High Wind Watch 23, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
1015 AM MST Sun Dec 6 2020

Aviation Section Updated

.SYNOPSIS...
Unseasonably warm temperatures and dry conditions continue
through Tuesday. An approaching weather system will bring
increased winds for Monday and Tuesday, before ushering in a
cooler and unsettled weather pattern for the remainder of the
week.

&&

.UPDATE...
Updated forecast is out. Very little changed for the morning
update. Confined fog mainly to the West Yellowstone area, along
with areas north of Havre through late this morning. Adjusted
temperatures close to current observations/along with forecast
highs today to similar to Saturday's high's in most areas.
Otherwise, it will be sunny/dry today.

Looking ahead, there is still the potential for a period of strong
winds from Monday into Tuesday over portions of North Central MT.
The high wind watch will continue. Brusda

&&

.AVIATION...
1015 AM MST Sun Dec 6 2020 (06/18Z TAF period)

VFR conditions, with mostly clear skies will prevail across the
region through the period. Some breezy surface winds possible at
times today, with low level wind shear possible in the Cut Bank area
when winds are light. Expect surface winds to gradually start to
increase a bit more after 15z Monday over North Central MT, along
with a gradual increase in high based cloud cover. Brusda

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.

&&

.PREV DISCUSSION...
/ISSUED 424 AM MST Sun Dec 6 2020/

Today and tonight...Quiet weather this morning as high pressure
continues to exert its influence over the region. The most notable
ongoing occurrence is gusty winds along the immediate eastern
slopes of the Northern Rocky Mountain Front as a weak H700 jet max
moves clips the Northern Rockies. Winds at the Deep Creek Raws
station have gusted up to 60 mph but these winds are expected to
diminish by mid-morning. Similar to the last few nights, there is
a wide temperature spread between the breezy plains and the wind
protected valleys. Relatively strong inversions continue to allow
lows to dip into the teens and single digits over the southwest
valleys and portions of Northern Hill and Blaine Counties, while
southwest breezes keep other areas in the 20s and 30s. Mostly
clear skies are expected this afternoon as high temperatures run
roughly similar to those of yesterday. Winds should remain on the
lighter side, though there will be some increased breeziness over
the plains this afternoon. Another quiet night is expected tonight
but there will likely be another increase in mountain top winds
along the Northern Rocky Mountain Front as the high pressure ridge
begins to break down.

Monday through Tuesday night...Westerly flow aloft will increase
ahead of broad troughing over the Pacific Northwest. Temperatures
will remain well above normal despite some height falls associated
with the breakdown of the high pressure ridge. Afternoon
temperatures will mostly be in the 50s to near 60 for many areas,
though cooler readings may still be found in the southwest valleys
and over the northern portions of Hill and Blaine Counties. As
the high pressure system loses its dominance, the inversions over
the southwest valleys will weaken and may lead to warmer nighttime
low temperatures. With the stronger flow aloft will come increased
surface winds, especially over the Rocky Mountain Front and the
plains. Both Monday and Tuesday will be on the windy side but
Tuesday may see the strongest gusts as 50 to 80 kt H700 winds move
directly over North-Central MT. The High Wind Watch in place for the
Rocky Mountain Front and Eastern Glacier County will stand as is but
will likely upgraded to a warning by future shifts. There was some
consideration to expand the Watch area deeper into the plains but
widespread wind gusts at or in excess of 60 mph are not anticipated
at this time. The combination of windy dry conditions, along with
well above normal temperatures raise the concern for increased
grassland fire risk for both Monday and Tuesday but will continue to
hold off on fire weather products because of the shorter durations
of a marginal threat. This period will largely remain precipitation
free but an increasingly moist westerly flow aloft will offer
opportunity for mountain snow showers along the Divide Tuesday
afternoon.

Wednesday through Sunday...Cooler and unsettled conditions can be
expected for this period as broad troughing settles over the
region. This will provide a daily chance for mostly mountain snow
showers, especially Wednesday into early Thursday as the first piece
of energy traverses the region, and again on Friday. Lower
elevations may also see some activity during this time but any
accumulation amounts will be light. The broad trough begins to exit
the region by Saturday but this looks to be replaced by
northwesterly flow for continued cool and unsettled weather.
Temperatures will likely cool to near or slightly above the seasonal
average for much of this period. RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  34  54  41 /   0   0   0   0
CTB  50  31  51  38 /   0   0   0   0
HLN  37  21  44  28 /   0   0   0   0
BZN  39  11  44  18 /   0   0   0   0
WYS  24  -7  34   3 /   0   0   0   0
DLN  36  16  43  23 /   0   0   0   0
HVR  44  27  47  33 /   0   0   0   0
LWT  52  29  53  35 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Monday afternoon through late Tuesday night
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

&&

http://www.weather.gov/greatfalls