Severe Thunderstorm Warning 212, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
1218 PM CDT Wed Jul 18 2018

.UPDATE...
Issued at 1215 PM CDT Wed Jul 18 2018

Showers and thunderstorms have been slow to move north today.
Short-term models are indicating within the next two hours more
robust and widespread development should occur.

UPDATE Issued at 850 AM CDT Wed Jul 18 2018

Not many changes made for this update. Slight tweaks were made to
precip chances based on latest radar and short-term model trends.
Showers and thunderstorms will continue across southwest North
Dakota and should spread further north and east through the day.
Fog has dissipated across northwest North Dakota.

UPDATE Issued at 601 AM CDT Wed Jul 18 2018

Current radar observations show showers with a few embedded
weak thunderstorms across southwest North Dakota streaming in
from South Dakota. These showers and storms will continue through
the morning hours, while spreading further north and east.
Manually adjusted probability of precipitation across the
southwest to better match observations and expected short term
trends. Manually adjusted sky cover conditions as well based on
current satellite observations.

&&

.SHORT TERM...(Today and tonight)
Issued at 210 AM CDT Wed Jul 18 2018

Scattered showers and thunderstorms across western and central
North Dakota today and tonight.

An upper level low over eastern Montana will slowly track eastward
through the Dakotas today and tonight, with the center of the
closed low located over the North Dakota/South Dakota border. This
low will provide the region with broad synoptic scale lift within
a weakly sheared yet unstable environment. This will lead to the
continued chances for scattered showers and thunderstorms across
western and central North Dakota today and tonight. With 0 to 6 km
bulk shear values below 20 kts across the area and weak winds
aloft, slow moving air mass thunderstorms will be the most likely
storm mode. These storms are unlikely to become severe, however
locally heavy rainfall may pose a threat. South central North
Dakota appears to have the greatest risk for heavy rainfall, where
the 00z iterations of the NAM/GFS both suggest moderate to high
precipitable water values. In addition, the latest suite of CAM
model guidance is in good agreement in showing moderate to heavy
storms training over south central North Dakota today and tonight.

.LONG TERM...(Thursday through Tuesday)
Issued at 210 AM CDT Wed Jul 18 2018

More showers and thunderstorms across North Dakota Thursday
through Thursday night, drying out for Friday and Saturday.
Seasonable to below average temperatures highlight the long term
forecast.

The upper level low that will affect the area on Wednesday and
Wednesday night will continue to affect the area on Thursday and
Thursday night. As this low slowly moves eastward into Minnesota,
scattered showers and storms will develop on the backside of the
low and affect mainly central and eastern North Dakota on Thursday
and Thursday night, moving out of the state Friday morning. The
environment is slightly more favorable for a few stronger storms
across southern North Dakota on Thursday, where bulk shear values
are between 30 and 35 kts and collocated with a narrow region of
instability where MUCAPE values exceed 2000 J/kg.

A ridge builds in from the west on Friday and Saturday, bringing
calm and dry weather with it for all of western and central North
Dakota. The latest blend of model guidance suggests high
temperatures in the 70s and 80s this weekend, which agrees well
with ECME MOS guidance and forecast GFS BUFR soundings.

Thunderstorms return to North Dakota late Saturday night through
Sunday night as both the GFS and the ECMWF show a potent shortwave
trough with an associated surface cold front moving through the
state. This looks to be the next chance for severe weather across
western and central North Dakota, with moderate to high shear
expected along with moderate instability and good forcing for
ascent.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1215 PM CDT Wed Jul 18 2018

Expect VFR at all terminals through the TAF period. The main
concern will be the continued development of scattered showers
and thunderstorms through tonight. Gusty and erratic winds are
possible near thunderstorms, with locally heavy rainfall and
occasional lightning.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

UPDATE...AJ
SHORT TERM...TK
LONG TERM...TK
AVIATION...AJ

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