621 FXUS63 KMPX 010454 AAC AFDMPX Area Forecast Discussion...UPDATED National Weather Service Twin Cities/Chanhassen MN 1054 PM CST Tue Feb 28 2023 .UPDATE... Issued at 920 PM CST Tue Feb 28 2023 The forecast remains on track. The first round of snow is developing across southern and western MN this evening. This round will weaken over the next few hours as it lifts north across east central MN and western WI. The heavier round will follow for the morning commute Wednesday, swinging through with a very potent short wave that has produced cloud-to-ground lightning over southeastern MT and northwestern SD this evening. This compact low will begin shearing out overnight as it continues to the east, so not expecting any thunderstorms. However, snowfall rates could still exceed an inch per hour for a short period early morning. More prolonged light to moderate snow, occasionally heavy, will soon develop across central MN where the highest accumulations are expected by Wednesday afternoon. && .DISCUSSION...(This evening through Tuesday) Issued at 313 PM CST Tue Feb 28 2023 KEY MESSAGES: - Winter Weather Advisory for 2-6 inches of snow this evening through Wednesday for central Minnesota, portions of the Twin Cities metro, & western Wisconsin. Satellite imagery this afternoon shows a strong shortwave moving into the Dakotas that has been ejected from the main upper trough centered over the Pac NW. This shortwave will sharpen up quickly this evening, but then shear out as it moves across central MN tonight and into northern WI Wednesday. This weakening shows up well with the HREF mean h7 forecast. It shows an h7 low closing off over the MO River in the central Dakotas this evening, which is when this system will reach its peak intensity. However, as this low moves into western MN Wednesday morning it will shear out, becoming an open wave again by noon Wednesday. This weakening of the wave and associated forcing is a big reason why we see snowfall values of near 1 foot in the southern Red River Valley fall off quickly to 5- 7" from Alexandria over to Mora. In addition, this snowfall looks to come in two waves. The first is the weaker one and will be associated with broad isentropic lift near the h7 level. Wave 2 is of more concern as it will come in during the morning drive and be associated with strong frontogenetic forcing in the h85-h7 layer. It's this second wave that the HREF shows some probabilities of having 1" per hour rates as it moves across central MN. As for how this forecast changed, the biggest thing is we really tried to tighten up the gradient on the southern end of this band. The net result is we have 5-7" of snow from Alexandria over to Mora, that falls off to just 1 or 2 inches as you get down to Willmar, the Twin Cities, and Eau Claire. The big difference between central MN and down to the US-12 corridor is up in central MN, there will be no break in the snow between the 2 wave, while the US-12 corridor will likely see a 2-4 hour break in snow between the 2 waves. As for the headlines, no changes were made. We initially had a warning drawn up for Douglas and Todd counties where we are forecasting 5-7" of snow. After coordination with Grand Forks, we kept the advisory going and a big reason was what we are seeing with probabilities for more than 0.5" of QPF from the NBM (a good estimate for where enough moisture will fall to support 6"+ snow totals). These probabilities are up between 70% and 80% in southeast NoDak, but fall off to just 30% in western Douglas county. This puts our current forecast up by Alexandria near the top end of the forecast spread, so with a borderline Warning event forecast and FGF not wanting to expand the warning east, we stuck with an advy, though a short term upgrade to a Warning is something that's not out of the question from Douglas, to possibly as far east as Kanabec county depending on what observation trends look like tonight. Even though we did drop snow totals in the southern end of the advisory, heavy snow coming in during the morning commute led us to keeping the southern boundary of the advisory unchanged. Only other change for Wednesday was to linger snow chances through the afternoon for central MN into northwest WI as we see moisture wrap around the backside of what is left of the h7 low. A quiet stretch of weather is expected for the second half of the week and into the weekend. Near seasonable temperatures in the mid 30s with mostly cloudy skies will prevail as a system passes well to our southeast Thursday evening through Friday. A slightly more active pattern emerges for the second half of the weekend and into the first full week of March. A series of shortwaves will bring low precip chances from late Sunday through the end of the forecast period. However, as of now, none of these waves look particularly impressive and there is not much model agreement. Looking at both the GFS and Euro ensembles, around half of the members have either no QPF or less than 0.05" for the Monday/Tuesday timeframe. A smattering of low PoPs (30% or less) has been introduced through the middle of next week while we wait and see how things evolve. With temperatures in the mid to upper 30s, p-type will be a concern should any of these precip chances materialize, but opted to stick with all rain/snow at this time range. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1054 PM CST Tue Feb 28 2023 Snow is overspreading central MN late this evening, which will likely persist through at least Wednesday morning. The initial band across EC MN and WI will diminish there by 07-08Z. Then, the low center will track east and with it will be a burst of heavier snow that could last an hour or two as it passes by early Wednesday morning. KMSP...The first round of a bit of light snow should end around 07Z, then a break will follow. The second should arrive around 11Z and continue into the mid morning. That round could see rates of a half inch per hour at times, so introduced a tempo of 3/4SM from 12-14Z. /OUTLOOK FOR KMSP/ Thu...VFR with MVFR cigs possible. Wind NE 5-10 kts. Fri...VFR with MVFR cigs possible. Wind NE 5-10 kts. Sat...VFR. Wind W 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Winter Weather Advisory until noon CST Wednesday for Chippewa- Douglas-Lac Qui Parle-Pope-Stevens-Swift. Winter Weather Advisory until 3 PM CST Wednesday for Anoka-Benton- Chisago-Hennepin-Isanti-Kanabec-Kandiyohi-Meeker-Mille Lacs- Morrison-Ramsey-Sherburne-Stearns-Todd-Washington-Wright. WI...Winter Weather Advisory until 6 PM CST Wednesday for Barron- Chippewa-Dunn-Polk-Rusk-St. Croix. && $$ DISCUSSION...MPG/Dye AVIATION...Borghoff