Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 191609
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1009 AM MDT Sun Aug 19 2018

.UPDATE...

An upper-air disturbance on the western side of an upper low is
bringing light rain to southern Carter County this morning. This
disturbance is moving southward so that it should be out of Carter
County and bring an end to the rainfall by around Noon MDT. Most
of the area should be dry the rest of today, with the exception
of the mountains where an isolated shower or thunderstorm is
possible. Otherwise, northwesterly flow is bringing in wildfire
smoke over the region, and subsidence is helping to bring this
smoke down to the surface in higher concentrations than what we
have experienced recently. The MT Department of Environmental
Quality has issued an Air Quality Alert for all of Montana due to
the smoke. Rest of forecast is in good shape. RMS

&&

.SHORT TERM...valid for Tdy and Mon...

Showers and a few thunderstorms were wrapping around the back side
of the upper low early this morning into the central and eastern
zones. The low was situated over far SE MT per water vapor
imagery. Models were in good agreement in moving the low to the
SD/NE border by 18Z today and pulling the precipitation out of the
area by 18Z. Used a blend of the WRF, NBM and Official Forecast
for the PoPs. A weak shortwave and limited moisture will bring
just a slight chance of showers and thunderstorms to the
Beartooths and NE Bighorns this afternoon. Kept mention of thunder
limited through the day due to lack of instability in models. Regarding
the smoke in the area, the Canadian Surface Smoke Model had a
good handle on the smoke N of the area along the highline. So,
went with areas of smoke across the area this morning, and limited
smoke to areas from KBIL-KSHR W this afternoon. Limited mixing
will keep highs in the 70s today.

Heights fall tonight in advance of the next Pacific system, and
energy moves E into the area. Moisture will increase over the W
and central zones, but PW`s will be lower than they have been with
values of /0.50-0.75/ inches. Had slight chance to chance PoPs
over the SW mountains and foothills this evening, expanding N and
E to include areas from KBIL W and the NE Bighorns overnight. The
areas of smoke will remain confined to KBIL to KSHR W.

The left-front quadrant of an upper jet will be in the southern
portion of the Pacific system, and will affect the area Monday
through Mon. night. Shortwave energy and moisture will increase
over the area during this period with decent q-vector convergence.
Upslope flow will also deepen over the region. The models were
not in great agreement with the placement of the moisture so
continued to use a blend for PoPs. Had chance PoPs from KBIL W
Mon. morning, then shifted good chances for precipitation S into
the SW mountains and foothills, as well as the NE Bighorns Mon.
afternoon. Went with lesser chances further N. Lift and moisture
overspread almost the entire area Mon. night, so spread mainly
chance PoPs E through the night. With good dynamics over the area,
chances for thunder looked good Monday afternoon into Mon. night.
Kept the mention of smoke from KBIL-KSHR W through Mon. night.
Monday will be slightly cooler than Sunday. Arthur

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

Models are not showing as much of a split in the low over Oregon
on Tuesday into Wednesday. This will result in the ridge not
building in as fast and the below normal temperatures will
continue through Tuesday and Wednesday. Also, as the elongated
trough slides across the area Wednesday, the chance for showers
and thunderstorms is a little bit better. By Thursday as the ridge
does start to work more into the area, temperatures will be back
up to around normal, then warming a little more for Friday, but as
another weak wave moves out of southern Canada the flow will turn
more zonal and the ridge will flatten out. This will keep
temperatures rising much above normal. There still does not look
to be much moisture with this wave. Reimer
&&

.AVIATION...

Smoke from western wildfires will cause local IFR conditions with
visibility occasionally dropping below 3 miles. Otherwise, MVFR
conditions due to visibility restrictions in smoke, will be
widespread across southern Montana and northern Wyoming. The
hardest hit areas will be from KBIL west. Smokey conditions will
continue tonight. Mountains will be obscured in smoke. Lingering
showers south of KBHK will slide south out of the sate by 18z. TWH
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 076 054/074 052/072 053/085 060/085 058/085 055/081
    1/K 23/T    32/T    11/U    21/B    11/U    11/U
LVM 078 048/073 047/072 046/081 051/082 049/083 046/081
    1/K 44/T    53/T    11/U    32/T    11/U    11/U
HDN 077 052/076 052/075 050/086 057/086 056/088 054/082
    0/K 13/T    42/T    10/U    22/T    11/U    11/U
MLS 077 050/076 052/076 053/087 060/088 059/089 057/083
    0/K 01/B    22/W    10/U    12/T    10/U    11/U
4BQ 075 046/076 052/075 052/086 058/086 057/089 057/084
    1/K 01/B    32/W    10/U    12/T    10/U    11/U
BHK 075 045/075 049/075 050/085 058/088 058/088 055/083
    0/K 01/B    12/W    10/U    12/T    10/U    11/U
SHR 074 048/077 049/074 050/083 055/084 053/086 052/082
    1/K 12/T    53/T    11/U    22/T    11/U    11/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings


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