Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Billings Montana
817 PM MDT Friday Jul 3 2015
Forecast in good shape this evening. Will see some residual
convection over southern higher terrain through late evening.
Otherwise a mostly clear night in store. Smoke filtering in from
Canada will continue tonight and tomorrow. No changes planned to
going forecast. Chambers
Short term...valid for Sat and sun...
Satellite showing a few buildups over them mountains this
afternoon so will keep isolated thunder in the forecast for the
higher elevations this evening. Big picture shows an unusually
deep upper low over northern Alberta with a strong shortwave
rotating around it into northern British Columbia. This system is prognosticated to
drop southward overnight and continue shifting southward Saturday.
Surface pressures over eastern Montana will fall this evening in
response to this approaching system which allow surface winds to
become westerly. This will set up for better mixing Saturday with
compressional warming driving temperatures into the middle 90s. It
will be dry except for high elevation isolated showers and
Big story number one is the arrival of a cold front driven by the
Canadian system at the gusty winds it will bring with it. Timing
is increasing in confidence for late evening for the northern
zones and closer to midnight for the Billings area. Believe the
front will arrive late enough to not impact fireworks displays in
Billings and Laurel...could be a bit more of an issue for folks
along the Musselshell river. Still will be a period of gusty
winds from the frontal passage but expect nocturnal inversions to
keep some of the strongest wind from reaching the surface.
Exception we are watching to this would be a chance for an
isolated thunderstorm to form over northern Montana and help
accelerate the front southward. Other concern is any thunderstorms
that develop along or advance of the front over southern Montana.
Do not think that instability will be deep enough so best chance
for activity will be in areas where the frontal upslope may help
release some brief convection over the foothills and heading into
Big story number two is how cold its going to be behind the front.
Guidance indicates enough cloud and upslope precipitation may be
around to limit insolation and GFS is consistently showing maximum
temperatures in the 60s. Have continued to trend precipitation
chances upward and have likely showers over some of the mountain
areas. One question with the northerly push of this system is
whether it will bring another round of smoke into the area.
Suspect combination of less fire activity under the airmass and
precipitation helping clean the atmosphere out a bit should limit
this impact. Borsum
Long term...valid for Monday...Tue...Wed...Thu...Fri...
Models are in good agreement regarding the first part of the
extended forecast with a northwest flow Monday transitioning to a
westerly low amplitude cyclonic flow by midweek. This will keep
the chance of precipitation low and mainly confined to the higher
terrain of the west and southern zones. At midweek...a closed
upper low off the California coast will drift inland producing
rising 500mb heights across our region with flow becoming
southwesterly. The GFS is the more progressive with dynamics
moving across our region in this pattern while the European model (ecmwf) is
keeping the ridge over US longer and is thus drier at
midweek...then wetter at end of the work week. Thus...there is a
potential for increased thunderstorm activity by Thursday and
Friday...but confidence is low. Therefore...I kept the probability of precipitation on the
plains generally around seasonal averages. Significant differences
continue into the weekend and thus kept forecasts near seasonal
temperatures and probability of precipitation. Bt
VFR conditions will continue through the next 24 hours. Smoke
from Canadian wildfires will continue to be less pronounced.
Preliminary point temp/pops...
Sat sun Monday Tuesday Wednesday Thursday Friday
bil 063/096 060/070 057/078 057/085 059/083 060/088 062/089
11/u 34/T 22/T 21/b 23/T 33/T 32/T
lvm 055/095 054/071 050/078 051/083 052/082 054/087 055/086
11/u 24/T 22/T 24/T 33/T 34/T 42/T
hdn 061/098 059/072 056/080 057/087 058/086 059/090 061/091
11/u 34/T 21/b 11/b 23/T 33/T 32/T
mls 063/097 061/073 054/077 056/086 058/084 060/090 064/090
10/u 34/T 11/b 01/u 22/T 23/T 32/T
4bq 062/095 060/071 056/077 057/084 059/084 060/088 062/089
11/u 25/T 21/b 11/b 22/T 23/T 32/T
bhk 060/092 058/070 052/073 052/080 054/079 056/085 059/085
00/u 25/T 21/b 01/b 32/T 23/T 32/T
shr 057/092 056/068 052/074 053/081 054/081 054/085 057/085
10/u 24/T 22/T 22/T 33/T 33/T 33/T