Tuesday, May 4, 2021

Current Conditions at Sanborn Field


Tuesday Night
- Mostly clear. Low: 40-44



Wednesday
- Clouds increasing in the afternoon. High: 64-68



Wednesday Night
- Mostly cloudy. Low: 46-50


Thursday
- Partly sunny with scattered showers. Possible thunderstorms and gusty winds in the afternoon. High: 62-66
 

Friday
- Mostly sunny. High: 62-66


 
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Discussion:

Tuesday's rain and cloudiness will move out by the evening, and clearer skies will return by nighttime. Wednesday will give your rain gear a break, as sunny skies and warmer temperatures are expected. However, Mid-MO will still remain below average for the beginning of May. Opportunities for rain return Thursday morning, where spotty, on-and-off showers will stick around until late afternoon. Isolated thunderstorms and strong winds are possible in the afternoon, but nothing severe is expected. Rain will move out of the region late Thursday evening and by Friday, nice sunny conditions return, making it the perfect day to go outside and celebrate the end of classes for the spring semester.

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Forecaster: Clemons, Orr
Issued: 5:00 PM CST 04 May 2021

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

This forecast was assembled using the 12Z GFS, SREF and GEFS plumes, and both GFS and NAM soundings to check for consensus on rain events. The GFS was chosen due to its accurate initial conditions and placement of the cold front in southeast Missouri. 

 

250-mb plots of heights, winds, and divergence depict a fairly active wave pattern over the contiguous United States. Missouri is currently under an upper-level shortwave trough with large amounts of divergence present over SEMO. This trough moves out by 03Z Wednesday and Missouri remains under a fairly calm pattern in the base of a large trough until 06Z Thursday. Active weather may return around 21Z Thursday when Missouri falls under the influence of the left exit region of a large jet streak as the upper-level pattern transitions from a trough to a ridge. Friday sees a return to calm conditions due to the influence of the ridge.

 

Plots of heights and vorticity at 500-mb show a fairly active atmosphere. Abundant vorticity associated with Monday's cold front still lingers in SEMO, but moves out by 03Z Wednesday. After this, flow over Missouri stay fairly zonal until around 18Z Thursday when an approaching cold front brings circulations back into the forecast area. The cold front moves out by Friday at 06Z and calm conditions return.

 

At the 700-mb level, heights and humidity provide timing and strength of the incoming rain events. Tuesday's rain will move out of Mid-Missouri by 21Z, and calm clear conditions will remain until around 06Z Thursday. Abundant moisture moves back into the forecast area, though its strength varies and could lead to on and off rain showers throughout Thursday. The possibility for rain moves out by 18Z Thursday, leaving clear conditions for the remainder of the forecast period. 

 

850-mb heights, winds, and temperatures provide timing for the passage of Thursday's cold front and give an idea of what temperatures will be like. The cold front that passed through Mid-Missouri on Monday is still sitting over SEMO, but moves out by 03Z Wednesday. Missouri remains dominated by strong northerly winds, fueling the cooler temperatures seen Tuesday night. Winds slowly begin to shift westerly, but soon return to the northerly direction after the passage of a cold front around 21Z Thursday. By Friday winds shift to a southwesterly direction, allowing for warmer temperatures to return. 

 

At the surface level, Thursday's cold front is seen once again. A high pressure system moves over the forecast area soon after, bringing calm conditions for Friday. Solenoids approaching Missouri Friday evening could lead to warmer temperatures, and is something that future forecasters should watch for. 

 

Soundings from both the GFS and NAM were overlaid to assess the timing for rain and the possibilty for thunderstorms Thursday. Rain chances are spotty Thursday morning as there is little agreement on how saturated the atmosphere will be. The most agreement for rain and potential thunderstorms is around 18Z Thursday, which is associated with the passing cold front. The GFS suggests 281 J/kg of MUCAPE at this time, though other parameters remain unfavorable for storms. NAM soundings favor storm chances even less. While anything severe is very unlikely, a few rumbles of thunder cannot be ruled out. Future forecasters should watch to see how this system develops.

 

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