Area forecast discussion
National Weather Service Billings Montana
346 PM MDT Thursday may 23 2013
Short term...valid for Friday and Sat...
Large upper level low will continue to remain stationary over the
Pacific northwest through Friday then begin to shift north into
Canada Friday evening/night. This will result in a southerly flow
aloft across our forecast area through early Friday then become
southwest Friday as the upper low moves north. Several
disturbances will also continue to rotate their way around the low
and eject north and northeast across mainly our central and
western locations. Best upper dynamics continue across our west
but will shift toward our central locations by late this afternoon
into the evening.
Surface low across west/central Wyoming has provided for a tight
pressure gradient across Sheridan County northeast to Baker where
sustained winds have been hovering near warning criteria. Guidance
shows the gradient tightening even more over the next several
hours across the east...and as a result have already issued a High
Wind Warning for Fallon and Carter counties through midnight.
Believe the strong winds across southern Big Horn County into
Sheridan County will weaken through the evening as the surface
pressure gradient shifts east. Although it will continue to be
windy across these areas tonight. Models take the low north into
northern Montana late tonight so winds are expected to decrease
after midnight across the far east.
Will continue with chance to likely probability of precipitation for showers and
thunderstorms west of Billings through midnight with best chances
across the far west and northwest as the surface low moves north.
Central and eastern areas remain capped this afternoon due to
strong easterly surface low and along with dewpoints in the 40s
and temperatures in the 60s. However...soundings do show the cap
weakening in the Billings area so can't rule out an isolated
strong thunderstorm. Soundings keep the cap in place all night
across the east.
The upper low shifts north into Canada Friday shifting the precipitation
north so not expecting any shower/thunderstorm activity for our
area except for a slight shower chance during the morning across
our far northern areas.
Southwest flow along with a few disturbances aloft are expected
for Saturday. At the same time...a strong low-level jet will be
across the eastern portions of the area. As a result...focus for
thunderstorms will shift to our eastern areas of our forecast area
Saturday afternoon and evening where a few storms may be severe.
Hooley
Long term...valid for sun...Mon...Tue...Wed...Thu...
Still looking at an unsettled extended period. SW flow with
shortwaves moving through it will affect the region through Monday.
Precipitable waters on the order of /.75/ inches to an inch will
be over the eastern half of the forecast area. This moisture will
combine with very unstable air to bring a good chance of showers
and thunderstorms to the region. Thunderstorms will likely produce
heavy rainfall based on the high precipitable waters. Difficult to
say if the cape on sun will be realized...as GFS was showing a
cap over the area. Have raised probability of precipitation during this period. Also
lowered temperatures due to the precipitation and lower 700 mb
temperatures.
Models diverged synoptically on Tuesday with the GFS developing an
upper low over The Four Corners region and the ecwmf developing
the same low further S. The GFS rotates the low north into the area
on Wednesday while the European model (ecmwf) again establishes SW flow aloft.
Differences continued into Thursday with the GFS moving the low into
the Dakotas and the ecwmf moving a shortwave through the area.
Despite the differences...these patterns suggested unsettled
weather through Thursday. Instability and high moisture will persist
through Thursday...so have raised probability of precipitation over many periods...as well as
lowered temperatures. Arthur
&&
Aviation...
Showers and thunderstorms will affect areas from kbil west this
afternoon. There will be a slight chance of thunderstorms east of
this area to west of kmls. Much of the area will have a chance of
showers and thunderstorms this evening with the greatest coverage
of precipitation expected northwest and west of kbil. A few showers will
linger overnight along and northwest of a Red Lodge to kbil to kmls line.
Due to the possibility of heavy rain with the thunderstorms...IFR
to LIFR conditions will be possible in the precipitation.
Otherwise expect MVFR conditions. Some stratus and fog may linger
over the region early Friday morning causing local reductions in
visibility and locally low ceilings...but otherwise VFR will
prevail over the area on Friday. Expect southeast surface winds of 35 to 45
knots east and southeast of kmls through 06z tonight. Winds will decrease later
tonight. Arthur
&&
Preliminary point temp/pops...
Friday Sat sun Monday Tuesday Wednesday Thursday
-----------------------------------------------------------
bil 050/074 047/077 052/077 053/073 051/073 053/076 051/071
41/b 02/T 23/T 44/T 43/T 44/T 44/T
lvm 041/066 037/075 040/077 042/072 041/071 043/073 041/069
61/b 02/T 23/T 34/T 44/T 44/T 44/T
hdn 050/076 046/079 053/080 052/074 051/076 054/079 052/074
31/b 02/T 24/T 44/T 43/T 44/T 44/T
mls 051/075 052/079 055/080 058/074 054/076 058/078 056/074
21/u 13/T 44/T 44/T 43/T 34/T 44/T
4bq 052/077 048/081 055/081 052/077 052/077 054/078 052/073
11/b 13/T 33/T 44/T 44/T 44/T 44/T
bhk 051/072 049/073 055/074 056/072 052/073 057/074 055/070
11/north 14/T 64/T 44/T 44/T 44/T 44/T
shr 046/073 043/078 047/080 048/074 046/072 051/075 049/070
21/b 02/T 22/T 34/T 44/T 44/T 44/T
&&
Byz watches/warnings/advisories...
Montana...High Wind Warning in effect until midnight MDT tonight for
zones 33-37.
Wyoming...none.
&&
$$
Weather.Gov/Billings
