Area Forecast Discussion
Issued by NWS Grand Forks, ND

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000 FXUS63 KFGF 202358 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 658 PM CDT Tue Apr 20 2021 .UPDATE... Issued at 646 PM CDT Tue Apr 20 2021 Forecast panning out nicely with a decreasing trend in cloud coverage beginning to reveal itself. Flurry activity should become more isolated as cloud coverage lessens, but there is a chance it continues into the overnight hours. Still unsure of how or where clear skies will develop, which will have implications on areas that could efficiently cool. While winds will start to lessen near sunset for the night, there still may just enough of a wind to keep temps from truly bottoming out (save local terrain effects). && .SHORT TERM...(This afternoon through Wednesday night) Issued at 327 PM CDT Tue Apr 20 2021 Limited impacts from scattered flurries/light snow showers through sunset. Near record lows possible once again tonight/Wednesday morning. Mid level shortwave trough within north-northwest flow continues to progress across our CWA, with cold pool aloft supporting daytime showers. Drier air aloft and especially in the lower levels has limited much of the activity from reaching the surface. Despite surface temps above freezing, wetbulb profiles have continued to favor snow as a predominant precip type and this has matched up with surface observations. We have still had sporadic reports of 5-9sm visibility in light snow where this activity is tracking. Best forcing and deeper moisture has generally remains west and south of our CWA, and outside of the convective (possibly lake enhanced) band earlier this morning most activity has melted on contact. As the sun goes down we should see a decreasing trend in stratocumulus and we should have at least some clear areas through the night. Lighter winds are also favored overnight, so where ideal radiational conditions occur lows may once again fall into the lower teens. Daytime record lows Wednesday morning will once again be at risk (current records are in the teens or lower 20s). Shortwave ridging builds into the region Wednesday-Wednesday night with rising heights and warmer West-southwest BL flow. This will support dry conditions and highs back to seasonal ranges in the 50s. RH values may fall into the 25 to 30 percent range in eastern ND, but winds should be under critical fire weather criteria (could still have sporadic gusts and near critical conditions in the Devils Lake Basin). .LONG TERM...(Thursday through Tuesday) Issued at 327 PM CDT Tue Apr 20 2021 SUMMARY...Fire weather concerns and the potential for precipitation are the main impacts expected in the longterm period. Brief periods of shortwave ridging on Thursday and Saturday will allow for temperatures to heat up and facilitate deep vertical mixing, which could allow for the potential for near critical fire weather conditions. The main limiting factor there is the weak winds aloft, inhibiting strong momentum transfer. Southwesterly flow returns to the area early next week, potentially allowing for some meaningful precipitation to the area, although there is a high degree of uncertainty as to how this impact evolves. THURSDAY...Ensemble guidance has picked up on a solid signal for near critical fire weather conditions. Main issue right now is with the wind speeds being low. As ridging breaks down over the area, an upstream longwave trough will allow for the development of a surface low over Canada and an attendant strong cold front. Ahead of this cold front, deep vertical mixing is expected to occur, with signals pushing the mixed layer above 800mb. Luckily, with the southerly wave keeping the pressure gradient at bay with the upstream wave, wind speeds aloft are not particularly eye opening. As such, vertical momentum transfer is a significant limitation in pushing for fire weather headlines. Regardless of wind speeds, however, the deep vertical mixing in an already dry environment would allow for relative humidities to drop into the 20s, possibly dipping into the teens in some spots, adding to potential fire weather concerns. FRIDAY...A rather strong cold front is expected to cross the area Thursday night into Friday, dropping temperatures in the afternoon back to the 30s. Along this cold front, some snow is possible, although impacts are not expected to be significant, with QPF signals not being particularly high. SATURDAY...Another day similar to Thursday is on hand. Deep vertical mixing and dry near surface conditions could create more fire weather concerns once again. Once again, however, wind speeds are very much in question and a significant limitation to fire weather risk on Saturday. Ridging is expected to settle back into the area, allowing us to heat back into the 40s. High pressure is expected to settle into the Northern Plains, however, which will keep wind speeds near the surface rather light. As such, fire weather concerns are there for Saturday once again, but is hardly a slam dunk for near critical conditions. SUNDAY...Ensemble guidance has had a tough time resolving potential precipitation on Sunday and Monday. For Sunday, the main issue is the struggle to resolve the upper flow over the northern plains. Some ensemble members have been resolving a rather subtle shortwave trough ahead of an upstream longwave trough, with other guidance washing it out. As such, there isn`t much confidence in the way of how Sunday works out. Further monitoring is necessary. REST OF THE PERIOD...Regarding Monday, a potent longwave trough over the Pacific northwest will transition our flow pattern to a more active southwesterly flow. Guidance has hinted at the potential for some meaningful precipitation for the area, but details are very limited due to the volatility of ensemble guidance at this time. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 646 PM CDT Tue Apr 20 2021 Overall, VFR conditions are expected throughout the TAF period. Remaining gusty winds will lessen to under 10 kt by 02 UTC for the night. Scattered to broken CIGS around 050 will remain in place through tonight and tomorrow, with some lingering flurries and virga still possible through 06 UTC. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...CJ SHORT TERM...DJR LONG TERM...Perroux AVIATION...CJ

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