Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 240851

Area Forecast Discussion
National Weather Service Billings MT
251 AM MDT Sat Jun 24 2017

.SHORT TERM...valid for Tdy and Sun...

Steady trend through the short term period of northwesterly flow
aloft but rising heights as an upper level shifts eastward across
the Pacific Northwest into western Montana by the end of the
period. At the surface high pressure over eastern Montana migrates
into the Dakotas with a general easterly pressure gradient across
the region with a thermal trough west of the Continental Divide.
There is a minor feed of moisture into the northwest flow aloft
from the Pacific and weak jet energy which will allow mid level
cumulus development. Model soundings indicate vertical growth of
this activity will be fairly shallow, so will not mention any
sprinkles but would not be surprised to see some virga. By Sunday
the moisture activity is shunted eastward which which reduce the
sprinkles. Spectacular weather for late June with temperatures in
the 70s and relatively low humidity.

There is a notable shift Sunday night as the ridge begins to
flatten as it starts to move into central Montana. This allows a
lee side trough to begin forming along the leeside of the Canadian
Rockies and the easterly surface flow becomes more southerly
across the western sections of the region. This allows
temperatures to be slightly warmer overnight. borsum

.LONG TERM...valid for Mon...Tue...Wed...Thu...Fri...

Did not make any large changes to the going extended forecast.
Models continued to show a progressive unsettled flow from Tuesday
onward with disagreement in the pattern details. Also the GFS was
showing run-to-run differences with a mid to late week system.
Thus for PoPs went with model blends given the uncertainty with
the details.

The area will be under an upper ridge on Monday, with energy
reaching the western zones late in the day. Models continued to
show +12 to +14 degrees C at 700 mb and GFS soundings showed
mixing above 600 mb. Thus it will be a hot day, and have again
gone above the blended guidance with highs in the low to mid 90s
in many areas. Humidities central and E will be in the teens to
around 20 percent and models showed SE winds picking up in SE MT.
These conditions will need to be watched for possible fire weather
highlights. An email was sent to customers, mentioning fire
weather concerns. For PoPs, kept a mention of thunderstorms over
the western mountains. The upper ridge breaks down and shifts E
Mon. night as a shortwave trough approaches from the W. A cold
front pushes into the eastern zones. Had chances for showers and
thunderstorms central and W, behind the front. The wave crosses
the area Tue. through Tue. night, and precipitable waters climb to
above an inch central and E. Spread chances for thunderstorms
across the entire area and tapered off precipitation late Tue.
night. Tuesday will be a post-frontal and cooler day with highs in
the 80s.

Jet energy and an upper trough will be over the area Wednesday
with chances for showers and thunderstorms. The trough with
reinforcing cooler air continues over the area through Thursday
with continued unsettled conditions. Highs on Thursday will be in
the 70s. Cyclonic flow will prevail over the region for the rest
of the period with chances for precipitation and seasonable
temperatures. Arthur



VFR will prevail over the area today and tonight. A few light showers
are possible from KBIL E. Localized mountain obscurations are also
possible in isolated showers. Arthur



    Tdy Sun     Mon     Tue     Wed     Thu     Fri
BIL 075 050/080 054/093 063/085 056/081 053/075 052/078
    0/U 00/U    00/U    23/T    22/T    23/T    33/T
LVM 073 042/080 047/090 055/079 048/075 045/073 044/074
    0/U 00/U    01/U    34/T    23/T    33/T    22/T
HDN 076 046/081 052/095 060/088 056/083 053/078 051/079
    0/U 00/U    00/U    23/T    22/T    23/T    33/T
MLS 075 049/080 051/093 063/090 059/084 055/079 052/079
    0/B 00/U    00/U    02/T    32/T    23/T    33/T
4BQ 073 046/078 050/090 061/090 057/082 053/078 052/078
    0/U 10/U    00/U    02/T    32/T    23/T    33/T
BHK 069 044/076 045/085 057/089 056/082 052/076 048/076
    0/U 00/U    00/U    02/T    32/T    22/T    22/T
SHR 071 046/077 048/090 056/085 052/078 049/074 048/076
    1/B 00/U    00/U    22/T    23/T    33/T    33/T




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