Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 191632
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1032 AM MDT Thu Sep 19 2019

.UPDATE...

Slow moving upper trof will stay mainly west of the forecast area
today, keeping a mainly dry forecast outside of isolated to
scattered showers/thunderstorms for western mountains and
foothills late in the day. By this evening will start to see
convection increase across the area in response to upper jet
arriving from the south and increasing low level jet/low level
convergence over SE Montana. Going forecast had this pretty well
in hand and only made minor adjustments. The severe thunderstorm
threat tonight looks weaker, so dropped severe mention but could
still see a few strong storms (mainly after midnight) with small
hail and gusty winds east of Rosebud county.

Friday morning will see scattered showers across the area, with
more steady heavier precipitation building in from west to east
through the day. Snow levels will drop through the day Friday to
around 7500 feet by Friday evening. Friday night football games
look to be wet with cool temperatures. Snow accumulations of 5 to
10 inches look reasonable for elevations above 7500 feet from
Friday afternoon through early Saturday for the Beartooth/Absaroka/Crazy
mountains, from precipitation accumulations totaling around 1.25
inches. Those heading out hunting should be prepared for cool wet
conditions, with snow in the mountains and maybe a dusting down
into the higher foothills. A Winter Weather Advisory is in effect
for the Beartooth highway with temporary closures a possibility so
check with MTDOT/WYDOT before making travel plans over the pass.
Chambers

&&

.SHORT TERM...valid for Tdy and Fri...

A deep upper trough will advance east across the northern Rockies
today and tonight. Today will be dry for most locations as
forcing will be slow to get into the area. Forcing will spread
into the area this afternoon and tonight, and cause showers and
isolated thundestorms to form over western zones this afternoon,
then shift east onto the plains overnight.

A cold front will shift into southeast Montana tonight and be the
focus for possible overnight convection. A return flow of low
level moisture will stream into the far southeast zones and cause
capes to rise to around 1000 j/kg. Not a great deal of mid to
upper level forcing present, but a strong low level jet ramps up
over eastern Wyoming and the Dakotas, for lift along and east of
the boundary. Enough shear and buoyancy for strong storms, mainly
east of a Miles City to Broadus line, so left the mention in. One
thing of note, HREF initiates activity late tonight (after
midnight), so lingered the severe threat over the east through the
night.

Lastly, mountain snow. Showers will overspread the high county
today and tonight, but timing looks a little slower. Have high
PoPs in tonight, but the heaviest precipitation is not expected
until Friday. That being said, rain showers will change to snow
showers very late tonight, with slow level falling to around 8
thousand feet Friday, with heavy snow likely. Emphasis has clearly
centered on Friday and Friday night for potential heavy snow, and
confidence has increased enough to go ahead and issue a Winter
Weather Advisory for the Beartooth Pass, as accumulations of 3 to
6 inches looks likely, with a possible 6 to 10 over the highest
peaks. Advisory will run from Friday through Saturday morning. TWH

Friday still looks like the main period of precipitation for the
area. There is not much of a change with the latest guidance. As
the trough moves in rainfall will move in mainly during the
afternoon. There is still a little instability on the plains that
could support a few thunderstorms. QPF amounts are still between
quarter inch to near an inch along the foothills, through
Saturday morning. Above 8000 feet, temperatures will be dropping
during the morning, which will change rain over to snow in the
higher elevations, including the Beartooth Highway. Snow amounts
will generally be 5 to 9 inches. Reimer

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

The trough will continue moving east during the day Saturday, but
some wrap around precip continuing across the area. However, QPF
amounts will generally be fairly light through the day, around a
tenth of an inch or less. Temperatures will continue to be below
normal. Sunday will be drier and will see temperatures returning
to normal. Monday will generally dry, but a deepening trough over
the Great Basin will bring a chance for precip to the mountains.
The rest of week will see zonal flow dominating, with temperatures
remaining close to normal. Reimer

&&

.AVIATION...

VFR conditions are expected today. Scattered showers and isolated
thunderstorms will develop over western zones this afternoon.
This activity will spread onto the plains late tonight. Heavier
showers with MVFR conditions are expected Friday. A few storms
over southeast Montana could be strong tonight, with strong winds,
hail and locally heavy rainfall. TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 073 050/062 048/064 047/073 049/073 050/074 049/073
    1/B 68/T    84/R    20/U    11/B    11/U    21/B
LVM 070 042/056 041/060 041/069 044/068 044/069 044/071
    3/T 69/T    84/R    20/U    22/R    11/B    21/U
HDN 074 047/064 047/064 045/073 047/073 050/073 048/072
    1/B 37/T    85/R    20/U    11/B    11/U    21/U
MLS 079 051/069 050/063 047/072 048/074 052/072 048/071
    0/U 44/T    66/R    30/U    01/U    11/U    21/U
4BQ 087 050/069 047/062 045/071 046/074 049/071 047/070
    1/U 44/T    85/R    30/U    01/U    11/U    21/U
BHK 084 053/070 049/061 045/070 048/073 050/070 047/067
    0/U 44/T    66/R    30/U    01/U    11/U    11/U
SHR 079 045/065 043/061 041/071 044/072 046/071 046/070
    1/B 47/T    84/R    20/U    02/R    11/U    21/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect from 6 AM Friday to noon
      MDT Saturday for the Beartooth Highway FOR ZONE 67.
WY...None.

&&

$$
weather.gov/billings


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