Current Conditions at Sanborn Field
Friday Night - Increasing clouds. Becoming cloudy overnight. Low: 44-48
Saturday - Cloudy. Scattered showers in the morning. High: 52-56
Saturday Night - Becoming mostly clear. Morning fog possible. Low: 42-46
Sunday - Mostly clear. High: 60-64
Monday - Clear skies. 68-72
Another period of fairly active weather is ramping up for the region this weekend. Went primarily with GFS guidance with blend of SREF, GEFS, and GFS/NAM MOS for narrowing down temps.
As the sun sets on Friday, clouds will begin to set in ahead of the system that will impact the majority of our forecast period. GFS 250-hPa and 500-hPa plots of geopotential height shows a shortwave disturbance propagating down from the Upper Midwest embedded in the greater longwave trough currently parked over the NE CONUS and SE Canada. 500-hPa vorticity shows a prominent circulating maximizing over MO Saturday morning (~12z). This, combined with the large swath of 80-100% RH saturated air over the Midwest as shown at 700 hPa, will bring chances for rain into Saturday morning. Overnight Friday winds at 850 hPa shift out of the SW and a prominent LLJ originating from the warmer, moister region Southern Plains will help advect the aforementioned moisture to fuel showers. Seeing as this LLJ originates in the more continental tropical (cT) airmass rather than a maritime tropical (mT) airmass over the Gulf, moisture does not look to be overly abundant. GFS Skew-Ts never favor a fully saturated column. Models have been continuous with a "zipper" closing in by 12z on Saturday. Though would not be surprised to have larger drops overcome evaporation in the surface dry layer and make it to the ground in the form of light rain beforehand. Seeing as the column never fully saturates, it is more likely that we will see scattered showers throughout the state. Widespread persistent rain looks much less likely. The lower levels of the atmosphere dry out fairly quickly due to the lack of abundant moisture. Precip most likely exists the area before 18z Saturday.
As Saturday progresses clouds will remain until overnight when the surface low-pressure system itself passes right to the south (over SW to SE MO) of mid-Missouri. This will cause our winds to be variable late Saturday night finally shifting out of the NNW as the cyclone moves off to the ENE following the pressure falls from the NE propagating SW at 500 hPa. As the shortwave moves out of our region, the parent LW begins to break down slightly and scoot off to the NE taking with it any significantly cooler air that may have wanted to surge southward.
GFS soundings point to a strong near-surface inversion setting up over Saturday night. This is probably helped by the evaporative cooling of the morning rain combined with decreasing cloudiness and allowance for decent radiational cooling. This knowledge combined with light winds at the surface bring with them the chances for fog Sunday morning. Seeing how skies clear out nicely overnight Saturday into Sunday, any fog that does form will likely burn off quickly after sunrise. Behind the exiting SW flow turns zonal. This is reflected by high pressure at the surface that will keep our Sunday and Monday calm and clear. As the center of the surface anticyclone sits just off to our east, south westerly winds will return. This will allow our temperatures to increase above average for early October potentially reaching into the lower 70s. The strength of the building anticyclone will determine how high our temperatures reach. Model continuity has been lackluster with temperatures as dprog/dt of the SREF has seen a substantial warming trend. As such have left room for potential continuation of the warming trend and thus went warmer than model guidance suggested for Monday.
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