Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 010310
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
910 PM MDT Tue Mar 31 2015

.UPDATE...

As a cold front continues to move across the area this evening,
gusty winds, scattered showers and isolated thunderstorms will
remain possible. Have kept highest PoPs for areas east of I-15,
but these showers should taper after midnight. Strong westerly
downslope winds will keep areas along and adjacent to the Rocky
Mountain Front mainly dry though there is a slight chance for a
light shower or sprinkle. Wind gusts of 55 to 60 mph will remain
possible for the Northern Rocky Mountain Front and thus will
continue the High Wind Warning into Wednesday morning. Have
expired the Red Flag Warning as relative humidity continues to
increase. The remainder of the forecast is on track. MLV

&&

.AVIATION...
UPDATED 2355Z.
A weather system aloft will be moving through the forecast area late
tonight into Wednesday morning. The associated cold front at the
beginning of the taf period will extend from Blaine County to near
KLWT and then to west of KBZN. The cold front will move out of the
forecast area by sunset. Meanwhile bands of showers will affect the
area near and and east of a line from KHVR to KGTF to KHLN this
evening. There still will be a threat of isolated thunderstorms
within these bands early this evening. Conditions should be VFR with
the showers. Another band of precipitation will affect southwest
Montana late tonight. Snow levels will have lowered enough that the
valleys will see primarily snow and with this snow there could be a
brief period of MVFR ceilings and visibilities in snow. A break in
precipitation is expected Wednesday morning before scattered showers
develop Wednesday afternoon. Gusty westerly winds will continue
through the night and then become stronger Wednesday afternoon and
shift to a more northwesterly direction. Confidence in forecast
winds is moderate except for gusty winds near showers. Blank

&&

.PREV DISCUSSION...
/ISSUED 555 PM MDT Tue Mar 31 2015/

Tonight through Thursday...The air mass generally remains dry across
Central Montana and radar shows sparse, weak echoes west of the
divide. But moisture will increase during the night and some
mountain snow should develop. The cold air associated with the cold
front is still west of the zones and will be moving into the region
during the night. A much tighter surface pressure gradient will
develop as well. Will continue the high wind warning over the
Northern Rockies until winds weaken towards morning...and also the
Red Flag Warning until cooler temps and higher humidities return
this evening. Heights aloft will continue to drop through the night
as the trof and cooler air move into the region and flow aloft will
switch to the northwest over Central Montana. Biggest concern will
be western Beaverhead county where snow levels will be dropping and
road surfaces freezing at pass level. Snow accumulations will remain
marginal, however, and have decided against any highlights. The
upper level low will deepen over Alberta/Saskatchewan during the
night and this will in turn deepen the surface low over
Saskatchewan. Strong winds will result over the zones along with an
increasing chance for some wrap-around precipitation. Broad cyclonic
flow will continue over the zones and the air mass will be unsettled
and slightly unstable Wednesday and Thursday afternoons. Scattered
showers will cover much of the region although totals will remain
low. By Wednesday night, a cold front associated with the surface
low in Canada should bring moisture across the Canadian border. The
northeastern zones will be the most affected but a deepening trof
over Nevada will keep a chance of precipitation across the central
and southwest zones as well. Temperatures will me much cooler
Wednesday and Thursday with below normal temperatures in place
Thursday. Zelzer

Thursday night through Tuesday...The medium range period begins with
an upper ridge over the western U.S. and moist and unstable
northwest flow aloft over the area. Shortwave energy moving within
this flow aloft will bring scattered showers to the mountains and
isolated showers across the plains Thursday night. The upper ridge
axis crosses the Continental Divide Friday allowing the airmass to
dry. The ridge flattens on Saturday with the flow aloft becoming
zonal. Precipitation will be confined to the western and southwest
mountains while the plains remain dry. A deepening upper trof moves
over the Pacific Northwest Easter Sunday. The resulting southwest
flow aloft will bring moisture and instability to the area with
scattered showers developing Sunday morning over southwest Montana
and then spreading north and east. A broad upper trof remains over
the area Monday and Tuesday continuing the possibility of scattered
showers. Temperatures will remain near to slightly above seasonal
averages through the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  36  53  30  49 /  20  20  30  40
CTB  34  50  27  47 /  10  20  30  30
HLN  35  52  30  50 /  40  30  20  40
BZN  30  51  22  49 /  60  40  20  30
WEY  22  43  10  42 /  30  30  30  40
DLN  30  48  22  46 /  40  40  20  40
HVR  36  57  28  51 /  40  30  20  30
LWT  35  51  28  46 /  60  20  20  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING until 6 AM MDT Wednesday Northern Rocky
Mountain Front.

&&

$$

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