Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 130304

Area Forecast Discussion...Updated
National Weather Service Billings MT
904 PM MDT Sat Aug 12 2017


Thunderstorm activity that was over far eastern Fallon County
this afternoon has moved east into North Dakota this evening. The
upper low responsible for this activity continues to move east
across North Dakota with drier air wrapping around into eastern
Montana. As a result, I removed precip chances for the remainder
of the evening and overnight hours across Fallon County. Expect a
mostly clear night across the forecast area with just an isolated
shower/thunderstorm chance over the mountains and adjacent
foothills. The only other update to the forecast tonight was to
add areas of smoke across the Beartooth/Absaroka Mountains and
adjacent foothills as visibilities at Livingston and Bozeman have
been in the 3 to 9 mile range at times. Updated forecast has been
sent. Hooley


.SHORT TERM...valid for Sun and Mon...

Upper trough over the northern high plains may lead to some
lingering thunderstorms over the eastern border counties late
today into the evening. A few convective cells may also form over
the higher terrain this evening. Otherwise, look for mostly clear
skies overnight. High pressure will build over the region for
Sunday leading to warmer conditions. That looks short lived
however, as an upper low centered over British Columbia exerts
its influence and pushes a good deal of energy and associated cold
front into the Pacific NW and northern Rockies. Newer progs
continue to suggest this will send a round of scattered
convection into our CWA tomorrow evening/overnight. Widespread
convection over the mountains is then expected to spread into the
plains Monday as the 500 MB jet moves into the region in a
favorable position to support upward forcing. The westerly flow
may negate much strong convection in our west and central zones,
but there may still be enough instability/CAPE and mid level wind
shear on the eastern border for some stronger thunderstorms.
Timing-wise though this is out of sync with max heating, so we are
still uncertain of the potential for severe storms. Speaking of
that westerly wind, NAVY aerosol models indicate a
stronger/thicker push of smoke into our western zones with that
front. Not confident how this will work out, but have added some
mention of smoke latter part of SUnday and Sunday evening for now.
Look for cooler temperatures Monday and breezy conditions at
times. BT

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

Relatively minor changes to the extended forecast period. Models
are in marginal agreement throughout the period. Strength of
waves crossing the region and timing are biggest issue to start
the period, while latter periods have models completely out of
phase. In general, the GFS appears to be slightly cooler and
unsettled throughout period.

A shortwave trof is progged to cross the region Tuesday, bringing
another chance of precip. Did expand pop coverage as this system
crosses the region, but kept pops low with ECMWF pointing to
significantly drier solution.

Semi-zonal, somewhat anticyclonic looks like will dominate the
pattern through Friday, with mainly try conditions. Models do point
to another wave crossing the region Wednesday night, but with
ECMWF indicating a stronger and wetter disturbance this time. Best
chances appear east with this system, with potential for low
level jet development in the east. Downsloping zonal flow should
keep conditions dry in the west.

ECMWF points toward ridging over the region by Friday night, while
GFS points to another wave crossing the region in somewhat zonal
flow, impacting mainly southern zones through Saturday. Carried
mainly mountain pops at this point. AAG



Areas of smoke will obscur visibility down to 5sm at times west of
Billings overnight. Local mountain obscuration can be expected due
to this smoke. A disturbance will bring isolated showers to areas
west of Billings in the early morning hours, with local MVFR
conditions possible due to rain and smoke. Otherwise VFR
conditions will prevail tonight. Chambers



    Sun     Mon     Tue     Wed     Thu     Fri     Sat
BIL 058/088 059/076 054/079 056/083 057/084 057/085 058/085
    01/B    34/T    32/W    11/B    10/U    00/U    11/U
LVM 053/084 052/075 046/078 048/081 047/083 048/084 050/083
    14/T    54/T    31/B    11/B    11/U    00/U    11/U
HDN 055/090 059/078 053/081 055/085 054/086 055/087 056/087
    01/U    24/T    32/T    11/B    10/U    00/U    11/U
MLS 055/087 063/081 056/082 057/086 058/086 057/086 058/087
    00/U    13/T    33/T    11/U    20/U    00/U    11/U
4BQ 053/087 060/082 055/081 055/085 056/085 055/086 056/087
    00/U    13/T    42/T    12/T    20/U    00/U    11/U
BHK 050/080 056/078 054/079 054/083 054/083 054/082 054/084
    10/U    14/T    53/T    12/T    21/U    00/U    11/U
SHR 052/087 056/078 051/078 051/082 051/083 050/084 052/084
    11/B    23/T    33/T    21/B    11/U    00/U    11/U


MT...Fire Weather Watch in effect from Sunday afternoon through
      Sunday evening FOR ZONE 117.


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