046 FXUS63 KFGF 081449 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 949 AM CDT Fri Oct 8 2021 .UPDATE... Issued at 949 AM CDT Fri Oct 8 2021 Adjusted POPs a bit as our line of showers/thunderstorms has been developing a bit further west than expected. Still expecting that line to move eastward slowly for the rest of the morning. CAMs continue to show additional development further south of the existing line into a larger portion of western MN this afternoon and evening, so continued to keep fairly high POPs going for that period. Some instability in that area thanks to not much going on this morning, but deep layer bulk shear is weak so think severe chances are not high. Will continue to monitor convective development throughout the day. UPDATE Issued at 643 AM CDT Fri Oct 8 2021 Showers with some embedded thunder has developed as expected across the northeastern ND over the past hour or so. Will continue to see the coverage area expand this morning across the northern valley as subtle wave lifts northeast and weak surface trough slowly tracks east today. && .SHORT TERM...(Today through Sunday) Issued at 345 AM CDT Fri Oct 8 2021 Impacts in the short term will be rainfall coverage and amounts through the weekend along with severe potential Saturday. Today will see increasing cloud cover as moisture continues to pool ahead of and along an inverted sfc trough across eastern ND. Elevated instability will fuel shower and possibly some embedded thunder as a band of precip is expected to develop within the 500 to 1000j/kg of MUCAPE. This band is expected to impact areas mainly along and north of the Hwy 200 corridor today and gradually spread to the east into NW MN this afternoon. 00Z HREF probability matched means indicate a half to one inch of localized rain is possible in the northern valley by this evening. A wide temp gradient is expected across the FA today with temps holding below 60 in the northern Devils Lake basin on the cool side of the slowing moving boundary with temps around 80 in the southern valley where some more sun is expected. Friday night into Saturday morning a brief lull in activity is expected before a potent short wave brings another more pronounced period of showers and storms. Depending on cloud cover and instability ahead of the track of the surface low pressure there is potential for severe storms on Saturday across much of the area. Impressive shear values ahead of the surface low and along the warm front indicate the potential for strong low level shear, rotating updrafts and supercellular characteristics leading to a rare October severe weather potential day for the northern plains. As highly anomalous moisture, PWats around 1.5" which occurs roughly once in ten years at this time of year per GEFS climate return intervals, wraps into the approaching 500mb wave overrunning the northward advancing warm front, highly efficient precip rates will occur with the strongly forced environment. Models are in fair agreement with track and location of the deformation zone rain band tracking across ND Saturday evening into Sunday with widespread rainfall amounts occuring. With the spotty nature of the showers and storms ahead of the upper low highly variable amounts area expected but with the backside precip band rainfall most areas are likely, 70%, to receive at least one inch with some locations, 10% chance, receiving up to 3 inches across the area by the time the rain departs Sunday. .LONG TERM...(Sunday night through Thursday) Issued at 345 AM CDT Fri Oct 8 2021 Focus within the long term was given mostly to analysis of forecast guidance regarding stout cyclogenesis within the central CONUS Wed/Thu. This may bring some impacts to the region through likely gusty winds and potential for a period of heavy rainfall. Sunday - Tuesday: Saturday's shortwave trough will be exiting the region into southern ON on Sunday. There may be some lingering showers wrapped behind the exiting wave that continue at least through the first half of Sunday. Cooler air wrapping in behind the trough as well as clouds should help keep temperatures generally in the 60s, with breezy north winds making it feel a bit cooler. As the shortwave exits, southwesterly flow aloft redevelops as the amplified Rossby wave over NOAM recharges the pattern for the next wave break. Wednesday - Friday: Ensemble guidance is in fairly good agreement of deep upper troughing near the Four Corners region to break eastward into the Central and Northern Plains mid next week. Consensus within guidance accompanies strong sfc cyclogenesis under this deep trough into the Northern Plains and Upper midwest. While exact location of this sfc feature is still in question, all guidance suggests the low will be well developed and matured by the time it reaches the Northern Plains. Because of its strength and expected stage in life cycle, we can draw out a few conclusions. First, strong cyclogenesis typically have gusty winds accompany them, and this case is no different. With the surface low likely to reach sub 990 mb, a tight pressure gradient surrounding the low is also likely which in turn brings high confidence in gusty winds both ahead and behind the low. What isn't certain is just how high winds may get, again owing to unknown sfc low trajectory through the Northern Plains. Second, with the mid lat cyclone likely near or undergoing occlusion, moisture should be well wrapping around the low, with long moisture fetch sourced from the GOM overspreading the FA within the cyclones warm conveyor/TROWAL. This also means the dry conveyor should be well under way bringing the potential for rain to quickly "turn off" from dry slotting. On the other hand, the cyclone could move through the Plains in such a way that deformation zone and residence time of steady rainfall still remains a potential scenario. These latter two features are again dependent upon the low's trajectory which still has a wide range of potential trajectories. Regardless, during the warm, moist conveyors passage (favored to be around Wednesday), steady rainfall is likely ranging from light to potentially heavy given forcing and moisture content/flux. Antecedent conditions primed by Saturday's heavy rain brings the potential for impacts from heavy rain, but uncertainty with Saturday's event as well as drought-laden soils currently in place further complicates flooding potential. Thus potential impacts from heavy rainfall Wednesday into Thursday has lowered confidence. Third, with the system well wrapped up into Thursday, lingering showers on the backside of the cyclone is likely. Colder air behind the low is also expected, although not expected to create any precip type issues, at least during the period of higher precip. Still, colder air will bring temperatures towards seasonal normals with highs in the 50s and 60s and lows in the 30s to 40s. This brings the chance for patchy frost/freeze late next week. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 643 AM CDT Fri Oct 8 2021 Increasing clouds and showers expected today with MVFR CIGs forecast to develop this morning at DVL and possibly spread into the GFK and TVF areas late this morning. Winds will be light through the period. Overnight MVFR CIGS will return to most TAF sites. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...JR SHORT TERM...JK LONG TERM...CJ AVIATION...JK