FXUS63 KBIS 051216 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 616 AM CST Tue Mar 5 2024 .KEY MESSAGES... - Medium to high chances for snow (50 to 80 percent) over south central North Dakota through this morning, with a general 1 to 3 inches of snow expected. There may be isolated areas of higher accumulations. - Another system will bring medium to high chances (50 to 70 percent) for snow across northern and eastern parts of the state late tonight through Wednesday evening. There is a medium to high chance for at least 2 inches of snow across most of north central North Dakota. - Near to below normal temperatures are expected the rest of the work week, with a warmup favored for this weekend and into next week. && .UPDATE... Issued at 616 AM CST Tue Mar 5 2024 Surface low continues to move through central North Dakota, with nighttime satellite imagery showing clear skies on the southern side of the low. A moderate area of snow continues rotating around the low, with two distinct bands evident in radar reflectivity. The further north band has almost reached the Bismarck/Mandan area, with NDDOT road reports showing snow- covered roads across far south central North Dakota where it has been snowing for two hours or so. The second band is close behind, slightly offset to the southeast but approaching the ND/SD state line. Automated observations in Linton has shown visibility down close to one mile, with Mobridge, SD reporting 3/4 of a mile, so in the heavier snow bands there are pretty significant visibility reductions. The second snow band might be a touch stronger, with SPC mesoanalysis highlighting this small area with mid level lapse rates of 8.5 C/km, and is also better co- located with 850-700mb frontogenesis. The snow is progressing a bit quicker than forecast, so we have adjusted POPs through the morning to try and capture radar trends. Special Weather Statement is in effect until 9 AM CT to account for the accumulating snow, which is still expected to be a general 1 to 3 inches across the south central, but can't rule out locally higher amounts. Still expecting this snow to be done by early afternoon, with low chances for light snow existing across northwest and central parts of the state through this afternoon from a weak wave upstream. && .DISCUSSION... Issued at 413 AM CST Tue Mar 5 2024 Early this morning, a shortwave most pronounced at 700mb was moving through the Dakotas, with an attendant surface low analyzed in west central South Dakota. A somewhat narrow band of radar reflectivities continues on the northeast side of the low, generally moving northeast as the surface low continues to rotate. SDDOT cameras show falling snow is mainly limited to the area of highest reflectivity, with some occasional light snow in the lighter reflectivities on the northern extent of the system. Time of arrival tool puts the band of highest reflectivity at the North Dakota state line within the next hour or so (10 to 11 UTC). UNR estimated 1 to 2 inches of accumulation in the enhanced band which would line up well with overall expectations. CAMs are advertising a broad 1 to 3 inches of snow from Sioux County northeast through the James River Valley Counties. The question still remains how high snow totals could end up in isolated pockets, and where those places might be. As the previous shift noted, predictability of the higher amounts is low with this system, similar to how we can't pinpoint the exact location of heaviest convection during the warm season. Q vector convergence and steep lapse rates would support higher snowfall rates, although there is uncertainty on if and how long the more favorable features would line up. SPC mesoanalysis page is highlighting modest surface frontogenesis, and in the past hour or so has started showing at least marginal frontogenesis at various levels aloft, although not stacked very well. The residence time of heavier snow at any one location could end up being pretty short, with how progressive of a wave this is. However, still want to emphasize that there could be areas of locally higher amounts, if everything lines up perfectly. Radar trends and some of the latest high-res guidance has us thinking there could be a bit of a westward shift in snow accumulations. We did blend in RAP QPF amounts to increase snow totals slightly, mainly in Grant, Sioux, and southern Morton Counties. Precipitation chances end in the south central by early afternoon. Aside from this system, the northwest into central North Dakota has a general 20-30% chance of light snow today, with a weak impulse on the northwest side of the surface low seen by very light radar returns in eastern Montana. Any accumulations from this would be light, maybe a few tenths of an inch, but there's not much forcing with this part of the wave. Focus then turns late tonight into Wednesday which brings higher chances for snow across a larger portion of the forecast area, as a closed upper low tracks through the southern Canadian Prairies. There could be some banding potential with this system as well, with deterministic guidance highlighting a band of frontogenesis, although latest guidance has this mainly east of the forecast area. We will start messaging the potential for at least 2 inches of snow late tonight through Wednesday evening, which the 7 UTC NBM is showing as 40-70% across north central North Dakota into the northern James River Valley. This same area of higher 2" probs has low to medium (20-40%) chances for at least 4 inches of snow, and low probs for at least 6" (~10%). Higher odds exist east of the forecast area across northeast North Dakota. We continue our pattern of a modest temperature spread from north to south across the forecast area, with the added difficulty of how much snowpack remains and where, and how much that influences temperatures. Today through Thursday, the general expectation is for highs in the teens north to 30s south, with single digit overnight lows in the north. For the upcoming weekend into next week, ensemble guidance strongly favors upper ridging building in across the Northern Rockies, with NBM temperature percentiles advertising a strong warming trend into the start of next week. Blended guidance also shows low chances for precipitation with the warming temperatures, with no signs of strong winds or expansive cloud cover. It should be a nice stretch of weather for early March, but with continued varied temperatures from north to south. There is modest confidence for highs by Monday to range from the 40s north to 50s and potentially some lower 60s south. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 616 AM CST Tue Mar 5 2024 VFR to start the TAF period at all terminals except KBIS. An area of snow is moving through south central North Dakota, bringing MVFR to IFR ceilings and potentially visibilities in any areas of snow. KJMS also has a chance for snow later this morning, although impacts are expected to be lesser compared to at KBIS. Some lighter snow could also fall across northwest and north central North Dakota this afternoon. MVFR ceilings are expected to develop across much of western and parts of central North Dakota later today, expanding south through the afternoon and evening before chances for snow increase towards the end of the TAF period. Winds will be from the east, around 10 to 15 knots. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Jones DISCUSSION...Jones AVIATION...Jones