NWS Forecast Discussion
335 FXUS63 KMPX 080459 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1059 PM CST Fri Feb 7 2025 .KEY MESSAGES... - Narrow Winter Storm Warning issued across central Minnesota into northwest Wisconsin. - Accumulating snow late this eveningthrough Saturday morning and early afternoon. - Widespread snow amounts around 3 to 5 across central Minnesota and western Wisconsin. Pockets of higher amounts (6+) are possible, especially across western Wisconsin. - Well below normal temperatures will move in behind the Saturday system, with sub-zero lows Sunday night and even colder lows (negative teens to 20s) Monday through Wednesday. && .UPDATE... Issued at 639 PM CST Fri Feb 7 2025 We decided to upgrade a narrow swath of our area into a Winter Storm Warning. This follows near where the HRRR is showing storm total QPF near 0.4", which when converting to snow with an expected ratio of 16 or 17 to 1 pushed snow totals up into the 6-7" range over about a 20-30 mile wide west-east oriented band. This enhanced snowfall is being largely aided by the appetizer of snowfall we`ve seen develop over central MN within a strong zone of h7-h6 fgen. With the main entree still back over southern NoDak (where the SPC issued an MCD for heavy snowfall), we felt comfortable enough to squeeze a very narrow extension of the Winter Storm Warning out of the south end of the Grand Forks NWS coverage area across the northern boundary of ours. This may not be the only headline update needed though. We`ll see what the 00z HRRR does, but right now, there is little difference in our snow forecast between Mankato and Albert Lea and Fairmont, so we may be looking to add the I-90 corridor into the advisory as well since there is currently little difference in the forecast for the I-90 corridor and the advisory off to its north. && .DISCUSSION... Issued at 251 PM CST Fri Feb 7 2025 The forecast has not changed much over the last 12 hours, with accumulating snow moving into western Minnesota by this evening. A deepening surface low to the south will provide weak warm air advection at the same time high pressure moves south from Canada. This setupwill lead to a frontogenetically-driven snow event for the Upper Midwest. As is often the case with fgen driven snow, there will be bands of higher QPF/snow amounts. Determining exactlywhere those bands will set up can be difficult, but a general consensus between the models indicates it will be just north of the Twin Cities Metro (but south of Duluth). From a timing perspective, light snow will begin in western Minnesota as early as 7-8PM, but the more intense snow wont start for a few hours after that. The Metro area likely wont see much snow accumulate prior to midnight, but the rates will peak shortly after in the 2-7AM timeframe. Western Wisconsin likely wont see anything until after midnight,but things will linger slightly longer into the early afternoon hours on Saturday. All-in-all, this event will take place when the vast majority of people are sleeping, which is good from an impact point-of-view. Areas in western Wisconsin may see more travel impacts due to the later arrival and shift into more of the daylight hours. As mentioned above, there will be a band of higher QPF in central/eastern MN and western WI. Guidance continues to indicate 0.3 to 0.4 QPF will fall within this band, tapering to 0.25 in the Metro, and quickly dropping to 0.15 or less for the far southern portion of Minnesota (Mankato and south). This will be a more light and fluffy snow, with snow to liquid ratios slightly above the climatologicalnorm in the 14-18:1 range. The lower ratios will be in areas just south of the Metro as weaker forcing and drier air will inhibit anything higher. Equating this to snow amounts, 3 to 5 can be expected for most across our forecast area, with lesser to the south.Again with the fgen banding, the location of the band will be where we see the highest ratios and snow rates. These locations are also most likely to see 6+ of snow. Although QPF amounts have noticeablydropped since forecasting for this event began, whether or not a specific location sees 5 or 6 wont make a difference in terms of impacts. The biggest takeaway should be that it will snow and it will need to be plowed for the majority of southern and central Minnesota and western Wisconsin. Taking a look at current Winter Weather headlines, we have expanded the Winter Weather Advisory to cover our entire area, minus the southernmost tier of counties in Minnesota (along I-90). This advisory is mostly due to expected snow amounts and associated travel impacts. There is a limited potential for blowing snow in SW MN, but nothing major due to lower snow amounts and a short time frame of concern. Looking to Sunday and beyond, things will get cold. Canadian high pressure will settle in behind the departing low, dropping high temperatures into the single digits with even colder apparent temps. Monday, Tuesday, and Wednesday night lows will be the coldest of the week, with wind chills in the negative 20s in western Minnesota. Western Wisconsin will be roughly 10 to 15 degrees warmer, but still below zero. Looking into longer term chances at any more weather makers, there is decent agreement between ensembles for a few systems over the next two weeks, but none of which are looking significant. This means our pattern of a light dusting to half inch here and there will continue beyond this weekends system. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1054 PM CST Fri Feb 7 2025 Main change with the 6z TAFs was to delay by an hour or two the arrival of snowfall at RWF, MKT, MSP, & EAU. Snow band across central MN and NW WI will remain stationary for the first few hours of the TAF, with snow expected to blossom over southwest MN between 8z and 10z and quickly shift east across southern MN. Primary snowfall is expected between 12z and 18z on Saturday. There will be a period of MVFR cigs behind the snow, but skies are expected to clear out Saturday evening. KMSP...Dry air is taking a bite out of the snowfall for MSP, with snow start time possibly coming as late as 11z. Because we`ve taken some snow out of the front end of this event, snow totals for MSP have dropped into the 2-3 inch range. Heaviest snow, with occasional vsbys down to 3/4sm is expected between 13z and 17z. /OUTLOOK FOR KMSP/ SUN...VFR. Wind NW 5-10 kts becoming SW. MON...VFR. MVFR ceilings possible late. Wind NW 5-10 kts. TUE...VFR. Wind NW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Winter Storm Warning until 3 PM CST Saturday for Benton- Douglas-Isanti-Kanabec-Mille Lacs-Morrison-Sherburne- Stearns-Todd. Winter Weather Advisory until 3 PM CST Saturday for Chippewa- Kandiyohi-Lac Qui Parle-Meeker-Pope-Redwood-Renville- Stevens-Swift-Yellow Medicine. Winter Storm Warning until 6 PM CST Saturday for Chisago. Winter Weather Advisory until 6 PM CST Saturday for Anoka-Blue Earth-Brown-Carver-Dakota-Goodhue-Hennepin-Le Sueur- McLeod-Nicollet-Ramsey-Rice-Scott-Sibley-Steele-Waseca- Washington-Watonwan-Wright. WI...Winter Storm Warning until 6 PM CST Saturday for Barron- Chippewa-Dunn-Polk-Rusk. Winter Weather Advisory until 6 PM CST Saturday for Eau Claire- Pepin-Pierce-St. Croix. && $$ UPDATE...MPG DISCUSSION...PV AVIATION...MPG
NWS MPX Office Area Forecast Discussion