Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 181150
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
548 AM MDT Fri Apr 18 2014

UPDATED AVIATION SECTION AND CORRECTED HYDROLOGY SECTION WHERE
PHRASE TUESDAY NIGHT THROUGH WEDNESDAY AFTERNOON SHOULD BE TUESDAY
NIGHT THROUGH THURSDAY AFTERNOON

.DISCUSSION...
Today through Sunday...An upper trof will move along the
U.S.-Canadian border today bringing scattered showers and cooler
temperatures as an associated cold front pushes across the area.
The surface pressure gradient will tighten and westerly winds will
become gusty by late morning. The strongest winds will occur along
the Rocky Mountain Front and over Glacier and Toole counties. A
high wind warning will remain in place for this area through
tonight. The upper trof moves quickly east and will cross into
northern North Dakota by evening. In it`s wake, high pressure will
build over the Pacific Northwest tonight and move east of the
Continental Divide Saturday. Dry conditions Saturday will also be
accompanied by temperatures reaching the 60s. The ridge,
unfortunately, will be short-lived as a weak upper trof moves
across southern Canada Saturday night/Sunday morning. This feature
lacks any significant moisture and its only effects should be an
increase in clouds and slightly cooler temperatures for Easter
Sunday. Winds will become gusty again Saturday night and into
Sunday though speeds will likely remain below warning criteria.
Temperatures will be near seasonal averages today and climb above
seasonal averages for the weekend.

Sunday night through Friday...Models are in decent agreement into
Tuesday but then significant differences show up. An upper ridge
will result in Sunday night being dry and quite likely Monday as
well. A strong upper trough off the west coast Monday will move into
the west coast states Tuesday with moisture increasing over the area
in the southwest flow aloft. Expect scattered showers to develop
over southwest Montana and spread to central Montana by afternoon.
There will also be a threat of thunderstorms. Precipitation will
increase Tuesday night. Will continue with the inherited forecast
which had chances of precipitation ranging from 70 pct to 100 pct
over a good portion of the forecast area. Models really begin to
diverge by Wednesday. The GFS is dry over most of the forecast area
and in particular over the plains. The ECMWF and GEM models continue
with precipitation over the entire forecast area. On Thursday the
GFS and GEM models have precipitation over the forecast area
associated with an upper low over the Dakotas. On the other hand the
ECMWF has an upper ridge over western Montana with dry conditions
except for possibly the western mountains and southwest Montana. Due
to model differences have stuck close to the inherited chances of
precipitation which show a gradual decrease. Still expect
unseasonably mild temperatures Monday and Tuesday before cooling
sets in the wake of a cold front Tuesday night. Blank

Hydrology for Sunday night through Friday...Expect increased snow
melt Monday through Tuesday as snow levels range from 7000 to 8000
feet in the north to 8000 to 9000 feet in the south. As for
precipitation from Tuesday night through Thursday afternoon have
high confidence that most locations should see at least a quarter of
an inch of precipitation but some models are showing small areas
receiving as much as 1.5 inches to 2.5 inches during that time
frame. Of course with the model differences confidence in
precipitation details is very low at this point. The threat for
flooding will increase with increased snowmelt followed by increased
precipitation. For Wednesday and Thursday with the cooler
temperatures snow levels should drop to near or below 6500 feet.
Blank

&&

.AVIATION...
UPDATED 1148Z.
A band of showers from KHVR to KGTF to KBTM will affect KLWT and
KBZN early this morning. More showers could develop SE of a
KGTF-KHLN line this afternoon ahead of a weather disturbance aloft
which will move through western and central Montana this afternoon
and early evening. In these showers there will be a threat of brief
MVFR ceilings. Still another band of showers could affect north
central Montana including KHVR this evening. A cold front will sweep
through the area this afternoon it should reach KCTB/KHLN/KGTF/KBTM
17z-19z then KHVR and KBZN around 21z and KLWT 22z-23z. Strong gusty
westerly winds will develop near and behind the cold front
especially over the plains where gusts of 45 kts to 55 kts are
expected over the Rocky Mountain Front and 35 to 45 kts farther
east. Behind the weather disturbance aloft mentioned above expect
decreasing clouds with the exception of north central Montana where
there could be some lingering showers as mentioned above. Blank

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  31  64  40 /  30  10   0   0
CTB  49  28  61  37 /  20  20   0   0
HLN  57  34  68  39 /  30  10   0   0
BZN  59  29  67  33 /  60  20   0   0
WEY  50  25  55  32 /  70  30   0   0
DLN  59  30  66  35 /  40  20   0   0
HVR  61  31  64  36 /  50  20   0   0
LWT  56  28  62  36 /  40  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING from 9 AM this morning to Midnight MDT tonight
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front...Toole.

&&

$$


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