Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 232351

Area Forecast Discussion
National Weather Service Bismarck ND
651 PM CDT Fri Aug 23 2019

Issued at 640 PM CDT Fri Aug 23 2019

Main update for this evening was to try and fine tune POPs a bit
based on latest guidance and regional radar. Storms trying to
intensify over the northwest along the instability axis. Weak mid
level lapse rates and shear acting to suppress severe convection
at this time. Better mid level forcing arrives this evening as
embedded waves lift north-northeast across western/north central
North Dakota. Shear will remain weak at around 20KTs though
instability high so perhaps a few stronger pulse-type storms to
monitor this evening.


.SHORT TERM...(This evening through Saturday)
Issued at 328 PM CDT Fri Aug 23 2019

The chance for scattered strong to severe thunderstorms highlights
the short term forecast.

The active pattern continues as a slow-moving, potent trough
aloft digs into southern Montana, while at the surface a frontal
boundary is draped across north-central and northeast Montana. As
the trough progresses eastward, scattered showers and
thunderstorms are expected to develop in southeast Montana and the
western Dakotas later this afternoon and into the evening. One of
the main factors regarding development will be sky clearing and
associated destabilization, with a low cloud deck still solidly in
place in southwest ND / northwest SD. Temperatures in this area
are currently only in the mid 70s, compared to the upper 70s and
low 80s in western ND along the Montana border. Some convection is
possible in the next few hours along this differential heating
boundary. The latest model guidance shows a narrow corridor of
instability in southwestern ND, with CAPE values of over 2000
J/kg. Shear remains the main parameter that could really limit the
severe threat, with deep layer shear only around 20-25 knots.
However, 0-1 km shear and 0-3 km SRH are both relatively high in
central, so shallow storms might be able to become well-
structured if they find a good overlap of instability and the low
level shear. As storms move north out of the more favorable
environment, the chance for them to be severe should quickly
lessen. Expecting the main threat to come later this evening with
development beginning to our southwest and eventually moving into
our forecast area.

Overnight, storms should weaken and diminish in area as
instability decreases. As temperatures warm back up to the upper
70s to mid 80s on Saturday, the chance of widespread showers and
thunderstorms returns, with an overall environmental setup similar
to today. The severe threat will again be somewhat conditional on
how much cloud cover remains in place from tonight`s precipitation
and how that limits destabilization for tomorrow afternoon and

PWATs continue to be very high, so heavy rainfall is certainly a
threat with these storms, especially with weak mid-level flow
producing slow storm motion. Minot already received an inch of
rain today from a slow-moving thunderstorm, so similar and higher
precipitation amounts are possible throughout the short term.

.LONG TERM...(Saturday night through Friday)
Issued at 328 PM CDT Fri Aug 23 2019

Multiple chances for showers and thunderstorms before cooling down
next week highlights the extended forecast.

A strong ridge is expected to build over the Midwest and northern
CONUS through the weekend, with multiple shortwaves moving
through and scattered showers and thunderstorms possible through
most of the extended forecast. The best chance for widespread
precipitation is Sunday as model guidance shows a surface low
passing through North Dakota. After this, a persistent cool
weather pattern will settle in, with a strong upper-level low
over central Canada that will bring continuous northwest flow to
the Northern Plains. The work week will see temperatures in the
60s and low 70s with periodic chances for rain showers.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)

Issued at 640 PM CDT Fri Aug 23 2019

Scattered showers and thunderstorms are possible throughout
western and central North Dakota through the 00Z TAF period. Low
VFR clouds persist across a good portion of the local area, though
also with pockets of SKC. Cloud cover a tricky forecast this
period. Would expect clouds to continue over much of the forecast
area and will likely stay through tomorrow, with ceilings dropping
to MVFR at times. Ceilings and visibilities may also drop with
any rain showers or thunderstorms. Southeasterly winds sustained
at 10-15 knots will continue through tonight, shifting to more
southerly tomorrow.




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