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000
FXUS65 KTFX 101147
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
546 AM MDT Mon Mar 10 2014

Updated Aviation Discussion

.DISCUSSION...

Today through Wednesday...Forecast area remains in the sights of
a late winter/early spring storm that will bring widespread snow
to the mountains with rain and snow at lower elevations.
Previously issued winter weather highlights appear to be in good
shape so have left them intact. However, models have brought the
heaviest precipitation northward and it now appears that
significant snow amounts will affect the Rocky Mountain Front as
well so have added this area to the Winter Weather Advisory. Other
than the widespread precipitation, the next problem for today
involves high temperatures. It appears likely that temperatures in
many locations will remain stable or drop through the day as
precipitation develops. Most lower elevation locations should
expect rain for much of the day, but as temperatures drop and snow
levels lower, the rain will change to snow during the afternoon or
evening hours. Snow continues overnight across Central and
Southwest Montana but the upper wave will begin to accelerate
southward after midnight with precipitation rapidly tapering off
from north to south. Only scattered showers are expected over
Southwest Montana on Tuesday morning and skies are expected to
become clear across the entire region by early evening. Quiet
weather prevails on Wednesday with temperatures rebounding
upward into the 50s across North Central Montana while 40s are
expected in the southwest. mpj

Wednesday night through Monday...Medium range weather models
continue to generally depict a ridge in the large scale upper level
weather pattern over the western US late this week into early next
week. Several fast moving shortwave troughs originating in the NE
Pacific migrate over the ridge and drop SE across MT, bringing
brief  periods of increased winds and slightly cooler temperatures
in an otherwise dry and somewhat mild weather regime. The first wave
tracks east along the US/Canadian border Thursday afternoon with
main impact likely being a period of stronger winds over north
central MT while the bulk of the moisture associated with the
shortwave remains north of the border. The next wave drops SE
through the Northern Rockies Friday night and looks to be more
potent and could bring a period of precipitation along with cooler
temps to much of the forecast area Friday night and Saturday, though
precipitation amounts are rather low and temperatures only cooling
to near seasonal averages. An upper ridge re-establishes itself over
the region Saturday night and Sunday before another shortwave trough
dives SE into the Northern Rockies and MT Sunday night and Monday.
Confidence in the timing of individual shortwave disturbances
decreases this weekend and especially early next week. Hoenisch

&&

.AVIATION...
UPDATED 1200Z.
A moist Pacific storm system moving into the Northern Rockies and
MT will bring a variety of aviation impacts today and tonight.
Lowering cigs across the region today as moisture increases with
widespread precipitation across central MT terminals this morning,
bulk of which will be rain at TAF sites with freezing levels
initially around 7000 feet this morning, lowering to valley floors
and plains by this evening. MVFR/IFR conditions will prevail at KHLN
and KBZN and expand into the KGTF and KLWT terminals late this
afternoon and evening. As freezing levels lower this afternoon and
evening, a change-over to snow is expected at KGTF, KHLN, KBZN and
KLWT, though confidence in specific timing is not high. Widespread
IFR conditions are expected in snow this evening before the system
begins to exit the region late tonight. Hoenisch

&&

.HYDROLOGY...
Another round of rain and snow Monday, followed by a warm- up
midweek, will likely increase snowmelt again and potentially
produce areas of flooding.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  24  43  26 / 100 100  10   0
CTB  40  20  43  25 /  90  80  10   0
HLN  45  27  44  23 / 100 100  30   0
BZN  44  26  39  15 / 100 100  40   0
WEY  43  22  36   5 /  90  90  60  10
DLN  45  24  39  17 / 100  90  40   0
HVR  44  23  46  23 /  40  40  10   0
LWT  44  25  41  24 / 100 100  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 3 AM MDT Tuesday Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

WINTER WEATHER ADVISORY from Noon today to 3 AM MDT Tuesday
Broadwater...Cascade...Central and Southern Lewis and Clark...
Jefferson...Judith Basin...Meagher.

WINTER STORM WARNING until 3 AM MDT Tuesday Beaverhead...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Gallatin...Jefferson...Judith Basin...Madison...Meagher.

WINTER WEATHER ADVISORY until 3 AM MDT Tuesday Beaverhead...
Gallatin...Madison.

AREAL FLOOD WARNING is in effect for Lewis and Clark County until
Tuesday afternoon.

Urban and Small Stream Flood Advisories are in effect for Gallatin,
Madison, Jefferson, Broadwater, Fergus, Meagher, Glacier, Teton,
Pondera and Judith Basin Counties until Monday.

&&

$$

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