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Area forecast discussion 
National Weather Service Billings Montana
209 am MDT Monday Jul 25 2016

Short term...valid for tdy and Tue...

A shortwave seen over the Pacific northwest on water vapor imagery early
this morning, will move into the area this afternoon, and cross
the area in pieces tonight into Tuesday. Precipitable waters will
increase over the area from the east tonight through Tue. Night to
an inch to /1.25/ inches due to a weak low-level easterly jet. A
weak cold front will push east into the forecast area tonight as an
inverted surface trough forms over southeast Montana and remains over this
area through Tuesday. It will not be overly unstable today based
on the sref, which just showed 500 j/kg of MUCAPE over the northwest and
southeast zones. Instability increases tonight with 1000 j/kg of MUCAPE
over the eastern zones. Some areas of 40 kt bulk effective shear
will also be over the area tonight.

Kept this morning dry, then kept the inherited pops for this
afternoon which highlighted the mountains and adjacent areas, as
well as the southeast. Based on the above, and model qpf fields, these
pops looked good. Pops will be more widespread this evening after
convective temperatures are reached, with the highest pops northwest and
southeast. There is a marginal risk for severe storms over parts of
Fallon and Carter counties this afternoon and evening in the area
of highest cape. Kept some lingering pops over the northern tier
late tonight. Mixing will be to around 600 mb today supporting
temperatures in the 90s. Humidities will be in the teens to lower
20s, but winds will be light so fire weather concerns will be low.

Instability increases across the area on Tue., With the sref
showing 1000 j/kg MUCAPES and some 2000 j/kg of MUCAPE in the far
east. There will also be some shear over the east on Tuesday. As
vorticity continues to cross the area, pops will be widespread
again in the afternoon and evening. A cold front will push into
the inverted trough late Tue. Night, supporting continued low pops
across much of the area. In addition, jet divergence from the
left-front quadrant of an upper jet will provide additional lift
Tue. Night. A few strong to severe storms are possible over the
eastern zones Tue. Into Tue. Night. Mixing will be to 600-500 mb
on Tue., But high temperatures will be hampered by the convection,
so expect them to be a little lower than today's highs. Expect
higher rh's on Tue. Due to the increased moisture. Arthur

Long term...valid for Wed...Thu...Fri...Sat...sun...

Active weather coming Wednesday and Thursday as a couple of
Pacific shortwaves interact with an increasingly moist airmass
courtesy of persistent easterly surface winds. Models continue to
be in some disagreement with regard to the timing and strength of
these waves, not surprisingly with a progressive flow, but the
overall theme of cooler mid level temps, veered flow aloft and
greater moisture/instability is consistent. Have raised pops each
of these periods, especially in our east where pwats will be near
an inch or more. The risk of strong to severe storms will exist in
our east as well, see day3 risk of marginal east of Rosebud
County. Increased lightning will be problematic of course with
regard to fire weather, but humidities will be running high for
late July with mins in the 20s/30s.

Should see a trend toward drier and more stable conditions on
Friday as final shortwave departs and heights begin to rise again
from the west. Could see some weaker storms in the east and over
the mountains.

Upper ridge builds in for next Saturday as next pac trof moves
near the coast. Models have been consistently suggesting a
monsoonal surge up the sierras and northern Great Basin, which
would translate to a risk of higher-based thunderstorms in our
area next weekend, especially as Pacific trof moves inland in some
fashion. Plenty of model spread here, but overall trend is toward
warmer temps and monsoonal thunderstorm potential next Sat/sun.

As for temperatures, expect modest cooling Wed/Thu as northwest flow taps
into some Canadian air. Warming looks to be in store for Fri/Sat,
and depending on fate of pac trof we could push 100 degrees again
next weekend.

Jkl
&&

Aviation...

VFR will prevail over the next 24 hours. Clear skies this morning
will give way to isolated to scattered showers and thunderstorms
late this afternoon and tonight as a weak disturbance moves
through the region. Thunderstorms in the east near kbhk may be
strong with local MVFR conditions. Thunderstorms to the west will
be higher-based and may produce erratic surface winds. Jkl

&&

Preliminary point temp/pops...

Tdy Tue Wed Thu Fri Sat sun
-------------------------------------------------------
bil 095 063/093 064/090 062/086 061/090 062/096 066/094
1/u 32/T 22/T 33/T 31/b 11/u 22/T
lvm 094 053/093 054/090 054/088 051/090 054/094 056/093
2/T 22/T 22/T 23/T 31/b 12/T 22/T
hdn 097 060/095 062/091 059/088 056/090 060/097 063/094
1/u 33/T 22/T 33/T 31/b 11/u 22/T
mls 098 066/095 066/090 064/087 061/089 063/096 068/095
1/u 23/T 34/T 43/T 32/T 11/u 22/T
4bq 100 065/095 063/092 061/087 060/090 061/096 065/096
2/T 24/T 33/T 44/T 42/T 11/u 12/T
bhk 096 062/092 061/085 059/082 058/085 058/091 062/093
2/T 34/T 45/T 54/T 42/T 11/u 12/T
shr 097 056/094 058/091 057/088 054/091 056/096 058/096
2/T 13/T 22/T 34/T 41/b 11/u 12/T

&&

Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.

&&

$$
Weather.Gov/Billings

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