Scientific Forecaster Discussion
fxus65 kbyz 251616
Area forecast discussion...updated
National Weather Service Billings Montana
1016 am MDT Tue Jul 25 2017
Push of relatively cooler air has been going through the County Warning Area this
morning with gusty northerly to northeast winds associated with it.
Winds will back off a bit by this afternoon with highs in the
upper 70s west to mainly 80s east expected. Monsoonal moisture
increasing from the south along with weak upslope flow will
combine to bring increasing chances for showers and thunderstorms,
generally over the mountains and along the foothills this
afternoon and evening. Most areas will see at least increased
cloud cover today. Have adjusted the sky, winds, and pops to
current trends. Otherwise, the rest of the forecast remains on
track and the previous forecast discussion and an updated aviation
discussion is below. Stp
Short term...valid for tdy and Wed...
Minimal changes to the inherited forecast, with cooler and at
least chance for precip over the next couple of days.
Today looks like it will be the coolest day so far in July as the
upper level ridge flattened by the Canadian low and northerly
pressure gradients create weak upslope winds. Models continue to
point at some moisture pooling over southern Montana, so have
continued with mainly inherited pops. Best precip potential
appears to remain south of Montana, with stronger monsoonal fetch
over Wyoming, but should still get mainly wet type thunderstorms.
Winds should be light, with exception of thunderstorm winds, and
relative humidity values at much higher in many areas, and at least not quite as
critically low in north and eastern zones.
Wednesday will be a bit warmer as ridging redevelops, but
southeast winds will limit mixing and therefore warmup..
southeasterly sfc flow appears to deepen moisture over the area,
which points to our best chance to pick up significant moisture.
However, forcing continues to appear somewhat limited, with the
exception of orographic lift. The moisture is progged to shift
northeast as the ridge axis strengthens Wednesday evening/night.
Long term...valid for Thu...Fri...Sat...sun...Mon...
Persistent troffing over the eastern half of the U.S. Will keep at
least low amplitude ridging over the area through the extended
period. A couple of Pacific disturbances will work to bump up the
ridge a bit at times, with the main impact being to draw
monsoonal moisture northward into the area. This happens Wed-Thu
and again sun-Mon. Afternoon and evening convection associated
with this moisture will help to keep temperatures in check during
this period. No sustained downslope winds are advertised in any
model which could produce an especially hot day or two. While
some operational models boost temperatures into the mid 90s with
the bumped up ridging, the latest GFS ensemble mean keeps
temperatures in the 85-90 degree range for most areas through
early next week, near seasonal levels. Mean precipitation chances
range from 15 to 40 percent for areas from Billings west, and 10
to 30 percent over the east, with southern half of the area seeing
the greatest chances due to the monsoonal moisture moving in from
the south. So, overall a pretty normal Summer set up in store
with highs upper 80s to lower 90s and a chance for
afternoon/evening thunderstorms each day. Chambers
Scattered afternoon and evening showers/thunderstorms are
expected, mainly south of a Livingston to Billings to Ekalaka
line. Locally gusty winds and MVFR visibilities are possible with
this activity. Aside from that VFR conditions expected. Walsh
Preliminary point temp/pops...
Tdy Wed Thu Fri Sat sun Mon
bil 083 061/088 063/088 064/091 063/090 063/091 064/091
1/b 22/T 23/T 31/u 11/u 11/u 21/u
lvm 081 053/086 057/084 057/086 056/087 057/088 058/087
2/T 22/T 34/T 32/T 22/T 21/u 22/T
hdn 086 060/090 063/090 064/093 064/092 064/093 064/093
2/T 22/T 23/T 41/b 11/u 11/u 21/u
mls 088 063/091 067/090 067/092 066/092 066/093 068/093
1/b 11/b 12/T 42/T 10/u 11/u 10/u
4bq 088 061/088 065/087 065/090 064/091 065/091 066/091
2/T 31/b 23/T 42/T 10/u 11/b 21/u
bhk 087 058/088 062/088 065/088 062/090 062/089 064/089
1/b 11/u 12/T 33/T 11/u 11/u 11/u
shr 084 056/085 058/085 059/087 057/087 060/088 058/088
3/T 44/T 44/T 42/T 22/T 22/T 22/T