689
FXUS63 KBIS 170817
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
317 AM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms are possible across
  western into central North Dakota this evening and tonight.

- An active pattern continues through the week, with low to
  medium chances for showers and thunderstorms most days.

- Temperatures will trend cooler through the week, after today,
  with forecast highs in the 60s to lower 70s by this weekend.

&&

.DISCUSSION...
Issued at 317 AM CDT Tue Sep 17 2024

This morning, the synoptic pattern was dominated by a deep upper
low over Nevada, with southwest flow aloft across the Dakotas.
At the surface, a low was analyzed in southeast Montana, with a
stationary front extending east from the center of the low
across North Dakota. Some isolated convection was ongoing just
north of the surface low, moving north.

Although there are still some high clouds left over from evening
convection, nighttime satellite imagery is showing the edge of a
low stratus deck that extends across much of northern North
Dakota, expanding into the northwest. There are some reduced
visibilities being reported underneath this stratus, although it
does seem to be a bit isolated for the moment, with NDDOT
cameras in these areas showing clear conditions. Regardless,
will be something to keep an eye on into the morning.

Southeasterly low-level flow will continue today on the east
side of the surface low, leading to another warm, humid day for
mid September. Forecast highs range from the lower 80s to lower
90s across western and central North Dakota, and dew points will
be mainly in the 60s.

Precipitation chances ramp up this evening into the overnight
hours as a secondary front from the surface low pushes northeast
across the forecast area, with falling heights spreading across
the area as the upper low approaches. Organized storms will be
possible across eastern Montana into western North Dakota, with
high-res guidance pretty consistent in convection developing in
Montana late this afternoon before moving into North Dakota this
evening. A moderate axis of instability is progged to be in
place from the warm and humid airmass, as the 00 UTC HREF shows
a plume of 1500-2500 J/kg of MUCAPE across northwest into
central North Dakota, along and ahead of the warm front lifting
north. 0-6km shear will be very marginal until the main upper
forcing gets closer, staying around 20-30 knots before
increasing to around 40 knots tonight. A low-level jet is
expected which will likely keep convection going through the
night as the entire system progresses east, and the latest NBM
PoPs do keep a 30-50% chance of showers and thunderstorms across
much of the forecast area through the night, with the highest
chances in the northwest. With not the most favorable overlap of
environmental parameters, and some uncertainty in storm mode,
will keep messaging of wind gusts up to 60 mph and hail up to
the size of half dollars. The most likely timing of any severe
storms in western North Dakota is after sunset.

The active pattern continues through the rest of the work week
as general troughing persists across the western CONUS, keeping
us under broad southwest flow aloft. Blended PoPs keep near-
daily low to medium chances for showers and thunderstorms across
the area through the end of the extended period. Cooler air
will be allowed to filter in across the region, with NBM
temperature probabilities continuing to show a cooling trend
into the weekend. Expect highs to be much closer to normal this
weekend heading into the next work week, generally in the lower
60s to lower 70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1237 AM CDT Tue Sep 17 2024

Thunderstorms are about out of north central North Dakota, with
precipitation chances low for the rest of the night. Later tonight
low status is expected to move into north central and parts of
northwest North Dakota, leading to areas of IFR ceilings through
late Tuesday morning. By Tuesday afternoon, VFR conditions are
expected across the area. Chances for showers and thunderstorms
return to western North Dakota late in the TAF period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Jones
AVIATION...Jones