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Area forecast discussion 
National Weather Service Great Falls Montana
1050 am MST sun Mar 1 2015

..update to aviation...

Discussion...forecast for today appears to be in good shape and
no changes/updates are anticipated. However, newest model runs
appear to be pulling back on the amount of quantitative precipitation forecast associated with
tomorrows weather system. Will continue to evaluate models as they
come in but it is possible that the afternoon package may have
lower snow accumulation amounts than the current forecast is
showing. Despite this possible change, the system tomorrow will
still be windy and much colder so the going advisory appears to be
mostly in line with expected conditions. Mpj

&&

Aviation...
updated 1750z.
Mostly clear skies will give way to increasing high clouds this
afternoon and evening but VFR conditions should prevail through
about 12z Monday. Beyond 12z Monday a strong surface cold front will
sweep south from Canada into north central Montana. Behind the front
there will be a strong wind shift to the north with IFR/MVFR
ceilings and developing widespread snow. The front should move as
far south as kgtf by 18z Monday and will continue to move southward
beyond the end of the forecast period. Mpj

&&

Previous discussion...
/issued 454 am MST sun Mar 1 2015/

Today through Tuesday...northwest flow aloft persists over the
region today and tonight with generally dry conditions expected.
Cold airmass in place over the region will will modify and
slightly warm today as surface high pressure currently centered
over Montana moves off to the east by this afternoon and weak Lee-side
troughing begins to extend south along the east slopes of The
Rockies tonight. Upper level shortwave and jet, currently moving
from Alaska into the yt, will dig sharply south late tonight through
Monday and continue south through the northern rockies Monday
night and Tuesday. This will allow an Arctic cold front to surge
south into north central Montana by mid-day Monday, continuing south
through SW Montana Monday evening. Models have been reliably consistent
with this feature producing a period of snowfall across much of the
area beginning Monday morning along the Canadian border and
spreading south into central Montana Monday afternoon and eventually
into SW Montana Monday evening. Strong pressure rises following the
frontal passage will likely produce a period of very windy
conditions with blowing and drifting snow likely impacting travel
for a period late Monday afternoon and evening. Short duration of
this event will limit snowfall amounts somewhat with 2 to 4 inches
across much of the lower elevations and 4 to 8 inches in the
mountains. Lowest snowfall totals will be across NE portions of
the forecast area where accumulations look to remain less than 2
inches. Much colder air flows into the region following the front
as well Monday night and Tuesday with many locations seeing wind
chill values 10 below to 20 below zero by late Monday night. Will
issue a Winter Weather Advisory to highlight wind/snow/blowing
snow and wind chill impacts Monday and Tuesday. Snow and winds
diminish Tuesday with cold airmass settling over the region and
temperatures mainly in the single digits and low teens above zero.
Hoenisch

Tuesday night through Sunday...the upper level low pressure trof
will move east of the zones Tuesday night, high pressure will build
aloft, and the airmass will dry. This will lead to an end of
precipitation and clearing skies. At lower levels, the surface high
pressure will be over central Montana and, with the clearing skies,
cold overnight low temps are expected. Some dangerous wind chills
are thus expected across the region. The surface high will be moving
east Wednesday and temperatures will begin to trend upwards. With a
high pressure ridge building over the West Coast, central Montana
will be underneath northwest flow aloft. A disturbance moving
through this flow will bring some increased cloud cover to the area
and strengthen a surface trof along the Lee of The Rockies. Brisk
winds along the slopes of The Rockies will result. Southwest flow
across The Rockies will also hasten the warming across western
portions of the region. A shortwave will move across the West Coast
Thursday and flatten the ridge. Moisture ahead of this system will
cross The Rockies late Thursday and bring a chance of precipitation
across the region. This shortwave will also strengthen winds and
breezy conditions will continue over The Rockies. The shortwave will
move east of The Rockies Friday and the airmass will dry again
Friday night. High pressure will build again through Saturday but
another shortwave will move through the Pacific northwest Saturday
night. This will bring another chance of precipitation to the area
Saturday night and Sunday but any snow accumulations should remain
low and at higher elevations. Temps will begin the period below
normals Tuesday night and Wednesday but rise to near and above
normals Thursday. Temps will remain moderate thought the end of the
period. Zelzer

&&

Preliminary point temps/pops...
gtf 30 16 29 -4 / 10 0 100 90
ctb 30 14 22 -6 / 10 10 100 30
hln 32 14 32 5 / 10 0 80 100
bzn 28 9 34 2 / 0 0 30 100
wey 31 2 34 -5 / 0 0 20 80
dln 31 10 38 4 / 0 0 20 90
hvr 29 12 28 -2 / 10 0 80 30
lwt 27 10 31 -4 / 10 0 100 80

&&

Tfx watches/warnings/advisories...
Winter Weather Advisory from 5 PM Monday to 11 am MST Tuesday
Beaverhead...Broadwater...Gallatin...Jefferson...Madison...
Meagher.

Winter Weather Advisory from 11 am Monday to 5 am MST Tuesday
Cascade...central and southern Lewis And Clark...Chouteau...
eastern Teton...Fergus...Judith Basin...southern Rocky Mountain
front.

Winter Weather Advisory from 5 am Monday to 5 am MST Tuesday
eastern Glacier...eastern Pondera...northern Rocky Mountain
front...Toole.

&&

$$

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