Area Forecast Discussion
Issued by NWS Billings, MT

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423
FXUS65 KBYZ 182149
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
249 PM MST Wed Jan 18 2017

.SHORT TERM...valid for Thu and Fri...

Strong winds continue over the Upper Yellowstone and Upper
Stillwater river valleys, with gusts to 55 mph. Have not hit
criteria since about 9 this morning. That being said, surface
pressure gradient from Idaho Falls to Lewistown remains very high
(around 24mb), and winds at Wicked Creek were still gusting around
50mph. So despite the strongest surface pressure falls sliding
into eastern North Dakota this hour, winds should stay up into
early evening. Would expect winds to start a gradual decline this
afternoon into this evening, but feel it is prudent to keep the
advisory in place. Evening crew may be able to cancel the
highlight early, depending on how the downturn evolves.

Attention then turns to the upper trough currently moving toward
the California coast. The trough is progged to move into the Great
Basin on Thursday. Energy cuts off a weak upper low over Colorado
early Friday. Montana will be under the influence of falling
heights and weakly cyclonic flow. A 110kt jet moves northward into
southern Canada and the right rear quad of this jet provides
decent qg forcing Thursday night into Friday. A weak 700mb low
works across southern Montana during this period. Models have come
together in producing much more QPF than previous runs, so
confidence growing for a potential precipitation event. Anywhere
from .10 to .20 of QPF projected by the models, with the emphasis
over the central zones. 850mb temperatures were quite warm, with
only the west dropping to 0c. This posses a challenge for
precipitation type. Soundings support a changeover from rain to
snow by late evening due to low wet bulb temperatures. Have raised
PoPs to likely for the Thursday night and Friday time frame.
Accumulations are going to be tricky as the snow should be wet and
soundings don`t show a deep dendrite growth layer. Have kept
accumulations to a trace to 2 inches.

The system slowly drifts into the east and forcing wanes as the
jet max moves away to the north. Have decreased PoPs during the
afternoon hours, and shifted the emphasis over southeast Montana
and the Bighorn mountains. Will keep low PoPs going through Friday
night with very weak cyclonic flow. Temperatures will be a little
cooler on Thursday with increasing cloud cover and weak cold
advection. The colder day looks to be Friday as 850mb temperatures
drop to around 0c. TWH

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

The extended forecast looked a bit unsettled, but there were no
large storms on the horizon. The GFS/GEFS showed a good deal of
model spread beginning on Sunday, while there was less model
spread on the ECMWF and it`s ensembles. The GFS 12Z run was
consistent with it`s 00Z run, while the ECMWF was not as
consistent with it`s previous run. There were also many model
differences between the GFS and ECMWF through most of the period,
so have used blended model solutions. This progressive pattern has
a lot of potential to change with time.

On Saturday, areas of low pressure were lifting N through the N.
central U.S.. Moisture will be present over the eastern zones,
allowing for a chance of snow showers in cyclonic flow. Chances
for snow showers in the E will continue into Sunday. Some
difluence/SW flow will bring moisture into the western mountains,
supporting a slight chance of snow showers. With 850 mb
temperatures at or below zero, expect highs in the upper 20s to
lower 30s for the weekend. SW flow, with energy in the flow, will
give way to a broad trough over the NW U.S. on Monday. Low chances
for snow will overspread the area from W to E under the trough.
Highs on Mon. will not change much from the weekend. On Tue., a
cutoff low develops and moves into NE/KS on the GFS, while the
ECMWF maintains a broad trough over the West. As a result, the GFS
wraps QPF into the SE half of the forecast area, while the ECMWF
is drier. Went with a low chance of snow across the entire area
with the best chances over the S and E. On Wed., the GFS brings
the low over IA while elongating it, while the ECMWF rotates a
weaker low S into the Dakotas. Dried out the NW zones and kept a
slight chance of snow over the SE part of the area closest to the
low pressure. Highs will be in the 20s for Tue. and Wednesday.
Will need to keep an eye on this pattern to see if the low
develops further W. Arthur

&&

.AVIATION...

VFR conditions will prevail over the area through Thu. morning.
WSW surface winds will gust from 40-50 kts at KLVM, with gusts to
30 kts extending as far east as KBIL. Winds will decrease late
tonight. Localized mountain obscurations will develop over the
Absaroka and Beartooth mountains late tonight and will continue
through Thu. morning. Scattered rain and snow showers will move E
into the area Thu. afternoon bringing possible MVFR conditions to
KLVM. There will be areas of obscuration over the western
mountains. Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Thu     Fri     Sat     Sun     Mon     Tue     Wed
-----------------------------------------------------------
BIL 028/042 029/036 021/032 019/031 017/031 016/027 014/028
    00/B    66/J    21/B    11/U    12/S    32/S    22/S
LVM 030/045 027/040 018/035 018/035 019/036 015/030 013/029
    03/W    66/W    21/B    21/B    23/S    32/S    22/S
HDN 020/039 020/035 016/031 010/029 008/027 011/026 008/025
    00/U    46/J    31/B    11/B    11/B    33/S    22/S
MLS 020/038 018/032 020/031 016/029 010/025 013/026 009/023
    00/U    12/J    32/J    21/B    11/B    22/S    22/S
4BQ 016/039 016/034 019/033 015/030 007/029 013/027 009/024
    00/U    13/J    32/J    21/B    11/B    22/S    22/S
BHK 018/039 014/033 020/032 020/031 009/026 014/025 010/021
    00/U    02/J    23/J    22/J    11/B    33/S    22/S
SHR 021/042 020/036 015/032 011/031 010/032 012/026 009/026
    00/U    36/J    31/B    11/U    12/S    33/S    22/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory in effect until 6 AM MST Thursday FOR ZONES
      65-66.
WY...None.

&&

$$
weather.gov/billings



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