Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300255
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
855 PM MDT Fri Aug 29 2014

.DISCUSSION...
Update forthcoming. Have made some minor adjustments to the PoP
grids for the remainder of tonight. Water vapor and IR satellite
imagery clearly show upper trof position as it approaches western
Montana. Showers and isolated thunderstorms have developed out ahead
of the trof and these continue to move across southwest Montana.
This precipitation should increase in areal coverage after midnight
and begin spreading north and east as noted by the latest RUC and
HRRR analysis. Wet and unsettled morning continues to look on track.
Temperatures look reasonable.

&&

.AVIATION...
UPDATED 2340Z.
A weather disturbance and cold front will move through the area
Saturday morning. Showers will develop ahead of the cold front over
southwest and central Montana late tonight then continue into
Saturday morning as the disturbance and cold front move through.
During the afternoon expect more showers and a few thunderstorms
near and south of a KLWT to KHLN line with scattered showers north
to near U.S. route 2. As mentioned in the previous discussion expect
generally VFR conditions with the showers/thunderstorms although can
not rule out local MVFR conditions. Blank

&&

.PREV DISCUSSION...Issued 250 PM MDT Fri Aug 29 2014

Tonight through Sunday...Isolated showers and thunderstorm will
develop in far Southwest Montana this evening then increase in
coverage overnight. Showers and storms spread into Central Montana
by Saturday morning then continue on into Eastern Montana as an
associated upper wave moves east. A reinforcing trough swings into
the state during the afternoon with additional showers and
thunderstorms developing in Southwest and Central Montana through
the afternoon; however, only isolated showers are expected over my
northwestern zones. Conditions will improve overnight as the
trough axis moves eastward leaving a cool and slightly unsettled
airmass in place over the forecast area for Sunday. mpj

Sunday Night through Friday...Relatively quiet weather conditions
expected for first half of next week.  A weak, quick-moving
shortwave trof will sweep across the state on Mon.  GFS and GEM
forecast models indicate little, if any, precipitation with the trof
while the ECMWF continues to indicate broad coverage of showers
mainly over the southwest counties on Mon aftn/eve. Since a
northwest flow pattern aloft (like we`ll have on Mon) usually will
generate isolated showers with even minimal moisture and
instability, have kept in a slight chance of rain showers over the
astern third of the forecast area on Mon.  Weak, transient high
pressure ridging will make for dry conditions from Tues through Wed,
with slightly warmer high temperatures (low to mid 70s) as winds
aloft transition to westerly.  Stronger shortwave trof is forecast
to arrive on Thurs, though model solutions still showing some marked
run-to-run differences on the shortwave`s timing and precipitation
coverage for Thurs and Fri. General model consensus is that most of
the precipitation will occur Thur eve through midday Fri, behind a
surface cold front that tracks across the region on Thurs morning.
Some locations, especially along/south of a Helena-Lewistown line
may see rainfall totals of 0.25-0.50 inch, with lighter amounts
further north.  The front will also usher in a cooler Canadian
airmass and bring snow levels down to the 6500-7500 ft range over
the central mountains and the Rocky Mtn Front.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  73  48  69 /  20  50  10  10
CTB  53  71  46  67 /   0  20  10  10
HLN  56  73  47  70 /  40  60  20  10
BZN  49  70  44  66 /  40  70  40  10
WEY  43  61  35  57 /  40  80  50  10
DLN  51  69  45  65 /  50  70  40  10
HVR  55  76  49  73 /   0  50  10   0
LWT  53  72  48  67 /  20  60  20  10

&&

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

$$

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