FXUS63 KFGF 040533 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1133 PM CST Tue Dec 3 2024 .KEY MESSAGES... - Blowing snow will impact the region late Tuesday night through Wednesday with significantly reduced visibility from blowing snow, including a 60% chance for blizzard conditions. - Uncertainty remains on severity and location of blowing snow impacts. - A winter storm watch is in effect for the potential of seeing blizzard conditions within eastern North Dakota and the Red River Valley and winter weather advisory for surrounding areas. && .UPDATE... Issued at 1133 PM CST Tue Dec 3 2024 Still not seeing any significant lowering of visibilities upstream, and winds remain off and on gusty. Temperatures remain quite mild too, with the true cold front still north of the border around Brandon Manitoba (where the temperature is still 34F). Temperatures behind the front drop off pretty quickly, with Dauphin at 18F. So with this event, we will probably not be able to watch bad conditions upstream drop southward. Think a lot of it will develop right over the FA. Currently think there will be a blast of strong winds as the cold front works from north to south through the FA. This may stir up some of the snow and produce up and down reduced visibilities overnight. Then models show winds only getting stronger through the mid to late morning. Think it may also take a while to loft the snow and develop convective streamers, so a consistent low visibility during the morning rush may not be there. However, believe conditions will only worsen through the mid to late morning, with impactful weather holding through the evening commute period. Winds should finally begin to decrease by late afternoon into the early evening. So this remains a tricky forecast, as the early morning may have up and down visibilities, before more consistent low visibilities arrive by the mid to late morning through the afternoon. UPDATE Issued at 926 PM CST Tue Dec 3 2024 The temperature peak is going through the Grand Forks area right now, with the airport at 34F and the NWS office at 32F. The wind here is also absolutely calm as well. Walked outside and looked at the snowpack, and the spot was not crusted, so the snow was still quite fluffy. With temperatures bumping up to the 30 to 34F range all across eastern North Dakota, made a request for snow quality information elsewhere and got quite a few responses. They all overwhelmingly said the snow is still fluffy. Winds are shifting to the northwest all across eastern North Dakota now, but the true cold front is still north of a Winnipeg to Brandon Manitoba line. So the strongest winds will still not get here until late tonight into tomorrow morning, then continue all day. With the snow looking to stay fluffy and blowable, impacts during the Wednesday commutes still look on track. UPDATE Issued at 618 PM CST Tue Dec 3 2024 Forecast is pretty much on track for early this evening. Will update to try to capture the area of mixed precipitation that is currently moving toward the highway 2 corridor across northwest Minnesota. Have had reports of mixed precipitation under these echoes and even had a photo sent to the office of a rainbow. Appears this activity will keep tracking southeast, and should exit the FA within another hour or two. Then the attention will shift to the bigger event for the overnight hours. The surface low is currently over eastern Manitoba, with a prefrontal trough extending southward along the western edge of the RRV. The cold front (switch to northwest winds) is still just northwest of the FA. Not anticipating making any headline changes on this shift, unless something consistent shows up across southern Manitoba (really low visibilities, more snow than expected, etc). However, when doing the 6 pm snow depth measurement, noticed a bit of a crust on the snow, and the depth had dropped an inch. This may not sound like a big deal, but the character of snow on the ground is a big one for this event, since not a lot of new snow is anticipated. Will keep an eye on observations upstream, but the strongest winds will probably hold off until late night into early Wednesday. && .DISCUSSION... Issued at 131 PM CST Tue Dec 3 2024 ...Synopsis... A potent arctic cold front will sweep through the northern plains tonight and bring widespread blowing snow impacts to eastern North Dakota and northwest Minnesota. Late in the week short term ridging will bring warmer temperatures Friday through Sunday with highs in the 30s possible. Ensembles and clusters at the same time hint at another system impacting the northern plains over the weekend but confidence in the overall pattern evolution degrades by this point leaving potential highly uncertain. - Blowing snow/Blizzard potential Behind this front winds of 30 mph frequently gusting to 45 and as high as 60 mph are expected as a strong pressure gradient positions itself parallel to the Red River Valley with the strongest CAA along and immediately following the passage of the cold front. Behind the front as the the boundary layer destabilizes through CAA and mixing HCR's will become favored with strong unidirectional shear up to the top of the boundary layer. The main question is whether the HCRs will be precipitating which feels like a 50/50 currently based on current guidance. NBM QMD which would be expected to handle winds better in this strong CAA/mixing regime shows a 60% or greater probability for the entire watch area of seeing sustained winds over 35 mph with a similar prob for 50 mph gusts in same respective counties. A 10th percentile (worst case) results in winds of 40 mph gusting to 60 mph and could result in an expansion of current headlines with a 60% chance the current watch is upgraded to a blizzard warning. Winds lessen as the PGF and CAA dissipate by tomorrow night allowing for much improved conditions by Thursday. Getting into late this week, upper ridging attempts to build eastward into the Northern Plains, although ensemble guidance still disagrees on how amplified this will be. This will dictate how warm our area gets, including the potential for above freezing temperatures this weekend. With the warming trend and potential for above freezing temperatures, this could impact current blow-ability of our snowpack as well as bring chance for advection fog. Upper ridging will be short lived as ensemble guidance also reveals a hybrid-type system moving into the Northern Plains region from the west. This may bring precipitation, including the potential for wintry mix given temperatures near freezing, and thus may bring winter impacts. With many factors at play confidence is low due to uncertainties in synoptic forcing as well as possibility for wave interactions and uncertain precipitation types. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1133 PM CST Tue Dec 3 2024 Pretty much stuck with the same thoughts as with the 00z set of TAFs. Winds will only increase through the rest of the night, probably peaking during the late morning and afternoon Wednesday. It should take a while to loft the snow on the ground, meaning it may take a while to develop consistently low visibilities. However, once they drop, they will likely stay there until Wednesday evening, when wind speeds finally begin to drop again. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Winter Storm Watch from 3 AM CST Wednesday through Wednesday afternoon for NDZ006>008-014>016-024-026>030-038-039-054. Winter Weather Advisory from 3 AM to 6 PM CST Wednesday for NDZ049-052-053. MN...Winter Storm Watch from 3 AM CST Wednesday through Wednesday afternoon for MNZ001>004-007. Winter Weather Advisory from 3 AM to 6 PM CST Wednesday for MNZ005-008-013>015-022-027-029-030-040. && $$ UPDATE...Godon DISCUSSION...MM/TT AVIATION...Godon