Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Billings Montana
903 am MDT Sat Oct 10 2015
increased wind speeds this morning over klvm and along the
foothills with klvm reporting a gust in the middle 50s. Gap flow was
responsible for the gusty winds in these areas this morning...with
a favorable pressure gradient...and large temperature difference
between klvm in the 60s and the park in the lower 30s. Based on
the rap soundings...the record/near record high temperatures were
in good shape with downslope flow helping to boost temperatures.
Gridded model dewpoints looked too high given the expected mixing.
Noted that the rap and hrrr soundings brought dewpoints down to at
least 30 degrees this afternoon. So...went for a compromise and
lowered dewpoints several degrees.
Checked mountain wave potential for today...and GFS kept strong
winds at mountain top level so this should not be a concern.
High cirrus...around 300 mb based on 12z ktfx sounding...was seen
over the area on satellite imagery and the GFS showed these clouds
decreasing over the forecast area through the day. This was
reflected in the going forecast.
Will wait for all the new model data before making any changes to
later periods...but one concern was possible increase in klvm
winds ahead of the approaching cold front tonight. Will evaluate
entire wind situation for tonight through sun this afternoon.
Short term...valid for today and sun...
Record warmth is expected today...followed by strong winds Sunday
in the wake of a cold frontal passage. Both scenarios will result
in elevated fire weather concerns as well and so caution is very
much advised with any open flames...but we Haven/T issued any red
flag warnings because fuel-based fire dangers are only in the low
to moderate category.
Highs today will reach well into the middle and upper 80s f and it/S
very plausible that places like Miles City /where mixing will be a
bit deeper with its River-Valley location/ will reach 90 f. An air
mass characterized by 700-mb temperatures of +10 to +12 c like we
expect by afternoon is exceedingly rare for early to middle October.
Current daily records for October 10th are 85 f at Billings...88 f
at both Sheridan and Livingston...and 90 f at Miles City. Expect
winds to be a bit gusty today...and tonight there will be a core
of 50-70 knots 700-mb winds over the mountains. The 00 UTC guidance
suggested wind gusts at Livingston may peak near 55 miles per hour /which is
just under advisory criteria/ and that high winds associated with
mountain wave activity will stay at elevations above Red Lodge...
but both those items will require close monitoring on our part.
On Sunday...strong west-northwest Post-frontal winds are expected.
We have posted a high wind watch for southern Wheatland County and
the Judith Gap area as the expected 700-mb winds of 50-55 knots are
well-correlated with wind gusts of 60 miles per hour around Harlowton. Else-
where...we chose to forgo any wind headlines at this point and are
instead calling for wind gusts to around 50 miles per hour across the rest of
the area. Significant deep-layer subsidence and moderate cold air
advection behind an early-day frontal and shortwave trough passage
will efficiently drive winds aloft to the ground. However...the 00
UTC GFS...NAM...and European model (ecmwf) generally keep peak winds at 850 mb near
45 knots...just shy of the 50 knots threshold we typically look for with
high wind events on the plains. The 00 UTC GFS does bring winds of
that magnitude into the Miles City and Baker areas by very late in
the day...which is a bit concerning...but that occurs in the model
simulation after the peak in diurnal mixing and it/S not linked up
with the isallobaric /pressure-rise-driven/ wind response. Other-
wise...we do have a low-end shower chance in the forecast on Sunday
as well...with highs from the middle 60s to lower 70s f. Schultz
Long term...valid for Monday...Tue...Wed...Thu...Fri...
Low impacts for the extended period. Zonal flow Monday turns
northwest as ridging builds into Nevada and Oregon. This northwest
flow will be dry and precipitation chances were minimal. The GFS
has come in a little warmer for Thursday and Friday with stronger
ridging into the northern rockies. This stronger ridging results
in a much weaker back cold front Thursday. The European model (ecmwf) was stronger
with shortwave energy driving into North Dakota Thursday afternoon
and thus stronger with the back door cold front. Have adjusted
temperatures up a little bit for Thursday and Friday...but did not
go as high as mex guidance with the European model (ecmwf) in mind. The main story
on the extended is mild and dry. Twh
Gusty west to southwest winds will impact the entire region
today. The strongest winds will be in the foothills areas and
around klvm...with gusts of 35 to 45 knots. Gusts of 20 to 30
knots will extend from about Columbus eastward today...beginning
in the west this morning and spreading into the east this
afternoon. Winds east of kbil will taper off later this
evening...while winds from kbil west are expected to remain breezy
through the night. Otherwise...VFR will prevail. Aag
Preliminary point temp/pops...
Today sun Monday Tuesday Wednesday Thursday Friday
bil 087 062/068 040/070 048/075 045/072 044/069 045/070
0/u 02/west 00/b 00/u 00/u 00/u 01/b
lvm 087 062/065 038/072 043/073 042/073 040/071 040/072
0/north 22/west 00/north 00/north 00/u 00/u 00/b
hdn 089 057/070 039/071 044/076 043/072 043/070 043/073
0/u 02/west 00/b 00/u 00/u 00/u 11/b
mls 090 057/069 040/069 046/072 044/070 042/067 042/069
0/u 02/west 10/u 00/u 00/u 00/u 10/b
4bq 089 057/070 039/067 045/073 043/071 042/070 042/072
0/u 02/west 10/u 00/u 00/u 00/u 00/b
bhk 086 056/069 041/065 044/070 042/067 039/065 039/067
0/u 02/west 10/north 00/u 00/u 00/u 00/u
shr 091 056/071 038/070 042/075 041/072 040/071 039/072
0/u 02/west 10/u 00/u 00/u 01/u 11/b
Montana...high wind watch in effect from Sunday morning through Sunday
evening for zones 28-63.