Current Conditions at Sanborn Field

Wednesday Night - Clear. Low: 32-36

Thursday - Becoming partly cloudy in the afternoon. High: 56-60

Thursday Night - Becoming clear. Low: 28-32

Friday - Becoming partly cloudy by evening. High: 46-50

Saturday - Cloudy. Rain beginning overnight, tapering off by noon. 58-62

 

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Discussion: 

Mid-Missouri will see a very autumn-like temperature pattern for the remainder of the week with temperatures "pogo sticking" between highs and lows. A couple cold fronts will help drive this rollercoaster of temperatures. High pressure sitting atop Missouri will begin its eastward march towards the eastern seaboard. A cold front will blow through Thursday night, knocking temperatures down well below freezing. Little moisture available will mean Columbia may see some brief overnight cloudiness, but should stay dry. Behind the front, another high-pressure system and much cooler temperatures set up over the region. High pressure and calm weather remain until early Saturday morning when clouds and showers infiltrate the area ahead of the next cold front. 

 

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Forecaster: Travis

Issued: 5 PM CST 11 November 2020

 

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

The main focus of this forecast period is the rollercoaster of temperatures normal for mid to late autumn. The forecast period should remain dry save for precip chances near the end on Saturday. Good consensus between the GFS and NAM meant that a blend of the two was used for this forecast. consulted SREF and GEFS ensemble plumes for temperatures, and to narrow down timing of precip at the end.

GFS plot of 250-hPa height and wind shows a longwave trough to the west deamplifying as it propagates to the northeast. The result will be flow turning more zonal by Thursday afternoon and remaining so until the approach of the next storm system early Saturday morning. GFS prognostics place a strong 160+ knot jet streak right over Missouri and keeps it there for the duration of the period. This southward track of the polar jet stream will allow colder air masses to infiltrate the Middle Mississippi Valley. More evident on GFS prognostics of 500-hPa height and absolute vorticity is the aforementioned northeastward propagating wave. As the wave flattens, a shortwave centered over the Upper Midwest clips the northern parts of Kansas and Missouri. Plots of 700-hPa RH and vertical velocity shows plenty of UVM, but a scarce supply of moisture. Model soundings support this lack of moisture throughout the rest of the column. Nevertheless, enough moisture could filter in at the middle to lower levels of the atmosphere to support brief cloud cover Thursday afternoon into Thursday night. The upper-level disturbance will be reflected at the surface by a cold front wedged between two high-pressure systems. The first being the anticyclone that the GFS currently has sitting just to the east of Columbia. This high-pressure system will move with the storm track and move ENE as the cold front moves in Thursday evening. As this systems moves eastward, Missouri will remain in low-level southerly flow allowing for a warmer Thursday than Wednesday. Building in quickly behind that front is the second anticyclone. This second system will keep low-level winds northerly resulting in much cooler high temperatures for Friday. 

By Friday evening, GFS 250-hPa and 500-hPa maps the large scale flow regime loses its zonal characteristics transitioning to meriodional. A wave will come off the Rockies By Friday afternoon. GFS plots of 250-hPa wind and divergence shows increased divergence in the entrance region of the jet streak mentioned above. This is well seen at 500 hPa with increased circulation propagating out of the SW long the storm track. Unlike Thursday's system, GFS shows no shortage of moisture with this disturbance. Plots of 700-hPa RH and vertical velocity shows large scale saturation collocated with the vorticity maxima at 500 hPa. At this point in the forecast period, consensus between the GFS and NAM begins to break down. The soundings from the GFS are quicker to saturate the column than those from the NAM. GFS soundings indicate precip beginning 03z and 06z Saturday while the NAM holds it off until after 09z. The NAM is also quicker to get the precip out of the region with the column losing deep moisture 15z on Saturday. The GFS keeps deep, precip-supporting, saturation closer to 18z. A look at ensemble guidance from the GEFS and SREF would suggest a blend of the GFS and NAM solutions with precip beginning closer 03z Saturday and ending closer to 18z. Regardless of timing, both models output K indices in the low 30s, so expect efficient, steady precip. Temperatures should stay well above freezing. As such, frozen precip is anticipated. 

Future shifts will need to watch the changes between model runs and how this will affect the timing of the rain. Forecasters should also play close attention to discrepancies between the models regarding duration of the rain as this will have a big effect on QPF totals.