Scientific Forecaster Discussion

000 fxus63 kfgf 201858 afdfgf Area forecast discussion National Weather Service Grand Forks ND 1258 PM CST Wed Feb 20 2019 Update... issued at 1256 PM CST Wed Feb 20 2019 Tweaked high for today...warmer some area cooler others. Radar showing more snow moving into the northern areas. Otherwise little change at this update. Update issued at 1032 am CST Wed Feb 20 2019 Water vapor loop indicated an upper low pressure system over eastern NE. Moisture continues to move north into the area. Short fused models suggesting more snow farther north and west. Increased quantitative precipitation forecast and snow for the Red River valley for today. Added more counties in the advisory to the north and west of current advisory. Update issued at 716 am CST Wed Feb 20 2019 Forecast and snow is arriving as anticipated. No changes needed attm. && Short term...(today and tonight) issued at 341 am CST Wed Feb 20 2019 500 mb vort Max seen moving north-northeast around an 500 mb low over southeast Wyoming early this morning. The 115kt 500 mb jet associated with this vort will move northeast and take the vort Max into Wisconsin today as the 500 mb low organizes a bit and moves into North Dakota. 850 mb warm advection driving the precipitation early this morning over eastern South Dakota into southern Minnesota along with lift associated with the mid level jet. Strongest lift does slide closer to the 500 mb jet Max and aims more toward eastern Minnesota during the day with an elongated area of precip wrapping back west around the organizing 500 mb in North Dakota. It is this precipitation wrapping back west which will be over the area today...with precipitation spreading south to north and lingering overnight in the far north but quite light intensity as the main energy and moisture is cut of to our east. Thus looking a prolonged period of light snow with this system...longest period of light snow in the north as moisture wraps back around the organizing 500 mb low while more intense is in the south parts of the fcst area closer to best warm adv/lift. Net result will be a rather wide area of 4-5 isold 6 inch snowfall over southeast ND into west central/northwest Minnesota. Based on qpf did add a strip of counties to the advisory where 4 inches of snow is most likely...and updated winter wx advisory now includes areas along and east of a Lisbon to Fargo to Fosston to Waskish line. Some concerns regarding snow ratio as they may be a tad high esp if the main lift bypasses our area so it could snow but rates not enough to produce the amounts fcst. Thus with this not ready to go warning for any part of the fcst area as main lift/dendrite snow should lift from Sioux Falls area across mpx area into northwest Wisconsin/dlh. Winds not an issue as they will be east-southeast today turning north tonight but only in the 10-15 mph range. Long term...(thursday through tuesday) issued at 341 am CST Wed Feb 20 2019 Main highlights beyond Thursday include snow (possibly heavy) on Friday, cold front Sunday to bring gusty winds and the return to much below average temperatures going into next week. Also of note are signals pointing to a very cold air mass moving into the region late next week, although confidence is low regarding this. Wednesday's mid level low will be flattening and moving away into Ontario ending snowfall south to north Thursday morning. Upper level flow orients itself southwesterly over the region late this week. This will draw north a warmer low level air mass composed of higher Theta-E content before stalling over eastern South Dakota into Minnesota. Parallel to the mean flow aloft, a stationary front will serve as a conduit for several subtle shortwave troughs embedded within the flow for snow to produce upon. Theta-E gradient tightens as warm air advection strengthens over Minnesota. This will promote frontogenesis near the stationary front. Thus forcing mechanisms include subtle synoptically induced lift aloft combined with warm air advection and frontogenesis. This would lead to the belief of potentially a broad area of snow with enhancement from snow bands within the area of warm air advection. Quantitative precipitation forecast signals in deterministic models are believed to be under-representative in terms of total amounts due to forcing mechanism recipe. However high resolution guidance coming into view of this timeframe and even some ensemble members suggest thin but intense snow bands somewhere within eastern South Dakota into Minnesota, possibly into southeast North Dakota, on Friday. Within fgf's area, southeast North Dakota into west-central Minnesota hold best chances for seeing heavy snow potential on Friday, although the majority of guidance does keep the stationary front and strongest warm air advection/fgen south of the region. Some good news: the forecast track of the expected potent late weekend storm looks to have trended further south pushing impacts from heavy snow away from the area. Not so good news: cold front on the nose of a 1040+ mb Arctic high sliding down the Canadian High Plains squeezes the surface pressure gradient Sunday while tanking temperatures. Tight pressure gradient, caa, and a northwest wind all point towards the potential for gusty winds and blowing snow. Still a bit unsure of how high winds will be so the extent and severity of blowing snow is still in question. After Sunday, upper flow has trended a bit more zonal. Shortwave troughs moving through the zonal flow will keep at least some chance of snow in the forecast early next week. Much below average temperatures start Sunday lasting into and possibly through next week. Given the advertised strength of Arctic air masses moving into the region, temperatures could be quite cold especially overnight should optimum conditions develop. Will likely be talking wind chills for the majority of next week. The Cherry on top will be the possibility of a very cold Arctic air mass combined with gusty winds late next week. Confidence is low on this late week event due large spread in phasing, timing, and location of coldest air interacting with synoptic players and the fact of this event being +200 hours away. Also lending to lower confidence is how relatively late in the season this is. && Aviation...(for the 18z tafs through 18z Thursday afternoon) issued at 1256 PM CST Wed Feb 20 2019 IFR conditions were across much of the area with cigs below 1 thousand ft and visibility under 3 miles in snow. Expect IFR conditions for this afternoon. IFR conditions will shift to the north and east tonight. Expect MVFR conditions to replace the IFR area as the area shifts north and east. && Fgf watches/warnings/advisories... ND...Winter Weather Advisory until midnight CST tonight for ndz027>030-038-039. Winter Weather Advisory until 6 PM CST this evening for ndz049- 052-053. Minnesota...Winter Weather Advisory until midnight CST tonight for mnz001>003-007>009-013>017-022>024-027-028-032. Winter Weather Advisory until 6 PM CST this evening for mnz029>031-040. && $$

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