016
FXUS63 KBIS 031221
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
621 AM CST Sun Nov 3 2024

.KEY MESSAGES...

- High chances (70 to 90 percent) for rain across the eastern
  half of the state late this morning through this evening.
  Rain chances decrease to very low (20 percent or less) across
  far western North Dakota.

- There is a low chance of thunderstorms in far south central
  and southeast North Dakota this afternoon and evening. Severe
  weather is not expected, but a stronger storm or two cannot
  be ruled out.

- Another round of precipitation is possible midweek, with
  medium chances Tuesday evening through Wednesday. The chance
  of measurable snow across western North Dakota during this
  period is 40 to 60 percent.

- Near to slightly above normal temperatures are expected this
  week, with highs mainly in the 40s and 50s and lows mainly in
  the 20s and 30s.

&&

.UPDATE...
Issued at 621 AM CST Sun Nov 3 2024

Low stratus is still locked in place over central and parts of
western North Dakota this morning. Visibilities have dropped
through the night, although have not been very spatially or
temporally consistent, and are rarely at one quarter mile or
less. We did issue a Special Weather Statement for the patchy
fog, but as of now visibilities have not been low enough to
warrant an advisory.

No change in our thinking regarding precipitation chances today.
A few scattered showers have developed in central South Dakota,
with lightning flashes recently detected. SPC mesoanalysis has
a small area of up to 500 J/kg of MLCAPE in this area, with
capped instability extending north into south central North
Dakota. Time of arrival tool puts this activity at the ND state
line around 1530 UTC, with CAMs still showing a rather quick
increase in activity late morning through the afternoon.

Did expand mention of thunder with this update, otherwise only
made minor tweaks to POPs based on latest blended guidance.

&&

.DISCUSSION...
Issued at 345 AM CST Sun Nov 3 2024

Early this morning, a deep trough was located over the western
CONUS, with the base placed over the Desert Southwest. Strong
southwesterly flow aloft was over the Dakotas, downstream of the
trough. At the surface, a trough extended from southwest
Saskatchewan down into western South Dakota, with a warm front
lifting through North Dakota. In the vicinity of this front, very
low stratus was in place across much of central and northern North
Dakota, with a line of showers oriented north-south across eastern
North Dakota. Although there is plentiful low-level moisture, mild
air temperatures haven`t quite cooled down to the dew point yet
underneath the low clouds, and breezy southeasterly winds from a
modest surface pressure gradient have prevented dense fog from
forming as of yet, although there are a few spots in the James River
Valley that have had visibilities in the 3 to 5 mile range over the
past couple of hours.

Rain chances will be increasing through the day today for most of
the forecast area, as an impulse embedded in the southwest flow
moves overhead while a 300mb jet streak approaches from the
south. POPs increase late this morning in south central North
Dakota with the initial push (40 to 60 percent), before peaking
this afternoon and evening across much of central North Dakota
with rain likely (70 to 90 percent). There will likely be a
sharp cutoff in rain from west to east, with rain showers
following along the surface trough slowly drifting east through
the day. Forecast rain amounts are generally one quarter to one
half inch in south central through eastern North Dakota, with
overall low chances of exceeding one inch. However, there is a
small area of enhanced probabilities for higher rain amounts
from McLean to Cavalier counties, likely from a combination of
an enhanced deformation zone and longer residence time as the
rain shield begins rotating off to the northeast. Isolated
thunderstorms are possible with today`s precipitation chances,
with a few hundred J/kg of instability, although it does look
like the chance has trended a bit lower with this morning`s
guidance. Highs today will be in the upper 40s to mid 50s.

Precipitation chances will taper off through the night tonight as
forcing moves off to our northeast, with potential for scattered
showers to persist in the eastern James River Valley on Monday as an
additional wave stays mainly to our southeast. It will be breezy on
the backside of the surface trough, with northwest winds around 15
to 20 mph. Highs will be a few clicks cooler, around 45 to 50
degrees F.

The deep trough from today gets somewhat cutoff to start the work
week, with the southern stream going through the Southern Plains
while the northern stream is dominated by a potent shortwave diving
south from the Canadian Prairies. This will lead to precipitation
chances increasing through the afternoon Tuesday as the trough base
and attendant surface low / cold front approach, with precipitation
chances peaking around 60 percent in northwest North Dakota
Tuesday night. With cooler air moving in Tuesday night and into
Wednesday, it is looking more likely that rain will transition
to all snow across western North Dakota. Latest blended
probabilities have a 40 to 60 percent chance of measurable snow
across the west, with the highest probabilities along the
Montana border. Chances for at least an inch of snow are under
20 percent.

Highs on Tuesday will be in the mid 40s to lower 50s again, while
Wednesday will be much cooler behind the front, with highs in the
upper 30s to upper 40s. Ensemble cluster analysis is then in fairly
strong agreement on broad upper ridging developing to end the week,
leading to a return of drier and milder temperatures.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 621 AM CST Sun Nov 3 2024

Low MVFR to IFR stratus deck, with pockets of LIFR, across
central and parts of western North Dakota to start the TAF
period, with potential to reach KXWA but not likely KDIK. Patchy
fog underneath the stratus is reducing visibilities on and off.
Expecting visibilities to slowly improve through the morning
with rain chances increasing across central and eastern North
Dakota, with rain expected at KBIS/KMOT/KJMS. Rain chances peak
this afternoon and evening before tapering off overnight
tonight. Stratus will slowly clear from west to east, with
generally VFR conditions expected at KXWA/KDIK, and a return to
VFR at KBIS/KMOT by 06Z. KJMS is expected to have IFR to LIFR
ceilings through the TAF period.


&&

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

&&

$$

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