FXUS65 KBYZ 210222

Area Forecast Discussion...Updated
National Weather Service Billings MT
822 PM MDT Tue Mar 20 2018

Quiet weather over the region as heights are starting to build
ahead of a ridge that will build into the region Wednesday. No
updates. borsum


.SHORT TERM...valid for Wed and Thu...

Building ridge in advance of deepening low off the Pacific coast
will bring a warming trend through Thursday. Warmest temps will be
along our western foothills where snow cover has diminished.
Large area of lingering deep snow cover east of Billings will have
its usual cooling affect, especially given a trend toward
easterly surface winds the next two days. The airmass will become
quite warm by Thursday w/ 700mb temps above freezing and 850mb
temps greater than +10C. This would yield temps easily in the 60s
if not for the snow, so will be interesting to see what happens.
Have bumped up our western foothills to the lower 60s, while
keeping the east in the 40s. Nights will fall below freezing in
the eastern valleys with the possible exception of Thursday night
w/ thermal low and cloud cover in place. All of this being said,
snow melt will be on the increase and with it will be the
potential for ice jams and low elevation snow melt run off. Things
to watch closely if you live along a river or stream.

Atmospheric river slamming into CA late Wednesday through Thursday
will bring our SW mountains a period of rain and high elevation
snow Thursday and Thursday night. Could see several inches above
9kft, with snow levels falling gradually through Thursday night.
Shortwave embedded in the SW flow aloft will bring a chance of
mainly rain showers to lower elevations Thursday night into
Friday. Some mixed precip (i.e. ZR-) cannot be ruled out in our
far east if/where valleys fall below freezing.


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

A trend toward lower heights and overall western CONUS troffing
will occur Friday through the weekend. This will bring a gradual
cooling and and an opportunity for rain/snow showers, but models
remain highly spread in the details, especially by late weekend.
Today's model runs show main area of baroclinicity/forcing to our
south, and a potential snow event in the central Rockies to high
plains. The latest ECMWF brings some precip to our southeast cwa
Sunday/Monday, but the GFS/Canadian are drier keeping us more
under the influence of the less interesting northern portion of a
split jet. Ensembles show a great deal of spread. Have adjusted
pops down slightly but will keep them near climatology (15-20 pct)
as we will be under below normal heights and general troffing
through this period. Will need to keep watch of model trends.
Consensus is for drying by Monday/Tuesday as central Rockies
system departs and we see a benign WNW flow for a day or two.

High temperatures will drop to the upper 30s and 40s by the
weekend, Sunday/Monday seeming to be the coolest days, with the
onset of a warming trend by Tuesday.




Expect some light rain/snow showers over the western mountains,
with occasional obscurations of the high terrain. Otherwise dry
weather and VFR flight conditions will prevail across the region
through Wednesday. There is a risk of spotty valley fog east of
KBIL late tonight and early tomorrow, but confidence is low that
fog will impact a terminal. JKL


Wed Thu Fri Sat Sun Mon Tue
BIL 028/052 032/054 039/053 031/047 027/042 025/045 027/048
00/U 01/B 22/W 23/W 22/W 21/B 11/B
LVM 027/055 035/061 039/055 031/046 023/042 022/044 024/049
01/B 13/W 42/W 34/W 32/W 21/B 11/B
HDN 022/052 027/053 034/052 027/048 024/043 021/045 021/048
00/U 00/B 22/W 13/W 22/W 21/B 11/U
MLS 020/041 024/043 032/044 026/042 024/038 020/039 022/043
00/U 00/B 32/W 12/W 22/J 21/B 11/U
4BQ 021/049 026/049 036/048 028/047 025/041 022/042 022/046
00/U 00/B 22/W 12/W 22/J 22/J 10/U
BHK 018/040 022/043 032/044 027/043 025/037 020/039 022/043
00/U 00/B 53/W 12/W 22/J 21/B 11/B
SHR 022/053 029/059 037/056 029/050 025/041 021/044 022/047
00/U 00/B 23/W 12/W 23/W 21/B 11/U




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