Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KBYZ 290845

Area Forecast Discussion
National Weather Service Billings MT
245 AM MDT MON AUG 29 2016

.SHORT TERM...valid for Tdy and Tue...

Water vapor imagery shows westerly flow over the area with a very
weak shortwave moving thru eastern MT, and a deeper trof taking
shape off the BC coast. Remarkably, the combination of weak
forcing and very elevated instability around 600mb is producing
some fair echoes from Rosebud County eastward. Not sure if any
pcpn is hitting the ground with a considerable depth of sub-cloud
dry air, but radar imagery is convincing enough to extend an area
of sprinkles across our east thru the remainder of the night.

Surface high dropping into the Dakotas will result in easterly
winds across our cwa today. Though low level moisture will be a
bit higher than the past couple days, modest instability will be
capped. The exception to this may be in our far west by this
evening as weak shortwave and warm front lift out of the great
basin. Could see isolated mountain convection drift over our
western lower elevations between 00-06z, with a few hundred j/kg
of cape to work with. Have adjusted pops accordingly. Otherwise it
will be a quiet weather day with highs in the 80s to around 90

Southwest flow aloft will become well-established by Tuesday with
a strong upper ridge over the central Rockies and trof along the
Pacific coast. Lee side sfc ridge will depart, opening the door
to downslope warming, with highs in the 90s likely as 700mb plume
to +14c noses into south central MT. Livingston record high of 96
may be approached. Will leave isolated mention of showers or tstms
over our mountains only, w/o any forcing to speak of.

Biggest impact over the next couple of days could be an increase
in smoke from nearby wildfires in northwest WY, per the backed mid
level flow. In fact, latest HRRR suggests a notable increase in
smoke into our cwa by this evening. Something to keep watch of.


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

Made a few changes to the forecast based on the latest model
trends. ECMWF ensembles still suggested quite a bit of uncertainty
with the pattern beginning on Friday.

Upper ridge axis moves just E of the area on Wed., and energy
increases in SW flow aloft over the western zones. Precipitable
waters are around /0.60/ inches with a few hundred joules of
MUCAPE over SE MT. Moisture was confined to above 10K ft in the
morning on the GFS time-heights, so just had low PoPs in the
highest elevations. The moisture was still aloft in the afternoon
so have trimmed back PoPs to just the far W and the NE Bighorns.
Chances for thunder looked limited due to the weak instability.
High temperatures are still expected to reach the 90s. SW flow
overtakes the entire area for Thu. and Thu. night with decent
precipitable waters. Trimmed PoPs westward on Thu. morning given
QPF forecasts, otherwise kept low PoPs across the area through
Thu. night. There was still not much CAPE during this period.
Temperatures should reach the 90s again.

On Fri., the ECMWF swings a shortwave through NW MT from the
pacific trough, while the GFS continues increasing SW flow over
the area. Kept the climo PoPs going, and blended temperatures
ranged from the lower 80s W to around 90 E. On Sat., both models
had the trough W of the area, then began to shift it E on Sunday.
Generally kept the inherited PoPs across the area with moisture
and lift moving across the region. The models bring a strong cold
front across the area Fri. night, ushering in much cooler weather
for the weekend with highs in the upper 60s to mid 70s by Sunday.
Cyclonic flow will keep unsettled and cool weather over the area
on Monday. If the models continue to show a strong cold front Fri.
night, this may prompt some fire weather concerns down the road.



VFR conditions will prevail today through tonight. Localized
mountain obscurations are possible over the Beartooth/Absarokas
and NE Bighorns this afternoon and evening due to isolated
thunderstorms. A few thunderstorms are also possible W of KBIL
this evening. Did not include thunderstorms in the KLVM TAF due to
low confidence of a storm affecting the TAF site. Arthur



    Tdy Tue     Wed     Thu     Fri     Sat     Sun
BIL 087 060/093 064/095 063/092 061/087 054/076 051/071
    0/U 00/U    01/U    22/T    22/T    22/T    22/T
LVM 088 052/095 054/094 055/090 052/083 044/073 042/069
    0/U 20/U    02/T    23/T    32/T    22/T    22/T
HDN 090 058/096 060/097 060/095 058/090 052/079 050/074
    0/U 00/U    00/U    22/T    22/T    22/T    23/T
MLS 089 062/096 065/097 065/095 063/090 056/080 052/074
    0/U 01/U    10/N    12/T    22/T    22/T    23/T
4BQ 089 059/094 062/093 063/094 061/091 056/079 053/076
    0/U 01/U    10/N    12/T    22/T    22/T    23/T
BHK 085 057/088 060/090 061/091 060/089 055/079 050/072
    0/B 01/U    10/N    12/T    22/T    22/T    23/T
SHR 090 054/094 056/094 056/092 056/089 051/078 048/075
    0/U 11/U    11/U    22/T    22/T    22/T    22/T




$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.