Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 171600
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1000 AM MDT Mon Mar 17 2014
Satellite imagery this morning shows the well developed upper trough
that will dig southeast across the Northern Rockies and MT today.
A Pacific cold front, associated with the upper trough, was moving
east and crossing the Continental Divide this morning, while
another cold front from the north was moving south through North
Central MT this morning, in response to deepening low pressure
ahead of the upper trough over Central/Southeast MT. Widespread
precipitation was occurring along and behind both frontal features
and will spread southeast across much of the forecast area by
early this afternoon. Snow levels have fallen quickly from 7000ft
last night to 3000-4000 ft immediately following the frontal
passages with additional cooling under the trough this afternoon
expected to change precipitation to snow for all areas. Have made
some adjustments to snow level and precip type through this
afternoon to better indicate timing of changeover. Also made some
adjustments to QPF with heaviest amounts today expected from
Rogers Pass east through the Little Belts. With higher QPF/Snow
amounts now forecast in the Rogers Pass area, have added
central/southern Lewis and Clark county to the Winter Storm
Warning for elevations above 5000 ft. Otherwise remainder of
forecast and associated winter weather highlights are on track. Hoenisch
A trough of low pressure and associated surface cold front is
beginning to move across the area. Conditions will continue to
deteriorate from north to south through much of the daylight hours
before precipitation begins to dissipate and ceilings lift around
sunset tonight. Periods of MVFR and IFR are expected in areas of
snow along with mountains obscurations. Suk
/ISSUED 634 AM MDT Mon Mar 17 2014/
This Afternoon through Wednesday Evening...Upper-level trof
currently centered in eastern WA/OR continues to make steady
eastward progress this morning. Large swath of moisture ahead of
the trof axis is generating widespread mid- and high-level cloud
cover, along with snow in the high elevations along the Rocky Mtn
Front and scattered light rainshowers over parts of the Hiline
counties. Additional scattered areas of light rain will develop this
morning east of the Continental Divide as more moisture arrives
while temperatures remain above freezing. The surface cold front
with this weather system is forecast to cross the Divide later this
morning. As the colder airmass behind the front settles across the
region, there will be a brief period of rain/snow mix in some
locations, but most spots will change over to snow fairly quickly,
with snow spreading south and east through the day. Current winter
weather advisories for the lower elevations remain in effect and
have added a small-area winter storm warning for the Little Belt
Mtns from Monarch to Kings Hill Pass as snowfall totals there may
reach 8 to 10 inches by this evening. Primary short-term forecast
models are all in good agreement on the snow through this afternoon,
but seeing some differences on when the snow will end. Half the
models taper off the snow by early evening over the central and
Hiline counties, while the remaining models have areas of light snow
continuing tonight into early Tues morning. Current forecast leans
toward the slower solution with a chance of snow showers through
tonight across the region. Tuesday looks mostly dry, though isolated
snow showers may linger over the southwest mtns and parts of the
central mtn ranges. West-to-northwest flow pattern aloft will bring
mostly cloudy but dry conditions on Wed, except for snow developing
again along the Rocky Mtn Front. Temperatures will reach low 40s
this morning ahead of the cold front, then decrease this afternoon.
But the airmass begins to moderate tomorrow with highs in the upper
30s, increasing to the upper 40s to low 50s on Wed.
Wednesday night through Monday...A return to cooler and wetter
conditions is expected as the next shortwave trough moves into the
area Wednesday night and Thursday morning. While the system does not
look too impressive right now it will usher in a pattern change to
wetter conditions and temperatures below seasonal averages. This
will likely produce rain snow mixtures over the lower elevations as
temperatures peak near freezing through the weekend and then drop
back into the 20s and teens overnight. There continues to be some
timing differences of subsequent shortwaves across the area through
the weekend, however a general northwest flow aloft will allow for
showers to develop under the moist flow aloft. This will create a
generally wet and cool outlook through the bulk of the long
term...however by Sunday afternoon and evening a shortwave ridge of
high pressure will begin to move into the area and could provide
some temporary drying.
.PRELIMINARY POINT TEMPS/POPS...
GTF 39 23 40 25 / 100 60 20 10
CTB 32 21 38 25 / 100 40 20 10
HLN 42 25 41 25 / 90 60 10 10
BZN 41 23 38 19 / 80 70 30 10
WEY 37 12 33 8 / 80 60 20 10
DLN 37 18 35 18 / 80 60 10 10
HVR 37 27 43 26 / 100 50 30 10
LWT 36 23 37 23 / 100 80 30 10
WINTER WEATHER ADVISORY until 6 AM MDT Tuesday Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Madison...Meagher...Northern Rocky Mountain Front...Southern
Rocky Mountain Front...Toole.
WINTER STORM WARNING until 6 AM MDT Tuesday FOR ELEVATIONS ABOVE
5000 FEET FOR Cascade...Central and Southern Lewis and Clark...
Judith Basin...Meagher...Northern Rocky Mountain Front...
Southern Rocky Mountain Front.
FLOOD ADVISORY until Monday afternoon for Jefferson.