Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 261518

Area Forecast Discussion...Updated
National Weather Service Billings MT
918 AM MDT Mon Jun 26 2017


Generally the forecast is on track this morning. Did adjust
dewpoints with the latest short term guidance, as the area has
been a little too moist overnight. Winds will still be a bit
gusty this afternoon as things mix out. Reimer


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

Morning water vapor imagery shows an upper level ridge moving into
western Montana with increasing energy going over the top of the
axis of this ridge in Alberta. Surface pressures are falling as a
leeside trough develops over Alberta and this pattern is going to
allow a more southerly flow across the forecast area today. With
warmer air aloft approaching with the ridge and the surface flow
more downslopish expect deeper mixing which will give summer like
temperatures around 90. The warmer temperatures will push humidity
to near 20 percent and increasing winds will support increased
wildland fire behavior but do not think highlights are warranted
with winds generally below 20 mph.

Cold front tracks across the region tonight bringing a chance for
high based thunderstorm activity especially for the western areas.
NSSL WRF hints that some activity tries to develop over
southeastern Montana where southeasterly flow is trying to bring
in higher dewpoints but guidance indicates dewpoints will only be
rising into the 40s overnight. Will be a shift to westerly winds
overnight which will maintain mixing and keep temperatures mild
behind the front.

Tuesday is the more active weather day as cyclonic flow aloft with
weak disturbances embedded in it flows over the area with surface
winds westerly. The dynamics help moisten the airmass by producing
a series of showers and thunderstorms with PW values beginning to
approach an inch by 21z. Models progging CAPE to be near 1000j/kg
with helicity around 30 so strong storms are possible just not
confident how activity will evolve and whether convection has a
chance to be discrete or develops as clusters. Storm Prediction
Center has a marginal risk of severe weather and the aggressive
NAM convective allowing runs hint at a few stronger storms with
more significant activity running across northern Wyoming.
Activity will persist in the overnight hours which is not uncommon
in the late June timeframe but do expect temperatures to be
cooler. borsum

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

Extended period still looked unsettled until Friday, when pattern
allows airmass to dry out. The models were in decent agreement
with the overall pattern into Friday, then began to diverge
somewhat in their solutions. Temperatures through most of the
period will be a few degrees on either side of normal, then the
warmest days will be Sunday and Monday.

A jet dives SE into the region on Wednesday, rotating an upper
trough into the area. Divergence will accompany the left-front
quadrant of the jet as it moves SE, then E through Thursday.
Vorticity moves through the area Wed. night into Thursday, then
the flow over the area becomes cyclonic behind the system`s upper
low on Friday. Models differed in their QPF forecasts through Wed.
night and came into better agreement for Thursday. Blends gave
isolated to scattered PoPs through Wed. night over portions of the
area. CAPES/shear did not look overly strong during this period so
threat for any strong to severe storms appeared low. Had scattered
PoPs over the area on Thu. with good model agreement on more
widespread QPF. Airmass then looked drier under the cyclonic flow
into Friday so had little in the way of PoPs. General ridging
overtakes the region Sat. and Sun. with mostly dry weather. Dry
weather continues into Monday with the GFS showing a ridge and the
ECMWF showing zonal flow. Arthur



VFR conditions will prevail over the area today. A few
thunderstorms will develop W of KBIL this evening ahead of an
approaching cold front. The cold front will push through KBIL late
tonight bringing a shift to westerly surface winds. Chances for
showers and thunderstorms will be from around KBIL W. MVFR
conditions are possible with the thunderstorms. Localized
mountain obscurations this evening will become more widespread
overnight. Arthur



    Tdy Tue     Wed     Thu     Fri     Sat     Sun
BIL 091 062/083 055/080 055/076 052/079 053/083 058/085
    0/U 14/T    42/T    43/T    11/B    10/U    11/B
LVM 087 055/077 047/076 046/074 044/077 046/080 049/081
    1/U 25/T    32/T    32/T    11/B    11/B    12/T
HDN 090 059/086 055/083 055/077 051/080 053/086 056/087
    0/U 14/T    42/T    42/T    12/W    10/U    11/B
MLS 089 062/089 057/083 056/078 052/079 053/084 058/087
    0/U 03/T    42/T    34/T    11/B    11/U    11/B
4BQ 087 062/088 056/082 054/077 050/078 053/083 057/086
    0/U 01/B    42/T    34/T    12/W    11/U    12/T
BHK 083 056/089 054/081 053/075 048/075 049/079 054/082
    0/U 01/B    31/B    25/T    32/T    11/U    12/T
SHR 087 057/083 052/077 051/073 047/076 049/081 053/083
    0/U 14/T    43/T    32/T    12/T    11/U    11/B




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