Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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593 FXUS63 KABR 252036 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 336 PM CDT Wed Sep 25 2024 .KEY MESSAGES... - Above normal temperatures will persist through the weekend. The warmest temperatures will occur on Thursday and Sunday, when some locations along and west of the Missouri River will exceed 90 degrees. - Thursday, Sunday, and Monday will see windy conditions, with some gusts in excess of 35 mph possible. && .SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/... Issued at 334 PM CDT Wed Sep 25 2024 The main concerns in the short range will revolve around stronger winds and the potential for elevated fire danger in some spots of the forecast area on Thursday. Prior to that, we are seeing severe clear across the region this afternoon. A sfc ridge as well an upper level ridge of high pressure has been the dominant weather players for us today. The sfc high is gradually shifting east into MN this afternoon allowing for winds to turn a bit more west to southwest at times. Temperatures have responded nicely warming into the upper 70s to mid 80s. For tonight, not much in the way of anything significant is on the way. Clear skies and mild overnight lows in the 50s. Deterministic and ensembles in agreement on shifting the upper ridge over our area now eastward into MN tonight into Thursday as an upper trough works its way into the Northern High Plains. At the sfc, a low pressure trough organizes from MT into WY tonight and shifts east. We`ll see a bit of an enhancement of the low level jet across the western half of SD. Increasing southerly breezes can be expected across our western zones(central SD) overnight. This will spill over into the daytime on Thursday. The gradient will continue to tighten across our forecast area. NBM wind data keeps speeds below advisory levels and the EC EFI values continue to indicate the absence of any evidence of a high chance for an advisory event. Nonetheless, gusty southerly winds between 30-40 mph look probable. The caveat element in the forecast will be the approach of a sfc trough or cold front into central SD during the afternoon and its effect on the wind gusts with respect to fire weather. Guidance looks to be in fair agreement on timing this thing to move in during the first half of the afternoon hours. This would effectively shut down the stronger gusts and allow wind direction to become more variable before turning west to northwest. With expected temperatures in the afternoon warming into the 90s, this will drive relative humidity values down into the 15-25 percent range for some of our West River zones. The combination of the gust winds and these RH values would prompt a fire weather headline. However, the thinking now is wind gusts will begin to diminish just before or at the time of peak heating and when the RH start to fall. So, have decided to have our incoming shifts have one more look at new data coming in tonight to see if a headline is warranted. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 334 PM CDT Wed Sep 25 2024 The flow at 500mb is still primarily strongest across southern Canada Fri-Sun, with mainly weak flow with high pressure aloft across the southwest CONUS, stretching northeast across the Northern Plains. Air mass remains warm over the region as 850mb temps stay in the upper teens and 20s C. This will translate to highs mainly in the 80s Fri-Sun which is above normal for this time of year, although central SD may see 90 degrees on Sunday. NBM probs for MaxT 90 degrees or higher is about 40-70% west of the Missouri River on Sunday. With the dry and warm air mass combining with dry soils and good mixing, tend to side on the warmer end of guidance. Sunday into Monday we begin to see some changes as a cold front begins to approach. Ahead of this front on Sunday, the pressure gradient looks to tighten, which is shown in decent agreement amongst deterministic/ensemble solutions. Inherited NBM winds do get gusty/breezy on Sunday, but current forecast remains below advisory levels (30mph sustained, 45mph gusts) at this time. Shortwave energy looks to track eastward across the Dakotas as well on Monday, along with the surface frontal passage. Subtle timing differences are noted with the cold front, as expected. But, it does look to bring us cooler air to start off next week. Cluster analysis reveals differing solutions in regards to the strength of the shortwave on Monday. There`s also some disagreement as to how cold the air is behind the front, with the Grand Ensemble 25th-75th spread being about 7 degrees C (1C-8C 25th-75th percentiles) at 12Z Tues. NBM high temps on Monday show about a 10 degree or greater spread between the 25th and 75th percentiles. It does appear strong northwest winds will accompany the front. As for precipitation, things look dry through the period. Even with the frontal passage on Monday, the atmosphere just does not moisten up appreciably and inherited PoPs remain below 5 percent. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1219 PM CDT Wed Sep 25 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions will continue for the next 24 hour forecast period. Winds will become more southerly with time and begin to increase overnight into Thursday morning. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Vipond LONG TERM...TMT AVIATION...Vipond