Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 230024

Area Forecast Discussion...Updated
National Weather Service Billings MT
624 PM MDT Wed Mar 22 2017


Updated forecast to increase precipitation chances this evening
as several bands of light showers and even a few thunderstorms
have developed mainly from Billings westward toward Livingston.
The isolated thunderstorms could produce wind gusts around 30 mph
along with some small hail and brief heavy rainfall. Satellite
imagery showing a broad leaf of moisture and diffluence heading
this way from the Great Basin and this should keep precipitation
chances on the rise overnight, especially for southern zones.


.SHORT TERM...valid for Thu and Fri...

Followed previous forecast fairly closely for the afternoon
package, as models did not appear that different from previous

Upper trough seen along the Pacific Coast in water vapor imagery
this afternoon will move inland tonight. A jet on the front side
of the trough will move NE into the region, bringing strong right-
rear quadrant divergence to the south central and eastern zones.
Shortwaves will also move NE through the area. Precipitable waters
on the order of a half inch to /0.75/ inches will be over the
aforementioned zones. Thus, precipitation focus will be over the
south central to SE zones with PoPs in the likely category in MT
and in the categorical range over Sheridan County. Most
precipitation will fall as rain in the lower elevations due to
Mins in the 40s, and 850 mb temperatures above zero degrees C.
Expect snow in the mountains, with QPF`s close to a quarter of an
inch in the NE Bighorns translating into around 2 inches of snow.
The time-height cross-section for the NE Bighorns looked favorable
for decent snow amounts tonight through Thu., as there will be
deep ENE flow, plenty of moisture and good dendritic growth in a
strong zone of omega.

Jet divergence continues over south-central and SE sections into
Thu., as the upper trough translates eastward. Precipitable waters
remain high, then decrease late in the day. QPF amounts are
expected to be from /0.40/ to /0.70/ inches with the heaviest
amounts in Sheridan County. Kept the high PoPs over the south-
central and SE areas through the day with around 7 inches of snow
over the NE Bighorns. It will be a bit cooler across the region
with highs in the 40s and 50s. Upper ridging starts building over
the region Thu. night and the airmass dries out. The Advisory
previously issued for the NE Bighorns was in good shape. Raised
snow amounts a few inches. Also dried out PoPs faster across the
area than the previous forecast based on new model trends.

The upper ridge crosses the area on Fri., keeping the weather dry.
Models disagreed on how warm it will get, and model blends gave
highs in the 60s. Temperatures may need to be raised in future
shifts. Surface pattern was supportive of gap flow by 00Z
Saturday ahead of the next Pacific front. Have winds just below
Advisory criteria for now. This will be something to watch in the
coming days. The front with accompanying shortwave energy will
bring a slight chance of western mountain showers late Fri. night.

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

The long term will feature somewhat unsettled conditions with a
few chances of rain through the weekend and in the middle of next
week. A weak disturbance will cross the region to the south
overnight Saturday and a broad area of rain showers will pass
through the region. A light shower could stick around the region
Sunday morning but conditions will generally clear as a ridge
takes hold of the weather pattern on Sunday afternoon and Monday.

Model differences begin to emerge Tuesday as an upper level low
approaches the western US. The GFS is strong with this wave and
forces it south, keeping our region mostly dry on Tuesday and
Wednesday while the EC and Canadian solutions are slower and
further north with the wave. The EC camp of solutions would lead
to a better chance for rain across the region. Took a mostly even
blend between these two camps and left chances for rain in the
forecast on Tuesday and Wednesday of next week.

Temperatures will be in the upper 50s through most of the week
with night time lows in the low to mid 30s. Dobbs


A disturbance will cross the region this evening and overnight,
bringing rain showers and ISOLD thunder to some areas. MVFR
conditions will spread across the region overnight, with
localized LIFR CIGS/VIS in heavier precip. The worst restrictions
will occur across southern routes near KSHR and SE Montana where
heavier precipitation is possible by morning. Mountain
obscurations will continue to increase this evening, and persist
overnight. Conditions will begin to improve from NW to SE late
Thursday. AAG



    Thu     Fri     Sat     Sun     Mon     Tue     Wed
BIL 042/055 034/063 043/059 038/058 037/058 037/057 037/057
    45/W    10/U    13/W    31/B    11/B    22/W    11/B
LVM 035/052 030/060 038/055 032/055 034/054 033/055 033/057
    33/T    10/N    24/W    41/B    12/W    22/W    21/B
HDN 040/055 031/065 037/061 037/061 035/060 036/058 036/059
    57/W    10/U    02/W    32/W    11/B    22/W    11/B
MLS 041/058 034/064 039/064 040/062 036/060 038/057 035/057
    35/W    10/U    01/E    32/W    11/B    33/W    22/W
4BQ 041/051 033/062 036/064 040/060 035/060 036/056 036/056
    69/W    20/U    01/B    52/W    11/B    34/W    22/W
BHK 036/053 031/060 033/064 037/058 032/056 033/052 033/053
    37/W    10/U    00/B    43/W    11/B    44/W    53/W
SHR 038/048 030/060 034/059 036/057 033/059 034/057 034/057
    89/W    40/U    02/W    52/W    11/B    23/W    21/B


WY...Winter Weather Advisory in effect from midnight tonight to
      midnight MDT Thursday night FOR ZONE 98.


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