Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 191525

Area Forecast Discussion...Updated
National Weather Service Billings MT
925 AM MDT Sun Mar 19 2017

Raising PoPs in the E this morning as radar echoes have been
strengthening with time and web cams showed some showers and
virga. Precipitation was being caused by weak vorticity advection
and weak jet divergence behind a cold front that moved through the
region earlier this morning. Models did not have a good handle on
precipitation over the E. Increased frontogenesis and upslope flow
will bring more precipitation to the area this afternoon.
Instability was marginal over western parts of the area this
afternoon, and cloud cover will be extensive so will continue to
leave thunder out of the forecast. Remainder of forecast in good
shape. Arthur


.SHORT TERM...valid for Tdy and Mon...

Moisture and energy moving through southwest flow aloft were
producing showers over the southwest mountains early this morning.
At the same time, a cold front was dropping south through the
region and had made it as far as Lewistown as of 09z. Shower
chances will increase through the day today as the cold front
works south through the area increasing frontogenesis and inducing
easterly upslope flow. Further, decent jet dynamics will be
overhead. Front then looks to stall out along the mountains and
southern foothills tonight into Monday. Baroclinic zone and jet
dynamics overhead will cause shower chances to increase Monday
into Monday night as easterly flow strengthens. Best precipitation
chances will be along the foothills and mountains with easterly
upslope flow. A rain/snow mix is possible for the plains tonight
into Monday, with mainly snow showers expected Monday night. Snow
accumulations through Monday night look minimal with an inch across
some of the lower elevations and a few inches over the mountains.

Temperatures will be much cooler today than on Saturday as cold
air advection works into the area. Highs are expected to be in
the 50s to lower 60s. Temperatures will cool further on Monday
with highs mainly in the 40s expected for the lower elevations. STP

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

A progressive pattern will be over the northern Rockies through
the extended period with a series of Pacific based troughs working
through the area. The first of these troughs will move onshore
Tuesday, sending bits of energy across the northern Rockies in
southwest flow Tuesday night and Wednesday. Nothing terribly
dynamic here, but enough to warrant a low PoP mention.

The main period of ascent looks to be Thursday as the western
trough moves closer. The models have wavered a bit on placement
and strength of this system over the last couple of days, but
appear to be coming together the last couple of runs. The core of
the trough slides to the south, with the ECMWF taking things into
northern New Mexico, with the GFS more so into northern Colorado.
Will keep PoPs in the scattered category, keeping the higher PoPs
over the mountains and areas south. System was not packing much
cold air, so most of the precipitation type will fall as rain
showers. Should be able to get a dry day in on Friday before the
next shortwave trough spreads showers in for Saturday and Sunday.
Temperatures will be coolest on Tuesday, with above seasonal
temperatures expected the rest of the time frame. TWH


The combination of a cold front with a moist Pacific flow will
bring increasing chances of showers through the day, with some
precipitation continuing through tonight across the region. Expect
areas of MVFR flight conditions, mainly north of KSHR, and
mountains will become frequently obscured. JKL



    Tdy Mon     Tue     Wed     Thu     Fri     Sat
BIL 059 033/044 030/048 036/064 040/057 035/059 034/061
    5/W 54/W    54/W    21/B    24/W    31/B    11/B
LVM 061 033/045 030/053 037/062 035/054 031/055 033/059
    6/W 55/W    54/W    33/W    25/W    32/W    12/W
HDN 062 034/049 030/051 033/066 036/058 033/059 032/063
    3/W 44/W    64/W    31/B    24/W    31/B    11/B
MLS 060 034/051 031/046 033/062 037/059 034/056 032/059
    3/W 52/W    53/J    21/B    13/W    21/B    00/B
4BQ 065 033/051 030/045 031/063 036/059 033/057 032/062
    3/W 33/W    74/J    31/B    34/W    21/B    00/B
BHK 060 031/050 025/040 028/056 034/057 030/053 030/054
    3/W 52/W    43/J    22/W    13/W    20/B    00/B
SHR 064 032/050 031/052 034/064 037/055 033/057 031/063
    2/W 24/W    63/W    21/B    44/W    31/B    11/B




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