Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 270358

Area Forecast Discussion...Updated
National Weather Service Billings MT
858 PM MST Sun Feb 26 2017

Made a few changes to tonight`s forecast based on current trends
and latest model guidance. Radar showed steady light to moderate
snow across the northern tier, W of Rosebud County. Webcams at
Judith Gap showed a steady snow but with small flakes and slow
accumulation. Increased PoPs to categorical in these areas, where
snow was being caused by NE flow/low-level convergence,
isentropic lift, jet divergence from the left front quadrant of a
jet nosing into the southern part of the forecast area, and
q-vector convergence from an approaching shortwave. Despite radar
echoes over the western zones, it was not snowing due to downslope
flow. Increased winds in KLVM area where winds were gusting to
around 40 mph. Checking the SNOTELS revealed little accumulation
in the western mountains. The likely PoPs looked good there
tonight. Spread slight chance PoPs E and S of KBIL due to the
above factors, even though models did not show QPF in these areas.
Did not see the need for an Advisory across the northern tier as
models showed QPF decreasing after 06Z as isentropic lift shifts
E, and q-vector convergence and jet divergence decrease.

Some temperatures had reached their forecast lows in the mountains,
so lowered mins in these areas. Raised mins in KLVM due to
current temperatures near 30 and expected cloud cover/wind through
the night.

Noticed 00Z models shifted most of the QPF N of the area Mon.
morning. However, shortwave approaching WY from the W had good
q-vector convergence associated with it, so will not change any
PoPs at this time. Arthur


.SHORT TERM...valid for Mon and Tue...

This afternoon some light snow showers continued from Lewistown
down to Hardin. This activity is mainly associated with some
instability from the Snowy Mountains. As the main trough moves
into the area more stratiform snow will take over. Both the high
resolution short term models and the larger scale models continue
to track a jet streak over southern Montana. This places the left
exit region over central Montana. This will keep much of the
snowfall mainly north of a line from Harlowton to Roundup.
Tomorrow winds will become northeasterly. This will bring some
upsloping, but it will be fairly shallow. Areas along the
foothills could see a couple of inches, but note expecting any
issues over the next 36 to 48 hours.

Through the remainder of the short term, the wave will move
through. This will result in some unstable northwest flow across
the area. Some some chance PoPs given the dirty flow, but not
expecting much accumulations. Temperatures will continue to be
seasonable. Reimer

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

Extended models are in good agreement through the week but
diverge by next week. Overall, a fast northwest flow aloft will
prevail across the forecast area. A few disturbances within the
flow will bring periodic chances for snow/rain showers across the
area. The main weather feature will be periods of strong gusty
winds mainly west of Billings Wednesday and again Thursday night
into Friday night. A couple of surface lows will move across
southern Canada and northern Montana resulting in tight pressure
gradients across the Upper Yellowstone and upper Stillwater
Valleys. This will result in strong gusty winds from Big Timber to
Livingston north to Harlowton. Models bring a strong upper level
disturbance across the forecast area next weekend but timing and
differences exist, but in any case, this may be the next chance
for the possibility of accumulating snow. Temperatures will be
near normal through the period with possibly above normal readings
on Friday. Hooley



A disturbance will move across central and east Montana tonight.
This will bring a chance for snow across much of the region
through Monday morning. Expect some MVFR to IFR conditions with
the snow.  The mountains will be obscured due to snow shower
activity. AAG/Hooley



    Mon     Tue     Wed     Thu     Fri     Sat     Sun
BIL 019/027 017/034 019/039 023/039 027/048 032/044 028/042
    33/S    42/S    12/W    33/W    11/B    12/W    23/W
LVM 018/026 011/028 016/034 022/036 026/043 030/043 026/038
    34/S    54/S    22/J    33/J    21/N    22/W    33/W
HDN 020/032 015/038 018/041 021/041 025/051 030/047 026/046
    22/S    31/B    12/W    32/W    11/B    12/W    13/W
MLS 020/033 019/037 021/038 022/039 024/050 032/047 030/044
    32/S    22/O    13/W    21/B    21/B    11/B    13/W
4BQ 020/038 019/038 020/040 022/041 025/052 032/052 028/051
    21/B    22/S    12/W    31/E    11/B    11/B    12/W
BHK 019/031 016/032 017/034 018/033 021/046 029/046 026/040
    22/S    32/S    24/J    21/B    22/W    11/B    13/W
SHR 016/031 012/033 013/037 018/037 020/048 027/048 025/045
    22/S    32/S    11/B    32/W    11/B    01/B    12/W




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