Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Billings Montana
929 am MDT Thursday Oct 23 2014

Update...

Strong jet stream currently moving across north central Montana
will flatten the ridge axis across our area today. Strong winds at
mountain top level are resulting in plenty of middle and high level
clouds across the forecast area so have increased sky grids some
to account for this. Lee-side troughing has kept tight pressure
gradients across the upper Yellowstone and Stillwater valleys
overnight and early this morning which has resulted in strong wind
gusts for the Livingston area. This gradient will weaken by late
morning and this is already showing as winds have decreased quite
a bit already at Livingston. A cold front will move across the
forecast area today. Compressional warming ahead of the front
along with Lee-side troughing will result in a downslope flow
today. As a result...still expecting to see some of these clouds
dissipate this afternoon allowing temperatures to warm close to 70
degrees for many areas today. Outside of adjusting sky grids...no
other updates planned this morning. Hooley

&&

Short term...valid for today and Friday...

130 knots jet moving in off the Pacific will move through the region
late today through Friday. The bulk of the jet divergence will remain
north of the area as models all keep the jet core to the north.
Weak upper ridging early this morning will give way to fast SW
flow through this evening. Pieces of vorticity will move through
the area with some q-vector convergence. Flow will then become
zonal late tonight through Friday...and upper ridging will return to
the area Friday night.

Plan view of moisture showed some approaching the western zones
by 00z Friday. Time-height cross sections kept the lower levels dry
so there will be quite a bit of cloud cover but no precipitation
today. Lee troughing this morning will give way to pre-frontal
mixing...and breezy conditions are expected over the central and
western zones. Temperatures were in good shape today...in the
upper 60s to lower 70s...given the combination of good mixing and
cloud cover.

Pacific cold front will cross the area tonight with some
frontogenesis. Moisture profiles suggested that scattered showers
are possible over the western mountains and klvm area after 06z.
Pacific moisture will continue streaming into the west on Friday through
Friday night bringing a chance of mainly mountain showers. Friday will
have less wind than today with a weaker pressure gradient over the
area. A cooler day is expected on Friday behind the Thursday night cold
front. Temperatures will still be above normal in the 60s. Arthur

Long term...valid for Sat...sun...Mon...Tue...Wed...

The extended period will begin with a dry and mild Saturday...
courtesy of upper level ridging ahead of Pacific coast trough. A pattern
shift to a more progressive Pacific flow...and thus cooler
temperatures...will begin Sunday. Timing of the initial wave and cold
front continues to trend a bit slower so have raised expected
highs on Sunday and pushed probability of precipitation back slightly. Best chance of precipitation
west/ this initial shortwave looks to be Sunday night as the GFS/ec
each hit our south parts with greatest quantitative precipitation forecast per middle level
frontogenesis and at least briefly veered north-northwest upslope surface winds.
Have raised probability of precipitation in this area Sunday night and have given our
southern mountains a couple inches of snowfall. Should be another weak
shortwave on Monday so have sustained isolated to scattered probability of precipitation here...
especially given the cyclonic flow/colder air aloft associated
with trough. Consensus continues to suggest brief ridging for
Tuesday. High temperatures should cool to the 50s for highs Monday/
Tuesday...about normal for late October. Its Worth noting that
Billings has not seen a cooler than normal day since October 3rd.

Models begin to diverge quite a bit by the middle of next week
with a great amount of spread involving the flow in the northeast
Pacific. This model uncertainty makes sense given the involvement
of Tropical Storm Ana northwest of Hawaii. So am expecting low
confidence in the far extended period to continue as we ease
ourself into a pattern shift over the coming days. In any
event...will sustain near climatology probability of precipitation and temperatures for next Wednesday
as both the GFS and ec each show some weak energy by then...though
in differing regimes. By 168 hours these models are completely out
of phase with each other with the flow over the western Continental U.S. And
eastern Pacific.

Jkl
&&

Aviation...

VFR ceilings will prevail across the area today. Winds in the
foothills which includes klvm...will gust to 45 kts this
morning dropping to around 35kts in the afternoon. Gusts to 25kts
will be common across the rest of the area this afternoon.
Chambers
&&

Preliminary point temp/pops...

Today Friday Sat sun Monday Tuesday Wednesday
-------------------------------------------------------
bil 071 047/064 041/069 045/061 037/054 031/056 037/058
0/b 00/b 10/u 02/west 32/west 11/b 12/west
lvm 069 045/062 040/069 043/055 032/048 028/054 034/054
0/north 22/west 20/u 13/west 32/west 11/b 22/west
hdn 073 042/068 037/072 039/063 035/054 028/058 033/060
0/b 00/b 10/u 02/west 32/west 11/b 12/west
mls 073 043/067 039/070 042/064 038/052 029/056 032/056
0/b 00/b 10/u 02/west 22/west 11/b 12/west
4bq 072 042/068 038/070 043/067 037/052 028/055 032/058
0/b 00/b 10/u 02/west 42/west 11/u 12/west
bhk 070 041/066 034/065 039/065 037/050 026/050 029/054
0/b 00/b 10/u 02/west 22/west 11/b 12/west
shr 071 041/067 034/073 039/066 033/052 025/057 028/060
0/b 00/b 10/u 02/west 42/west 11/b 12/west

&&

Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.

&&

$$
Weather.Gov/Billings

National Weather Service Glossary of Abbreviations