Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 221537

Area Forecast Discussion...Updated
National Weather Service Billings MT
937 AM MDT Wed Mar 22 2017

Fog was burning off across most of the central and eastern zones
this morning. The exceptions, per web cams, were around Aberdeen
Hill, Ekalaka/Alzada, and around Billings. Thus left some patchy
or areas of fog in these locations for about another hour. Removed
morning PoPs. Echoes on radar in the E were likely mid clouds per
KMLS observation. For the afternoon, weak shortwave energy will
move into the area from ID producing light QPF over and near the
mountains. Paired back the PoPs and added a slight chance for
thunder given KLVM RAP sounding of steep mid-level lapse rates and
GFS lifted indices around zero degrees c. Updated sky/winds per
latest obs and ADJLAV. Temperatures were tricky depending on how
much low cloud burns off and how much mid high cloud replaces it,
so left them alone for now. Arthur


.SHORT TERM...valid for Tdy and Thu...

Upper ridge was sliding east and this will allow downslope
gradients to kick in for a warmer day eventually today. In the
mean time this morning, low level flow was still east to southeast
over most of the area and this weak upslope flow was keeping
moisture around and a good deal of the area had low clouds, patchy
fog and stratus. Surface pressure falls were shifting into
eastern Montana and the Dakotas this hour and this will allow low
level winds to turn to the west by around mid morning for south
central zones and early afternoon over the east. This will lift
the low clouds and provide a warmer day today. Have trimmed highs
back a bit with morning cloud cover, but should still reach the
60s most locations today. Weak shortwave energy is progged to work
into the area on southwest flow aloft and these weak waves could
generate a few showers, so added low PoPs.

A western trough will move into Utah/Arizona tonight and this
will set up a period of upper divergent forcing over southern
Montana and northern Wyoming. The GFS was very robust with lift
and thus QPF for southern Big Horn county into Sheridan county and
the southern parts of southeast Montana, with upwards of an inch
of rainfall late tonight through the day Thursday. The ECMWF was
lighter, only generating a half inch of rainfall in the heavier
bands. At any rate, looks like a solid precipitation event in
these locations with a half inch to three quarters of an inch of
rainfall likely. Have raised PoPs and QPF totals for these
locations. Billings will be on the northwest edge of the
precipitation shield, with the best chance of seeing precipitation
being Thursday morning. This system looks on the warm side for
lower elevations, so would expect the precip type to be mainly
rain below 6 thousand feet. Snow will fall, and be heavy at times,
over the Bighorns and have decided to issue a Winter Weather
Advisory there for 6 to 10 inches of wet snowfall.

The precipitation will taper off and sink southeast quickly
Thursday evening. Thursday will be cool with clouds and rainfall
around, especially over the southeast. Upper ridging will build in
briefly for Thursday night and Friday for drier and warmer
weather. TWH

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

Models continue to indicate an unsettled weather pattern
persisting through the extended. Shortwave ridging will build
over the area on Friday bringing a mainly dry day to the area. A
shortwave trough will move through the area Saturday evening into
Sunday bringing showers and mountain snow. Shortwave ridging then
looks to build over the region Sunday night into Monday, before
a more significant trough moves into the western US. Shower
chances continue over the area Tuesday and Wednesday as multiple
waves of energy cross the region. Have continued with broadbrushed
pops for this timeframe as it is hard to pin down any specific

High temperatures across the lower elevations will range from the
50s to 60s through the extended, with the warmest days being
Friday and Saturday. STP



Conditions were quickly improving across the region with VFR
conditions at most terminals. The lone exceptions were in low
lying areas in eastern Montana (east of KMLS), and at KSHR along
the Bighorn Foothills. Fog and low IFR/LIFR cigs will slowly lift
through the morning with VFR conditions likely prevailing
regionwide after 20z. Mountain obscurations are possible through
the TAF, though the heaviest obscurations will be in the morning
and early afternoon. MVFR/IFR restrictions could return late in
the TAF period as a disturbance brings rain showers to south and
east portions of the forecast area near KSHR, KMLS, and KBHK.


    Tdy Thu     Fri     Sat     Sun     Mon     Tue
BIL 065 041/058 035/063 042/061 038/058 037/057 037/054
    1/B 35/W    20/U    13/W    42/W    12/W    33/W
LVM 060 034/055 031/060 038/058 033/055 033/055 033/054
    2/T 34/W    21/N    24/W    42/W    23/W    33/W
HDN 065 039/058 033/065 037/064 037/059 035/060 035/056
    1/E 35/W    20/U    12/W    43/W    12/W    33/W
MLS 064 040/059 034/064 038/065 040/060 036/059 037/052
    0/E 25/W    10/U    01/B    33/W    12/W    34/W
4BQ 066 041/053 033/062 036/065 039/059 035/059 036/054
    0/E 69/W    30/U    01/B    33/W    12/W    35/W
BHK 059 036/054 031/060 034/062 036/056 031/055 032/050
    0/N 27/W    10/U    00/B    33/W    11/B    35/W
SHR 063 039/049 032/061 034/063 037/057 033/058 035/055
    1/E 79/W    50/U    01/E    43/W    12/W    33/W


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


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