Area forecast discussion
National Weather Service Billings Montana
247 PM MDT Wednesday may 22 2013
Short term...valid for Thursday and Friday...
Large upper level low will be stationary over the Pacific
northwest states this afternoon through Thursday night. This will
provide a southerly and divergent flow aloft to our forecast area
through Thursday. Several disturbances will rotate their way
around the low and eject across mainly the western half of our
forecast area. Best upper level dynamics will be west of Billings
through tonight before slowly shifting east Thursday into Thursday
night. Will continue with chance to likely probability of precipitation from Billings west
from late this afternoon through Thursday.
Soundings show a cap across the entire area this afternoon due in
part by an easterly surface wind which has allowed a low stratus
deck to remain in place across our central and western locations
keeping temperatures on the cool side. Livingston has remained in
the 40s all day except the past hour when they broke 50 degrees.
Dewpoints are a bit low and only in the upper 30s to lower 40s.
Soundings do show the cap over the Livingston area weakening this
evening so can't rule out an isolated severe thunderstorm west of
Billings as shear remains quite good. However...cape is quite
limited and mainly over the beartooth/Absaroka Mountains and there
is also not much of any disturbance moving overhead to trigger too
much at this time.
Same pattern holds Thursday with the focus shifting slightly
further east toward Billings as the upper level divergence and
wind shear shift into the central and eastern zones. However...a
very strong low level jet will be in place resulting in sustained
winds in the 20 to 35 miles per hour range with gusts near 50 miles per hour for Fallon
and Carter counties. Soundings show a very strong cap across our
eastern areas through the day Thursday and into Thursday night. At
this time...given upper low placement well west of the area...no
strong disturbance looks to move across the east to help erode the
cap so thunderstorm activity looks limited.
Upper low begins to shift north into Canada Friday. Models show
quite a bit of drying at middle and lower levels so have lowered probability of precipitation
quite a bit to just a slight chance for the day Friday and into
Friday night. Hooley
Long term...valid for Sat...sun...Mon...Tue...Wed...
Unsettled SW flow will be over the forecast area through the
extended period as several upper lows move through the Pacific
northwest. The airmass will be moist...as Pacific moisture and Gulf
moisture merge over the region. In addition...there will be
periods of strong instability based on model lifted indices and
BUFKIT soundings. The strongest instability will be over areas east
of kbil through Monday. A fair amount of shear will accompany the
instability...so the possibility exists for severe thunderstorms.
Rainfall could be heavy at times over central and eastern areas based
on high precipitable waters on the GFS. Otherwise...there was a
moderate to high amount of model spread in terms of probability of precipitation...as the
GFS and ecwmf varied in how they handled the energy in the SW
flow. Inherited forecast of scattered probability of precipitation through most of the
period handled the situation well and have made only a few
adjustments based on new model data. Temperatures in the upper 70s
to lower 80s were also on track given forecast 700 mb mixdown
temperatures. Arthur
&&
Aviation...
Showers and thunderstorms will increase over areas west of kmls
through this evening. The best chances for precipitation will be
from Harlowton to Red Lodge west. Isolated to scattered showers will
occur west of kmls overnight and Thursday morning. Thunderstorms will
redevelop over the same areas Thursday afternoon. Expect VFR to MVFR
conditions. IFR to LIFR will be possible in some of the stronger
storms. Surface winds will be east at 15 to 25 knots across the area
through tonight. On Thursday...winds will increase from the southeast over
areas east of kbil to 25 to 35 knots. Low-level wind shear will be
possible late tonight and early Thursday over kmls. Arthur
&&
Preliminary point temp/pops...
Thursday Friday Sat sun Monday Tuesday Wednesday
-----------------------------------------------------------
bil 049/073 050/075 049/077 053/080 053/077 051/078 053/077
34/T 42/T 12/T 33/T 33/T 33/T 33/T
lvm 045/065 041/070 039/078 041/080 042/078 041/076 043/075
66/T 62/T 22/T 23/T 33/T 33/T 33/T
hdn 048/077 050/078 047/079 053/082 052/080 051/080 054/080
22/T 22/T 12/T 33/T 33/T 33/T 33/T
mls 049/072 051/078 052/079 057/083 058/079 054/080 058/080
11/north 22/T 23/T 33/T 44/T 33/T 33/T
4bq 046/074 052/079 049/081 055/085 052/081 052/082 054/081
11/north 12/T 12/T 33/T 33/T 33/T 33/T
bhk 044/066 047/075 050/073 056/077 056/077 052/077 057/077
11/north 12/T 24/T 43/T 33/T 33/T 33/T
shr 045/074 046/075 045/079 048/083 048/079 046/077 051/078
22/T 22/T 12/T 22/T 23/T 33/T 33/T
&&
Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.
&&
$$
Weather.Gov/Billings
