Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 210232

Area Forecast Discussion
National Weather Service Billings MT
732 PM MST Tue Feb 20 2018

Water vapor imagery and 500H analysis shows low heights across the
region with a weak shortwave dropping through NW Montana. Other
than some light snow showers over the western mountains, and an
eventual increase in high cloud from the west, our weather will be
quiet tonight. Cold surface ridge remains in control and we will
see below zero temperatures again across the cwa. Areas with a
drainage wind and ridgetop exposure will be a bit warmer, while
eastern valleys will see the teens to near -20F below. Have
tweaked temps, winds and sky cover a bit. Otherwise forecast is in
good shape. Record low of -18F at Miles City will be challenged.



.SHORT TERM...valid for Wed and Thu...

Upper trof axis exiting to the east/southeast today with clearing
skies over the region. We do have another short wave within the
mean cyclonic flow diving quickly down into the northern Rockies
tonight. This still look like it may produce some light snow or
snow showers over our Absarokas/Beartooths tonight through
Wednesday evening, but not much lift or moisture over our lower
elevations. So we are not currently expecting anything more than
maybe a flurry over the plains in the short term.

Lows tonight will not be quite as bad as last night in the
west...possibly colder in the east. Near record lows possible at
Miles City and Billings tonight.

Aforementioned short wave will drop into the Great Basin and
reinforce the broad upper trof over the inner mountain west for
Thu. This will mean a slow temperature recovery across our region
as there is no westerly wind component to help push the cold air
out. BT

.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...

Only minor changes for the extended forecast period, as overall
pattern remains fairly quiet, with the exception of persistent mountain
snow showers. Temps will return to 30s by Saturday, with
persistent 30s through early next week.

A dry upper level trof finishes crossing the area Friday morning,
bringing a return to zonal flow by late Friday. This opens the
door for downslope winds to increase and finally begin to scour
out stubborn Arctic airmass. Increased moisture advection in this
flow should bring a good shot of snow to the higher elevations on
west facing slopes.

Temperatures hit the 20s west and teens east on Friday, with wind
aided 20s and 30s on Saturday and Sunday. Gap wind potential for
Friday night Thrus Sunday indicate possible highlights, so will
need continued attention in future shifts. A cold front is
progged into the region Sunday afternoon, which will calm winds
down and increase lower elevation snow chances through Monday. GFS
looks a bit better for this system bringing snow across the
region, while the ECMWF holds most of the moisture over the
mountains and near foothills. Additionally, this system is moving
fairly quickly, so snow amounts should be somewhat limited in
most areas. That said, there is a period of upslope flow, that
could result in a bit more significant snow accumulations, and
would jive with what the ECMWF is currently advertising. Zonal
flow transitions to southwest flow on Monday ahead of an
approaching broad upper level weather system. Southwest flow will
bring continued snow to western mountains, with GFS indicating a
better chance of a snow into the western and central zones. This
initial activity ties directly to the large weather system progged
to cross the region for the latter half of next week. This system
impacts much of the western CONUS over the past several GFS runs.
The latest ECMWF continues to trending closer the GFS solution,
but at this time is favoring more of a glancing blow, and dry
slotting much of the CWA, before shifting quickly east. This type
of system is a one of the northern rockies heavy snow patterns so
will continue to keep close tabs on it as it develops over the
next week or so. AAG



Expect mainly VFR conditions to prevail overnight, with a mid
level cloud deck is expected to develop over much of the area late
this evening and overnight. Snow showers are possible over the
Beartooth/Absaroka mountains tonight, with mountain obscurations
possible. AAG



    Wed     Thu     Fri     Sat     Sun     Mon     Tue
BIL 904/016 902/020 904/024 011/033 014/032 017/033 015/028
    00/B    00/U    01/B    12/J    22/S    22/J    32/J
LVM 906/019 001/024 001/026 016/034 017/035 019/035 017/031
    01/B    11/B    11/B    13/S    23/S    33/J    32/J
HDN 913/017 907/019 907/023 006/032 010/031 012/032 012/027
    00/B    00/U    01/B    11/B    22/S    22/J    22/J
MLS 917/012 910/017 909/017 002/027 007/025 008/026 008/021
    00/U    00/U    00/B    01/B    22/S    22/J    21/B
4BQ 918/015 913/019 905/020 003/030 009/029 011/031 012/027
    00/U    00/U    01/B    01/B    12/S    21/B    22/J
BHK 915/015 907/020 906/017 001/027 007/025 007/027 008/022
    00/U    00/U    00/B    01/B    22/S    22/J    21/B
SHR 914/019 904/024 904/023 002/032 010/031 012/034 012/028
    00/U    00/B    01/B    01/B    22/S    22/J    22/J




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