379 
FXUS63 KBIS 060456
AFDBIS

AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1156 PM CDT Sat Nov 5 2022

.UPDATE...
Issued at 1140 PM CDT Sat Nov 5 2022

No significant changes for this update. Latest surface
observations show that wind direction has shifted west across all
but the far eastern CWA. Initial surge of CAA and strongest 
isallobaric wind component is pushing through this area currently.
Farther to the west, winds have backed off a bit from the initial
surge, but are still gusting to around 45 to 50 mph in many 
areas. We did update short term temperatures with a blend of the 
latest short term guidance, tempering the cool off in the 
northwest a bit. No changes to the current headlines at this time.
Will send updated products shortly.


UPDATE Issued at 940 PM CDT Sat Nov 5 2022

Wind reports have been tame so far this evening outside of the
initial 59 mph reports at Williston and Tioga. The analyzed
surface pressure rises have been somewhat slow to push in and
the boundary layer may be somewhat decoupled with as cold air
advection has been less than impressive this evening so far.
Additionally model soundings show ascent in the lower levels,
rather than the subsidence that would promote momentum transfer of
stronger winds aloft. Strong pressure rises still exist upstream
into southern Saskatchewan and central Montana, thus the wind
threat is not out of the question overnight, but the greatest wind
gusts may wait until the boundary layer mixes out again in the
morning.

UPDATE Issued at 647 PM CDT Sat Nov 5 2022

The potent upper level jet and associated shortwave were evident
on water vapor imagery, with the low circulating over southern
Saskatchewan and eastern Montana. The surface low was moving into
western North Dakota with strong pressure rises creating gusty
westerly winds this evening. So far strong wind gusts have been
observed in Divide and Williams counties, but this should continue
to spread east and south tonight. Though boundary layer decoupling
may mitigate the highest wind gusts somewhat overnight, the
greater pressure rises and cold air advection closer to the upper
low to the north should allow for high wind gusts across northern
North Dakota tonight, spreading south through the central in the 
morning. Some light snow will also be possible with this process 
and though accumulations are not expected, brief periods of lower 
visibility in light falling snow are possible.

&&

.SHORT TERM...(This Evening through Sunday)
Issued at 325 PM CDT Sat Nov 5 2022

High winds are expected to impact the region this afternoon
through Sunday. High winds could make travel difficult for high 
profile vehicles.

A strong upper level low over southern Saskatchewan will be the
main driving force for this weekends weather. Prefrontal showers
continue to move across western and central North Dakota causing 
very light rain. Showers should weaken later this evening. A cold 
front spanning across eastern Montana continues to make it's way 
eastward reaching the Dakotas later this afternoon. Substantial 
pressure increases behind the front with upstream observations 
suggest gusts around 50 mph are possible with the frontal passage.
High post frontal winds are expected, forecast soundings show 
50kts at 850mb is going to mix down to the surface leading to 
gusts up to 65 mph. In addition cold advection and subsidence on 
the southward side of the low is also going to help mix high 
winds to the surface thus boasting our confidence for high winds. 
A Wind Advisory across the county warning area has been upgraded 
to High Wind Warning starting this evening until Sunday evening.

The upper low is going to move eastward along the international 
border tonight through tomorrow. Wrap around precipiation is
possible for northern portion of North Dakota. Low temperatures 
are forecast to drop into the 20s tonight, thus making snow 
possible across the northern portion of North Dakota. Snow 
accumulations are expected to remain light with minor impacts.

West winds Sunday will help warm high temperatures back into the 
upper 30s and lower 40s for much of south. However wrap clouds are
going to keep the north fairly cold. Near critical fire weather 
conditions are possible along the North and South Dakota border 
due to dry and windy conditions. The window for critical fire 
weather is small as fair to good overnight recoveries will delay 
drying in the morning and cooler temperatures will keep relative 
humidity around 30%. Colder weather is in store. in the long 
term.

