Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 151704
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1004 AM MST Mon Dec 15 2014

.UPDATE...
The main change to the forecast was to cancel the freezing fog
advisory for Judith Basin and Fergus Counties. Visibilities have
improved in the advisory area. Otherwise made some minor tweaks to
the sky cover forecast for the remainder of this morning. Latest
guidance suggests that Cut Bank and Great Falls will not get as
warm as forecast in part due to snow cover and upslope flow so
have lowered their forecast highs several degrees. Blank

&&

.AVIATION...
UPDATED 1220Z.
A band of mid level cloudiness and light snow extending from the
Little Belt Mountains south into KBZN and southeast toward KBIL will
continue to diminish through 18Z, keeping occasional MVFR conditions
in the KBZN area until 15Z. Otherwise, low clouds have spread over
much of north central and southwest Montana overnight. The clouds in
southwest Montana will remain south of KHLN and west of KBZN before
dissipating after 16Z. Patchy fog with localized MVFR/IFR conditions
may then form there after 03Z, including the KHLN and KBZN areas.
However, over north central Montana, the low MVFR/IFR clouds will be
more widespread and persistent. Currently, the clouds are along and
east of Interstate 15, east of KCTB and very near KGTF. Am thinking
that these clouds will occasionally move in and out of these areas
through 17Z, remain east of these areas between 17Z and 00Z, then
move back into the terminal areas after 00Z as winds shift more
easterly. Low clouds will likely be more persistent east of these
areas through at least 12Z Tuesday, including the KHVR and KLWT
areas. In fact, dense fog and very low clouds causing LIFR
conditions in the KLWT area will likely persist there until at least
16Z, then ceilings should lift to low MVFR/IFR levels. Forecast
models differ on whether or not these low clouds will dissipate, so
forecaster confidence on the persistence of the clouds is low, but
the current depth and extent of the clouds tends to lead to more
persistent cloudiness.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 520 AM MST Mon Dec 15 2014/

Today through Wednesday...Weather system that brought widespread
snow to the region on Sunday continues to move off to the east
this morning. Behind the weather system widespread low clouds have
moved into central and eastern portions of the state while areas
immediately adjacent to the Rocky Mountain Front are currently
clear. Latest regional model runs suggest that these low clouds
will most likely remain entrenched across much of central Montana
today and a good portion of tonight. Given the low cloud cover
have also opted to add areas of fog to the forecast tonight and
Tuesday morning. It is also possible that some persistent low
cloud cover could persist throughout much of the short term as
winds are expected to remain generally light through the period
with a strong inversion in place. It appears that the best chance
for this inversion to be broken will be Tuesday night into
Wednesday as the next batch of shortwave energy sweeps across the
northern Rockies bringing increasing mid-level clouds and a chance
for precipitation to the southwestern portion of the forecast
area. mpj

Wednesday Night through Monday...Forecast models continue to
indicate that the region will be under the influence of a
splitting westerly flow aloft through the period. Overall, there
will be a chance of snow in the mountains of western and southwest
Montana, but the plains will generally stay dry due to breezy
westerly downsloping winds. Two upper level low pressure troughs
will move through the western CONUS. The first one will move
through Wednesday night into Thursday, while the second one
effects the area Saturday into Sunday. However, the flow aloft
will move only some of the energy over Montana and send the bulk
of the energy over the southwestern CONUS. As a result, there will
be a slightly better chance of snow in the mountains during these
times, but am not anticipating enough snow to warrant winter
weather highlights at this time. After the second trough passage,
the flow aloft becomes quite strong (700 mb winds of 60 to 70 kt)
for Sunday night into Monday, which may cause winds to approach
High Wind criteria, especially along the Rocky Mountain Front.
Have therefore increased winds during this period and will
continue to monitor the situation for potential High Wind
highlights. Temperatures are expected to remain near normal
through most of the period. However, as the winds increase Sunday
into Monday, temperatures should warm to about 10 degrees above
normal across most of the area. Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  26  17  31  23 /   0   0   0  10
CTB  20  15  29  19 /   0   0   0  10
HLN  30  14  32  21 /   0   0  10  20
BZN  28   8  30  19 /  10   0  10  20
WEY  27   6  30  17 /  10   0  20  30
DLN  30  15  34  23 /   0   0  10  20
HVR  28  12  30  15 /   0   0   0   0
LWT  31  16  35  21 /   0   0   0  10

&&

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

$$

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