Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 230908

Area Forecast Discussion
National Weather Service Billings MT
308 AM MDT Fri Jun 23 2017

.SHORT TERM...valid for Tdy and Sat...

Unseasonably cool surface high pressure centered over the region
will move little today as northwest flow aloft streams over it.
Water vapor and PW guidance show the deeper moisture has moved
south of the area so expect a dry day with some fair weather
cumulus forming. Bufkit supports by showing about 70mb of
vertical growth potential above an LFC near 650mb today so would
not expect any precipitation that could reach the ground.
Temperatures will be unseasonably cool and in the lower 70s
despite good sunshine. Momentum aloft will be stronger over
southeast Montana so will still be breezy at times but the western
half of the area will see much less wind.

With the surface high pressure over the area for a second night
record low temperatures will still be possible over southeast
Montana but could be some high level clouds over the western half
of the area to keep temperatures a bit higher.

Saturday surface high pressure retreats to the east as an upper
level ridge begins approaching Montana from the west. Winds switch
to a more upslopish flow from the northeast which will keep
temperatures cooler even though skies in the western sections do
look to be clear during peak heating. With air warming aloft
minimum temperatures Saturday night look to be a bit warmer.

.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...

The period with the highest confidence in the extended was Sunday
through Sunday night, when the jet will be mostly E of the
forecast area, allowing an upper ridge to build in. This period
will be dry with highs near normal on Sunday.

The forecast becomes more uncertain after Sunday as dynamics and a
progressive flow move back over the region leading to pattern
detail discrepancies between the deterministic models and the GFS
ensembles showing uncertainty in the Tue. through Wed. time frame.
The GEFS plumes highlighted Monday as the hottest day of the
extended period with Tuesday not much cooler than Monday. Jet
energy with increasing divergence approaches the area from the W
through Mon. night, causing the upper ridge to break down with
time. Brought in some mountain PoPs Mon. afternoon, with models
developing QPF in the W. Monday looked hot with 700 mb
temperatures at KBIL of 12-14 degrees C, and mixing up through
600 mb. Given the plumes, and the above, have raised highs above
the blended guidance into the lower 90s over much of the area.
RH`s will be low in spots, but light winds will likely preclude
the need for an eventual Fire Weather highlight. Spread PoPs for
thunderstorms over the W and central zones Mon. night as a
shortwave trough and surface cold front move into the region.
Spread PoPs through the entire area on Tue with the shortwave
moving through the area and a post-frontal airmass in place.
Noted the GEFS plumes had decent CAPES over the area, but kept
them below 1000 j/kg. Highs on Tue. will reach the 80s to lower

Model timing and placement with shortwave troughs begins to
differ for Tue. night and Wednesday. Kept slight chances across
the area and tried to blend model solutions. Wed. will be cooler
with highs closer to seasonal normals. Model differences and the
continued threat of unsettled weather continued through Friday.
Continued to blend model solutions and went with climo PoPs on
Friday. Models did agree on a cooling trend into Friday. Did lower
highs below blended guidance on Thursday. Arthur


VFR conditions will prevail today and tonight. A few showers are
possible over the mountains and from KBIL to KSHR E today.
Localized mountain obscurations are possible. Otherwise, expect
gusty NNW surface winds from KMLS to KSHR E today. Gusts will be
around 25 kt. Arthur


    Tdy Sat     Sun     Mon     Tue     Wed     Thu
BIL 072 049/074 049/080 054/092 061/088 058/083 055/079
    0/B 01/B    10/U    00/U    23/T    22/T    22/T
LVM 071 040/073 042/079 047/089 053/083 049/078 046/075
    0/U 01/U    00/U    01/U    24/T    22/T    32/T
HDN 073 048/075 047/082 052/094 060/091 057/085 054/081
    1/B 11/B    10/U    00/U    22/T    22/T    21/U
MLS 071 044/075 047/080 052/092 062/092 061/086 056/081
    0/B 01/U    00/U    00/U    22/T    22/T    21/B
4BQ 069 045/073 046/078 050/091 059/091 058/085 055/080
    0/B 01/U    10/U    00/U    02/T    22/T    21/U
BHK 066 040/070 041/075 046/087 056/089 058/083 053/077
    0/N 00/U    00/U    00/U    02/T    22/T    21/B
SHR 069 044/071 044/077 047/089 055/087 053/081 050/077
    1/U 01/U    10/U    00/U    22/T    22/T    22/T




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