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Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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972 FXUS63 KFGF 140256 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 955 PM CDT Tue Aug 13 2024 .KEY MESSAGES... -Showers and thunderstorms are likely late Wednesday into Thursday, with lightning and locally heavy rainfall being the main impacts. && .UPDATE... Issued at 952 PM CDT Tue Aug 13 2024 VWP profiles at KBIS and KMVX indicate an intensifying low-level jet with the maxima centered in the western half of the state of North Dakota. Instability really diminishes as you go from west to east, falling below 1000 J/kg of MUCAPE in the Sheyenne River Valley. For this reason, despite intensifying shear profiles, severe storms continue to not be expected overnight. The low- level jet direction favors more moisture advection west of the Red River Valley, progressing northward through time overnight tonight. PW values and observations from ongoing convection west of the area indicate high confidence in efficient rainfall rates from any storms that can develop overnight. There remains a low probability for flash flooding with any training heavy thunderstorms west of the Red River Valley. This appears to be a low probability scenario given forcing is really weak over our CWA. UPDATE Issued at 641 PM CDT Tue Aug 13 2024 A few thunderstorms have developed along I-94 in central North Dakota and are tracking east. High uncertainty plagues these thunderstorms as they progress eastward as there is low confidence in continued forcing and instability in southeast North Dakota later this evening. Observations indicate these thunderstorms are dropping pretty hefty rainfall rates of 4+ inches per hour, but the forward propagation has been enough to offset potential flash flood impacts. There is high confidence in a low-level jet setting up away from our CWA to the west, so this lends to a lower probability for thunderstorms to make it to southeast North Dakota. In any case, flash flooding may arise this evening if storms can survive long enough to make it to southeast ND. && .DISCUSSION... Issued at 315 PM CDT Tue Aug 13 2024 ...Synopsis... Low pressure system continues to develop over eastern Montana this afternoon, with preceding showers moving through North Dakota. Strong moisture return ahead of the low pressure and warm air advection will continue to translate eastward as we progress into Wednesday and Thursday. Current Satellite shows an expansive area of cumulus development that is diurnally driven. This should diminish and help increase ceilings later this evening and into the overnight period. Hazy conditions will be possible today and into Wednesday as high level smoke from the western United States shifts eastward across the area. General flow aloft will be zonal through the rest of the week bringing chances for shortwaves to shift through the region. After the work week, we start to see a slow shift in the pattern flow as ridge begins to intensify in the southwestern and western United States. ...Showers and thunderstorms Wednesday through Thursday... Our next chance for precipitation comes Wednesday into Thursday as the low pressure over Montana translates eastward into North Dakota and Minnesota. As this happens, warm air advection surges into eastern North Dakota and northwestern Minnesota along with moisture. PWATS reach up into the 1.5 to 2 inch range. An axis of strong theta- E sets up in central North Dakota and into portions of the Devils Lake Basin and Sheyenne River Valley. This is where we suspect a boundary to become stationary Wednesday and in Thursday. Thunderstorms develop along this boundary and the probability of seeing locally heavy rainfall exists along said boundary. This would be due to back building and training thunderstorms. Locally heavy rainfall of 1.5 inches or higher will be possible (20-30% chance) within the Devils Lake Basin through the Sheyenne River Valley Wednesday through Thursday. There is a conditional threat for severe thunderstorms Wednesday afternoon, but environmental parameters of shear and instability are weak across the western Devils Lake Basin through the Sheyenne River Valley. None the less, there is a chance for stronger storms over those areas Wednesday afternoon, with small hail and brief gusty winds being the main impacts. Rain will gradually shift eastward Wednesday night and into Thursday. The low pressure system becomes very progressive in its movement toward the Great Lakes Thursday afternoon and Friday, but lingering showers and isolated thunderstorms will still be possible across the region. Our best chances for dry conditions will be over the weekend as the system moves east of the area and ridging develops out west bringing northwesterly flow. Further precipitation chances are possible next week, but confidence is low at this time. Temperatures will be seasonal over the next several days, with highs in the upper 70s to lower 80s. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 641 PM CDT Tue Aug 13 2024 The primary aviation impacts for the TAF period will be the potential for lightning. Showers and storms may impact FAR later this evening, mainly after 06z, but the probability is too low to add to the TAF. Thunderstorms will arrive from west to east, mainly after 18z, with falling ceilings to MVFR. There is also a signal for potentially IFR ceilings in southeast North Dakota, including FAR. These will continue for the remainder of the TAF period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Perroux DISCUSSION...Spender AVIATION...Perroux