Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
406 AM MDT Sun Jul 9 2017

.DISCUSSION...The morning cloud cover and showers previously
forecast are a little bit delayed this morning, but should arrive
shortly after sunrise. The delay has allowed most locations to
cool decently well overnight, though morning low temperatures in
many locations are to remain largely well above normal. The
morning rain showers will be light and may not amount to more than
sprinkles.

The cooler morning temperatures plus lowering heights aloft (a
mark of overall atmospheric cooling aloft) will prevent afternoon
high temperatures from approaching the record values of the past
two days. But still will be running about 10 degrees above normal
for most locations. Afternoon showers and thunderstorms are
forecast to develop, mainly across SW Montana, and be a bit more
intense/widespread than yesterday. However, the chance for severe
thunderstorms appears to be delayed until Monday when the slow
moving cold front finally reaches Idaho and Montana. The
temperature forecast will be highly dependent upon the timing of
this cold front and thus have hedged towards cooler over central
Idaho with somewhat warmer conditions over SW and West Central
Montana where the front will likely not pass until late in the
afternoon.

This is also where the greatest potential for strong and
potentially severe thunderstorms will occur. At this time gusty
and quite possibly damaging winds appear the be the greatest
public threat. Though small hail cannot be ruled out given the
increased shear that should support somewhat deeper updrafts. A
heavy rain threat will begin to develop later in the evening as
the atmosphere moistens.

Tuesday looks to be quite a nice day with temperatures finally
return back to normal, which will most certainly be a welcomed
change after this prolonged heat wave. Unfortunately, the brief
break from the heat wave early in the week will be short-lived. By
mid week into the coming weekend, upper level southwest flow
returns associated with the rebuilding of a strong, hot ridge
pattern. Temperatures are on track to return to well above normal,
reaching values of 90s and low 100s once again. A series of waves
will introduce isolated shower/thunderstorm activity for Lemhi
County and southwest Montana each afternoon and evening.

&&

.AVIATION...Hot temperatures with high density altitude concerns
will continue today. Isolated showers and thunderstorms are
expected to develop in the vicinity of KSMN and KBTM after
09/2000Z, with gusty, erratic outflow winds and lightning being
the main aviation concerns. Otherwise, expect occasional
afternoon/evening wind breezes of 15-25 kts at TAF sites.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

Special Weather Statement
National Weather Service Missoula MT
221 PM MDT SUN JUL 9 2017

IDZ009-010-MTZ006-007-092145-
Eastern Lemhi County ID-Western Lemhi County ID-
Bitterroot/Sapphire Mountains MT-Butte/Blackfoot Region MT-
221 PM MDT SUN JUL 9 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN LEMHI...DEER
LODGE...SOUTHEASTERN GRANITE...SOUTHEASTERN RAVALLI...SILVER BOW AND
SOUTH CENTRAL POWELL COUNTIES UNTIL 345 PM MDT...

At 216 PM MDT, Doppler radar was tracking thunderstorms along a line
extending from Shoup, Idaho to Deerlodge, Storms developing along
this line were moving northeast at 25 mph.

Thunderstorms will continue to develop rapidly across southwest
Montana this afternoon.

Wind gusts up to 50 mph and small hail will be possible with these
storms.

Locations impacted include...
Salmon, Deer Lodge, Butte, Anaconda, Silver Bow, Walkerville, Galen,
Divide, Warm Springs, Gregson Hot Springs, Garrison, West Valley,
North Fork, Gibbonsville, Lost Trail Pass, Carmen, Leesburg,
Fishtrap, Cobalt and Racetrack.

LAT...LON 4576 11250 4563 11269 4575 11276 4588 11310
      4588 11321 4576 11337 4594 11351 4570 11394
      4560 11381 4552 11384 4525 11368 4501 11422
      4545 11457 4663 11274 4636 11242 4624 11260
      4610 11247 4585 11243 4575 11219
TIME...MOT...LOC 2016Z 000DEG 0KT 4627 11290 4543 11443