Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250259

Area Forecast Discussion...Updated
National Weather Service Billings MT
859 PM MDT Mon Jul 24 2017

A few showers and thundestorms developed this evening, but had a
difficult time staying organized. Some gusty winds with the
stronger activity, but mostly shortly lived cells. Have trimmed
back some of the PoPs for the remainder of the evening. High
resolution models were pointing toward the cells north of Billings
holding on until around midnight and then weakening out. GFS
wants to keep the cells going over eastern Montana through the
night. Went with a combination of the two for this update. TWH


.SHORT TERM...valid for Tue and Wed...

Broad range of temperatures across the region this afternoon with
areas north of the Musselshell river under cloud cover in the 70s
and near 100 degrees over portions of southeast Montana. Higher
dewpoints have moved into the area from the north so humidity is
not quite as low as previous days. Upper level low over
Saskatchewan moving east with strong westerly flow aloft over the
region. A series of cold fronts have moved through most of the
area already and one more push of reinforcing cooler air expected
after midnight. Ahead of this front a weak impulse moving in from
southwest Montana tapped into a piece of monsoonal moisture is
projected to bring a round of isolated thunderstorms across the
area. Convective allowing models trended weaker with this activity
and have it pretty fast moving so expect mainly dry thunderstorms
with out much precipitation. Outlier is the GFS which looks wetter
but GEFS plumes and HRRR accumulations look much lighter so have
trended drier overnight. Maybe a strong wind gusts from the storms
but with higher dewpoints downburst potential is lesser.

Coolest day so far in July on tap for Tuesday as the amplitude of
the upper level ridge is weakened by the Canadian low and
northerly pressure gradients create weak upslope winds. Models
hint at moisture pooling a bit over southern Montana so
thunderstorm activity expected later in the afternoon and evening
as a ripple moves through southern Montana. Deepest moisture
appears to remain to the south of Montana with monsoon stronger
over Wyoming and ECMWF is drier solution so have gone with
thunderstorms without a shower mention. Winds will be lighter and
humidity not as critically low so Tuesday will be a very welcome
day for firefighters aside for some lightning triggering new

Warmer weather on tap for Wednesday as heights build but thermal
trough to the west of the area pulls southeasterly winds across
the forecast area which cuts of some of the mixing. This
southeasterly flow does try to deepen moisture over the area and
this may be the best chance to pick up significant moisture but
with lack of much forcing it looks to be diurnally terrain driven
so best chance for picking up rain will be over the mountains. As
the ridge axis strengthens Wednesday night it tries to pull this
moisture northward into the plains but again the GFS is much
wetter than the ECMWF and have leaned towards the drier solution.

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

Semi-zonal southwesterly/westerly upper flow pattern should
persist through the extended period. This pattern generally means
periods of isolated to scattered showers and thunderstorms over
the area mainly during the afternoon and evening hours. Best
chance of showers/storms looks to be on Thursday as a better-
defined shortwave trough crosses Montana. These showers/storms
should be high-based so main threats would be gusty winds and
lightning but little rainfall.

High temperatures will be in the upper 80s to lower 90s on
Thursday, lower to middle 90s Friday and Saturday, then lower to
upper 90s Sunday and Monday as upper ridge builds northward into
our area. Highest readings should generally be east of Billings.



Isolated showers and thunderstorms will continue to move east
across the area tonight. Expect the activity to be over around
KLVM and KBIL by 06Z, and over around KSHR by 09Z. The chance of
precipitation will persist until around 12Z Tuesday in KMLS. Brief
MVFR conditions are possible with the precipitation, as well as
gusty winds in the evening. There will be areas of obscuration
over the Absaroka and Beartooth mountains with localized
obscurations over the NE Bighorns. VFR will prevail on Tuesday,
with areas of obscuration over the Absaroka/Beartooth and NE
Bighorn mountains in the afternoon. Expect a surface wind shift to
the NNE over most of the area Tue. morning. Arthur



    Tue     Wed     Thu     Fri     Sat     Sun     Mon
BIL 064/083 061/088 063/090 064/093 064/094 064/097 065/095
    21/B    22/T    23/T    32/T    22/T    22/T    12/T
LVM 056/081 053/086 057/087 054/090 054/091 054/093 055/091
    32/T    22/T    34/T    22/T    22/T    22/T    12/T
HDN 062/086 060/090 063/092 061/095 062/095 062/098 062/098
    22/T    22/T    23/T    32/T    22/T    22/T    12/T
MLS 065/088 063/091 067/093 066/095 065/097 067/098 067/099
    31/B    11/B    12/T    32/T    22/T    21/U    11/U
4BQ 065/088 061/088 065/090 063/093 063/095 064/096 064/096
    22/T    31/B    23/T    32/T    22/T    21/U    12/T
BHK 062/087 058/088 062/089 061/092 061/094 061/094 062/094
    21/B    11/U    11/B    31/B    01/U    11/U    11/U
SHR 059/084 056/085 058/088 057/090 057/092 057/092 057/093
    23/T    44/T    43/T    32/T    22/T    22/T    22/T




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