Area Forecast Discussion
Issued by NWS Bismarck, ND

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KBIS 250247

National Weather Service Bismarck ND
947 PM CDT TUE MAY 24 2016

Issued at 947 PM CDT Tue May 24 2016

The forecast message is generally on track, but we did go ahead
and increase the spatial extent of PoPs greater than 60 percent
late tonight over western and south central ND. That is based on
recent radar trends that show showers and storms increasing and
gradually spreading northeast out of western and central SD, and
indications of a bit stronger batch of vertical motion that will
move out of southeast MT and into western ND overnight. Surface
analyses have revealed increasing dewpoints over much of southern
ND and central and eastern SD this evening, which is reflective
of the increasing low-level moisture content that will help drive
a chance of thunderstorms tonight and Wednesday, as well.

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

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 947 PM CDT Tue May 24 2016

Coverage of showers and thunderstorms will increase overnight and
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 any 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 tonight and Wednesday.


.BIS Watches/Warnings/Advisories...


AVIATION...CJS is the U.S. government's official web portal to all federal, state and local government web resources and services.