Thursday, September 26, 2019

Thursday Night- Clouds roll in, partly Cloudy. Low: 63-67

Friday - AM clouds/PM of rain showers. High: 80-84


Friday Night - Clouds with a possibility of showers. Low: 66-70


Saturday Periods of rain.  High: 80-84

Sunday - Periods of rain. High: 84-88

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Cloud cover will move into Columbia over the course of the evening hours with a low temperature in the mid 60's. Friday morning cloud cover will persist and turn into showers in the afternoon, with highs in the low to mid 80's. Overnight conditions will persist and showers will continue, with lows in the upper 60's. On Saturday rain will move into Columbia with isolated thunderstorms, highs will be in the low 80's. Sunday will see a continuation of Saturday's conditions with highs in the mid 80's.
Forecasters:   Owens, Lead Forecaster: Bongard
Issued:  05:00 p.m. ; September 26,  2019

Technical Discussion (The nerdy stuff we are discussing in class!)
12Z chart analysis is showing a primarily zonal pattern at the 300mb level with a jet max entering the base of the trough, which will cause it to deepen. On the 500mb level, there is a ridge to the south of the station causing moist air advection and instability to push into the AOR, with an area of low pressure over the California/Mexico border, aiding in the process. The 700mb level is reflecting the 500mb level well, only with increased moisture and a minor short wave trough upstream of the station. The 850/925mb level is showing moist air advection to the south of the station and is continuing to stack with the upper levels.

On Thursday high pressure is dominating the AOR causing clear/blue and 22 conditions. As moist air advection continues to spill over the ridge to the south of the station, cloud cover will increase in the low and into the mid-levels. This will continue into Friday until the evening time frame, as the ridge continues to build.

The NAM and the GFS are in conflict about where the precipitation will develop, with the NAM keeping the bulk of the precip to the north of the station. Due to this discrepancy, the model of choice for this time frame is the SREF and HREF. The SREF is currently showing a 30% prop on the 3-hr TS product and the HREF showing probs of 90% about 16Z. The SREF also shows LI values of -4 (MDT), and 90% prob of CAPE GT 1000 (MDT), Ref: AFWA TN 98-002, Table 3-2 pg 3-15. The HREF, in turn, is showing that the highest probability of precip is at 03Z on Saturday with 3 and 6 hour probabilities supporting this. Whist these indices diminish overnight, they do return during the daytime hours on Saturday and Sunday.

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