Area Forecast Discussion
Issued by NWS Billings, MT

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584
FXUS65 KBYZ 310221
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
821 PM MDT TUE AUG 30 2016

.UPDATE...

Energy and moisture embedded in southwest flow aloft were moving
over western portions of the area this evening producing some very
light radar returns. Suspect that most of this is just mid to high
level clouds. Only changes made to the forecast this evening were
to adjust sky cover and winds to current trends. Otherwise, smoke
and haze associated with wildfires in Idaho and Yellowstone
National Park continue to plague portions of the area, but
especially across western areas and near the southwest mountains
and foothills. This will continue to be the case over the next few
days. The rest of the forecast remains on track and the previous
forecast discussion and an updated aviation discussion are below. STP

&&

.SHORT TERM...valid for Wed and Thu...

An upper ridge was building over the central rockies this
afternoon, while a trough was deepening off the Pacific northwest
coast. This combination was producing southwest flow and bumping
700mb temperatures up to around 14c across southern Montana. The
ridge will gradually slide east through Friday, but this will only
serve to increase downslope flow. Therefore, temperatures will be
hot through the rest of the week. The strongest energy will get
deflected north, so will confine the PoPs to mainly mountainous
locations this evening.

Mid levels will gradually moisten over time and the eastern edge
of the trough will push farther into western Montana Wednesday and
Thursday. This will allow for a slightly better chance of
convection the next two days. Will keep PoPs low, however, as warm
700mb temperatures will be very hard to overcome. Storms will be
very high based and produce erratic winds. Southeast winds will
increase over southeast Montana tonight and Wednesday, with some
gusts to 35 mph possible. These winds will carry in some higher
dewpoint air, and this could cause areas in Carter and Fallon
counties to be slightly cooler then the rest of the southeast.

For fire weather, the continued hot temperatures with humidities
falling into the teens, and near 10 percent over the west, will
cause concerns to elevate. That being said, do not see enough
thunderstorm coverage, frontal passage, or combination of
increasing winds with humidities falling into the teens, to raise
issue a fire weather highlight. Winds over the southeast will be
gusty on Wednesday, but humidities will be borderline for Red Flag
criteria. Mid level winds will increase over the west on Thursday
ahead of a cold frontal passage on Friday. These increasing winds
will likely be met with very low humidity values, but the latest
guidance has been pointing to mid levels slightly moistening over
time. Will not issue any highlights at the present time but pass
word along to the midnight crew for a closer look at the Thursday
Red Flag potential for the west. TWH

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

Overall pattern does continue to be in pretty good
agreement...but the extended forecast period continues to be full
of timing and track discrepancies...with ensembles showing
uncertainty for entire period. Therefore have made only minor
changes to the inherited forecast.

The cold front progged for Friday appears to be much later
getting into the area...just reaching western zones by about 00z
Saturday and crossing the region overnight...therefore raised
temps some for Friday. Have kept slight pops in place through the
day Friday...as it appears a weaker wave will cross the region
ahead of the front...but moisture availability will be limited.
The difficulty with the FROPA is the differing paths of the front.
GFS favors a much deeper and stronger wave...while the ECMWF
points toward best energy associated with the front shifting
north of the CWA. Chose to keep slight pops in place for this
reason. Southwest flow aloft will bring periodic shortwaves
through the region saturday and sunday...but again timing varies
significantly. Main trof axis appears to push into the region
early Monday morning...this should bring best potential for
widespread precip for the region...so raised pops slightly for
Monday periods.

As for temps...Guidance continues to look cooler...so continued
trending temps downward. Expect to see below average temps
following FROPA on Friday night...with highs in low 60s by Monday. AAG

&&

.AVIATION...

VFR conditions will prevail across the area tonight and into
Wednesday. LLWS should be expected near KMLS, and KBHK after 03z
Wed, and possibly near KBIL after 06z Wed. BT

&&

.PRELIMINARY POINT TEMP/POPS...

    Wed     Thu     Fri     Sat     Sun     Mon     Tue
-----------------------------------------------------------
BIL 064/095 064/094 061/090 051/074 049/068 047/064 045/069
    00/B    22/T    32/T    22/T    34/W    43/W    32/W
LVM 055/096 056/093 053/087 042/069 038/064 039/062 039/067
    12/T    23/T    32/T    22/T    34/W    43/W    32/W
HDN 060/097 060/098 059/095 051/076 046/070 044/068 042/071
    00/U    12/T    32/T    22/T    34/W    43/W    32/W
MLS 065/097 065/097 065/096 054/077 050/071 047/065 046/071
    00/N    12/T    32/T    22/T    34/W    43/W    32/W
4BQ 062/093 063/096 063/097 053/078 049/072 048/068 046/071
    00/N    02/T    22/T    22/T    34/W    43/W    32/W
BHK 061/091 061/092 061/095 052/076 047/070 046/064 045/068
    10/N    02/T    22/T    22/T    34/W    43/W    33/W
SHR 056/095 056/095 057/094 048/076 045/070 044/067 042/069
    10/U    02/T    32/T    22/T    34/W    43/W    32/W

&&

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

&&

$$
weather.gov/billings



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