Area Forecast Discussion
Issued by NWS Bismarck, ND

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519
FXUS63 KBIS 142021
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
321 PM CDT Mon Aug 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 322 PM CDT Mon Aug 14 2017

Main forecast issue in the short term period will be precipitation
chances and thunderstorm risk tonight and Tuesday.

Deterministic global models have been fairly consistent the last
few runs regarding the precipitation timing and placement. The
overall trend has been slightly slow with the onset coming into
the west this afternoon, with a lower threat of thunder, and thus
severe weather.

The latest satellite imagery indicates an upper level trough
extending from western Canada into California with a series of
impulses tracking through Montana into Idaho and northern Wyoming.
The strongest dynamic forcing this afternoon and this evening will
lift from eastern Montana into southeast Saskatchewan, but
instability and bulk shear are weak in this area, and into
northwest ND. Cape and shear are greater over the northern high
plains around 21-06Z but the greatest instability remains well
south of southwest ND. There is some quite weak CAPE to around 500
J/KG that pushes into southeast MT around 00 UTC with bulk shear
to around 25 to 40 kts, so a few storms could approach the
southwest around this time, with a marginal threat of reaching
severe levels. Certainly not enough to add severe wording in the
gridded forecast. As we go through the night, precipitation
chances increase across the west with the threat of thunder mainly
limited to the southwest quarter.

On Tuesday, synoptic scale forcing and frontogenetical forcing
swing through central and eastern ND bringing scattered to
numerous showers and isolated thunderstorms to the area. The
greatest instability remains south of the forecast area so the
severe threat appears limited. The far southern tier counties of
the southwest and south central, and the far western tier counties
appear to be the only areas where a limited severe threat would
exist. Limited surface heating with cloudy skies and forecast
highs in the upper 60s to mid 70s will limit the severe potential
Tuesday but isolated thunder is possible across the forecast
area.

.LONG TERM...(Tuesday night through Monday)
Issued at 322 PM CDT Mon Aug 14 2017

Warmer and drier weather expected in the long term period

Widespread precipitation exits the eastern forecast area Tuesday
night. Thereafter, upper level ridging tries to become more
established over the region. Generally, Wednesday and Thursday
appear dry. A shortwave trough drops through the area on Thursday
night and Friday bringing a chance of showers and thunderstorms
northwest to southeast across the forecast area. Then another
chance of storms Sunday. After highs in the 70s Wednesday, daytime
highs are expected to be mainly in the low to mid 80s Thursday
through Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 322 PM CDT Mon Aug 14 2017

Low clouds from the Missouri River Valley near KBIS through the
James River valley (KJMS) to start the TAF valid period. MVFR
ceilings will burn off between now and 1830Z with latest satellite
imagery showing stratus thinning rapidly. VFR weather today and
tonight but with scattered showers and thunderstorms KISN-KDIK
today, and across the area tonight. At this time severe storms are
not in the forecast for today or for tonight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...TWH
LONG TERM...TWH
AVIATION...NH



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