Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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229 FXUS63 KABR 300813 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 313 AM CDT Mon Sep 30 2024 .KEY MESSAGES... - Critical fire weather conditions expected through today due to dry and windy conditions. Wind gusts of 40 to 45 mph at times, which will cause any fires that ignite to spread rapidly and be difficult to control. Burning should be avoided. - Cooler air will be in place for today and Tuesday with temperatures around average. Warmer air moves in Wednesday with temperatures around 15 degrees above average. && .SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/... Issued at 312 AM CDT Mon Sep 30 2024 Southerly winds gusts of 15 to 30 mph continues across the eastern half of the forecast area early this morning ahead of a cold front. The front will sweep across the CWA before 18Z, bringing cooler, but still near to above average temperatures and strong northwesterly winds. Buffer soundings indicate the highest winds occurring within an hour or two after the cold frontal passage, with peak gusts of 45 to 50 mph. These winds may occur as far east of Aberdeen. However, after the initial gust, the winds should subside later this morning and early afternoon with gusts around 35 to 45 mph at times, mainly west of the James River valley. Winds appear to slowly diminish late this afternoon and through the evening hours, with some model guidance showing no gusts after 0Z. While temperatures will be cooler today, the airmass post-frontal remains dry with RH values remaining at or below 25 percent. The dry conditions and gusty winds will create critical fire weather today with a Red Flag warning for the entire CWA. Seasonal temperatures should move into the CWA tonight with 925 mb temperatures in the single digits above zero C to around 11C. These readings are normal for this time of year. Low temperatures should range in the 30 for most locations, with patch frost possible if winds fully diminish. The probability of lows dropping below 34 degrees is 10 to 35 percent, only in north central SD. Will hold off on mentioning frost in the grids for now. Winds begin to increase once again on Tuesday with southwesterly gusts of 20 to 25 mph possible along and west of the Missouri River. RH values remain low, or below 20 percent, with elevated fire weather a concern once again. Later shift may need to issue a fire weather headline for counties along the Missouri River on Tuesday. && .LONG TERM /TUESDAY EVENING THROUGH SUNDAY/... Issued at 312 AM CDT Mon Sep 30 2024 The upper-levels have a low pressure over the Hudson Bay and an associated trough over the Great Lakes, leading to zonal flow over SD starting Tuesday evening until Thursday evening, when the models show a ridge starting to build over the Pacific Northwest, pushing the flow over SD from the northwest. The models keep this flow over SD till Sunday, however there are some differences in the positioning of the ridge. The GFS and ECMWF start moving the ridge over SD Friday evening, while the Canadian model moves it west Saturday morning. At the same time, the GFS and ECMWF have a shortwave moving east over ID, which the ECMWF has reaching SD Saturday evening and the GFS has over SD Sunday morning. By Sunday evening, the ECMWF has moved the low to the southeast creating stronger northwest flow, while the GFS moves it to the east creating zonal flow over SD. Wednesday morning the models have mid-level moisture over northern counties in central SD, while areas to the south are dry. This leads to widespread surface RH values below 30% over central and eastern SD, as well as values below 20% around/west of the Missouri River Tuesday evening and Wednesday afternoon. The deterministic models show a faint signature for strong surface wind, but because of weak lapse rates, these winds don`t get to the surface. However, the clusters show strong wind gusts over the Coteau Tuesday evening into Wednesday morning. The NBM also shows wind gusts greater than 25kts over the Coteau starting 6z Wednesday until 15z, and in the afternoon, there are gust over 25kts in Corson and Dewey counties. Drier surface RH values from previous days and Wednesday, along with some stronger wind gusts could lead to more critical fire weather conditions occurring Wednesday. Continuing past Wednesday, the mid-level moisture spreads across central and eastern SD Thursday morning and stays there Friday. Thursday and Friday afternoon, the surface RH values increase, with areas in northern SD above 40% with some pockets below 40-30%. By the evening, the ECMWF and Canadian have mid-level dry air over SD, but there are some disagreements with surface RH as the models shoe opposite patterns. The ECMWF has RH values below 40% west of the James River Valley and below 30% west of the Missouri River, and the Canadian has areas around the Missouri River below 40%, with widespread values below 30% to the east. Sunday increases surface RH values, with the ECMWF having values above 40% north of Potter, Faulk, and Dewey counties, and below 40% to the south. However, the Canadian is a bit drier with widespread area below 40% with pockets below 30%. Monday afternoon, the Canadian has surface RH values below 40% and the ECMWF shows area west of the Coteau below 40% and west of the James River Valley below 30%. 0.5km winds don`t show strong winds lining up with strong lapse rates until late Saturday evening, when the ECMWF shows widespread areas of wind speeds greater than 30kts over eastern and northern central SD which continues into Sunday evening. While the other deterministic models do not show this, the clusters pick up on it, with gusts around 25- 30kt. The NBM also shows wind gusts picking up Saturday morning over the James River Valley and the Coteau, with widespread gusts over 25kts until Saturday evening. There is mid-level WAA over SD Tuesday evening into Wednesday, leading to surface temperatures Wednesday being around 15 degrees warmer than normal. After that, the models do vary slightly on when mid-level CAA moves in, as the GFS and Canadian models move CAA into central SD early Wednesday morning, and the NAM and ECMWF move it in Wednesday afternoon. This CAA stays over until the GFS and EC moves in WAA Friday morning, leading to surface temperatures being around normal Thursday and Friday, The Canadian joins the other models Saturday morning with the mid-level WAA over SD, causing surface temperatures to be 10-20 degrees warmer than normal Saturday. The GFS and ECMWF then moves mid-level CAA over central and eastern SD late Saturday evening and the Canadian moves the CAA in Sunday afternoon, leading to surface temperatures Sunday and Monday being around 5-10 degrees warmer than normal. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1220 AM CDT Mon Sep 30 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions will prevail through the TAF period. Breezy/gusty southerly surface winds early in the period will gradually switch to the northwest as a strong cold front moves across the region. Low- level wind shear will also be a concern through the early morning hours. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Red Flag Warning from 11 AM this morning to 8 PM CDT this evening for SDZ006>008-011-018>023. Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for SDZ003-004-009-015-016-033>035-045-048. Wind Advisory until 4 PM CDT /3 PM MDT/ this afternoon for SDZ003-015-033-045-048. Wind Advisory from 7 AM this morning to 4 PM CDT this afternoon for SDZ004-005-009-010-016-017-034>037-051. Red Flag Warning from 7 AM this morning to 8 PM CDT this evening for SDZ005-010-017-036-037-051. MN...Red Flag Warning from 11 AM this morning to 8 PM CDT this evening for MNZ039-046. && $$ SHORT TERM...SD LONG TERM...Vernon AVIATION...SD