Friday, October 4, 2019

Current Conditions at Sanborn Field

Friday Night - Becoming Cloudy. Low: 50-54


Saturday - Cloudy. Scattered showers possible in the morning becoming more widespread in the afternoon. High: 69-73

 Saturday Night - Becoming partly cloudy. Low: 48-52

Sunday - Becoming cloudy in the afternoon. Showers likely in the afternoon. High: 63-67

Monday - Clear Skies. High: 63-67

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There is a low pressure system moving through Missouri this weekend.  This will bring about weather conditions conducive for rain.  We expect an overcast weekend with intermittent showers in Saturday morning which will become more persistent and widespread later in the afternoon.  Sunday we expect afternoon showers as well.  Throughout the weekend, we expect max high temperatures ranging from 67 to 73 degree and minimum low temperatures between 63 and 69 degrees.  We expect clearer skies on Monday though. 
Forecasters: Balkissoon, Travis, Heaven
Issued:  3:30 p.m. ; October 4,  2019

Technical Discussion (The nerdy stuff we are discussing in class!)
It finally feels like fall in mid-Missouri after the cold frontal passage that occurred early Thursday morning. The main focus of this period is narrowing down the rain chances into this weekend associated with another approaching cold front. Temperatures will continue to fall after FROPA occurs. The 12z GFS and 12z NAM are in good agreement at both the timing of the precip and timing of FROPA. Consulted HRRR and RAP in narrowing down the beginning of precip.

The rain that was expected to move through the state late last night into this morning dissipated as models suggested. RAP analysis loops of 700 hPa, seem to suggest that drier air moved in allowing for the breakup of that rain. Sanborn Field and KCOU recorded no rain last night. RAP Analysis of both 250 hPa and 500 hPa shows the general trend of the long wave trough continuing to dig into the western CONUS, breaking down the massive ridge that has kept mid-Missouri very summer-like. GFS 250-hPa heights and winds favor a continued eastward progression of the ridge and trough. Saturday morning will see our first chances for rain. Models have trended toward an early start to the rain. According to soundings, GFS seems to be slightly more aggressive than the NAM. Both solutions favor a large dry layer near the surface with a saturated column overnight. The issue is how quickly evaporative cooling can erode the dry layer until full saturation can be achieved. NAM falls into line with CAMs suggesting full saturation and ample lift around 16z to 17z. Rain will continue into the afternoon and taper off in the evening.

GFS 500-hPa height and vorticity as well as soundings indicate FROPA occurring 00z Sunday. Skies will partially clear overnight Saturday. GFS soundings indicate the presence of mid-level saturation into the early morning hours accompanied by high level saturation. This should allow temperatures to fall slightly more than Friday night as radiational cooling will be stronger. As the day progresses, Sunday, the next disturbance moves in. GFS 250-hPa heights and winds show strong divergence associated with this dip in the jet stream. 500-hPa height and vorticity depict a s/w embedded in the larger longwave moving into the region from the northwest. A strong ribbon of circulation extending from the parent longwave passes through the region Sunday night into Monday morning. GFS soundings once again saturate into Sunday evening. There is ample life present in the mid to upper levels, but a dry layer and downward motion towards the surface. This is likely subsidence induced as most of this looks to be elevated behind the initial cold front. GFS MSLP and thickness place a very weak high off to the west at this time. As this system moves out, dry air will replace it, the column dries out completely as depicted by soundings, and skies clear.

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