Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/13/20
Area Forecast Discussion
National Weather Service Great Falls MT
849 PM MDT Thu Mar 12 2020
.SYNOPSIS...
A major winter storm is expected to impact portions of the
Northern Rockies, especially the plains of Central and North
Central Montana to end the work week and through the weekend.
Snow, blowing snow, and cold temperatures are expected to
accompany this storm. Motorist should be prepared for hazardous
driving conditions, especially from Friday through Saturday
&&
.UPDATE...
The evening update has been published. Snow showers over the
Little Belts and the eastern portions of the CWA will continue to
wind down for the remainder of the evening into the overnight.
Then the focus turns to the winter storm, which moves in from
northwest to southeast tonight through Saturday night. No changes
were made to the current winter weather headlines but the
situation will continue to be monitored for the potential of
blizzard conditions along and west of the I15 corridor northwest
of Great Falls to the Canadian border.
&&
.AVIATION...
Updated 600 PM MDT Thu Mar 12 2020 (13/00Z TAF Period)
A few lingering snow showers may persist over North-central Montana
through 4Z but should mostly stay in between terminals. Mostly VFR
conditions will begin to degrade toward MVFR/IFR from north to south
tonight into Friday morning as a major winter storm approaches the
region. KCTB may see consistent IFR/LIFR conditions due to snow and
blowing snow from 12Z Friday through the end of the TAF period.
Other Central/North-central terminals will see more sporadic snow
and associated low ceilings and visibility but conditions will
worsen as the day progresses. Mostly VFR or MVFR are expected for
KBZN and KEKS for this period but condtions will likely degrade just
beyond that. North to northeasterly surface winds develop over most
Central/North-central locations Friday morning. Mountian
obscurations and aircraft icing will increasingly become more
widespread, especially for areas receiving snow.
&&
.PREV DISCUSSION...
/ISSUED 617 PM MDT Thu Mar 12 2020/
Rest of this afternoon through Saturday night...biggest concern and
focus with the afternoon forecast was on the major winter storm set
to impact the region beginning late tonight and persisting through
much of the day on Saturday, only to be followed by record to near
record low temperatures Saturday night/Sunday morning across North
Central and Central Montana.
First, not to be ignored or slept under the proverbial rug of the
"major winter storm", is the on-going snow showers over North
Central and Central Montana this afternoon. These snow showers,
which are being drive by a combination of moist, northwest flow
aloft and steep low-level lapse rates, will likely continue into the
late evening hours before gradually decreasing in areal coverage.
Brief reductions in visibility and some accumulations on road
surfaces are the primary impacts with these showers, but given the
scattered nature and briefness of said showers we will continue to
just highlight through Special Weather Statements.
As the showers gradually dissipate in coverage this evening over the
plains of Central and North Central Montana, expect snow to begin to
fill in along the Rocky Mountain Front around midnight as the low
level flow becomes more east to northerly. Snow will spread south
(east) along (away from) the Rocky Mountain Front Friday morning
through Friday afternoon, continuing into Saturday
morning/afternoon. Of biggest concern with today`s forecast issuance
is the potential for blizzard condtions, especially along and west
of the Interstate 15 corridor. For these areas, a push of pressure
6hr rises of 3-6mb along the Rocky Mountain Front combined with H850
winds of 25-35kts is expected to lead to a prolonged period strong
and gusty northerly winds. The one question that remains is whether
or not a sustained period of blizzard condtions can be observed, but
given uncertainty and that the onset of the winds are still 18-24hrs
out I will defer possibly upgrading (to a Blizzard Warning) to
future shifts should trends continue. Regardless of if a Blizzard
Warning is needed, I have continued to message within the current
Winter Storm Warning that near-blizzard conditions are possible and
could lead to hazardous conditions for both driving and ranching
interests. Otherwise, snowfall amounts continue to remain relatively
steady across the region, with the only major change being an
increase in amounts along and west of Interstate 15. Finally, a very
cold night is expected Saturday night/Sunday morning as a strong
surface high settles over the area, with the potential for record or
near-record temperatures. - Moldan
Sunday through next Thursday...The low pressure area will
continue to move south along the Pacific coast Sunday through
Tuesday, which will help decrease the snow across the area. High
pressure at the surface will also start to slowly exit the area to
the east, relaxing the surface pressure gradient and allowing the
winds to decrease. However, cold air will remain in place over
much of the area due to the expected widespread snow cover.
Temperatures over the plains could potentially fall into the teens
below zero Sunday night and Monday night, with even colder
temperatures possible if skies clear out and winds stay light. A
weak westerly flow aloft will then reside over the forecast area
through the middle of the week, keeping much of the area dry with
only gradually warming temperatures. Daytime temperatures should
warm above freezing in Southwest Montana, but they should remain
below freezing over the plains. - Coulston
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 18 24 0 8 / 20 100 100 100
CTB 12 14 -8 3 / 80 100 100 100
HLN 20 29 4 14 / 10 70 80 90
BZN 17 33 15 28 / 0 20 40 70
WYS 2 34 17 36 / 10 0 60 80
DLN 19 35 18 35 / 0 0 20 60
HVR 16 24 9 18 / 50 70 100 100
LWT 16 25 12 20 / 40 90 90 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Friday to 4 PM MDT Saturday
Broadwater...Jefferson.
Winter Storm Warning from 9 AM Friday to 4 PM MDT Saturday
Central and Southern Lewis and Clark...Meagher.
Winter Storm Warning from 9 AM Friday to 4 PM MDT Saturday
Blaine...Cascade...Chouteau...Fergus...Hill...Judith Basin...
Liberty.
Winter Storm Warning from midnight tonight to 4 PM MDT Saturday
Eastern Glacier...Eastern Pondera...Eastern Teton...Northern
Rocky Mountain Front...Southern Rocky Mountain Front...Toole.
&&
$$
http://www.weather.gov/greatfalls