Friday, October 23, 2020

 


Current Conditions at Sanborn Field





Friday - Showers and thunderstorms early with temperatures falling through the day. Clearing by evening.

Friday Night - 
Clear and cold. Low: 30-34

Saturday - 
 Clear skies. High: 48-52

Saturday Night - 
Clouds developing late. Low: 36-40 

Sunday - 
Cloudy. Rain likely late afternoon. High: 46-50
 
 
                          
 
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Discussion: 
Post frontal conditions leave falling temperatures and rain for our Friday. The rain will exit the area by afternoon and skies will clear tonight. There will be a Freeze Watch for Columbia tonight that could be converted to a Warning as temperatures are expected to fall to or slightly below the freezing mark. Game day for the Tigers on Saturday will be chilly despite sunshine in the afternoon with highs around 50F. Clouds will find their way back into the region late Saturday night into Sunday morning ahead of the next front which will bring precipitation late Sunday afternoon. 
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Forecaster: McGuire, Ozdas, Bongard
Issued:  10 AM CDT 23 October 2020
 
Technical Discussion (The nerdy stuff we are discussing in class)

Conditions as the start of the forecast period reflect the passage of a strong cold front between 08-09Z according to archived KCOU Metar data. Columbia Regional Airport reported a loss of about 4 degrees/hour temperature drop from 08-10Z with about a degree/hour drop from 10-13Z. The region has already achieved its high temperature for the day just before fropa and temperatures will continue to tumble through the day and evening. A Freeze Warning will go in effect this evening for portions of west and northwest Missouri as overnight lows will plunge into the mid-upper 20's. A Freeze Watch will go into effect for Boone County late tonight as temperatures in central Missouri are expected to drop as low as 30F overnight. Visible and IR satellite imagery shows a large swath of clouds and precipitation from eastern Canada down into north central Texas with radar imagery depicting a narrow line of developing showers and thunderstorms from northern Michigan down into southeast Missouri. For this forecast period we will use the GFS model as NAM data has not been updated since 06Z of 10/22.

The broad longwave trough that is draped over the northern portion of the CONUS from the Northern Rockies through the Great Lakes region that is responsible for dragging the cold front through the Midwest is housing a brisk 190+ KT jet core in its downstream flow. This places the forecast area in it's convergent right entrance region aiding the development of the aforementioned precipitation impacting Columbia this morning. The region will transition from a southwesterly flow to a zonal flow aloft by 00Z Saturday. Zonal flow will persist over the region through Saturday evening. Overnight Saturday night into Sunday the Polar jet streak extending from the northern Plains into New England will encounter coupling with a Subtropical jet streak reaching from the Desert Southwest into the Mid-South. This dynamic coupling will occur over the central Plains and the two jet streaks will merge just after the end of the forecast period. 

500-hPa vorticity this morning reveals not much in the way of circulation over Missouri though the frontal system has plenty of vorticity to play with over Texas and Arkansas. Vorticity values will remained confined to the north of the region as the flow becomes zonal for much of the forecast period. Vorticity will begin to advect back into mid-Missouri towards the close of the forecast period as a very dynamic and well amplified system begins to materialize to the northwest extending from the Mountain West northeastern into central Canada where the parent low pressure center will reside by Sunday evening. 

 Low-level model charts paint a very dynamic picture for the forecast period. High moisture values over the area this morning will quickly dry out as central Missouri settles into a postal frontal weather regime. Northwesterly winds will advect moisture away from Columbia and introduce colder temperatures this evening and tonight as high pressure builds in from the north-northwest prompting the Freeze Watches/Warnings for Missouri. This CAA will be short-lived as the region will again transition to a low-level southerly flow by mid-morning on Saturday. Temperatures and moisture in the column overhead will rebound just a bit as a result though 850-hPa wind speeds lack a significant LLJ through the period. By Sunday morning the region looks to be re-moistening slowly again ahead of the encroaching system from the northwest.

GFS model soundings expectedly show a moist profile this morning that will dry out from the top down as the cold front pushes further east and northwest flow takes over. Overnight soundings drop the low to near freezing in central Missouri as PWAT values bottom out near 0.3 inches. Southerly flow in the low-levels will advect some warm air into the region though easterly winds near the surface will undermine this effort and keep temperatures regulated at the surface. PWAT values will increase gradually to about 0.8 inches by the end of the period. The profile moistens up at 850-hPa and eventually higher up in the column and K-Index values struggle to reach 20 through 00Z Monday lending evidence to a cloudy Sunday before precipitation chances increase late Sunday afternoon.

Precipitation accumulations for the rainfall experienced at the start of the period are estimated to be 0.4 inches which is more on par with RAP estimates than the underwhelming GFS estimates at 0.15 inches. The remainder of the period will be dry until Sunday evening when GFS models depict the chances for more rainfall in mid-Missouri as the forecast period comes to a close. Current models show a chance for snow Sunday night into Monday.


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