Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Billings Montana
306 PM MDT Wednesday Mar 12 2014
Short term...valid for Thursday and Friday...
Dry weather will persist across the area through Thursday night as we
stay under the influence of high pressure aloft. Shortwave over
British Columbia will push east across southern Canada and give eastern Montana a
glancing blow tomorrow...but with little moisture to work with we
will remain dry...though probably with a Post frontal cumulus
field in our east. Cool advection will be offset by increased
mixing and we should see highs into the upper 40s to middle 50s again
Thursday...though if the cold front were a few hours slower to
arrive we would probably see 60f. Prefrontal downslope gradients
will tighten up somewhat late tonight into tomorrow...so expect
wind gusts to around 45 miles per hour again along the western foothills.
Pacific energy near 45n 170w will drive into the northern rockies on
Friday...associated with a 100+ knots 300 mb jet. These stronger dynamics
will allow for increased chances of showers over our western mountains
by afternoon...and across our County Warning Area Friday night. Mountains will be
favored for another few inches of snowfall...including the big
horns as flow turns northwesterly late Friday night...per orientation of
upper jet. Western lower elevations will be strongly downsloped...
but locations along and east of surface trough should pick up up some
precipitation in the form of rain and snow. This will be mainly east of
Billings. Given forcing aloft and at low levels per inverted
trough...have raised eastern probability of precipitation to likely Friday night. 850mb
temperatures near 0c suggest a rain/snow mix...with perhaps a little
accumulation over the higher ridges. Temperatures on Friday should again
climb into the 50s.
long term...valid for Sat...sun...Mon...Tue...Wed...
The extended forecast starts off with a period of slightly cooler
and wetter weather on Saturday...before the weather turns warmer
and windy on Sunday.
A shortwave moving across the area on Saturday will develop
showers along and east of the surface trough set up across eastern
Montana. Downslope winds will help to keep the western zones and
as far east as Billings from seeing much if any precipitation.
Cooler temperatures working in behind the wave will cause a
transition from rain to snow for far eastern Montana by Saturday
afternoon and keep daytime high temperatures cooler. Any
accumulations from this system are expected to be light.
As that shortwave departs the area Saturday night...heights build
over the forecast area and some Pacific energy moves into the
Canadian rockies. This will induce warming across the forecast
area as pressure falls to our north strengthens the downslope flow
and 850 mb temperatures rise to around +10c by Sunday afternoon.
The combination of downslope flow and steep lapse rates will
promote mixing and above normal temperatures. The increasing
pressure gradient will support strong winds from Livingston to Big
Timber...and possibly Harlowton for Sunday and Monday. The rest of
the area will see breezy conditions Sunday afternoon.
Model solutions diverge beyond Sunday...with problems handling a
Pacific wave...and whether or not it will split before moving into
the Pacific northwest. The ec/Gem solutions split the wave and
move a portion of the wave into Montana by Monday
evening...whereas the GFS/gefs solutions keep the wave together
and progress it into Montana more slowly due to the more amplified nature.
Thus there is high confidence in that wave eventually bringing
cooler weather and potentially some snow...however given the
timing difference have spread chance probability of precipitation across Monday and
Tuesday and slowly started bringing temperatures down Monday and
Tuesday. However...will need to zero in the forecast once model
VFR will prevail over the area through Thursday with periods of
high cloud. Expect SW wind gusts of 25-35 kts at klvm. Jkl
Preliminary point temp/pops...
Thursday Friday Sat sun Monday Tuesday Wednesday
bil 035/054 032/056 035/049 032/065 039/056 033/046 030/046
00/north 00/b 42/o 10/north 02/west 33/west 22/west
lvm 029/050 028/052 032/047 029/060 035/052 030/046 027/047
00/north 01/north 52/o 10/north 12/west 33/west 22/west
hdn 031/054 029/057 034/050 033/067 038/057 034/048 032/048
00/u 01/b 55/o 10/north 03/west 43/west 22/west
mls 031/053 028/054 034/043 032/060 039/055 033/045 029/047
00/north 01/b 66/o 20/north 13/west 33/west 22/west
4bq 030/054 029/055 035/046 032/062 038/058 033/046 030/044
00/north 01/b 66/o 30/north 12/west 33/west 22/west
bhk 029/054 027/050 030/039 027/057 035/055 030/042 028/045
00/north 00/b 66/o 20/north 23/west 33/west 22/west
shr 025/054 026/054 031/049 026/063 033/057 029/046 025/045
00/north 00/b 65/o 20/u 02/west 44/west 33/west