Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 240931

Area Forecast Discussion
National Weather Service Billings MT
331 AM MDT Sat Sep 24 2016

.SHORT TERM...valid for Tdy and Sun...

Active weather in one way or another for the entire forecast area
today. The active weather will come in the form of heavy rain,
strong winds and accumulating mountain snow in the Bighorns. This
all attributable to a deep upper low moving into central Wyoming.

This upper low will move northeast into western North Dakota late
this afternoon as a strong upper ridge over the Ohio valley
deflects it in that direction. That will spread strong divergent
flow into northern Wyoming and southern Montana this morning.
Current regional radar mosaics were painting a large area of rain,
(heavy at times), over central and northern Wyoming. As the upper
low moves northeast, this area of rain will move into south
central and southeast zones this morning. Bands of heavy rain are
expecting from around around Hysham to near Hardin to Sheridan and
locations east. Rain amounts could exceed one inch today in these
locations. Totals will drop off dramatically to the west of these
areas, including Billings. Models want to keep the heaviest rain
east of Billings as northwest surface winds produce downslope flow
off the Bull mountains. Will keep high PoPs high from around
Roundup to Columbus to Nye and areas east early today and then
back off PoPs over central zones this afternoon.

The heaviest rain will stay over southeast Montana this afternoon
and then shift into the western Dakotas this evening. Have
adjusted PoPs to reflect this. Snow was just starting to fall over
the Bighorn mountains as the colder air has been a little slow to
move in. As the low moves into Montana, this will provide strong
wrap around precipitation into the Bighorns today. Will keep the
Winter Weather Advisory going but total snow amounts will be
lowered a bit as rain has been slow to change to snow.

Strong winds will develop today as a surface low strengthens over
the western Dakotas. 850mb winds of 45-50kts show up over
southeast Montana this afternoon. This is actually a bit weaker
than model runs yesterday. Guidance was coming in quite a bit
weaker for today too. Strong ascent with periods of moderate to
heavy rain should not allow the strongest winds to reach the
surface. Will not issue a highlight for high winds over southeast
Montana with this in mind but keep advertising gusts of 45-50mph
in the forecast. Winds gusts will decrease as you move west into
south central zones, but should still expect gusts of 30-40mph
from Billings to Livingston.

Precipitation will taper off this evening. Winds will stay strong
over far southeast Montana but will back off overnight. Monday
looks to be a dry day as an upper ridge builds in from the west.
Highs will respond to more sunshine and more back into the mid to
upper 60s, compared to the 50s of today. The east will be cooler
and just get to around 60 degrees around Baker and Ekalaka. TWH

.LONG TERM...valid for Mon...Tue...Wed...Thu...Fri...

Made no significant changes to inherited extended forecast. An
upper level ridge of high pressure will dominate the pattern
through Wednesday. Temperatures will be well above normal...with
highs in the mid to upper 70s and lower 80s and dry conditions are
expected. A weak backdoor cold front will move through on
Wednesday evening...with greatest impact of helping shift ridging
eastward...and helping southwest flow aloft to develop.

A weak disturbance will slide up into the region from the
southwest by Thursday morning...bringing a small chance for
showers to western mountains...and nearby foothills. This marks
the beginning of a pattern another upper level Pacific
trof begins push eastward. Models are a bit disjointed with regard
to timing and strength of waves moving into the area...but
generally agree on another stretch of cooler and unsettled weather
beginning Friday evening. AAG



Weak showers continue to push into southeast and south central
Montana...but best area of precip is across northern Wyoming this
morning where heavy rain is being reported in KSHR...with snow in
the BIghorn Mountains. IFR conditions are occurring in heavier
rain in KSHR. Otherwise...mainly VFR conditions prevail across the

We still expect more widespread light rain into eastern and
central routes today...with best chances generally east of
KBIL. MVFR to IFR conditions are expected in rain.
Snow is expected to spread into the Beartooth/Asbaroka Mountains
this morning. Mountains will be obscured throughout much of the

Northwest winds will be on the rise later this morning and into
this afternoon. Gusts nearing 40 kts are possible across south
central and southeast Montana this afternoon/evening. Winds will
decrease from west to east overnight tonight. AAG



    Tdy Sun     Mon     Tue     Wed     Thu     Fri
BIL 059 042/067 045/075 051/080 052/073 050/072 050/074
    7/W 20/U    01/U    11/U    11/U    11/B    12/T
LVM 057 037/068 040/076 047/080 046/075 046/073 048/071
    4/W 10/U    01/U    11/U    11/U    12/T    22/T
HDN 057 041/066 043/075 047/081 050/077 049/073 049/075
    8/W 20/U    01/U    11/U    11/U    11/B    12/T
MLS 055 042/065 042/073 049/080 052/077 051/073 050/073
    +/W 70/U    00/U    10/U    11/U    11/B    11/B
4BQ 052 041/063 041/072 048/080 051/080 052/074 050/075
    9/W 60/U    00/U    10/U    01/U    11/B    11/U
BHK 055 041/060 040/069 046/077 048/074 050/072 048/071
    8/W 90/N    01/U    10/U    01/U    11/B    11/U
SHR 052 038/063 041/072 046/080 048/077 048/074 047/076
    9/W 30/U    01/U    10/U    01/U    11/B    11/B


WY...Winter Weather Advisory in effect until 6 PM MDT this evening
      FOR ZONE 98.


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