Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 240553
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1253 AM CDT FRI JUN 24 2016

.UPDATE...
Issued at 1253 AM CDT Fri Jun 24 2016

No major changes with the update other than to blend with latest
hourly obs and minor adjustments to pops. Elevated convection was
ongoing across southeast Montana and northwest South Dakota where
MUCAPE of 1000 J/KG and 50kts of 0-6km bulk shear was in place.
Less favorable condtions across southwest ND and storms have
weakened somewhat the last 30 minutes. Guidance indicates this
band of elevated instability shifting into ND, so current forecast
with increasing pops moving into southwest part of the state looks
reasonable. Will also continue to monitor convection over
northeast Montana, which high res models bring toward northwest ND
late tonight.

UPDATE Issued at 923 PM CDT Thu Jun 23 2016

Little change with this forecast update other than to blend to
observed trends through 02 UTC. The 18-01 UTC CAMs continue to
suggest isolated to scattered elevated convection late tonight
across western North Dakota, possibly continuing north central
Friday morning. See the 645 pm CDT update for threats.

UPDATE Issued at 645 PM CDT Thu Jun 23 2016

The main challenge for tonight will be the coverage and strength
of overnight, elevated convection across western North Dakota. The
21-22 UTC RAP iterations suggest around 1500 j/kg of CAPE from
850 mb associated with the warm front across southeast Montana and
western South Dakota early this evening that will propagate
northeast into western North Dakota through the night. Increasing
low level moisture with the low level jet and a few mid level
impulses support the potential for elevated convection. Effective
deep layer shear will be marginal for organized convection.
However, a few storms could be strong to possibly severe with hail
and damaging winds being the primary threats.

&&

.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 06Z TAFS through 06Z Friday night)
Issued at 1253 AM CDT Fri Jun 24 2016

A vcts is possible at KDIK/KISN mainly between 08z-12z Friday.
Otherwise threat for thunderstorms may increase at KMOT after 19z
Friday, although enough uncertainty to hold off any mention of
timing at this point. A cold front will impinge into the western
terminals between 03z-06z Saturday with an area of showers and
thunderstorms expected, which will shift into central North
Dakota Friday night, possibly severe.

&&

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

$$

UPDATE...JNS
SHORT TERM...JV
LONG TERM...CJS
AVIATION...KS



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