Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 210251

Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Thu Apr 20 2017

Issued at 951 PM CDT Thu Apr 20 2017

Forecast remains on track. Latest RAP run has backed off
considerably on fog coverage later tonight, much closer to HRRR
solution. Models still indicate good fog coverage across central
ND, but have backed off across the south. Light winds, clear skies
and recent rainfall across this area in particular should support
fog development overnight.

UPDATE Issued at 646 PM CDT Thu Apr 20 2017

No changes with the update other than to blend with latest obs.
Satellite imagery continues to show clearing from west to east.
Main concern for overnight will be fog development. RAP continues
to hit fog the hardest, while the latest HRRR has backed off
slightly southcentral, with most extensive coverage across the
southwest and James River valley.


.SHORT TERM...(This evening through Friday)
Issued at 302 PM CDT Thu Apr 20 2017

Mid/upper level synoptic pattern favors a brief omega type block
forming over western and central North Dakota through the short
term period. Although this will result in a dry forecast, prospects
of fog formation will increase tonight into Friday morning.

For the near term, through this afternoon and early evening, popcorn
type/isolated rain showers remain on track this afternoon south
central into the James River Valley with a tail end shortwave
trough shifting through south central ND. Sufficient low to mid
level lapse rates will result in isolated showers until sunset.

Latest water vapor shows a closed upper level low in northeastern
Minnesota and another shortwave in western Idaho which is forecast
to develop into a closed low as it traverses into Wyoming later
tonight into Friday. A brief omega block pattern evolves across
western and central North Dakota. Main concern will be radiational
fog/possibly dense, developing after midnight especially in
central and southern North Dakota. Subsidence aloft with a clearing
sky in the west this afternoon will expand into central ND
tonight. Expecting to see a gradual clearing from west to east
this evening, however clouds in central ND may inhibit or delay
fog formation until late tonight. Low level moisture remains with
southeasterly winds developing as surface high pressure builds
into the Turtle Mountains. High resolution models in combination
with the BUFKIT Hydrolapse/CrossOver Temperatures and Modified
Richardson Number all point to fog. Expecting areas of
fog/possibly dense after midnight into Friday morning with
overnight lows in the 30s.

For Friday after the morning fog, blocking high pressure results
in subsidence and mostly sunny conditions with highs in the 60s.

.LONG TERM...(Friday night through Thursday)
Issued at 302 PM CDT Thu Apr 20 2017

Mid/upper level high is shunted south Friday evening as northwest
flow with an embedded shortwave trough and associated cold front
move into northern North Dakota. This front then sags to the
southern ND border Saturday afternoon. A chance of rainshowers
resides mainly across the north Saturday as depicted by the
alignment of synoptic scale forcing and low level frontogenesis.
There could be a period of rain/snow mix Saturday morning across
the north. Very cool in the north with high temperatures 40s to
lower 60s south. Frontal boundary stalls in northern South Dakota
Saturday evening with a chance of showers developing north of the
front, into southern North Dakota. Thereafter the pattern remains
progressive with a series of systems mostly tracking from west to
east across South Dakota. The GFS and ECMWF are not as wet with
the initial system slated for Sunday night and Monday across
central and southern ND. Still a high chance of pops to likely
pops remain in the gridded data. Periodic chances for precipitation
continue Tuesday through Thursday but confidence for anything
significant and organized remains low at this time. Highs will be
in the 40s and 50s through the period.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 646 PM CDT Thu Apr 20 2017

Clouds continue to erode from west to east early this evening.
Expect fog development most areas overnight into Friday morning,
with IFR possible at most locations and LIFR currently in the
forecast from KDIK-KBIS-KJMS.




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