Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 270452
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1152 PM CDT TUE JUL 26 2016

.UPDATE...
Issued at 1152 PM CDT Tue Jul 26 2016

Latest water vapor imagery shows a shortwave through now into the
James River Valley and resultant showers/thunderstorms fro
Stutsman county south into LaMoure and Dickey counties late this
evening. Following the Experimental HRRR which is verifying the
best, this area of precipitation will exit between 06z-08z.
Current forecast has this depicted well. The next upstream shortwave
was seen over north central Montana, near Great Falls. This is
forecast to ever so slowly shift east, as it closes off in the
mid and upper levels per 00z NAM/00z GFS. The HRRR shifts an area
of showers/thunderstorms which is now west of Glasgow, into
northwest ND around 12z Wednesday. Due to the slow movement of the
low, precipitation will favor the west Wednesday with drier
conditions central. Areas of stratus/fog still indicated on the
HRRR/Rap13 overnight, especially from Dickinson to Bismarck. No
significant changes to the current forecast.

UPDATE Issued at 901 PM CDT Tue Jul 26 2016

Scattered convection continues across central North Dakota through
02 UTC resulting from multiple outflow boundary interactions
further influenced by a slowly propagating upper level low. With
the approach of sunset, convective intensity has decreased with
heavy rain continuing to be the primary threat with precipitable
water values near 1.60 inches and continued slow storm motions.
Trends in the 23-01 HRRR/HRRRX suggest convection will decrease
across the James River Valley around 05-06 UTC.

UPDATE Issued at 536 PM CDT Tue Jul 26 2016

Heavy rainfall is expected to be the main threat with
thunderstorms this evening across the south central and James
River Valley along a boundary over the Cannonball River northeast
into the upper James River Valley. The 23 UTC RAP analysis depicts
precipitable water values around 1.50 inches with rather slow
Corfidi vectors of 15-20 kts, and tall/skinny CAPE profiles. This
all points to heavy rainfall as the primary threat, which has
been the trend thus far today. Will have to closely watch McIntosh
and Dickey counties through the evening for flood potential in the
wake of heavy rainfall earlier today. Finally, did add a mention
of fog across the south central and southwest tonight with high
moisture in place and weak upslope flow.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 325 PM CDT Tue Jul 26 2016

The main forecast issue in the short term period will be
thunderstorm chances and the potential for severe storms.

Currently, low pressure is situated over north central South
Dakota with high pressure over Saskatchewan and nosing into
northwest North Dakota. In the mid and upper levels northern
portions of the forecast area are within the right entrance region
of a strong upper level jet situated over southern Manitoba and
Ontario. Numerous impulses also continue to track across the
Rockies and into the northern plains within a quasi-zonal upper
level flow. Thus we remain slightly to moderately unstable across
the forecast area. Meager low level lapse rates over areas of
morning convection and low mid level lapse rates and lack of bulk
shear across the north are the limiting factors. An axis of high
pwats extends from south central into northwest ND so any storms
that do develop will have the potential to produce very heavy
rainfall. And a severe storm can not be completely ruled out
either.

Short term models are not completely out of line but are having a
hard time pinpointing convection this afternoon. Will likely
utilize a blend of short term models with current forecast pops to
depict isolated to scattered convection across the north and over
the south central this afternoon with overall trend in convection
sliding south. Medium range models as well as short term models
are pointing to convection tonight along the ND/SD border and
southward as a couple of shortwaves move across the northern
rockies and into the plains. Thus have trended pops down across
the north this evening, and higher across the far south central
into the James River Valley from mid to late evening.

Late tonight and through Wednesday surface high pressure builds
over the eastern Dakotas which pushes the instability axis sitting
along the ND/SD border, west into the western dakotas and eastern
Montana. Shower and thunderstorm activity will be suppressed to
only western ND. Highs are expected to be mainly in the 70s.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 325 PM CDT Tue Jul 26 2016

Wednesday night through Friday, surface high pressure moves
slowly east across the forecast area with building upper level
ridging over the region downstream of a digging upper trough
moving onto the British Columbia coast. This will keep shower and
thunderstorm activity mostly confined to western ND. Morning lows
will be in the mid 50s to lower 60s with daytime highs in the mid
70s to mid 80s.

Upper ridging remains over the area through the weekend but upper
flow backs and thermal ridging pushes into western ND. Daytime
highs will climb back into the 80s to lower 90s with increasing
humidity as low level flow turns southerly ahead of lee side
troughing in the northern rockies. We likely become unstable each
afternoon but probably with some capping issues. Overnight
convection can not be ruled out either. But in general, with
upper ridging still over the area, our current slight chance pops
look reasonable for now.

Late Sunday night through monday, the upper low to our north
pushes a cold front through the area, with another upper trough
trailing the first, providing a chance of thunderstorms into
Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1152 PM CDT Tue Jul 26 2016

Areas of stratus and fog expected to develop 09z-14z Wednesday
from KDIK to KBIS. Expecting ifr cigs at both terminals, along
with mvfr vsbys at KBIS and lifr vsbys at KDIK. A return to vfr
cigs/vsbys will occur by 15z. Elsewhere, vfr conditions expected.
An area of showers/thunderstorms will move into KISN around 12z-
13z Wednesday, and may continue through the afternoon and
evening.

&&

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

$$

UPDATE...KS
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...KS


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