Current Conditions at Sanborn Field
Friday Night - Mostly clear. Low: 30-34
Saturday - Mostly sunny. High: 48-52
Saturday Night - Becoming cloudy. Low: 38-42
Sunday - Cloudy skies. Rain beginning overnight. High: 42-46
Monday - Cloudy. Rain transitioning to wintry mix, potentially transitioning to snow later in the day. High: 30-34
An active and uncertain forecast period is ahead of us this weekend and into early next week. The main focus of this period is the incoming precipitation Sunday night into Monday and what type of precipitation it will be. The NOMADS outage at NCEP means that the NAM was unavailable. As such the GFS and GEFS were mainly used for forecasting with comparisons to the ECMWF and Canadian for nailing down the potential for winter precip.
The GFS plots of 500-hPa heights and vorticity show that the shortwave which brought showers and thunderstorms to mid-Missouri has since moved off to the northeast. Large scale, upper-level flow behind the disturbance has turned zonal and remain so until the arrival of the next system. As such, high pressure will build in at the surface behind the surface cold front that continues to push to the SE. GFS shows winds at 850 hPa and lower will remain out of the NNE and keep our temperatures slightly below normal for late October with highs reaching into the upper 40s/50s. GFS soundings do show brief periods of partial saturation in the upper levels. The result will be mostly clear skies with some cirroform clouds through the day. Saturday night, GFS soundings show an increase in moisture in the lower levels as clouds move in ahead of the next system. This is supported by GFS plot of 700-hPa RH showing a southward surge of saturation from the Upper Midwest.
Upper level flow shifts again by Sunday. GFS 500-hPa heights and vorticity show an amplified trough digging into the CONUS. By Sunday night and into Monday, Missouri sits at the inflection point of the trough ridge pattern, putting us in the ideal location for an active storm track. The amplified wave will allow a cold arctic air mass to penetrate into the Mid-Mississippi Valley by Sunday night. A developing jet streak associated with the amplifying wave will develop and move in overhead providing ample upper-level dynamic support for a precip event. Consensus inside of the GEFS members all point to precip beginning late Sunday night around 03z as rain and eventually transitioning to a wintry mix by 09z to 12z Monday. Temperatures continue to drop Monday until the GFS favors a full transition to snow by 15z at the latest. Soundings support the GEFS members. Temperatures teeter on the edge of freezing, but keeps the wet-bulb temp well below 0. Above the surface, GFS soundings show that the rest of the profile remains well below freezing.
Consensus outside of the GFS and its ensemble members breaks down. Unfortunately the NOMADS issues at NCEP have resulted in an outage of the NAM in our lab at the time of forecasting. Looked to the foreign models to compare with the GFS. The ECMWF keeps the cold air slightly to the north showing the 850-hPa 0C isotherm staying over southern IA and far northwestern MO. The Canadian outputs a solution in between the two extremes. It is slightly warmer than the GFS and slightly cooler than the Euro. The Canadian shows the surface freezing line passing over mid-Missouri near the end of the event, bringing a brief shot at wintry mix later in the evening Monday.
Regardless of p-type. Precip sticks around in one form or another until Monday night at the end of our period. Seeing as how 2 in and 4 in soil temperatures at Sanborn field are 52 and 54 degrees respectively and how no models take surface temperatures too far below freezing, winter accumulations will most likely be below an inch. Would not be surprised to see a glaze of ice on elevated surfaces such as bridges or cars if freezing rain dominates.
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