Scientific Forecaster Discussion
fxus65 kbyz 260300
Area forecast discussion
National Weather Service Billings Montana
900 PM MDT Mon Sep 25 2017
No major updates tonight. Only minor changes involving
temperatures and precipitation chances in eastern Montana tonight.
Bumped up rain chances slightly in and east of Miles City. I also
adjusted temperatures down a degree or two in eastern zones due
to observed afternoon temperatures trending cooler than forecast.
Still expecting some patchy fog to develop tonight in eastern
Montana. Previous discussion is below. Dobbs
Short term...valid for Tue and Wed...
A quiet fall forecast through mid-week across the northern
rockies. Upper level low will continue to work across southeast Montana
and into the Dakotas tonight. Expect a few showers as the system
pushes through the area, but any precipitation will be light and
tapering off in the early morning hours. Could be a few areas of
fog from Rosebud County east overnight. Flow aloft turns
northwest tonight over western zones and an weak embedded
shortwave could produce a few light showers over western Montana
that leak east of The Divide, but any precipitation with this
activity will be very light. Lows tonight will be mainly in the
Will see warmer and dry conditions on Tuesday, with downslope
west/northwest winds spreading across the area. High cloud cover
will diminish in the afternoon as temperatures climb into the 60s.
More sun expected Wednesday as ridging increases. Temperatures
will be well into the 60s with a few lower 70s likely. Chambers
Long term...valid for Thu...Fri...Sat...sun...Mon...
Run-to-run model consistency with the GFS and European model (ecmwf) was not very
good from the 00z run to the new 12z runs. Both models did show a
high over low situation and a dry forecast for Thursday which was
consistent with the old runs. The European model (ecmwf) maintained a high over low
on Friday, while the GFS brought the low north as an open wave into
the region. Kept the forecast dry for now. Models showed Lee
troughing over the area Fri. Night/Saturday morning, which will
increase gap flow winds. Have reflected this in the forecast.
Otherwise, both models had a trough over the area on Saturday.
Strong westerly flow limited the moisture over the area, so
continued low pops for thunderstorms in the west. A cold front was
progged to cross the region Sat. Night with a chance of
precipitation across the area. Old GFS had a longwave trough over
the intermountain west on Sunday, while the New Run showed a cutoff
low over Montana. The 12z European model (ecmwf) had the low north of the Canadian border.
Kept showers over the area in the morning per blended guidance.
The GFS maintained the low over the region on Monday, which
differed from the previous run which showed a large ridge. The
European model (ecmwf) pushed the low east along the border, and brought another
cutoff into the Pacific northwest. Had a chance of showers north and west of
kbil for Monday.
Given the above, confidence in the details of this forecast was
not very high. Will need to watch and see if the models come into
better agreement and maintain consistency. For temperatures, model
blends gave near normal highs through Saturday, with cooler
conditions Sunday and Monday. Arthur
Areas of MVFR will occur east and southeast of kbil through tonight due to
isolated showers and patchy fog. Patchy fog will persist into mid
to late morning on Tuesday. Areas of mountain obscuration will
affect the NE bighorns through this evening. Localized
obscurations will affect area mountains late tonight and Tue.
Preliminary point temp/pops...
Tue Wed Thu Fri Sat sun Mon
bil 041/066 044/069 044/069 045/071 042/070 047/061 043/061
01/b 10/u 00/u 00/u 01/u 22/west 11/b
lvm 037/065 036/067 036/068 038/071 039/068 039/058 039/059
11/b 10/u 00/u 00/u 02/T 21/b 22/west
hdn 039/066 041/071 042/072 044/073 040/073 045/063 042/064
11/b 11/u 00/u 00/u 01/u 32/west 11/b
mls 036/065 043/071 045/071 047/073 043/073 047/063 043/062
20/u 11/u 00/u 00/u 10/u 32/west 11/b
4bq 038/064 040/069 042/071 044/071 041/072 045/061 041/061
20/u 01/u 00/u 01/u 11/u 32/west 11/b
bhk 039/063 041/069 043/070 044/070 041/071 045/062 042/062
31/b 01/u 00/u 00/u 11/u 22/west 11/b
shr 035/061 037/066 039/068 040/070 038/070 042/059 039/060
21/b 10/u 00/u 00/u 01/u 33/west 11/b