Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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461 FXUS63 KFGF 220428 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1128 PM CDT Sat Sep 21 2024 .KEY MESSAGES... - There is potential for localized frost in portions of west- central Minnesota Sunday night into Monday morning. && .UPDATE... Issued at 1022 PM CDT Sat Sep 21 2024 Skies are almost completely cleared with only a few pockets of lingering mid level clouds in the region and sky trends were adjusted to reflect this. Tds have dropped to the upper 30s to lower 40s and temperatures are rapidly falling with ideal radiational conditions in place. Based on the current trends low temps were adjusted to the NBM 25th percentile with matches up with the idea of colder spots in the upper 30s and most locations falling to the lower 40s by sunrise Sun morning. Otherwise, the forecast for the rest of the night remains on track. Issued at 640 PM CDT Sat Sep 21 2024 Most CU is transitioning east or dissipating with the setting sun, and winds are on the expected downward trend. Very dry air arrives with the northwest flow aloft, so while radiational conditions are good, there isn`t a signal for fog development. Shallow/ground fog may still develop near sunrise Sunday, but impacts are highly uncertain/limited. Guidance doesn`t support adding fog at this time, so I held off with this update. There are no other changes from previous forecast/discussion. && .DISCUSSION... Issued at 241 PM CDT Sat Sep 21 2024 ...Synopsis... Post cold frontal, continental air mass is infiltrating the Northern Plains with surface high pressure building into the region from the northwest. This is bringing in drier air with closer to average temperatures for this time of year. Winds decrease around sunset this evening, with calm and clear conditions tonight promoting some ground fog Sunday morning. Although a lack of higher moisture content should prevent more widespread chance for dense fog. Surface high pressure moves into Minnesota late Sunday into Monday. This may help bring some localized frost to some areas in Minnesota late Sunday night into Monday morning. Quasi-zonal flow aloft with progressive shortwave trough early next week will bring a period of breezy winds, but lack of moisture keeps dry conditions favored. Mid to late week, anomalously strong upper ridging builds into the Intermountain West and Canadian Prairies. This will eventual lean into the Northern Plains and Upper Midwest, promoting another period of above average temperatures at least into the 70s and 80s. As this ridging builds, continued lack of moisture and forcing for ascent will keep conditions dry. ...Sunday Night Frost Potential... Dry air mass comprised of dew points into the mid to upper 30s will overspread the region Sunday night into Monday. Surface high pressure will be migrating into Minnesota by this time, with a increasing surface pressure gradient and cloud cover from the west into North Dakota and Red River Valley SUnday night. Areas that can remain calm and clear to mostly clear hold the chance of efficient radiational cooling, bringing temperatures below 40, and potentially to the mid 30s. Current guidance presents areas within west-central Minnesota hold potential for localized frost conditions Sunday night into Monday morning. Uncertainty in whether or not this happens (and more precise locations) stems from differences in guidance with respect to cloud cover and surface winds. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1128 PM CDT Sat Sep 21 2024 VFR conditions should prevail through the TAF period. Clearing skies/light winds raises the potential for patchy fog early in the TAF period, but the amount of dry air immediately off the surface (and no guidance highlighting development) lowers confidence in impacts/coverage. Surface gradient remains weak through the day Sunday. Prevailing winds should increase with mixing in the west- northwest direction (6-10kt) for most locations and there is a low chance for 5000 FT AGL CU redeveloping in northeast ND during the afternoon (ceiling development unlikely at the CU). && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...DJR DISCUSSION...CJ AVIATION...DJR