120
FXUS63 KBIS 171749
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1249 PM 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 lower 60s to lower 70s by this
  weekend.

&&

.UPDATE...
Issued at 1248 PM CDT Tue Sep 17 2024

The fog across the north has completely dissipated, with a
residual bank of low stratus lingering around across the north
central. Winds have been a bit slow to increase across most of
the area, so the main adjustment was just slightly tweaking the
wind speeds, as well as some cloud coverage adjustments. We`ve
been looking into the potential for fog tonight once again, but
confidence remains relatively low given that the winds across
the area will be a bit stronger overnight than it was the
previous night. It will be something to keep an eye on
throughout the rest of the day. Otherwise, the forecast remains
on track.

.UPDATE...
Issued at 1108 AM CDT Tue Sep 17 2024

Just a quick update to add that we have cancelled the Dense Fog
Advisory, as visibilities have improved across the area.

.UPDATE...
Issued at 942 AM CDT Tue Sep 17 2024

Patchy dense fog continues to linger across the northwest, with
some areas still not seeing any improvement in visibilities. NDDOT
webcams also indicate plenty of dense fog in that area. As a
result, we`ve extended the Dense Fog Advisory until noon CDT.
Otherwise, the forecast remains on track, with low stratus still
present in the north, clear skies in the south, and continued
light winds across the entire area. Winds are still forecast to
increase with continued surface heating through the day.

.UPDATE...
Issued at 642 AM CDT Tue Sep 17 2024

Dense fog and low stratus extends from Crosby, to Maxbass, to
Minot, to Hazen, covering most of the area across northern North
Dakota. The expectation, from the general pattern and from
high-res guidance, is for gradual improvement through the
morning, although low clouds could linger in far northern North
Dakota into the afternoon. Dense Fog Advisory is in effect until
10 AM CDT. Made some minor adjustments to PoPs and sky cover
with this update, otherwise going forecast looks good for most
of the day, before we get to more severe weather potential.

.UPDATE...
Issued at 439 AM CDT Tue Sep 17 2024

Update for the issuance of a Dense Fog Advisory for northwest
and portions of central North Dakota. Many locations under the
low stratus deck are reporting visibilities of one quarter mile
or less, with NDDOT webcams adding to the certainty of areas of
dense fog.

&&

.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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1248 PM CDT Tue Sep 17 2024

VFR conditions are present across all terminals with the
exception of KMOT, which is currently stuck under an LIFR
stratus deck for the next 2 to 3 hours. Southeasterly winds are
forecast to increase throughout the day, with sustained wind
speeds near 15 kts, and occasional gusts up to 25 kts. Winds may
taper off a bit overnight, but will remain somewhat elevated in
speed, before increasing once more again on Thursday. A frontal
boundary moving through the state from south to north late this
evening and into the overnight hours may bring about some
showers and thunderstorms, with the greatest chances at KDIK
from 04z to 09z, and at KXWA from 07z to 12z.

&&

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

&&

$$

UPDATE...Besson
DISCUSSION...Jones
AVIATION...Besson