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085
FXUS65 KBYZ 240307
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
907 PM MDT Mon Apr 23 2018

.UPDATE...
Forecast was in good shape this evening and have made just minor
adjustments to PoPs and temperatures based on latest obs and model
data. Water vapor imagery showed upper low centered over SE MT
this evening. Coolest cloud tops on IR imagery were over NE MT and
ND. Convection was occurring in SD, keeping the far SE zones from
filling in yet. Plenty of moisture was wrapping around the low
bringing mainly snow to areas from the foothills to Big Horn
County, then ENE through much of the eastern zones. Many areas
were reporting a half inch to an inch of QPF from this system. KMLS
had 36 degrees and was currently reporting rain, but the rain has
been mixing with snow this evening. Upper low shifts slowly SE
overnight and models shift QPF SE with time. NE Bighorns have
reported 3 to 5 inches of snow so far and the going Advisory was
in good shape for them to receive at least 6 inches in total by
Tuesday morning. As the SE zones continue to fill in overnight,
Advisory looked good there as well, given expected precipitation
amounts. Did receive a lone report of 9.5 inches over the Ashland
Divide which stands out at 4300` in elevation accounting for
higher snow totals. Given track and amount of precipitation
overnight, see no need to issue additional highlights.
Temperatures will fall very little overnight given the moist
airmass and have kept patchy fog across the area. Metro model
indicated that roads may develop slushy or icy patches overnight
over SE MT, so morning commute may be tricky. Arthur

&&

.SHORT TERM...valid for Tue and Wed...

Potent spring storm has generated some impressive dynamic cooling
to produce some hefty snow totals in a few areas. So far a report
of 10 inches in the Bull mountains is leading the way, but several
4 to 6 inch reports have also come in from Stillwater, Golden
Valley and Musselshell county. The Billings airport has picked up
2.6 inches to smash the seasonal snowfall record that was set in
2014. On the west end of Billings 1.0 inches of snow was measured
at 1pm. Rainfall totals have ranged from around an inch in the
western foothills and Bull mountains to just under half an inch
here at the office to a tenth of an inch so far around Miles City.
Will endeavor to have another statement out with updated
precip/snow totals by 5pm.

Storm system over the area this afternoon will make a slow
progression to the southeast tonight into tomorrow, with clearing
developing from the northwest as it does so. Models indicating H8
temps dropping well below freezing late this afternoon as
precipitation increases over southeast Montana and Northeast
Wyoming. As a result expect travel conditions (US212, Hwy59,
Hwy7) to become difficult this evening as snow begins to
accumulate on the road surfaces, so will issue a winter weather
advisory for this area through Tuesday morning. Expect 1 to 2
inches below 3500 feet with 3 to 5 inches in the higher hills,
from around Ashland to Ekalaka. For other areas travel may become
difficult in spots as wet roads try and freeze up tonight with
temperatures dropping near to below freezing. Remember that
bridges and over- passes will be first to get slick. With skies
clearing and light winds expect at least some patchy fog
development overnight into tomorrow morning which may impact the
morning commute.

Ridging flops in from the west tomorrow to melt the snow that fell
today. After fog burns off temperatures rebound into the mid-50s.

Wednesday will be warm and breezy with westerly downslope winds
and sunny skies pushing temperatures near 70 degrees. A fast
moving clipper system drops in from western Canada late in the day
shifting winds to the north and bringing a chance of showers and
maybe a few thunderstorms Wednesday evening into the overnight
hours. Best chance for precipitation will be west and south of
Billings where upslope enhancement is greatest. Temperatures
behind the front fall enough that a mix of rain/snow is possible
late evening into the overnight hours. This system quickly exits
to the south by sunrise Thursday. Chambers

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

Ridging builds in behind the clipper system on Thursday for dry
but seasonally cool conditions with highs around 60 degrees. Ridge
axis pushes over the area on Friday with dry and warmer
conditions, highs bump into the mid 70s.

Saturday through early next week is looking very uncertain as a
deep trof develops over the western U.S. and pieces of energy get
ejected out into the northern plains. Lots of uncertainty as to
how this plays out and where the more substantial energy goes.
Right now think Saturday will be warm with breezy downslope winds
and a chance of late day/evening showers/tstms west.

Sunday/Monday look unsettled and the ECMWF is progging a multi
day widespread precipitation event with 850 temperatures cold
enough for low elevation snow. The GFS is warmer with less
precipitation. Looking over the ensembles there are huge spreads
in how things will play out. For now kept going forecast in there
with some seasonal precipitation chances and temperatures and will
wait for a bit better clarity. Certainly potential exists with
this system for a prolonged precipitation event, some more snow,
and even thunderstorms,so will monitor how it evolves carefully as
we go through the week. Those with outdoor plans this weekend
into next week should stay tuned to the forecast this week for
more details. Chambers
&&

.AVIATION...

Conditions will continue to improve from northwest to southeast
overnight. Skies will continue to clear for KLVM to KBIL, with
KMLS clearing out shortly after 06Z. This will give an environment
favorable for patchy fog to develop, but may not impact any
terminals. The Bighorn Mountains will remain obscured through the
night. Reimer/RMS

&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 030/056 034/068 037/066 039/077 044/078 044/071 043/066
    40/U    00/U    20/U    00/U    01/U    22/W    33/W
LVM 023/054 030/063 032/066 035/075 036/072 037/065 037/061
    20/U    00/U    31/U    01/U    12/W    22/W    34/W
HDN 032/058 032/069 035/067 036/078 042/079 043/073 042/068
    71/U    00/U    21/U    00/U    01/U    22/W    32/W
MLS 033/056 032/068 036/064 036/074 044/076 045/072 044/066
    70/U    00/U    10/U    00/U    00/U    11/B    23/W
4BQ 033/051 030/066 036/061 034/072 042/075 043/070 043/065
    91/U    00/U    21/U    00/U    01/U    12/W    22/W
BHK 032/053 031/065 037/060 037/070 043/072 044/069 043/063
    +0/U    00/U    10/U    00/U    00/U    01/B    22/W
SHR 029/052 026/070 036/065 034/076 040/078 042/070 041/066
    71/B    00/U    31/U    00/U    01/U    22/W    32/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect until 10 AM MDT Tuesday FOR
      ZONES 36-37-58.
WY...Winter Weather Advisory in effect until 10 AM MDT Tuesday FOR
      ZONE 98.

&&

$$
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