Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Billings Montana
920 am MDT Thursday Mar 26 2015
no significant changes to the going forecast for today. We still
have an unstable northwest flow over US that is slowly becoming
more anti cyclonic. Any measurable precipitation today should
generally be limited to the southeast and along the big horns
Short term...valid for today and Friday...
Strong upper level ridge exists along the West Coast but it is
dirty...with an abundance of Pacific moisture spilling over the
ridge in the northwest flow over our region. Weak energy dropping into
the northern plains with a 140kt 300 mb jet over eastern Montana is
producing some light precipitation near the Dakotas border...which will
shift east of our County Warning Area over the coming hours. Northwest flow is also
generating some light showers or sprinkles in upslope areas S/southeast
of Billings and over the mountains looking upstream...areas of light
precipitation impact western Montana as well. Overall we should see cloudy skies
persist today despite the slowly building heights with areas of
light showers or sprinkles...mainly over the mountains and in upslope
regions but there may be enough diurnal instability with steep middle
level lapse rates to produce some sprinkles elsewhere including
Billings...as recent hrrr runs suggest. Another piece of energy
will drop into the northern plains tonight and this should enhance
precipitation again near the Dakotas border...ie near and east of surface trough.
Otherwise we will see drying from west to east late tonight into
Friday as the ridge continues to push east into the northern
rockies. Downslope gradients will persist for gusty winds along
our foothills over the next two days. Do not expect any highlights
but Big Timber has been gusting into the 40s already. Have raised
wind speeds some from Big Timber to 3ht as these areas are favored
in a northwest flow Chinook. Temperatures will rise into the lower to middle 60s
today in west and central parts...and into the lower 70s Friday.
Highs will approach records at Livingston and Billings on Friday.
Things get more interesting Saturday as the upper ridge breaks
down with the passage of a Pacific shortwave and cold front.
Models continue to disagree in the amount of splitting that this
energy will undergo in the eastern Pacific before it moves inland.
Latest European model (ecmwf) and Canadian have trended slower and stronger with
the wave...whereas the GFS is continuing with a weaker northern
split and is thus faster. Given this feature is in a data void
area over the Pacific am not sure which scenario is preferred so
will stay with a compromise at this time. Overall expect a frontal
passage by afternoon with increased shower activity along and
behind the front. A slower timing of this front would yield warmer
prefrontal conditions and the possibility of a few thunderstorms...as the
NAM and European model (ecmwf) show lifted indices near zero. Main issues on
Saturday will revolve around fire weather and wind and will
continue to highlight potential for high temperatures...low rhs...strong
winds and a frontal passage in the fire weather forecast. All
models showing near 50 kts of middle level wind with this system so
an afternoon onset of subsidence could produce very strong winds
especially for our western parts. Strong west-northwest winds should push
across our plains by Saturday night. Again...stress the timing
Anyone planning outdoor activities on Saturday should be aware of
the potential for strong winds and monitor the forecast.
Long term...valid for Sat...sun...Mon...Tue...Wed...
Medium range guidance in overall good agreement into the extended.
Upper heights build across the northern rockies for Sunday into
Monday behind saturdays system for dry conditions. Next vigorous
system to break down the ridge on Tuesday. This system not looking
like a big precipitation maker with downslope flow...but could be
another wind producer. Behind the Tuesday system...an overall
prgressive flow pattern develops with much less amplification.
This will push several impulses through the flow and keep a few
showers in the forecast into next Thursday. High temperatures will
cool to more seasonal levels into the 50s. Frieders
VFR conditions can be expected through tonight. Isolated light
showers are possible mainly east of a kbil to kshr line...and near
the mountains. Otherwise...mainly middle level clouds will be around
with some virga into this afternoon. Twh
Preliminary point temp/pops...
Today Friday Sat sun Monday Tuesday Wednesday
bil 065 045/073 048/073 040/065 041/070 045/065 038/058
1/east 00/b 03/west 20/b 00/u 03/west 22/west
lvm 065 044/073 047/067 037/065 040/068 042/058 031/055
1/north 00/north 03/west 21/b 00/u 14/west 22/west
hdn 065 038/075 042/076 035/066 035/072 039/068 036/059
2/west 00/b 03/west 20/b 00/u 03/west 22/west
mls 059 041/071 044/074 035/063 037/069 038/067 037/057
1/east 10/b 03/west 20/b 00/u 02/west 22/west
4bq 059 039/071 040/077 036/064 036/070 039/069 035/058
2/west 20/b 03/west 30/b 00/u 01/b 21/north
bhk 052 035/065 039/073 035/061 033/066 037/066 035/054
1/M 30/east 02/west 30/u 00/u 02/west 31/north
shr 060 038/070 039/077 035/065 035/070 038/069 034/055
2/west 10/b 03/west 31/b 00/b 02/west 32/west