporational cooling by precipitation. Storm chances will be limited by the immense amount of moisture being brought in from Imelda remnants. Mean RH of the column is well above the 45% to 75% range suitable for severe convection. Partial clearing may also help to destabilize the atms for convection. Skew Ts do show ~600 J/kg  of CAPE Saturday morning, so thunderstorms are not completely out of the question.

Rain chances drop off after sunset Saturday evening. According to Skew Ts omega diminishes and the surface to ~600 hPa dries out. This dry time will not stick around for long as the entire column saturates with plenty of omega to support widespread precipitation. Rain will likely stick around until cold frontal passage Sunday night into Monday. GFS Skew T shows evidence of a classic cold FROPA occurring around 06z Monday. Winds shift from the S to NW and the column drys out significantly. SREF wants >10 F drop in dew points. This cold front will not make much progress in knocking down our temperatures as we will quickly be under the influence of a new upper level ridge according to GFS 500-hPa heights.

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