.LONG TERM...(Sunday Night through Saturday)
Issued at 325 PM CDT Sat Nov 5 2022

Key messages:

- Light snowfall potential Monday and Monday evening, highest in 
  northwestern North Dakota where the chance of 1" or more of snow
  is 60-70%

- Potential for a stronger system Wednesday and Thursday, but with 
  considerable uncertainty and only about 1 in 5 odds of a winter 
  storm

High confidence exists with the evolution of the large-scale
pattern  this week, highlighted by a strong middle- and upper-
level trough developing and gradually moving eastward through the 
western United States. Global ensembles strongly agree that this 
trough will move into the central United States by mid to late 
week, resulting in a significant cool-down locally from Thursday 
through next weekend. We are confident in forecast temperatures 
Thursday through Saturday in the wake of the trough , with highs 
in the 15 to 25 F range and lows mainly 5 below zero to 5 above 
zero.

Prior to the late-week cold air surge, we will experience a period 
of warm air advection downstream of the upper-level trough tied to
southwesterly flow aloft. A low- and midlevel warm frontal 
passage is expected to occur from south to north Monday into 
Monday evening on the leading edge of this pattern shift, and 
global ensembles are supportive of precipitation with the warm air
advection regime. The thermal profile ahead of the warm frontal 
zone suggests the dominant precipitation-type will be snow, and 
probabilities of 1" or more of snow range from 10% along the I-94 
corridor to around 60% across northwestern North Dakota. In 
northwestern North Dakota, residence time of forcing aloft may be 
longer and thus there is a low chance of reaching advisory 
criteria for snowfall of a few inches there.

Tuesday will likely be the warmest day of the week, though timing
of  the most substantial warm air advection could be overnight 
Monday night, and cloud cover could play a role in what 
temperatures end up being realized. Nonetheless, we have forecast 
highs Tuesday ranging from the mid 30s in western ND to around 50 
F in south central ND. Gradually-increasing forcing for ascent 
aloft Tuesday into Tuesday night will favor a gradual increase in 
precipitation probabilities, and steep lapse rates aloft and weak 
bouyancy suggest some potential for a few thunderstorms in central
North Dakota, too.

Wednesday into Thursday is the timeframe of greatest interest
during  the week when the upper-level trough finally crosses the 
region. We see two potential outcomes that could come to reality:

1) An open, full-latitude but more dynamically-starved trough
moves through the region with lighter precipitation, but still 
strong winds and much colder air in its wake. Odds of this 
scenario being the end result are currently 4 out of 5.

or

2) A strong embedded shortwave trough and potentially low aloft is 
ejected along with the main full-latitude trough. This scenario is
reminiscent of the 12 UTC GFS and ECMWF deterministic 
simulations, but we have to stress that these represent a fraction
of the full global ensemble membership, and indeed only about 20%
of all the global ensembles (around 100 model simulations) have 
this scenario. Thus, while this represents the possibility of the 
first winter storm of the season, its odds are only about 1 in 5 
at this point. NBM 4.1 snowfall probabilities of 6" or more of 
snow are also in the 20% range, though the probability of 1" or 
more of snowfall is high (around 60%) in western ND, since either 
of the two dominant outcomes would produce snowfall in the western
third of ND (just with much different maximum amounts, with lower
amounts in scenario 1).

As a result of the uncertainty and range of outcomes, we encourage 
anyone with interests in the weather for mid to late week to avoid
focusing on any individual model runs or cycles, including both 
the GFS and ECMWF deterministic simulations, and instead to check 
back with later updates to which of the two aforementioned 
scenarios becomes more or less favored.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1140 PM CDT Sat Nov 5 2022

A low pressure system will track across southern Canada tonight
through Sunday morning, bringing strong westerly winds. Wind 
gusts exceeding 50 kts at times are likely. Additionally some 
periods of MVFR cigs are also expected, mainly north across KXWA-
KMOT, but could approach KDIK and KBIS in the 12-16 UTC timeframe.
Winds are expected to diminish from west to east Sunday afternoon
and evening. 

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 6 PM CST Sunday for NDZ001>003-009>011-
017>021-031>034-040>045.

High Wind Warning from 3 AM to 6 PM CST Sunday for NDZ004-005-
012-013-022-023-025-035>037-046>048-050-051.

&&

$$

UPDATE...TWH
SHORT TERM...Johnson
LONG TERM...CJS
AVIATION...TWH