Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 252028

Area Forecast Discussion
National Weather Service Bismarck ND
328 PM CDT Tue Apr 25 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 328 PM CDT Tue Apr 25 2017

Weather concern is for a potential mesoscale banding of snow
setting up across the far southern James River Valley late tonight
through Wednesday. Per Oakes NAM/RAP13 Oakes BUFKIT sounding, even
without mesoscale banding, there is enough large scale ascent/omega
occurring within the dendritic growth zone (-12c to -20C) along
with steep mid level (700mb-600mb) lapse rates to produce
snowfall amounts of between 2 and 4 inches tonight through
Wednesday afternoon. This covers central/eastern LaMoure and
Dickey counties, with some potential to extend a bit farther west
into Logan and McIntosh counties per RAP13.

Collaborated with WPC and surrounding offices, and the overall
assessment is that the NAM12 holds merit with regards to large
scale forcing/ascent, but mesoscale processes associated with the
high qpf/snowfall has enough uncertainty at this time to question
its validity. Thus confidence is low at this time for heavy
snowfall. The banding of snow, if it does setup, would not do so
until 3 to 6hr prior to the event, so a close monitoring with
later tonight into Wednesday for any indications of mesoscale
banding is the best course of action at this time.

Confidence is higher with the 2 to 4 inch range in the southern
James River Valley, as the experimental HRRR/GFS20/ECMWF/SREF are
more in line with WPC snowfall amounts.

Latest suite of satellite imagery shows a mid/upper level closed
low circulating over eastern Wyoming. This is forecast to slide
and transfer east into western and central Minnesota Wednesday.
With the 500mb low lingering over the far southern James River
Valley Wednesday along with a 60kt jet streak, precipitation is
expected to continue for most of the day Wednesday before tapering
off in the evening. The 12Z NAM12 holds this jet through most of
the day, while the GFS shifts it east after 12z Wednesday.

Rest of forecast area is dry and cold with sky conditions improving
from mostly cloudy to mostly sunny, from west to east in the
afternoon. Highs will range from the upper 30s Turtle Mountains
south into the James River Valley to the 40s elsewhere.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 328 PM CDT Tue Apr 25 2017

Overall a dry and cool pattern continues initially (through
Friday), with temperatures moderating into the 50s Saturday
through Tuesday. The storm track remains with the southern jet
stream which remains south of North Dakota. Other than a weak
frontal passage Saturday with a chance of pops northwest, expect a
fairly tranquil pattern through Sunday. Monday and Tuesday the
pattern looks to become active again as the northern stream eventually
pushes a cold front through by the end of the extended period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 328 PM CDT Tue Apr 25 2017

Mvfr cigs will improve to vfr at KMOT/KISN through 00z Wednesday;
otherwise rest of the terminals remain in mvfr status until 12z
Wednesday, except KJMS will fluctuates between mvfr/ifr through
the entire period. Gusty north-northeasterly winds of 15kt to
25kt expected through 00z Wednesday, but forecast to continue at
KJMS through the taf period.




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