Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 230401 AAA

900 PM MST Mon Dec 22 2014

Update forthcoming. Moist northwest flow aloft continues to impact
north facing slopes of the Little Belt Mountains. Radar returns
indicate snow continuing over the higher peaks though intensity has
dropped off. Have lowered PoPs to scattered after midnight and snow
should gradually end by daybreak. Tuesday should be dry. Winds will
increase and become gusty along the Northern Rocky Mountain Front by
afternoon. Temperatures look good.


An unsettled northwest flow aloft will continue over Montana through
Tuesday.  Weak disturbances and pockets of moisture in the flow will
create isolated/scattered snow showers, along with VFR ceilings.
Scattered showers will diminish by 02Z, with wind gusts in the 20-25
kt range. Skies are expected to clear out overnight with only light
winds expected Tuesday morning. By Tuesday afternoon, mid and high
level clouds will be on the increase, with gusty winds along the
northern Rocky Mountain Front. db


.PREV DISCUSSION...Issued 302 PM MST Mon Dec 22 2014

Tonight through Thursday...An moist and unsettled northwest flow
continued to generate orographic snow showers over central and
southwest Montana today. This activity will end tonight as ridging
begins to strengthen over the Pacific Northwest. Fair weather
prevails on Tuesday with temperatures continuing slightly warmer
than average. A lee surface trof begins to form Tuesday evening
causing winds to strengthen along the Rocky Mountain front. Wind
gusts will peak near 58 mph at the usual locations in this area
early Wednesday. Will continue to monitor for possible High Wind
headlines. Warm advection and downslope winds push temperatures
back into the 40s on Wednesday. Precipitation will begin over the
Northern Rockies early Wednesday. Then a strong cold front is
poised to cross the International border Wednesday afternoon.
Models consistently produce precipitation along the cold front,
combining strong surface with lift associated with an upper level
jet entrance region. Precipitation will begin as rain at lower
elevations but quickly change to snow Wednesday night as the cold
front advances through central Montana. Areas of mixed
precipitation are possible with the frontal passage. Flow turns to
a northerly upslope pattern beneath a region of strong
ageostrophic divergence. Snowfall will peak in intensity Christmas
eve, continuing through morning of Christmas day. Snowfall totals
remain on target for 2 to 5 inches over the central plains, and 6
to 12 inches over mountain passes. Headlines will likely be
warranted as details come into focus. Temperatures will be colder
on Christmas Day as well across the region. Travel conditions will
be fine early Wednesday but will deteriorate over Rocky Mountain
passes Wednesday afternoon. Travel will be difficult most areas on
Christmas day. Nutter

Thursday night through Monday. Upper-level trof that
moves through our region in the midweek period now looks to linger
over the Central and Southwest Counties into Friday morning. The
main area of moisture accompanying the trof is still expected to
head toward Southeast MT on Thurs night, so any additional snowfall
into Friday morning should be light.  The system fully exits the
state by Fri night, with a short period of high pressure ridging and
dry conditions forecast for Sat.  The next weather system makes its
initial approach into MT on Sat night, and like the midweek trof,
makes a somewhat slow progression through our region on Sun.  Latest
GFS and ECMWF model solutions for the second system are not in close
agreement at this point, with the GFS moving the system about 6-12
hrs quicker than the ECMWF.  However, both models line up well on
maintaining slightly colder-than-average high temperatures, with
daily highs only reaching the mid 20S through Mon. MPJ


GTF  22  37  31  44 /  10  10  10  40
CTB  20  36  31  38 /  10  10  20  50
HLN  19  32  23  38 /  10  10  10  40
BZN  10  25  14  34 /  10  10  10  20
WEY   4  27  12  30 /  10  10  10  20
DLN  11  28  19  34 /  10  10  10  30
HVR  20  37  27  42 /  10   0  20  40
LWT  21  38  28  46 /  10   0  10  20



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