Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 301537

Area Forecast Discussion...Updated
National Weather Service Billings MT
937 AM MDT TUE AUG 30 2016

A batch of showers and thundestorms were cruising across
northeast Montana this morning with the tail end of them brushing
the northeast parts of our southeast zones. Have added low PoPs
at Baker for the rest of the morning. Also raised winds over the
southeast at Baker already gusting to 35 mph. TWH


.SHORT TERM...valid for Tdy and Wed...

Tail end of weak shortwave lifting through north central MT,
combined with a southeasterly low level jet and elevated
instability, is actually producing a few light showers in northern
Rosebud County as of 2 am. This activity should not amount to much
and diminish by sunrise, but have added an isold pop to cover it
thru 12z.

Upper ridge axis over the northern high plains and troffing off
the Pacific coast will result in a very warm and dry SW flow into
our cwa through the short term period. 700mb temps to near +14c
translate to highs in the 90s, with smoke being the potential
limiting factor. Thunderstorm chances will be confined to the
mountains today. Increased monsoonal moisture and area of PV
lifting into western MT should bring an increase in t-storm
coverage over our far west late Wednesday and Wednesday evening.
Latest models trended a bit further west with the axis of greatest
moisture, so have scaled back eastern extent of pops slightly.
This activity, though isolated, will be high-based and could
produce erratic sfc winds.

Regarding fire weather: Winds and t-storm coverage will not be
great enough to warrant any highlights over the next two days, but
the combination of hot temps and RHs to 10-15 percent in our
western areas will obviously elevate concerns. Should also note
that mid level lapse rates and moisture are sufficiently steep/dry
to push Haines index in our west to 6. Our east, especially fire
wx zone 133, will see a notable increase in S-SE winds the next
couple days, greatest on Wednesday. Boundary layer moisture will
be greater and should keep min RHs to 20 percent or higher, so
again no fire weather highlights needed. JKL

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

Friday continues to be the day of model discrepancies in the
extended forecast. The GEFS and ECMWF ensembles showed lowered
confidence beginning Fri. and continuing through the end of the
period. Despite this lower confidence, did raise PoPs for the
weekend/early next week system.

SW flow with energy moving through the flow will be over the area
Thu. and Thu. night, along with high-level moisture. The slight
chance PoPs central and W in the morning still looked on track,
with low PoPs across the area in the afternoon. A low-level jet
will be over the far eastern zones into Thu. night bringing with
it some high MUCAPES. There also was some increase in Bulk Shear
in the afternoon and evening, so will need to watch for any strong
storms. Raised PoPs Thu. evening into the chance category, and
left low PoPs overnight. Highs in the 90s were still on track for

On Fri., the ECMWF moved the Pacific trough faster toward the area
than the GFS. By 12Z Sat., the GFS had an upper low over S.
Alberta/NW MT and the ECMWF had strong SW flow over the region. In
addition, the ECMWF was faster in pushing a cold front across the
area by 06Z Sat., while the GFS was slower with the frontal
movement. Both models brought in windy conditions behind the front
into Saturday. Went a bit higher with PoPs during this period, but
the moisture was still restricted to the upper levels, and QPF
was scattered in the models, so kept PoPs in the slight chance
category with chance PoPs in the mountains. It will be very warm
on Fri., ahead of the system, then 700 mb temperatures cool down
to around +4 degrees c on Sat., allowing for highs in the 70s to
around 80. If these trends continue, will likely need a fire
weather highlight to cover the warm and dry conditions ahead of
the front, as well as the changes with the frontal passage.

Model differences with the handling of the trough continue
through Tuesday, but given the unsettled pattern, have raised PoPs
into the chance category across the area for Sun. and Mon. and
went near climo for Tuesday. It will be cooler, with highs in the
60s and 70s. Arthur



A few showers are occurring this morning northeast of
KBIL and north of KMLS-KBHK. These showers could produce MVFR
conditions near KMLS and KBHK through about 18z today. Also, MVFR
CIGs over far SE MT should lift to VFR by 17z today. Otherwise,
VFR will prevail across the area through tonight. There will be
localized mountain obscurations due to isolated thunderstorms this
afternoon and evening. LLWS possible near KMLS, KBIL, KSHR, and
KBHK after 03z Wed. RMS/TWH



    Tdy Wed     Thu     Fri     Sat     Sun     Mon
BIL 094 064/095 064/092 061/088 054/076 051/069 047/067
    0/U 00/B    22/T    32/T    22/T    34/W    43/W
LVM 095 055/096 056/091 053/085 045/072 042/065 039/064
    1/B 12/T    23/T    32/T    22/T    34/W    43/W
HDN 096 060/097 060/095 059/093 054/079 049/071 044/071
    0/U 00/U    12/T    32/T    22/T    34/W    43/W
MLS 097 065/097 065/095 065/094 057/080 053/072 047/068
    2/T 10/N    12/T    32/T    22/T    34/W    43/W
4BQ 094 062/093 063/093 063/095 056/080 053/073 047/070
    1/U 10/N    02/T    22/T    22/T    34/W    43/W
BHK 090 061/091 061/090 061/093 055/078 050/071 045/066
    2/T 00/N    02/T    22/T    22/T    34/W    43/W
SHR 095 056/095 056/092 057/092 051/079 048/071 043/069
    0/U 00/N    02/T    32/T    22/T    34/W    43/W




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