Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 020456
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT Wed Apr 1 2015

UPDATED AVIATION SECTION

.DISCUSSION...
Area remains under the broad circulation of a mid level closed low
centered over southern Saskatchewan this evening. Scattered showers
over much of the region late this afternoon into earlier this
evening have largely ended as the airmass has stabilized. As the low
over SK slowly moves SE east later tonight, moisture wrapping around
to the north and west of the low will spread south into north
central MT tonight while additional cooling aloft also moves in and
winds aloft become more northwesterly. Band of rain/snow showers
currently along the Hi-line will sag south tonight with additional
snow showers possible later tonight primarily focused along the
Rocky Mtn Front and central MT mtns as flow aloft becomes more
northwesterly. Hoenisch

&&

.AVIATION...
UPDATED 0455Z.
A disturbance aloft and a weak cold front continues to move across
the area. Scattered showers will continue to develop behind the
front and will likely continue beyond 12z. Winds will shift to the
north-northwest behind the front and become gusty for a few hours.
The airmass will remain unstable with showers developing again after
18z. VFR conditions prevail with MVFR conditions possible in the
vicinity of showers.

&&

.PREV DISCUSSION...
/ISSUED 600 PM MDT Wed Apr 1 2015/

Tonight through Friday... Central Montana will be underneath a broad
trof tonight. Circulation around the low pressure in Saskatchewan
will bring a push of cooler air across the border. This will affect
mainly the northeast zones where light snow will be possible. The
remaining portions of the CWA will also be affected by a weak
shortwave moving through the northwest flow aloft. This will
continue the chance of showers into the night. Temperatures will be
cold enough in most locations for snow but accumulations are not
expected to be significant. The air mass will become slightly
unstable Thursday afternoon and, in addition, another weak shortwave
will move through the region. A slight chance of showers will
again be expected especially in the afternoon. Heights will be
rising aloft and the air mass will dry during the night. A high
pressure ridge will be over the Rockies Friday, the air mass will
remain dry, and temperatures will rise back to near normals. Zelzer

Friday night through Wednesday...Medium range models start out the
period with shortwave ridging over Montana for mostly dry conditions
Friday night. Models show good agreement that a trough in the Gulf
of Alaska will drop southward along the West Coast with a moist and
somewhat unstable southwesterly flow aloft developing over Montana
through the weekend. Unfortunately, model solutions begin to diverge
significantly by the end of the weekend as the main trough along the
coast ejects energy in the southwest flow. The GFS, in particularly,
uses this energy to develop a secondary low that tracks across
Montana Sunday night and Monday while the ECMWF keeps the core of
the trough firmly ensconced near the Oregon-California border. Have
increased the chance for precipitation during this time frame but
have not gone as cold as the GFS guidance suggests could be possible
for early next week. Model solutions begin to agree once again by
Wednesday as both models gradually strengthen the upper trough over
the southwestern US as ridging develops along the West Coast. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  29  47  29  54 /  20  40  30  10
CTB  26  46  26  51 /  30  40  30  10
HLN  30  49  29  55 /  10  40  30  10
BZN  21  48  20  54 /  20  40  40  10
WEY  14  41  11  45 /  50  50  30  10
DLN  22  45  21  53 /  20  40  30   0
HVR  27  50  25  57 /  30  20  20  10
LWT  27  46  27  54 /  20  30  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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