Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/12/22
Area Forecast Discussion
National Weather Service Great Falls MT
824 PM MDT Mon Apr 11 2022
.SYNOPSIS...
A strong spring snowstorm will impact a large portion of the
Northern Rockies and High Plains from tonight through Wednesday.
Snow, heavy in some areas, combined with strong winds will lead to
significant reductions in visibility, especially tonight through
Tuesday morning. Significant snowfall accumulations are expected
across portions of Southwest and Central Montana, especially in
northerly upslope areas. In addition, cold temperatures are
expected through the middle of the work week, with overnight lows
potential approaching zero degrees by Wednesday night.
&&
.UPDATE...
A springtime winter storm contiues across The Treasure State.
During this evening`s forecast update, I lowered overnight lows a
bit, especially in the valleys, and increased maximum forecast
Relative Humidity (RH) values in some areas. Also, I adjusted
winds to make them more representative of occurring conditions.
Probability of Precipitation (POP) looks fine; however, having
touched temperatures and RH values, I reran the snow amount
forecast grids, and brought the Storm Total forecast grids
current. No other changes will be made, at this time.
- Fogleman
&&
.AVIATION...
620 PM MDT Mon Apr 11 2022 (12/00Z TAF period)
Widespread snow and blowing snow cause conditions to fall into the
IFR/LIFR range. Expect moderate to heavy snowfall rates overnight
tonight and into tomorrow morning. Snowfall decreases as the day
progresses on Tuesday, and continues lightly into Wednesday.
Mountain obscuration is forecast. Gusty winds are forecast. The KHLN
and KBZN TAFs include Low Level Wind Shear Conditions. Expect
significant impacts to light aircraft flying near mountains and
through valleys.
- Fogleman
Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.
&&
.PREV DISCUSSION...
/ISSUED 620 PM MDT Mon Apr 11 2022/
Rest of today through Wednesday night...primary concern over the
period will be a potent spring snowstorm, which will bring
accumulating snow, strong and gusty winds, and cold temperatures to
the region.
As of 21z this afternoon, H500 closed low was located over Northeast
Oregon/Southeast Washington, with a surface low developing along the
Northeast Idaho/Southwest Montana border. The aforementioned H500
low is forecasted to dig southeast towards Southwest
Montana/Northwest Wyoming through Tuesday morning, before lifting
northeast towards Eastern Montana/the Western Dakotas by Wednesday
morning. The upper level low track, combined with the H700 low
tracking over/near the I-90 corridor across Southwest Montana is
an ideal track for heavy snow across most of the region, with the
exception of the Hi-Line where drier air being entrained in from
the north will keep most if not all the precipitation to the
south. In addition, strong easterly (downsloping) winds across
Gallatin, Broadwater, and Meagher counties will also keep snowfall
amounts lower within the valleys. Snow was already beginning to
overspread southern and western portions of Southwest and Central
Montana this afternoon, with the snow expected to continue to
spread north and east across the remainder of Central and southern
half of North Central Montana through the late afternoon/early
evening hours as additional lift overspreads the region. Heavy
snowfall rates, possibly as high as 1-2"/hr, are expected across
most of Southwest and Central Montana from this evening through
Tuesday morning. Northerly surface winds will increase further due
to the strong pressure gradient that develops as the surface low
moves through southern Idaho this evening, which could result in
near-whiteout conditions along/near the I-15 corridor from Great
Falls to Dillon due to terrain funneling of the winds through the
north-south orientated valley here. Travel will become very
difficult tonight and Tuesday due to snow covered roads and
reduced visibility in snow and blowing snow. Snowfall rates begin
to decrease by Tuesday afternoon, although light snow will
continue into Wednesday, along with areas of blowing snow. As the
storm system moves away and winds up into a blizzard for far
eastern Montana and the northern High plains, it will continue to
draw colder air into our forecast area. Thus, the other
unseasonable aspect of this storm is the cold temperatures. Expect
highs in the teens and 20s on Wednesday. As skies finally begin
to clear Wednesday night, most locations will see temperatures
drop into the single digits, and possibly below zero for some
locations. These cold temperatures are nearing record low values.
- Moldan/ PN
Thursday through next Monday...Fair but cold weather prevails across
the region on Thursday. A new, but weakening upper level low
arrives sometime Thursday night or Friday, producing some areas of
light snow. Details in timing and track of this system remain
unclear, with uncertainty in the forecast continuing through next
weekend. However, the overall ensemble blend favors gradually
moderating temperatures. - PN
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 14 20 11 23 / 100 100 80 50
CTB 13 20 11 22 / 60 80 40 30
HLN 18 22 12 24 / 100 100 30 20
BZN 17 25 9 24 / 100 100 50 20
WYS 10 25 -3 24 / 100 100 30 20
DLN 15 24 6 25 / 100 90 10 10
HVR 16 25 15 27 / 30 50 60 40
LWT 12 18 9 19 / 100 100 90 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM MDT Wednesday Central and
Southern Lewis and Clark...Gallatin...Jefferson...Southern Rocky
Mountain Front.
Winter Storm Warning until midnight MDT Tuesday night
Beaverhead...Madison.
Winter Storm Warning until noon MDT Wednesday Broadwater...
Cascade...Fergus...Judith Basin...Meagher.
Winter Weather Advisory until 3 AM MDT Wednesday Chouteau...
Eastern Glacier...Eastern Pondera...Eastern Teton.
Winter Weather Advisory until 6 AM MDT Wednesday Northern Rocky
Mountain Front.
Winter Weather Advisory from midnight tonight to noon MDT
Wednesday Blaine.
&&
$$
http://www.weather.gov/greatfalls