Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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488 FXUS63 KFGF 121737 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1237 PM CDT Sun May 12 2024 .KEY MESSAGES... - Smoke from Canadian wildfires will be present across the region throughout the day today. - There is a chance for frost for areas north of US Highway 2 tonight into Monday morning. && .UPDATE... Issued at 1237 PM CDT Sun May 12 2024 Near term trends are still in line with last update, with RH values already around 25 percent even without reaching forecast highs yet in parts of MN. Winds continue to gust as high as 30 mph over parts of the Red River Valley, but RH is remaining higher. RAP/HRRR smoke models show the main periods of smoke exiting the region to the south this evening, but patchy smoke may still linger longer into the night if trapped by the nocturnal inversion. Adjustments were made to reflect this into the nighttime period during this update. UPDATE Issued at 1018 AM CDT Sun May 12 2024 Despite surface smoke, the smoke aloft so far has not been opaque enough to limit incoming daytime radiational heating, and mixing is better than originally anticipated. Td trends are a bit lower, temps a bit higher, and gusts 20-27 mph have been reported. Considering these trends I made some adjustments to better reflect potential afternoon conditions. Result is RH values likely in the 20-25% range with gusts continuing around 25 mph. Considering this, I issued an SPS for near critical fire weather conditions based on previous partner coordination in our MN counties. UPDATE Issued at 650 AM CDT Sun May 12 2024 There is uncertainty in the affect smoke will have on fire weather conditions today. Very dry air mass moving into the area along with gusty winds up to 30 mph are forecast today. Initial thought was that smoke was going to hinder daytime mixing potential, keeping fire weather conditions from developing by limiting minimum relative humidity values and to an extend wind gusts. However, looking at yesterday`s observations in this air mass upstream in Saskatchewan showed that despite thick smoke cover, RH values still dipped into the teens to low 20s percent. Should this happen in our area today, near critical to critical fire weather conditions will develop. There is around a 30-50% for near critical fire weather conditions developing, along with 20% chance in critical fire weather conditions. Highest chance for this to occur exists in northwest Minnesota. && .DISCUSSION... Issued at 410 AM CDT Sun May 12 2024 Synopsis: A cold front is passing through our area this morning as observed by surface observations. This cold front will be south of our area by mid morning, with relatively cooler air pushing into the region behind a passing upper low moving through MB and ON. Smoke from Canadian wildfires will fill into the region behind this front, lingering throughout the day today, possibly into Monday. North Dakota and Minnesota will remain in the subsident region south and behind the passing upper low, followed by upper ridging Monday keeping conditions dry today and Monday. Upper troughing aloft then extends into the Northern Plains and Upper Midwest mid to late next week bringing one or more rounds of showers and weak thunderstorms. The chance for widespread hazardous weather during this mid to late next week period. Smoke from Canadian wildfires today: Surface observations early this morning are revealing reduced visibilities from smoke, signaling smoke at the surface behind the passing cold front. Given continued weak cold air advection behind the front, smoke is expected to remain near surface level throughout the day today. High confidence in this is backed by most if not all smoke allowing models depicting this as well. Smoke may thin a little during the afternoon as highest concentrations may advect away from the area closer to the frontal passage, but still will be noticeable throughout the day. Smoke may may also hinder daytime heating some keeping temperatures in the 60s to low 70s. Frost potential tonight into Monday morning: Optimal radiational cooling conditions in a dry air mass forecast to reside over lower Canada into the Northern Plains and Upper Midwest will allow temperatures to dip into the 30s. There is still some uncertainty in where lowest dewpoints will reside come nightfall tonight, but dry air mass filtering in from the north would keep best chance for driest air in northern counties north of US Highway 2. This in turn would give highest frost potential at these locations with temperatures cooling to their dewpoints under light winds and clear skies. Even with smoke expected to be present, smoke does not affect radiational cooling efficiency. As of now, there is a 40% chance frost develops for these locations, with other areas within Minnesota liable to see frost as well. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1237 PM CDT Sun May 12 2024 MVFR to VFR conditions due to the wildfire smoke. Visibilities are going to hard to predict as there are some patches of thicker smoke moving through. Overall the visibilities should improve by the evening and with the smoke moving out completely later tonight. Winds will remain out of the north through tonight, but KDVL will begin shifting to the east around 05z while the rest of the TAF sites remain northerly. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...CJ/DJR DISCUSSION...CJ AVIATION...MM/DJR