Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 190430
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1028 PM MDT Fri Apr 18 2014

UPDATED AVIATION SECTION

.UPDATE...A strong cold front blasted through Montana during the
mid to late afternoon hours producing strong gusty winds across
much of my forecast area. Scattered showers and isolated
thunderstorms accompanied the frontal passage with a line of
severe thunderstorms coalescing in northeast Montana during the
evening. Activity is quieting down this evening as the most active
weather pushes into the Dakotas but gusty winds continue to blow
along the Rocky Mountain Front. Also, isolated strong winds have
been occasionally popping up in unexpected locations through the
evening hours and could continue to do so. As a result, I will
continue the High Wind Warning through midnight at which time
conditions will be reassessed to determine if it is safe to drop the
warning or whether an extension will be required. For update
purposes have made a few changes to overnight winds to keep them
close to observed and expected conditions across the area while
still keeping strong winds in the warning area. Have also made
changes to lower clouds and pops for much of the area. Best area
for isolated showers to continue will be in my northeast zones
including the City of Havre. Temperature forecast continues to
look good and the remainder of the weekend should see quieter
weather. mpj


&&

.AVIATION...
UPDATED 0428Z.
VFR conditions are expected across north central and southwest
Montana through at least Saturday evening. Clouds and strong and
gusty westerly winds have mostly decreased across the area. However,
with a surface low pressure area moving slowly east across southern
Saskatchewan, gusty winds with mid level clouds and isolated showers
will persist through 09Z along the Canadian border (including KCTB
and KHVR). An upper level ridge of high pressure will then move into
the area for Saturday, with only areas of mid and high cloudiness
passing overhead. Westerly winds will become breezy again for
Saturday as well, but they will not be nearly as strong as those
today.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 535 PM MDT Fri Apr 18 2014/

Today through Sunday...Isolated showers and thunderstorms will
continue this afternoon as an upper-level trough continues to move
over the Treasure State. Some showers may continue brief heavy
rain, gusty winds over 40 mph and graupel. These showers and
thunderstorms will diminish after sunset with loss of daytime
instability. Strong westerly winds will persist along the Rocky
Mountain Front and adjacent plains with wind gusts up to 60 mph
and a High Wind Warning remains in effect until Midnight. Drier
and warmer conditions are expected on Saturday as an upper- level
ridge of high pressure builds into the Northern Rockies. The ridge
will quickly shift east by Saturday night as the next upper- level
trough approaches. Another period of strong and gusty westerly
winds are expected along the Rocky Mountain Front with a slight
chance for showers across north- central and southwest Montana.
Any precipitation will be light with less than one-tenth of an
inch of liquid expected. As for winds, confidence is low on the
potential for high winds exceeding 57 mph, however will continue
to monitor for possible high wind highlights. Temperatures will
climb above seasonal averages on Saturday and lower a few degrees
to near seasonal averages on Sunday in the wake of the upper-
level disturbance. MLV

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  31  65  40  59 /  10   0  20  20
CTB  29  61  36  56 /  10   0  10  10
HLN  34  68  39  62 /  10   0  20  10
BZN  28  68  33  63 /  10   0  20  10
WEY  24  56  33  56 /  10   0  20  10
DLN  29  67  34  62 /  10   0  10  10
HVR  31  64  38  64 /  20   0  20  20
LWT  27  63  35  58 /  10   0  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING until Midnight MDT tonight Eastern Glacier...
Northern Rocky Mountain Front...Southern Rocky Mountain Front...
Toole.

&&

$$

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