Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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229 FXUS63 KABR 220306 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 906 PM CST Thu Nov 21 2024 .KEY MESSAGES... - Patchy fog is possible tonight. - Fresh snow cover could cause overnight low temperatures to fall into the single digits tonight. Otherwise, temperatures Friday and Friday night should be close to normal. - There is a 15 to 25% chance of light snow over portions of north central and northeastern SD into west central MN Sunday through late Sunday night. Little to no accumulation is expected. - Average to slightly below average temperatures this weekend and around 5 to 10 degrees below average early next week. && .UPDATE... Issued at 905 PM CST Thu Nov 21 2024 Current forecast is on track, therefore no changes made at this time. && .SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/... Issued at 117 PM CST Thu Nov 21 2024 At 1 PM CST, other than overcast skies on the Prairie Coteau and west central Minnesota, the CWA is basically sunny or mostly sunny with some higher level clouds streaming by. Temperatures under the cloudy skies are in the upper teens to mid 20s (also the area with the most snowfall the other day), while sunny sky areas were warming through the 20s into the low 30s. Winds were northwest at 5 to 15 mph, with some areas east in the CWA gusting to around 25 mph at times. Surface high pressure is over the Missouri River valley region of the CWA. It is forecast to re-align along the Dakotas border with Minnesota by 12Z Friday. If the clouds over the eastern zones dissipate or continue their move off into Minnesota, the portion of the CWA that received 2in to 5-6in of snow Tuesday night into Wednesday could be staring a clear sky/light wind night square in the face; meaning there is the potential for low temperatures over this new snowfield to bottom out a good 5 to 10 degrees (or more) lower than surrounding bare ground areas. Have attempted to draw in that potential some in the min T forecast grid, while maintaining bordering CWA integrity with neighbors. There could also be some fog on/near this snow field later tonight as winds go light and temp/dewpoint depressions narrow to just a degree or two at the surface. Also worth noting, the HREF skycover guidance is hinting that the scattered coverage higher-level cloudiness happening now will be ongoing overnight, which could end up pumping the breaks on snowfield ultra-cold low temperatures, and on fog development. During the day on Friday, there is an attempt made for low level WAA over the CWA, in particular across the western third of forecast zones (Missouri River valley region), in response to lee of the Rockies/Black Hills surface pressure falls. So, fully expecting high temperatures to warm into (at least) the low to mid 40s across much of central and north central South Dakota. Something to watch, though, is how far south into the CWA a shallow cold airmass can push Friday night. The latest RAP output shows a cold front beginning to work into Corson County by 00Z Saturday, potentially reaching as far south as a line from Pierre to Miller to Watertown to near Appleton, MN by 12Z Saturday. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 117 PM CST Thu Nov 21 2024 Starting out the long term on Saturday, models are consistent on a ridge overhead with zonal winds turning southwesterly. Just west of the ridge, the low continues to spin off the coast of WA/OR with a trough, south of this low, extending over the Pacific Ocean. The ridge overhead will slide eastward with a negative shortwave forming over southern Alberta/Saskatchewan/northern MT along with several embedded shortwaves/pulses over the Rockies Saturday evening. At the surface, an elongated area of low pressure will form over this area, pushing east/southeast with the broad surface low extending from the Northern Plains southward through Texas by 12Z Sunday. The low then track east/northeast Sunday into Monday with the upper level waves following behind. Models keep most of the precip along the ND/Canadian border Saturday night through Sunday (closer to the 700-850mb low skirting east within this wave). However, ENS brings the chance of precip a bit further south, brushing our northern/northeastern CWA Sunday through early Monday as it indicates the wave aloft plunging further south than GEPS/GEFS. NBM does a good job indicating this with pops of 15- 25%, highest along the ND/SD border, with Ptype being mainly snow. EC meteograms do indicate a 10-15% chance that ptype could be light freezing rain/drizzle at 8D3 and less than 10% chance at KATY mixed in with the snow early Sunday. EC soundings at 8D3/KATY shows a potential warm nose (and dry air above this) with GEFS soundings for these locations keeps the column at or below freezing indicating all snow (which GEFS plumes do indicate). Low confidence exists on this potential as of now. No ice accumulation expected with little to no snow accumulations. Otherwise, behind the system, high pressure moves in and will be the dominant weather pattern through the midweek, keeping the area dry and quiet. Aloft, winds will mainly be zonal through the midweek as models indicate a broad positive tilted trough moving west to east over the CONUS with lots of variability between the models on track and intensity and whether it the pattern remains phased together or becomes split flow. Both EC/GEFS do hint at a possible lee low forming near CO/OK/TX area Wednesday and tracking northeast through end of next week. Depending on track this may bring the return of snow (under 20% chance for now). Confidence is low this far out on the overall pattern and where/if precip will fall and where. Temps will be around average to a few degrees below average for the weekend. As that high moves in early next week, it will bring in colder air with it with 850mb temps ranging to the single digits below zero to -11C with the coldest air over the northern CWA with GEFS being the most aggressive on this colder air. Temps are forecasted to run about 5 to 10 degrees below average. Even colder air is forecasted to move in for the end of the week (again GEFS being the most aggressive) with 850mb temps ranging from -10 to -13C by early Saturday morning with this colder air hanging around at least through the early following week. Latest NBM has a 30 to 60% chance of low temperatures below zero by Sunday morning (12/1) and 30-55% chance Monday morning (12/2). CPC highlights this well with a slight risk (20%) of "Much Below Normal Temperatures" 11/28-12/4 and a moderate (40% chance) over the north central CWA 11/28-11/30. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 525 PM CST Thu Nov 21 2024 Terminals KABR,KATY,KPIR,KMBG For the most part, VFR conditions will prevail across the area tonight and through the day Friday. The exception will be across far eastern parts of the area where some patchy fog and MVFR cigs may develop late tonight into Friday morning. KATY may be affected. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Dorn LONG TERM...MMM AVIATION...Parkin