207 FXUS63 KFGF 271301 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 701 AM CST Fri Dec 27 2019 .UPDATE... Issued at 701 AM CST Fri Dec 27 2019 System propagating across Canada has placed the region in a warm sector with a weak warm front transitioning through the region. Not much moisture and any forcing is very weak so no impacts (or even clouds) are anticipated. Will be watching clouds across northeast South Dakota and if the southerly low level flow can advect these clouds northward. Otherwise, should be a relatively pleasant day with temperatures climbing into the 20s. No changes required to the forecast. && .SHORT TERM...(Today through Tonight) Issued at 345 AM CST Fri Dec 27 2019 Clouds are clearing from west to east and the region will be under the influence of weak ridging into tonight. No impacts expected until later tonight. .LONG TERM...(Saturday through Thursday) Issued at 345 AM CST Fri Dec 27 2019 The main concern for late tonight into the weekend/start of the work week will be the potential for major winter impacts. Water vapor imagery indicates a strong upper low across southern California that will begin to propagate to the northeast providing winter impacts to much of the upper midwest and northern plains. Guidance indicates a surface low will propagate to somewhere near the ND/MN/SD border by midday Sunday, stall for a bit, and then propagate eastward by Monday afternoon. A lead shortwave and resultant mid-level warm air advection will bring light snow to the region late tonight into Saturday, with 1 to 3 inches by late Saturday afternoon. Do not see much more than 3 inches of snow by late Saturday afternoon considering transient nature of synoptic forcing. There may be a brief lull in snowfall before stronger forcing commences Saturday evening into Sunday. Strong deformation along with mesoscale forcing potential (mid-level Fgen) and PWATS above 0.5 inch will lead to intense snowfall rates (and heavy snow). Of course, details such as how much snow and where the heaviest snow falls are still uncertain, but confidence is increasing as per ensemble systems (i.e. NBM, GEFS, etc). In fact, we are very near the confidence threshold to be able to issue a warning for snowfall alone. Confidence is highest along and south of a line from Valley City to Grand Forks to Bemidji, with areas to the north having lower confidence (i.e. northern extent to the edge of heavier snowfall). Winds are the next concern, and should increase Saturday night and continue strong into Monday. Guidance indicates good mixing to at least 925mb with up to 40 knots available to mix, leading to north winds 30 to 40 mph with higher gusts along and west of the valley. With expected winds, Canadian Blowing Snow Model suggests we may be just shy of widespread/constant whiteout conditions, but certainly will have periodic whiteout conditions (near blizzard conditions at times in open country). The last concern is freezing drizzle/rain potential with the warm layer aloft near the region. Kept with the idea for the potential of ice accumulation Sunday into Sunday night along and east of the valley. Highest impacts will be Sunday into Sunday night. Made some minor adjustments to the timing of the watch, and expanded the watch to the north/northwest to account for uncertainty in this region. Monday night...The problem for this period will be brisk winds and lingering snow early in the period from storm system. The ECMWF ensemble mean was a little slower then the GEFS mean but still in reasonable agreement. While precipitable water will be decreasing and SLP increasing, some light snow and winds will persist. Impacts may still remain with some blowing snow and some light snow still expected on Mon night. Snow should move out and winds should settle down Mon night. Tue-Thu...Long wave trough strengthens a bit across the Northern Plains during this period. A short wave will be possible about Wed in northwest flow aloft. Short wave may produce light snow. Little impacts are expected with the system. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 555 AM CST Fri Dec 27 2019 Most of the area was VFR under a clear sky. However mostly MVFR cigs were located over the far southeast zones or roughly east of a line from west of BJI to Elbow Lake MN. Satellite indicated the trailing edge of cloud deck was moving to the southeast around 15 knots. Cloud deck should clear the forecast area around 16Z. However another area of IFR clouds were developing over northeast SD. This cloud deck is expected to move into parts of southeast ND this morning and should dissipate by late morning or early afternoon. Otherwise VFR conditions are expected today and most of tonight. Some MVFR/IFR conditions will move into the southern forecast area late Fri night. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Winter Storm Watch from late tonight through late Sunday night for NDZ038-039-049-052-053. Winter Storm Watch from Saturday morning through late Sunday night for NDZ007-008-014>016-024-026>030-054. MN...Winter Storm Watch from late tonight through late Sunday night for MNZ003-027>032-040. Winter Storm Watch from Saturday morning through late Sunday night for MNZ001-002-004>009-013>017-022>024. && $$ UPDATE...TG SHORT TERM...TG LONG TERM...TG/JH AVIATION...JH