Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Billings Montana
304 am MDT sun Jul 5 2015
Short term...valid for today and Monday...
Active night across northern Montana where strong wave rotating around
Canadian upper low has triggered a line of severe thunderstorms.
Attendant cold front has combined with outflow boundaries from
these storms and was through Judith Gap per strong pressure rises
and surface observations at 08z. Mesoscale models had a good
handle on the convection and brought thunderstorms into Fallon
County by 15z. Kbhk sounding from the WRF had abundant elevated
cape and decent shear this morning...so will be watching for
possible strong to severe storms there early.
Model consensus had the cold front surging into the area from kbil
west before 12z. Southeast Montana was forecast to remain in the warm sector for
part of the morning before frontal passage around 15z. WRF
soundings showed that southeast Montana will have around 2000 j/kg of surface
cape this afternoon...likely aided by the morning prefrontal
conditions. Sref also had decent convective available potential energy over southeast Montana...areas S of
kbil and the SW mountains. Southeast Montana will also be under favorable
shear today based on the sref. Will have plenty of lift and
moisture available for precipitation today as the right-rear
quadrant of the upper jet rounding the Canadian low brings upper
divergence to the area and shortwaves produce q-vector
convergence. In addition...precipitable waters climb to 1-1.5
inches behind the front...aided by monsoonal moisture from the S.
Adjusted morning probability of precipitation to be more in line with mesoscale
models...then increased afternoon probability of precipitation due to good support for
precipitation. Added isolated thunder this morning over southeast
Montana...areas S of kbil and the SW mountains. For the
afternoon...will forecast showers and thunderstorms for these
locations...with showers elsewhere. Some storms could be strong to
severe in the southeast...but due to the frontal timing in the east...will
leave severe mention out of the forecast...but will put out an severe weather potential statement
and weather story advertising this possibility.
Temperatures will range from the 60s west and will likely be falling
today. Expect highs in the 70s east. Soundings suggested a breezy day
with 15 to 25 miles per hour winds so increased winds in the forecast.
Lift decreases over the area tonight and airmass will be
stable...so had decreasing probability of precipitation for showers through the night.
Cyclonic northwest flow will be over the region Monday and Monday night
bringing continued cool conditions and chances for mountain
Long term...valid for Tuesday...Wed...Thu...Fri...Sat...
We remain confident in a warming trend during the latter parts of
this week...and we are still advertising a low chance of storms on
many days. The 00 UTC model suite remained in agreement showing a
backing of the flow aloft from northwest on Tuesday and Wednesday
to the southwest by next weekend as an upper-level trough migrates
into the West Coast and Pacific northwest. That transition will be
a driving force behind the warming trend...which will push highs
back above 90 f beginning Thursday.
The evolution of ridging to the south and east of the local area
and resultant path of the Pacific-based trough by next weekend is
uncertain. The 00 UTC European model (ecmwf) would support more isolated...but also
stronger convection than the 00 UTC GFS owing to stronger winds
aloft in the European model (ecmwf) solution. Regardless...at this juncture both of
those ideas are covered by 20 to 30 percent probability of precipitation. Schultz
MVFR ceilings will likely develop over much of the area today as a
cooler and more moist air mass filters in behind an overnight cold
frontal passage. Showers and a few thunderstorms are expected with
some mountain obscurations and local MVFR to IFR conditions too.
Preliminary point temp/pops...
Today Monday Tuesday Wednesday Thursday Friday Sat
bil 068 054/076 054/083 059/083 060/092 064/092 063/090
6/west 31/b 11/b 21/b 11/u 22/T 22/T
lvm 070 048/077 047/081 051/082 052/090 056/089 056/087
6/west 32/west 13/T 32/T 22/T 22/T 23/T
hdn 073 054/078 053/086 058/086 058/095 061/095 061/092
7/T 31/b 11/b 11/b 11/u 22/T 22/T
mls 075 054/075 052/084 058/084 060/093 064/095 065/092
6/west 21/b 01/b 11/b 11/u 22/T 22/T
4bq 078 055/075 052/083 058/082 058/090 062/094 064/090
7/T 41/b 11/b 22/T 11/u 22/T 22/T
bhk 073 053/071 048/079 055/079 055/087 060/091 062/087
7/T 31/b 01/b 22/T 11/u 12/T 23/T
shr 074 052/072 049/079 054/078 054/088 057/089 057/087
8/T 62/west 13/T 32/T 21/b 22/T 22/T