490
FXUS63 KFGF 132347
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
647 PM CDT Tue Aug 13 2024

.KEY MESSAGES...

-Showers and thunderstorms are likely late Wednesday into
 Thursday, with lightning and locally heavy rainfall being the
 main impacts.

&&

.UPDATE...
Issued at 641 PM CDT Tue Aug 13 2024

A few thunderstorms have developed along I-94 in central North
Dakota and are tracking east. High uncertainty plagues these
thunderstorms as they progress eastward as there is low
confidence in continued forcing and instability in southeast
North Dakota later this evening. Observations indicate these
thunderstorms are dropping pretty hefty rainfall rates of 4+
inches per hour, but the forward propagation has been enough to
offset potential flash flood impacts. There is high confidence
in a low-level jet setting up away from our CWA to the west, so
this lends to a lower probability for thunderstorms to make it
to southeast North Dakota. In any case, flash flooding may arise
this evening if storms can survive long enough to make it to
southeast ND.


&&

.DISCUSSION...
Issued at 315 PM CDT Tue Aug 13 2024

...Synopsis...

Low pressure system continues to develop over eastern Montana this
afternoon, with preceding showers moving through North Dakota.
Strong moisture return ahead of the low pressure and warm air
advection will continue to translate eastward as we progress into
Wednesday and Thursday. Current Satellite shows an expansive area of
cumulus development that is diurnally driven. This should diminish
and help increase ceilings later this evening and into the overnight
period. Hazy conditions will be possible today and into Wednesday as
high level smoke from the western United States shifts eastward
across the area. General flow aloft will be zonal through the rest
of the week bringing chances for shortwaves to shift through the
region. After the work week, we start to see a slow shift in the
pattern flow as ridge begins to intensify in the southwestern and
western United States.

...Showers and thunderstorms Wednesday through Thursday...

Our next chance for precipitation comes Wednesday into Thursday as
the low pressure over Montana translates eastward into North Dakota
and Minnesota. As this happens, warm air advection surges into
eastern North Dakota and northwestern Minnesota along with moisture.
PWATS reach up into the 1.5 to 2 inch range. An axis of strong theta-
E sets up in central North Dakota and into portions of the Devils
Lake Basin and Sheyenne River Valley. This is where we suspect a
boundary to become stationary Wednesday and in Thursday.
Thunderstorms develop along this boundary and the probability of
seeing locally heavy rainfall exists along said boundary. This would
be due to back building and training thunderstorms. Locally heavy
rainfall of 1.5 inches or higher will be possible (20-30% chance)
within the Devils Lake Basin through the Sheyenne River Valley
Wednesday through Thursday. There is a conditional threat for severe
thunderstorms Wednesday afternoon, but environmental parameters of
shear and instability are weak across the western Devils Lake Basin
through the Sheyenne River Valley. None the less, there is a chance
for stronger storms over those areas Wednesday afternoon, with small
hail and brief gusty winds being the main impacts.

Rain will gradually shift eastward Wednesday night and into
Thursday. The low pressure system becomes very progressive in its
movement toward the Great Lakes Thursday afternoon and Friday, but
lingering showers and isolated thunderstorms will still be possible
across the region. Our best chances for dry conditions will be over
the weekend as the system moves east of the area and ridging
develops out west bringing northwesterly flow. Further precipitation
chances are possible next week, but confidence is low at this time.
Temperatures will be seasonal over the next several days, with highs
in the upper 70s to lower 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 641 PM CDT Tue Aug 13 2024

The primary aviation impacts for the TAF period will be
the potential for lightning. Showers and storms may impact FAR
later this evening, mainly after 06z, but the probability is too
low to add to the TAF. Thunderstorms will arrive from west to
east, mainly after 18z, with falling ceilings to MVFR. There is
also a signal for potentially IFR ceilings in southeast North
Dakota, including FAR. These will continue for the remainder of
the TAF period.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...Perroux
DISCUSSION...Spender
AVIATION...Perroux