Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 260416
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
916 PM MST Wed Feb 25 2015

.UPDATE...
Issued a winter weather advisory for flash freeze conditions
earlier this evening as road surface temperatures were forecaste
to drop below freezing. Limited the advisory to locations where
the heaviest precipitation was forecast to fall. Otherwise no
major changes to the forecast this evening with temperature
remaining on track for low generally in the single digits across
much of Central and North Central Montana. Lowest confidence
remains in the temperatures in the early morning hours when cloud
cover will be at a minimum and radiational cooling could be
maximized. Some light snow showers will continue in the area
however no additional heavy accumulation is expected. Suk


&&

.AVIATION...
UPDATED 2340Z.
Predominantly MVFR/IFR conditions expected through the evening hours
as moisture continues to stream south from Alberta, generating
extensive low-level cloud cover and areas of light snow.  KBZN and
KHVR will mainly be VFR as main precip area is through central MT
from KCTB to KLWT.  Conditions should steadily improve back to VFR
tonight as last remnants of moisture exit to the southeast.
Forecast models hinting that partial clearing vcnty KCTB/KLWT may
result in IFR/LIFR conditions in fog on Thurs morning, so have added
mention of that in 00Z TAFs, but will re-evaluate fog chances when
evening data package arrives.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED 440 PM MST Wed Feb 25 2015/
Tonight through Friday...Northwest flow will be gradually weakening
during the period as scattered snow showers gradually taper off
tonight through Thursday. Plan to let the winter weather advisory
for the Rocky Mountain Front and central Montana expire at 5 pm
this afternoon. Any additional snowfall through Thursday will be
light. The passage of a weather disturbance through eastern
Montana will usher in a drier airmass Thursday into Thursday
evening but isolated snow showers will linger over far southwest
Montana. An upper trough will develop over northwest Montana on
Friday and associated with it expect increasing moisture. By
afternoon expect a slight chance of snow showers for the lower
elevations with scattered snow showers over the western mountains.
Also during the afternoon the next surge of cold air from Canada
will move south over the east slopes of the Rockies.

Wind chills...The combination of easterly winds and temperatures
near to a little below zero tonight into Thursday morning will
result in pockets of wind chills in the range of 10 below zero to
20 below zero near the Canadian border. Readings are not expected
to get cold enough in that area to warrant a wind chill advisory
but the situation will need to be monitored this evening. Blank

Friday night through Wednesday...An upper level low pressure trof
will be over Central Montana Friday night. The trof will have
developed a large split with most of the dynamics in the southern
split which drops well the south of the zones. The northern split
will will cross the Canadian border Friday night with the associated
cold front already well into the central and southwest zones. The
GFS is more aggressive than the ECMWF with the moisture but with
upslope flow at the surface, expect that the low levels will remain
saturated with widespread light snow in the forecast through
Saturday. Accumulations will remain on the light side, however.
Heights will build aloft late Saturday night and Sunday and the
airmass will dry. Several weak disturbances will move through the
northwest flow aloft Sunday and Sunday night. The main effect of
these will be to develop a surface lee trof along the Rockies but at
the moment models are keeping this north of the Canadian border.
Another shortwave will be approaching the West Coast Monday.
Moisture ahead of this system will cross the Rockies late Monday. An
associated cold front will bring another cold airmass into the
region from Canada. This will be another system where widespread
snow will occur across the zones although snow accumulations will
again be on the light side. However, cold temperatures and strong
winds will cause dangerous winds chills. High pressure aloft will
build again late Tuesday, the airmass will dry, and temps will once
again trend upwards by Wednesday. Several large swings in
temperature will occur during this forecast period. Temperatures
will drop to well below seasonal normals Saturday, moderate Sunday
and Monday before dropping again on Tuesday. Temperatures will
remain below seasonal normals, however, throughout the period.
Zelzer

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   4  19   4  21 /  20  10   0  10
CTB   1  17   2  18 /  30  10   0  20
HLN  13  27  10  28 /  20  10  10  20
BZN  10  26   4  29 /  20  10  10  20
WEY   0  29  -2  32 /  30  20  20  30
DLN  13  30  10  32 /  10  10  10  30
HVR  -3  17  -4  20 /  10   0   0  10
LWT   0  17  -1  23 /  20  10   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 10 AM MST Thursday Central and
Southern Lewis and Clark.

&&

$$

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