Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 242353
AFDBIS

AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
653 PM CDT TUE MAY 24 2016

.UPDATE...
Issued at 653 PM CDT Tue May 24 2016

No significant changes were made with this update, though we did
blend observational and recent rapid-refresh model guidance into
hourly forecast fields through late tonight. Updrafts have become
deep enough to produce lightning in southwestern ND over the last
60 minutes, so we expanded the lightning mention a bit during the
evening hours. Otherwise, the convection blossoming in southwest
SD as of 2345 UTC will eventually move into ND with the shortwave
trough driving it overnight. Later updates may need to increase
the extent of likely PoPs after 06 UTC given recent radar trends.

UPDATE Issued at 517 PM CDT Tue May 24 2016

Quick update to expand/move up the chance of showers over western
ND from now through the early evening in response to the showers
developing out of the cumulus field in southwestern ND through 22
UTC. We have a slight chance of thunderstorms expanding northward
with time, too, but so far the dry boundary layer is tending to
minimize instability, updraft depth, and thus lightning chances.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 240 PM CDT Tue May 24 2016

Thunderstorm chances highlight the short term.

An upper level low currently located over southern Saskatchewan
will keep the region in southwest cyclonic flow. Most of western
and central North Dakota will remain dry through the afternoon,
but precipitation chances will increase through the late afternoon
and evening hours from west to east as a surface trough and
associated upper level short wave approaches from Montana.

Tonight, showers and some thunderstorms will develop in the
southwest and spread east overnight. Any thunderstorms that
develop will remain sub severe with modest CAPE and shear
forecast.

Wednesday, a more potent shortwave and surface low will approach
the Dakotas as the upper low approaches, bringing widespread rain
and scattered thunderstorms. The 12z NAM and GFS iterations show
more instability than previously forecast. If these solutions were
to verify, potentially anywhere from 1000 J/KG to 2500 J/KG of
MLCAPE will be in place by 21z, along a line from near Bismarck to
Jamestown and south to the state border. This instability will be
collocated with deep layer shear values of 25-35 knots. These
parameters would suggest a conditional severe weather threat in
south central and southeast North Dakota. However, quite a bit of
uncertainty remains about how much destabilization will actually
occur. Widespread precipitation is likely over the area early
Wednesday, potentially limiting daytime heating. If we can get
some breaks in the clouds, then some storms could produce some
marginally severe hail and winds. SPC has placed parts of south
central and southeastern North Dakota in a marginal risk of severe
weather, which matches up well with our current thinking. Clusters
of multicell or marginal supercell structures seem to be the most
likely storm modes.

Overnight Wednesday, rain chances will continue on the back side
of the surface low.

.LONG TERM...(Thursday through Tuesday)
Issued at 240 PM CDT Tue May 24 2016

Persistant southwesterly flow remains through the period with a
variety of short waves sliding through the area. Models are having
a tough time timing out the individual waves, so most periods will
have a broad-brushed chance for showers and thunderstorms.
Temperatures will remain near to slightly above average.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 653 PM CDT Tue May 24 2016

Coverage of showers and thunderstorms will increase overnight and
especially during the day Wednesday across western and central ND.
Most of the 00 UTC TAFs included prevailing showers and a lengthy
period of VCTS given the expected widespread coverage of that
activity and low confidence in timing of longer-lived breaks in
precipitation. MVFR ceilings are forecast over western ND late
tonight and Wednesday, with local IFR ceilings possible. Heavier
showers and storms may produce local MVFR conditions area-wide.

&&

.BIS Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...CJS
SHORT TERM...ZH
LONG TERM...JJS
AVIATION...CJS



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