Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 152055
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
255 PM MDT Tue Apr 15 2014

.DISCUSSION...

Tuesday through Thursday...A low pressure shortwave will move east
of central Montana tonight but the air mass will remain under the
influence of both disturbed flow to the west and an approaching trof
from the north. At lower levels, surface low pressure to the east
and building high pressure to the west will keep brisk, westerly
surface winds in the forecast. The air mass will become fairly
saturated at low levels by late evening across the plains and
central zones. Moist upslope flow will continue across this area
into early Wednesday morning and the air mass will dry during the
day. However, moisture will be sparse to the west from Lewis and
Clark county down to Beavherhead. Snow accumulations continue to be
an area of low confidence. ECMWF and GFS show more moisture than the
NAM and GEM. In addition, change-over from rain to snow and the warm
surface temps will limit amount of snow on the ground. Will continue
the current high lights, including the warning at higher elevations
over the Northern Rockies. A high pressure ridge will be over the
Idaho Panhandle Thursday and the air mass will warm and dry...and
temps generally recover closer to normals. Zelzer

Thursday night through Tuesday...Expect a few light showers over the
Rocky Mountain Front on Thursday night...with the showers spreading
eastward out over the Plains on Friday. The main upper level
disturbance producing the precip during this period will move across
southern Canada...but enough moisture/instability will move across
MT that showers will develop...especially over North Central MT. The
precip activity should come to an end by early Saturday
morning...and overall a very nice weekend is expected for all of
North Central and Southwest MT. There is a very small chance for an
isolated shower over the mountains of the Rocky Mountain Front and
around Big Sky this weekend...but otherwise...most areas will be dry
with spring like temperatures. Afternoon highs on Saturday will be a
few degrees above normal...but on Sunday high temperatures should
average 4 to 8 degrees above normal. There is the potential that the
high temperature for Sunday could be a few degrees warmer than
currently forecasted if the GFS model pans out.

Then looking ahead to next Monday through Wednesday...the storm
system that was previously forecasted to move into the region for
Monday into Tuesday...now looks like it will move into the region on
Tue/Wed. Both the GFS and EC have different solutions on this event.
The GFS is very wet/mild and flood highlights would probably be
needed. The EC is not quite as wet...but it would favor the
potential for severe thunderstorms. Thus for now...with the
uncertainty...I will lean more towards climo pops and temperatures
that are near/just above normal...and see how the GFS/EC models work
themselves out over the next few model runs. Brusda

&&

.AVIATION...
UPDATED 1750Z.
A cold front moving southward out of Canada will lower ceilings to
IFR conditions, mainly after 03z/Wednesday. Precipitation will be
showery in nature but best chances will be at KCTB, KGTF, KLWT, and
KBZN. A rain/snow mix is likely initially but with evaporative
cooling expect mainly -SN after 03z or 04z. Visibilities will
occasionally drop to LIFR in the stronger showers. The low ceilings
will continue through Wednesday morning but -SHSN will become more
isolated in the 15z-18z/Wednesday period. Also, mountain
obscurations will continue through Wednesday. Uttech

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  31  40  31  55 /  80  70  30  20
CTB  28  37  25  50 /  80  40  40  30
HLN  33  47  32  61 /  70  60  30  20
BZN  28  48  28  62 /  70  60  40  10
WEY  19  42  22  51 /  70  50  40   0
DLN  28  49  29  61 /  40  40  20  10
HVR  30  41  26  53 /  70  30  30  20
LWT  28  36  25  52 /  90  70  40  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from 6 PM this evening to 6 PM MDT
Wednesday Broadwater...Cascade...Eastern Glacier...Eastern
Pondera...Eastern Teton...Fergus...Gallatin...Judith Basin...
Madison...Meagher.

WINTER WEATHER ADVISORY until 6 PM MDT Wednesday Central and
Southern Lewis and Clark...Southern Rocky Mountain Front.

WINTER WEATHER ADVISORY until 6 PM MDT Wednesday FOR ELEVATIONS
BELOW 5000 FEET FOR Northern Rocky Mountain Front.

WINTER STORM WARNING until 6 PM MDT Wednesday FOR ELEVATIONS
ABOVE 5000 FEET FOR Northern Rocky Mountain Front.

&&

$$


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