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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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025 FXUS63 KABR 090213 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 913 PM CDT Mon Jul 8 2024 .KEY MESSAGES... - Isolated showers and thunderstorms (15-25% chance of precipitation) possible over northeastern to eastern SD into west central MN Tuesday afternoon and evening. - Hazy conditions continue this evening through Tuesday as northwest flow is bringing in periodic waves of smoke from the Canadian wildfires. This should not impact air quality across the region as the smoke remains aloft. - Heat and humidity will be on the increase through the week into the weekend. Friday through Sunday, temperatures will be about 5 to 10 degrees above average, with highs for the weekend in the upper 80s to mid 90s and lows in the upper 60s to low 70s. Dewpoints are expected in the mid 60 to low 70 degree range, with heat index values in the mid/upper 90s to near 100F. && .UPDATE... Issued at 912 PM CDT Mon Jul 8 2024 UPDATE Issued at 909 PM CDT Mon Jul 8 2024 The scattered thunderstorms that affected the area earlier today have now come to an end with the loss of daytime heating. No changes made to winds or temperatures at this time. && .SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/... Issued at 226 PM CDT Mon Jul 8 2024 HREF and deterministic models agree on weak northwest flow continuing over the CWA on the left side of the trough this evening and on the right side of a large amplified ridge located over the western CONUS. The northernmost shortwave/vort max continues northeast and is forecasted to be over MI/WI through IA this evening. This wave will continue to shift northeast and over southeastern Canada/Northeastern part of the US through the day on Tuesday. Within this flow, another highly positive tilted weak shortwave will swing down from Canada into the Northern Plains Tuesday evening through Wednesday morning, pushing south/southeast. Earlier today with this northwest flow, satellite showed elevated smoke being brought down, from to the wildfires in Canada, over the Northern Plains with much of the more dense smoke staying over ND. HRRR Vertically Integrated Smoke Model shows periodic waves of elevated smoke moving in, from the northwest to southeast, over the CWA tonight through at least Tuesday. Nothing noteworthy in the near surface smoke model, so this should not impact air quality or visibilities at this time. Otherwise, surface high pressure will be over the area tonight through Tuesday with keeping winds light and variable. Dew points late this afternoon and evening will continue in the upper 50s to the lower 60s and 700mb temps between 3-4C/500mb temps -11 to -12C. With daytime heating and steepening low level lapse rates (cooler air aloft) isolated afternoon showers and thunderstorms are possible but meso-parameters remain weak. ML/MU CAPE increases up to 1000 j/kg with the highest values over northeastern SD into west central MN with shear remaining weak and mid level lapse rates at 6C and under. Sounding profiles are very skinny indicating more of a chance of precip loading, keeping the storm short lived. Also there really isn`t much in the way of upper level forcing (especially west of the MO River, closer to the ridge/high), as winds remain weak. So the latest HREF/HRRR indicates any convection will be limited in coverage and intensity with no severe weather anticipated. However, HIRES ARW/NSSL WRF tries to show some isolated convection further west, but low confidence exists to put any pops this far west as of now, it may need to be added in. So latest grids indicate a 15-20% chance of thunderstorms mainly over northeastern/eastern SD into western MN with any thunderstorms diminishing by sunset. We will see this threat again Tuesday afternoon/evening as dewpoints will be similar to today and CAPE values up to 1000 j/kg over the eastern CWA with 15-25% chances of pops in this area as we get a little more help with the next shortwave. Lows tonight will range in the upper 50s to the lower 60s. Highs for Tuesday will be in the 80s to possibly a few 90 readings around and west of the Missouri River. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 226 PM CDT Mon Jul 8 2024 Models continue to maintain their consensus and consistency with the overarching large scale pattern through the coming week, contributing to high forecaster confidence. Wednesday will be the last day of northwest flow aloft before the SW CONUS high pressure ridge moves over the region. Low level moisture will remain abundant with persistent 60+ degree dewpoint temps across the region. Add in steep low level lapse rates and daytime heating, and its likely there will once again be isolated shower and thunderstorm activity. 0-6 km shear will be limited, although models are hinting at maybe up to 20-25 kts, which could certainly help aid in the development of a stronger storm or two Wednesday afternoon. The hi-res models that extend into Wednesday do show convection developing across our eastern CWA and tracking quickly into Minnesota. 500 MB heights build and the warm air really starts to move into the region on Thursday and persist through the weekend. Models still show a train of shortwaves riding the ridge and moving across the northern plains during this period. For the most part, the region should be sufficiently capped, although, the persistent southerly low and mid level flow will allow dewpoints to rise into the 70s beginning Friday and persisting through the weekend (likely some influence of the maturing corn crop as well). A highly unstable air mass will develop. If there was any concern about capping potential and thunderstorm development it would be our far northeast CWA. While timing of shortwaves is pretty far out in the predictability window, the probability of 700 MB temps over the coteau region exceeding 14 C really never exceeds a 30-40% so the door is not completely closed on thunderstorm development across the far northeast through the end of the week into the weekend. Of course the concern for heat related impacts extends through the period. High confidence in the western CWA exceeding 90 degree MaxTs although the NBM deterministic spits out a few 100 degree readings west of the Missouri River on Sunday. Meanwhile the the LREF probabilities of exceeding 100 degrees really never exceed 30-40% and these highest probs are limited to our southwest CWA, so a little bit of uncertainty in reaching the 100 degree temperature mark. As for the probability of exceeding heat index criteria, the LREF has increased the odds pretty significantly for Sunday, now ranging from 50-65% chance for most of the region on Sunday, with lesser values over north central South Dakota and the coteau region. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 626 PM CDT Mon Jul 8 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions will prevail across the area tonight and through the day Tuesday. Cannot rule out a few thunderstorms this evening, then again late Tuesday afternoon, mainly across the eastern part of the area. There could be brief periods of MVFR vsbys with any thunderstorms that develop. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...MMM LONG TERM...Serr AVIATION...Parkin