Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191734

Area Forecast Discussion
National Weather Service Great Falls MT
1140 AM MDT Wed Oct 19 2016

Latest satellite/radar/webcam imagery shows weak shortwave trof
continuing to exit our area and heading into southeast MT. Still
have some very isolated light valley rain/mtn snow showers mainly
along and south/east of a line from the Bears Paw Mtns to Three
Forks/Whitehall. Any additional rain/snow amounts will be minimal.
A weak high pressure ridge currently over eastern WA/OR will move
east of the Continental Divide by late aftn/early evening, bringing
clearing skies across the region. Just minor forecast adjustments
this morning to lower precip chances behind the departing shortwave


Updated 1740Z.
Light showers are exiting the region while some patchy fog developed
in the Havre area. The fog should burn off by 21z or so...with
mostly VFR conditions expected overnight. Expect increasing
clouds/showers along the Rocky Mountain Front late tonight and
through the morning on Thursday. The western mountains will be
obscured at times on Thursday. Gusty west winds will also develop
over the northern Plains by late Thursday morning. Brusda


/ISSUED 552 AM MDT Wed Oct 19 2016/

Today through Friday...As a weak shortwave trough exits our CWA
to the east by this late afternoon, a shortwave ridge and
associated drier airmass will build-in from the PAC NW.
Accordingly, lingering rain and snow showers, mainly over higher
terrain, should taper-off by early evening. Dry and quiet weather
is then expected tonight as the aforementioned ridge crests over
our region. On Thursday, the ridge will exit to the east as a
fast-moving shortwave trough approaches from the Pac NW. This
disturbance will renew the potential of scattered rain showers
and higher-elevation snow showers, especially over and near the
mountains. At this time, expect this disturbance to move through
our CWA Thursday evening through early Friday morning. In
addition, this disturbance will allow a lee surface trough to
develop/strengthen over the plains of Alberta and north-central
Montana Thursday into Friday morning. Thus, the environment will
become favorable for gusty southwest to west surface winds along
and near the Rocky Mountain Front. At this time, gusts look to be
marginal at worst for any high wind highlights. By late Friday
morning, another shortwave ridge should begin overspreading north-
central and southwest Montana from the west, allowing dry weather
to return to the bulk of the area. However, a few rain showers and
higher-elevation snow showers may linger along the Rocky Mountain
Front, including Glacier National Park. In addition, surface winds
will ease as the surface pressure gradient relaxes.

Snow levels will be variable throughout the period and range
between about 5000 feet and 8000 feet MSL. At this time, none of
the mountain passes are expected to receive significant or
impactful amounts of snow accumulation. This afternoon`s highs
will reach the upper 40`s to mid 50`s for most places and will be
near-normal to about 10 degrees below normal. Thursday and Friday
will have highs in the mid 50`s to lower 60`s for most locations.
These highs will be near-normal. Jaszka

Friday Night through Wednesday...The general forecast trend is
still on track for much of this period, but some differences have
developed in the Friday night through Saturday period and for the
Tuesday through Wednesday period. There is agreement in bringing
a weak shortwave trough through the westerly flow aloft Friday
night into Saturday, but the difference is in the timing and
placement of potential showers associated with it. The ECMWF
moves a band of precipitation over the forecast area Friday night
into Saturday morning, with the focus being over Southwest and
Central Montana. The GFS delays it until during the day on
Saturday and keeps it more so across North Central Montana. With
this significant of a discrepancy, will stay with more of a
compromise solution until models come into better agreement. Will
go with a broad brushed chance of precipitation mainly over North
Central and Central Montana. The upper level high pressure ridge
will rebuild over the Rockies/Great Plains for Sunday into Monday
as a deep upper level low pressure trough digs south off the
Pacific coast. Under the resulting southwest flow aloft, a few
showers will likely develop over the mountains, but the plains
will mostly remain dry. After Monday, the forecast models move
shortwave troughs of varying timing and strength over the forecast
area. However, they generally yield a solution similar to that
from Sunday into Monday, of showers mainly over the mountains with
less of a chance over the plains. High temperatures will likely
remain within 5 degrees above and below normal through the period
(mostly upper 40s and 50s), and lows will be a bit warmer than
normal (mostly 30s). Temperatures will likely warm through Monday,
then cool a bit with the shortwave passages Tuesday into
Wednesday. Coulston


GTF  55  35  57  42 /  10  10  20  20
CTB  52  31  53  37 /  10  10  20  10
HLN  52  32  58  38 /  40  10  10  20
BZN  50  30  55  38 /  30  10  10  10
WEY  39  22  44  28 /  20  10  10  10
DLN  49  29  54  35 /  10  10  10  10
HVR  50  31  55  40 /  10  10  10  20
LWT  50  33  55  40 /  10   0  10  20




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