Scientific Forecaster Discussion
fxus65 kbyz 202102
Area forecast discussion
National Weather Service Billings Montana
302 PM MDT Fri Sep 20 2019
Short term...valid for Sat and sun...
Upper low is currently sitting just south of Yellowstone Park and
is on a slow northeasterly trajectory that should take it over
Sheridan County by midnight and into Carter County by sunrise
tomorrow morning. Heaviest precipitation with this system will be
to the north of this track from Livingston to just south of
Billings to Baker/Ekalaka. Already seeing reports of around an
inch of precipitation from Nye to Red Lodge and as far north as
Columbus this afternoon. Expecting another half inch to inch and a
half along this heavier precipitation band overnight into tomorrow
morning. No big changes to the snow forecast and going Winter
Storm Warning this afternoon, with 10 ot 18 inches of snow
expected above 7500-8000 feet. Temperatures above 7000 feet are
in the 30s at mountain reporting sites and radar shows the
freezing level around 7700 feet at this time.
The storm system will shift to the east tomorrow morning with
gusty northwest winds building in behind it. Gusts over Sheridan
County and across southeast Montana could gust over 40 mph at times.
While the heavier steady precipitation will taper off during the
morning, isolated to scattered instability showers under the
upper trough will continue into early evening.
Sunday looks sunny with highs in the 70s. Chambers
Long term...valid for Mon...Tue...Wed...Thu...Fri...
Split flow over the western Continental U.S. On Monday will mean little
chance of any impact weather with only weak forcing and moisture
available over our region, but we could see a few light showers
over the mountains and foothills. Otherwise, a transition to
faster zonal flow will bring dry conditions for our lower
elevations thru Tuesday. Flow aloft will veer to the northwest Tuesday
night and Wednesday. As heights drop at midweek we will see an
increasing chance of light showers in the northwest flow. We could also
possibly see our First Gap wind highlights of the season at
midweek. Mid level temps will fall enough to bring a risk of more
snow showers for the high elevations.
Information from ensembles analysis provides increasing confidence
of a deep trough developing over the western Continental U.S. Toward the
latter end of next week. This pattern change would lead to
cool/wet weather setting up for our region beginning Thursday and
potentially lasting thru the weekend.
Temperatures will begin near or a little above normal Monday thru
Tuesday, then fall below normal thereafter. Significantly cooler
temps are then possible by next weekend. Bt
Showers and storms will impact the area over the next 24 hours,
spreading from west to east through Friday afternoon and evening.
Widespread heavy rain is likely at all terminals. A severe storm
or two can be expected in far southeast Montana near kmls and kbhk this
evening and into the night, which would bring about gusty and
erratic winds, hail, and localized heavy rain. Snow is starting to
fall in the mountains, and help to obscure them through Saturday.
Preliminary point temp/pops...
Sat sun Mon Tue Wed Thu Fri
bil 048/064 046/073 049/075 051/075 049/065 046/064 043/059
+6/west 20/u 01/b 10/u 22/west 22/r 44/r
lvm 041/061 040/070 043/070 044/070 042/064 039/060 037/056
+6/west 10/u 12/west 10/north 22/west 23/r 45/o
hdn 046/062 043/072 046/075 047/074 046/064 043/064 042/060
+8/west 20/u 01/b 00/u 22/west 22/r 34/r
mls 050/063 045/073 048/076 050/071 046/063 043/063 042/060
98/west 10/u 00/u 00/b 21/b 22/r 33/r
4bq 046/062 042/071 044/076 047/073 045/063 042/065 041/061
99/west 20/u 01/u 10/u 21/b 21/east 23/r
bhk 048/062 043/071 046/076 048/070 044/061 041/062 040/060
9+/west 20/u 00/u 00/b 21/b 22/r 33/r
shr 042/060 038/071 042/074 043/073 043/063 039/064 039/061
98/west 30/u 01/b 10/u 22/west 22/r 33/r
Montana...Winter Storm Warning in effect until noon MDT Saturday for