Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 182313 AAA

Area Forecast Discussion...CORRECTED
National Weather Service Great Falls MT
510 PM MDT Sun Mar 18 2018


Areas of snow and some fog will continue to cause minor impacts
across central and north-central Montana through tonight and Monday.
Temperatures moderate early this week, before a cooler and more
unsettled pattern potentially returns late in the week.



Today through Monday night...Areas of light snow and snow showers
will continue into this evening and overnight across the area in
association with a weakening shortwave that had been a closed upper
low across our area. A more focused area of snow will develop this
evening along the Northern Rocky Mountains this evening in
association with another disturbance rotating the upper low in
southern Canada. This will bring another round of accumulations from
Marias Pass north as well as extending eastward along and east of
the Hi-Line. A Winter Weather Advisory continues for the Northern
Rocky Mountain Front beginning at 9 pm this evening and extending
through Monday morning. Advisories may need to be extended east once
confidence increases in snow accumulations to the east across far
north-central Montana. In the wake of the upper level disturbance
passage, downsloping and subsidence aloft should help to scour out
the lower clouds that have plagued Central MT of late. Precip will
wind down as well, but may linger a bit longer in the mountains. CC

Tuesday through Saturday...Main forecast concerns are warming
temperatures, followed by a return to wet and unsettled weather.

H500 ridge over the Desert Southwest/Great Basin will amplify over
the Rockies Tuesday and into the day on Wednesday, all the while a
shortwave over the Gulf of Alaska digs towards the Pacific Northwest
and deepens. A weak shortwave traversing the amplifying ridge
Tuesday afternoon will bring some slight chance POPs to Southwest
Montana where better low- to mid-level moisture resides, but
otherwise will generally just bring some high clouds to the
remainder of North Central Montana for the afternoon/evening hours
on Tuesday. During the day on Wednesday the H500 ridge axis slides
east across Southwest and North Central Montana, with the flow
becoming increasingly southwesterly by the evening/overnight hours.
1000-500 mb thickness values on Wednesday climb to around 435-445dam
and warm air advection increases ahead of the approaching H500
trough over the Pacific Northwest, which should support high
temperatures in the 40s/50s south and west of a Browning, to Great
Falls, to Lewistown line, and the 30s north of this line (with the
coolest reading over Blaine and Hill counties where a substantial
snowpack still resides). Precipitation chances over the mountains of
Southwest Montana and along the Continental Divide on Wednesday will
be on the increase as the H700-H500 southwest flow begins to usher
in additional Pacific moisture, but will likely be very showery in
nature. High temperatures on Thursday will be similar to that of
Wednesday as 1000-500mb thickness values remain in the 435-445dam
range, however, increasing mid-level clouds and precipitation
coverage could hold temperatures down slightly. As just stated,
precipitation coverage is expected to be on the increase across most
of Southwest and North Central Montana during the day and night on
Thursday, as synoptic scale ascent associated with a shortwave
rotating through the main H500 trough moving from the Pacific
Northwest and towards the Northern Rockies overspreads the region.
Model solutions begin to diverge with the evolution of the upper
level pattern from Friday onwards, which will have an affect on the
timing of additional rounds of precipitation for Southwest and North
Central Montana. However, continued wet and unsettled weather is
expected to end the work week and persist into the first half of the
weekend. - Moldan


Updated 2310Z.

Snow showers continue across much of the area this afternoon and
will continue...but diminish somewhat this evening. Low
clouds/fog/mtn obscurations will remain a concern areawide with
LIFR/IFR/MVFR conditions likely. A band of heavier snow will develop
after 00z this evening over the Northern Rockies, then will
move/expand east-southeast across the northern tier counties during
the overnight into the early morning Monday. Fog will develop over
much of north central Montana, with visibilities and ceilings
gradually improving Monday afternoon. CC/db


Updated 18/400 AM.

Daytime high temperatures will be on the rise at both low and high
elevations into the middle of the upcoming work week, with
temperatures peaking on Wednesday and Thursday in the 40s and 50s
across most of Southwest and North Central Montana. Precipitation
coverage will be on the increase from Wednesday and into the first
half of the weekend, with some of the precipitation falling in the
form of rain, especially at lower elevations (i.e. valleys and over
the plains of North Central Montana). Increased snowmelt is likely
by the middle of the week, as the combination of warming
temperatures and rain falling on the antecedent snowpack occurs.


GTF  22  40  24  43 /  20  10  10   0 CTB  17  34  21  38 /  80  60
10  10 HLN  22  41  25  44 /  20  10  10  10 BZN  20  39  21  43 /
60  20  20  10 WEY  12  31  12  34 /  30  20  30  20 DLN  17  36  17
 39 /  20  10  10  10 HVR  16  31  18  35 /  60  80  30  10 LWT  19
37  23  40 /  30  30  20   0


Winter Weather Advisory from 9 PM this evening to noon MDT Monday
Eastern Glacier...Northern Rocky Mountain Front.

Flood Advisory continues until further notice for snowmelt in
Jefferson...Broadwater...and Northern Gallatin Counties until Monday


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