Area Forecast Discussion
Issued by NWS Great Falls, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KTFX 151807

Area Forecast Discussion
National Weather Service Great Falls MT
1207 PM MDT Thu Mar 15 2018


Late morning update included an extension of the Winter Weather
Advisory for Beaverhead, Madison and Gallatin Counties till 3PM
MDT. Conditions and recent reports indicate scattered, heavy snow
showers within these areas. A thorough analysis of short-range
guidance shows these showers, which are mostly terrain driven,
should continue for a few more hours before diminishing.
Otherwise, northwest flow now dominates central Montana around the
SW quadrant of the northward progressing H700 low. These continue
to produce snow bands across Cascade, Teton and Chouteau
Counties. Within these bands, quick burst of heavy, wet snow or
rain/snow mix is possible which may lead to limited visibility
and difficult travel. Next update will be included with the
afternoon forecast package. KLG

.930AM UPDATE...

Changes this morning to the forecast package included a fresh
ingest of updated short-range guidance including refreshening
PoP`s with radar trends. This morning, we had a very impressive
band of heavy, wet snow roll through central MT from Cascade
County on east that brought a quick coating of snow from Great
Falls to Lewistown. This band is continuing its progress to the
north. Latest scans from KTFX illustrate a small, comma head
feature tracking across far western Chouteau County indicating
the position of the H700 low. Within the better convergent/dynamic
ascent associated with the low, there will be a heaver area of
wet snow as it progresses to the north across Liberty and Havre
Counties in the next few hours. Within these areas, travel may
become difficult, especially along the Hi-Line through late
morning. Behind the northward tracking low, surface to low-level
winds are shifting back from the northwest causing small,
mesoscale snow banding in its place. Expect light snow showers to
persist through the afternoon across central areas, especially
near higher terrain due to upslope. Light snow continues across
the southwest this morning, with mixed rain/freezing rain at
times, especially in the valleys but should slowly diminish by
this afternoon. Otherwise, conditions will improve areawide
tonight as far as snowfall is concerned, however cold temperatures
may cause some refreezing issues. Additionally, afternoon high
temperatures along the Milk River Valley in Hill and Blaine
Counties were brought down several degrees, as precipitation moves
into the area in the next few hours. If necessary, more updates
will follow. KLG



Areas of rain and mountain snow are spreading across western
Montana this morning. Rain is expected to change to snow over
western portions of North-central Montana. Light freezing rain or
sleet are possible at times during the transition to snow.
Precipitation ends from south to north Thursday afternoon and
evening. Fair weather follows for most areas of North-central and
Southwest Montana on Friday.


Updated 1800Z.

MVFR/IFR conditions will continue in bands of snow extending from
KCTB to KGTF...along with a few lingering snow showers across the
southwest. Light freezing rain or sleet is still possible
although mostly snow or possibly a rain snow mix is expected
through the weekend. Snow begins to taper off later this afternoon
into the evening hours. With lingering moisture and clearing
skies...areas of fog will be possible for most sites tonight into
Friday morning. Best chances of IFR to LIFR fog will come from
KHLN to KGTF to KLWT and northward to sites along the Hi-Line.


Updated 300 AM.

The flood advisory will continue for portions of Southwest MT, as
impacts from minor flooding continue to be reported via emergency

Rain/snow will fall over the region today. Overall liquid
rainfall should be less than 0.25 inches in most areas, thus
significant new flooding issues are not anticipated at this
time. However, rain may bring some minor flooding or ponding
issues. The remainder of the week will see slightly cooler more
normal temperatures, likely decreasing the threat of new flooding


/ISSUED 530 AM MDT Thu Mar 15 2018/

Today through Saturday...A compact shortwave system lifting north
along the Continental Divide is producing areas of rain and
mountain snow. Steady rain has been concentrated to the west of
I15 from Helena north through Great Falls and Shelby. Temperatures
rose a few degrees into the low- to mid-30s in this area as
precipitation mixed down the warmer air aloft. There have been
isolated reports of freezing rain or sleet, but no reported
impacts from the freezing precipitation at this time. We still
expect colder air to arrive from the west, with rain changing to
snow through the early morning hours. For these reasons, the
Winter Storm Warning remains in effect for this area along and
west of I15. The Winter Storm Warning was converted to a Winter
Weather Advisory generally east of I15, as no precipitation has
yet been observed over eastern portions of North-Central MT. Short
term model guidance indicate a secondary surge of moisture
crossing the area later this afternoon, lifting north from its
present location in south-central MT. Colder temperatures over
this area could support better chances for a light glazing of ice
as precipitation develops this afternoon. Rain and snow over
southwest Montana is expected to continue through mid-day. Skies
clear later tonight as the shortwave system moves away to the
north. Fair weather follows for most areas Friday. Another
shortwave trough is forecast to rotate through the area Friday
night into Saturday, producing light rain and snow across Northern
Montana. PN

Saturday night through Thursday...Expect periods of snow to affect
much of Southwest and Central MT Saturday night through Sunday, as
an upper level low moves through the region. Overall snow
accumulations of 1 to 3 inches seem possible at lower elevations,
but 4 to 8 inches are looking more likely for the mountain areas of
Southwest MT, especially south of I-90. Most of the precipitation
diminishes by Monday, as shortwave ridging gradually builds over the
region for Tuesday and Wednesday. By Thursday morning, the flow
aloft will be more southwesterly, as a series of upper level
disturbance are progged to move northeastward through the region.
Thus the chances for rain/snow will be increasing on Thursday,
especially over Southwest MT. Overall temperatures will generally be
below normal through the entire period, but a trend towards near
normal temperatures is expected Tue/Wed as the weak shortwave ridge
builds over the region. Brusda


GTF  36  22  37  21 / 100  20  20  30
CTB  32  13  33  18 / 100  40  10  30
HLN  37  25  40  23 / 100  20  20  20
BZN  39  24  41  20 / 100  10  10  10
WEY  33  17  33  14 /  60  40  30  20
DLN  36  20  39  19 / 100  30  10  20
HVR  22  13  31  19 / 100  10  20  50
LWT  37  25  37  22 /  90  10  40  40


Winter Weather Advisory until 3 PM MDT this afternoon below 5500
feet for Broadwater...Central and Southern Lewis and Clark...

Winter Storm Warning until 3 PM MDT this afternoon above 5500
feet for Broadwater...Central and Southern Lewis and Clark...

Winter Weather Advisory until 3 PM MDT this afternoon Blaine...
Cascade...Chouteau...Fergus...Hill...Judith Basin...Liberty...

Winter Weather Advisory until 3 PM MDT this afternoon

Winter Storm Warning until 6 PM MDT this evening Eastern
Glacier...Eastern Pondera...Eastern Teton...Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

Flood Advisory for snowmelt in Jefferson...Broadwater...and
Northern Gallatin Counties until Friday night.


$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.