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Area forecast discussion...updated 
National Weather Service Billings Montana
853 PM MDT Monday Oct 20 2014

no update needed tonight. Water vapor imagery showed upper ridge
axis centered over the western Dakotas with upper jet oriented north-S
over the Pacific northwest. Strong shortwave was moving into north California.
Forecast area will remain under a gradually moistening SW flow shortwave rotates toward SW Idaho. Right-rear
quadrant of jet will slide east toward the forecast area. Some
showers were noted this evening on radar associated with the jet
over Idaho and far west Montana. Other echoes were over the higher terrain
in southeast Idaho/northwest Wyoming earlier this evening...but have since dissipated
with loss of daytime heating. Hrrr showed some possible shower
development over the SW corner of the forecast area at 12z...but
GFS and WRF time-heights kept it dry near the surface. Will keep
the forecast area dry overnight. The morning probability of precipitation over the
mountains looked good. Will likely see a gradual increase in
clouds over the far western forecast area through the night. 850
mb temperatures will be in the teens to around 20c tonight. These
temperatures combined with Lee troughing and increasing clouds
will keep lows mainly in the 40s. Winds should be gusty at times
in The Gap areas but not strong enough to warrant any headlines
given the limited strength of the pressure gradient.

New WRF had the cold front reaching southeast Montana by 00z Wednesday with
increasing precipitation chances Post-frontally. This was in line
with the other models and current forecast. Arthur


Short term...valid for Tuesday and Wednesday...

Amplified upper ridge was situated over the eastern Dakotas at
the moment. This has allowed downslope warming with readings
reaching well into the 70s this afternoon. The ridge was being
pushed east by an approaching West Coast trough which will be the
weather maker Tuesday and Tuesday night.

A strong disturbance at the base of the trough was sitting just
off the northern California coast. This wave will move northeast
into eastern Idaho Tuesday afternoon. This will produce a chance
of showers over western zones and increase clouds over central
zones. The wave will continue to drive northeast and move over
south central Montana Tuesday evening. This...along with an
advancing cold front...will generate ascent for a chance of
showers. The system was lifting farther north now...and thus the
chance for showers looks less...but the chance of stronger winds
looks better.

The cold front will drive through western and central zones
Tuesday evening. The front was moving a bit quicker and the
gradient was tighter than in previous model it
appears this front will have a little more wind than earlier
thought. 850-700mb winds were now prognosticated at bumped
winds up Tuesday night. Still not expecting winds much over 40 miles per hour
with the exception out west. The gradient looks good for stronger
winds in the Harlowton to Big Timber corridor. 700mb winds were
still not projected that high...only will not issue any
highlights. Bumped winds up to reflect some gusts to 45mph.

Humidiities will fall to right around 20 percent in a prefrontal
environment Tuesday afternoon. Some humidities might actually
slide just below 20 percent over central zones. Humidities should
recover well enough by the time the stronger winds move in to keep
a check on fire weather concerns. Will need to keep a close eye on
this however.

The system moves into the Dakotas Wednesday for a decent cool
down. Temperatures will be around 10 degrees cooler on average but
still maximum out above seasonal averages on Wednesday. The area will
be void of shower chances as the forcing will shift into the
Dakotas. Winds will be a little breezy over far eastern Montana in
the early part of the day...but a slackening gradient should cause
winds to decrease as the day wears on. A Lee trough will develop
Wednesday afternoon and tighten Wednesday night. This will drive
increasing winds at Livingston and bumped winds up. Twh

Long term...valid for Thursday...Fri...Sat...sun...Mon...

Although some subtle differences exist...overall...the extended
models continue to be in fairly good agreement with the large
scale features for the end of this week into next weekend. An
upper low and trough will move onto the Pacific northwest coast
Thursday providing a southwest flow aloft across our forecast
area. By Friday...the upper low digs a bit southward allowing for
the flow to buckle and ridge across the central and northern
rockies for the day Friday. This ridge combined with jet and upper
level energy that will remain to our west and northwest both days
will result in keeping our area dry along with continued above
normal temperatures.

The upper low and trough move inland Saturday and across the
northern rockies Saturday night and Sunday. This will sweep a cold
front across the area late Saturday night or early Sunday morning.
The system is Pacific in nature so winds will just become more
westerly during the day Sunday but it will still be a gusty day.
Gusty downslope winds will help to inhibit precipitation but enough
dynamics will move across the forecast area to warrant a chance
for showers Sunday into Monday. After above normal temperatures
Thursday through Saturday...temperatures will cool to around
normal Sunday to slightly below normal for Monday. Hooley


VFR conditions will prevail at all flight terminals tonight
through Tuesday afternoon. Richmond


Preliminary point temp/pops...

Tuesday Wednesday Thursday Friday Sat sun Monday
bil 047/076 045/065 043/071 048/069 043/071 044/060 037/055
02/west 31/b 00/u 00/b 00/u 12/west 21/b
lvm 041/069 040/061 040/068 044/067 042/069 042/058 034/053
03/west 50/north 00/north 00/b 11/u 22/west 21/b
hdn 042/079 043/067 038/071 043/071 039/072 039/062 035/057
00/u 32/west 00/u 00/b 00/u 12/west 21/b
mls 041/078 045/065 038/071 044/069 041/069 041/062 035/054
00/u 32/west 00/u 00/b 00/u 11/b 21/b
4bq 042/081 044/065 037/070 042/071 040/071 042/062 035/054
00/u 22/west 00/u 00/b 00/u 01/b 21/b
bhk 038/078 044/062 036/068 041/067 038/066 039/059 033/049
00/u 12/west 00/u 00/u 00/u 11/b 22/west
shr 038/080 040/065 034/072 039/073 037/073 038/063 032/055
00/b 22/west 00/u 00/b 00/u 02/west 21/b


Byz watches/warnings/advisories...



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