Area Forecast Discussion
Issued by NWS Bismarck, ND

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865
FXUS63 KBIS 232024
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
324 PM CDT THU JUN 23 2016

.SHORT TERM...(This evening through Friday night)
Issued at 325 PM CDT Thu Jun 23 2016

The surface high currently over eastern North Dakota will shift
eastward into Minnesota tonight with return low level flow
continuing across eastern Montana and much of North Dakota. The
setup for elevated thunderstorms begins this evening. A low level
jet develops this evening across the western plains - from Texas/New
Mexico northward through the western Dakotas/Montana into
Saskatchewan. The upper level low over the Pacific Northwest tonight
begins moving towards the Rockies...and upstream southwest flow
aloft across the Rockies and into the Front Range becomes well
established. The leading edge of upper level energy impulses in the
southwest flow aloft is progged to approach the western Dakotas late
this evening/after midnight. Plenty of elevated CAPE with values of
up to 1500-2000 J/Kg and 0-6km bulk shear values of 40-50 knots
along the nose of the strengthening low level jet will allow
elevated convection - mainly around/after midnight in the southwest
and over all of the west before daybreak. Some storms could be on
the stronger side, but at this time we are not expecting any
widespread severe storm risk.

The low level jet and coincident upper level impulses shift east
into the central and eastern Dakotas around daybreak Friday. Thus
the central - and especially north central part of North Dakota are
favored for thunderstorms before noon.

Meanwhile the building mid-level thermal ridge builds quickly behind
the low level jet/upper level impulse feature, with H700
temperatures of +12C to +14C. This should inhibit convection in the
west and south central during the afternoon on Friday. However, a
lifting surface warm front and increased dewpoints north central and
eastern North Dakota - coincident with the continued development of
the low level jet well northward from the eastern half of the
Dakotas into Manitoba, will quickly increase the instability. By
early/mid afternoon the surface low should be located over the north
central part of the state, with increasing CAPE to 3000-4500 J/Kg
over the eastern half of the state. The north central (and areas to
the north and east) - will perhaps be just far enough away from the
convection-inhibiting mid-level thermal cap - and would be favored
for any afternoon thunderstorm development.

Friday night attention then turns to our west. The approaching upper
level low moves east across Montana Friday night...reaching the
northeast Montana/Saskatchewan border by daybreak Saturday. Plenty
of upper level energy impulses, combined with very strong 0-6Km bulk
shear of 50-70 knots associated with the strong upper low, will
allow for widespread thunderstorms - especially late Friday evening
and overnight. CAPE increases quickly during the evening in the
western part of the state, along and ahead of the associated cold
front.

Friday evening we are expecting thunderstorms to develop over
western North Dakota during the early/mid evening...and spread
eastward into central North Dakota mainly after midnight Friday
night. Strong to severe storms are possible, with the best
possibility for severe storms along and north of I-94.

.LONG TERM...(Saturday through Thursday)
Issued at 325 PM CDT Thu Jun 23 2016

The weekend weather will be cooler and windy, but dry across most
of western and central ND.

The 00 and 12 UTC GFS, NAM, and ECMWF are in agreement showing a
deep 500 MB low moving through south central Canada Saturday. This
will leave the area in a cooler post-frontal air mass. Gusty west
winds are expected thanks to a well-mixed boundary layer with cold
air advection driving momentum transfer. Forecast soundings taken
across western ND on Saturday reveal mixing to 700 MB with maximum
wind speeds in that layer around 45 kt, supporting gusts to around
45 mph. A wind advisory will likely be needed Saturday in western
ND. The main uncertainty appears to be how far east advisory-type
gusts of 45+ mph extend, as the 12 UTC GFS supports them all the
way to Minot and Bismarck, while the 12 UTC NAM keeps the core of
strongest winds further west. Sunday will remain windy, but peak
speeds will be less, likely around 30 mph, as the low- and mid-
level pressure and height gradients slowly relax.

The chance of showers and thunderstorms this weekend is expected
to be relegated to northwest and north central ND, mainly along
and north of Highway 2, where cyclonic flow will be sharpest. The
12 UTC 4 km NAM-Nest even suggests a strong storm is possible due
to the cold temperatures aloft and strong deep-layer winds during
the afternoon hours Saturday, but in general no organized strong
storms are expected this weekend.

Heading into next week, a mean western ridge and eastern trough
will keep zonal or northwesterly flow across North Dakota. Some
shower and thunderstorm chances are possible Tuesday and
Wednesday, but only going with low chances due to uncertainty that
far out in the forecast period.


&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu Jun 23 2016

A cumulus cloud shield had moved northward from central South
Dakota,and added a scattered deck at around 4000 feet to KBIS for
the afternoon. Otherwise, VFR conditions expected through the
evening with high pressure over eastern North Dakota moving east and
southerly/southeasterly winds becoming dominant. Late tonight there
is a chance of elevated convection moving in from the southwest. The
best chance of precip is Friday morning after 15z in KMOT. However,
later TAF issuances may need to bring a chance of mid cloud based
thunder into other TAF sites. Better chances of strong to severe
thunderstorms is Friday afternoon at KMOT, and all TAF sites after
00z Saturday.


&&

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

$$

SHORT TERM...JV
LONG TERM...CJS
AVIATION...JV



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