Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/31/20
Area Forecast Discussion
National Weather Service Great Falls MT
724 PM MST Thu Jan 30 2020
.UPDATE...
An upper level ridge dominates the pattern during this 24 hour
update period. Moisture from an upstream major short wave trough
spills over the ridge increasing cloudiness across the region.
Mountain showers are expected. Squeezed between higher heights to
the southwest and the trough approaching from the northwest, a
strong westerly cross-barrier flow sets up across The Great Divide.
A leeside trough forms, and wind speeds increase. Day shift forecast
remains accurate; therefore, no adjustments will be made to the
forecast, at this time.
- Fogleman
&&
.SYNOPSIS...
Clear skies will give way to increasing cloudiness tonight into
Friday, but with increasing winds. Strong to high winds can be
expected at times Friday through Saturday, with winds peaking
Saturday along with near-record high temperatures for February 1st.
A cold front will then bring a good chance for widespread snow to
the area Saturday night into Sunday, with below normal temperatures
to start next week.
&&
.DISCUSSION...
Rest of this Afternoon through Tonight...
Mostly sunny skies with light breezes are expected through the
remainder of the afternoon into early evening, with increasing
cloudiness and surface winds as the pressure gradient increases.
Of note, winds along the immediate Rocky Mountain Front may
approach 60 mph or higher, at least briefly, given how
significantly the lee side trough strengthens this evening and
overnight. This is not part of the High Wind Warning which becomes
effective Friday afternoon but a separate event, and this event
should remain below warning-level limits for that specific area.
Friday through Monday Night...
A disturbance in the strong westerly flow aloft will bring mainly
mountain precipitation to the forecast area, but a few light
showers may move east out onto the plains. The surface pressure
gradient will also increase along the Rocky Mountain Front again
Friday afternoon into Friday evening, which will help mix down the
80- to 100-kt 700-mb winds. Forecast models have been fairly
consistent with this situation, so High Wind Warnings have been
expanded to include the entirety of north-central Montana.
Additionally, a High Wind Watch is in effect for higher-elevation
areas of west-central Montana (Central and Southern Lewis and
Clark, Jefferson, and Meagher counties). Mid-level winds may be a
bit more difficult to mix down farther out onto the plains
(Liberty, Chouteau, Hill, and Blaine Counties), but there is the
potential for winds to translate down some of the island mountain
slopes. (Please see FIRE WEATHER section for grassland concerns.)
The cause of this increase in winds is a powerful jet streak aloft
along with a shortwave trough and associated cold front from
southwest Canada. Moisture ahead of this disturbance will bring
precipitation to areas along the Continental Divide. The cold
front will swing through Montana Saturday night into Sunday,
bringing a good chance for mountain snow, along with rain changing
to snow along and just behind the cold front. Most areas over the
plains are not forecast to receive significant snowfall, but the
situation will need to be monitored for potential winter weather
highlights. The passage of this front will also bring a
significant change in temperatures, as highs will be near record
levels ahead of the front on Saturday, cool through the 30s on
Sunday, into the 20s on Monday behind a second frontal passage,
with overnight lows in the teens. A few light snow showers may
also linger over the area Monday into Monday night, though that
trend seems to be decreasing with the latest model trends.
Tuesday through next Thursday... High pressure aloft will start
building back into the western United States during this period,
which should help warm temperatures back above normal. However,
there will be more of a moist northwest flow aloft with embedded
disturbances over the forecast area, which will keep a chance of at
least mountain precipitation over the area. Coulston
&&
.AVIATION...
Updated 504 PM MST Thu Jan 30 2020 (31/00Z TAF Period)
Expect VFR conditions throughout this TAF period at KCTB, KHVR, KGTF
KLWT and KHLN. KBZN and KEKS can expect periods of MVFR conditions
with KWYS falling into the IFR/LIFR range. Mountain obscurations are
forecast along The Great Divide as well as throughout southwest
Montana. Aircraft icing is forecast, as well. Expect strong winds.
Mountain wave activity will develop. Low level wind shear is
forecast. Expect the associated turbulence.
- Fogleman
&&
.FIRE WEATHER...
Grassland fire danger will increase Friday and then peak Saturday
over the plains of north central Montana. A Fire Weather Watch for
potential high grassland fire danger is now in effect for
Saturday, though the threat could begin as early as Friday night.
West to southwest winds will increase across much of the area on
Friday. The strongest winds will be likely Friday night into
Saturday, as sustained winds of 25 to 40 mph with gusts to 50 mph
or higher spread east over the plains, with strongest winds likely
closer to the Rocky Mountain Front and Central Montana mountain
ranges. Well above normal temperatures will also cause moderate to
poor relative humidity recover Friday night, with values falling
in the 15 to 30 percent range on Saturday due to near record high
temperatures. Much of this plains area has not had snow cover for
many days, which has made dormant grasses somewhat dry. Anyone
planning on doing prescribed burns should consider alternate
plans. Check with your county in case burning has been suspended.
All should be mindful of any errant sparks that may ignite dry
grassy fuels. There already have been a few small fires reported
this week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 31 52 43 66 / 10 10 0 0
CTB 30 49 39 58 / 0 10 0 30
HLN 25 48 36 63 / 10 20 0 0
BZN 20 46 30 55 / 10 30 0 0
WYS 8 29 18 34 / 20 30 10 10
DLN 20 39 28 49 / 10 10 0 0
HVR 27 49 41 60 / 0 20 10 0
LWT 25 51 38 61 / 10 20 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Friday evening through Saturday evening
Central and Southern Lewis and Clark...Jefferson...Meagher.
High Wind Warning from midnight Friday night to 11 PM MST
Saturday Blaine...Chouteau...Hill...Liberty.
Fire Weather Watch from Saturday morning through Saturday
evening Central and Eastern Lewis and Clark National Forest
Areas...Chouteau and Fergus Counties...Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and
Townsend Ranger Districts of the Helena National Forest...Hill
and Blaine Counties...Lewis and Clark National Forest Rocky
Mountain District-Rocky Mountain Front.
High Wind Warning from midnight Friday night to 11 PM MST
Saturday Cascade...Eastern Pondera...Eastern Teton...Fergus...
Judith Basin...Toole.
High Wind Warning from noon Friday to 11 PM MST Saturday Eastern
Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.
&&
$$
http://www.weather.gov/greatfalls