Wind Advisory 3, NWS Missoula, MT

519 
WWUS75 KMSO 200245
NPWMSO

URGENT - WEATHER MESSAGE
National Weather Service Missoula MT
845 PM MDT Wed Jun 19 2019

MTZ005-007-043-200345-
/O.EXP.KMSO.WI.Y.0003.000000T0000Z-190620T0300Z/
Missoula/Bitterroot Valleys-Butte/Blackfoot Region-
Potomac/Seeley Lake Region-
845 PM MDT Wed Jun 19 2019

...WIND ADVISORY WILL EXPIRE AT 9 PM MDT THIS EVENING...

$$

IDZ009-010-200345-
/O.EXP.KMSO.WI.Y.0003.000000T0000Z-190620T0300Z/
Western Lemhi County-Eastern Lemhi County-
845 PM MDT Wed Jun 19 2019

...WIND ADVISORY WILL EXPIRE AT 9 PM MDT THIS EVENING...

$$

MTZ003-200345-
/O.EXP.KMSO.LW.Y.0004.000000T0000Z-190620T0300Z/
Flathead/Mission Valleys-
845 PM MDT Wed Jun 19 2019

...LAKE WIND ADVISORY WILL EXPIRE AT 9 PM MDT THIS EVENING FOR
FLATHEAD LAKE...

$$

Area Forecast Discussion
National Weather Service Missoula MT
311 AM MDT Tue Jun 18 2019

.DISCUSSION...Today will be a day of brief ridging over the
northern Rockies with temperatures about 5 degrees above average
for this time of year. Tomorrow, Wednesday, will bring a dry,
windy cold front and usher in a cool troughing pattern that will
persist for a week or two.

Wednesday will be breezy to start with and very windy in the late
afternoon and evening. Models continue to show late afternoon and
evening winds 20 mph with gusts over 30 mph in most of the valleys
of western Montana. The Missoula Valley is well aligned with the
upper level winds. This combined with the direction of the front
and the time of day will make winds stronger in Missoula with a
couple hours of winds around 30 mph with gusts near 40 mph.
Ovando, Helmville, and the Highway 200 corridor towards Roger's
Pass will have similarly strong winds. Garrison Junction to
Anaconda will be similar with the potential for some mountain
wave winds as the front passes causing strong cross winds on
Interstate 90. Butte will have winds in the mid and upper 20s in
the evening. The strong winds will extend south into Lemhi county
Idaho too while central Idaho and northwest Montana will generally
be around 20 mph or less.

Behind the cold front the upper level low pressure system will
linger for a few days and cause a cool and wet Thursday and
Friday. For more on the cool temperatures see the climate
discussion section below. Most of the rain will occur on Friday
with only the mountains of central Idaho getting more than a tenth
of an inch for the whole event. Much of western Montana will pick
up 0.3 to 0.5 inches of rain over a 36 hour period starting
Thursday afternoon. The exception will be an area from Seeley Lake
north through Kalispell and includes Glacier National Park and the
Flathead National Forest. The lower elevations in this area will
see 0.75 to an 1.0 inches in that same period with more in the
higher elevations. The high elevations of Glacier Park will likely
see 1.5 to over 2.0 inches of liquid equivalent precipitation over
that 36 hour period. With snow levels dropping to around 6,000
feet Friday, some of that will fall as a wet, slushy snow at
places like Logan Pass. All of this on the summer solstice, the
longest day of the year! And a lot of people in western Montana
might not even see the sun at all that day.

Next weekend and beyond the region remains under the influence of
a trough, keeping the weather unsettled with temperatures at or
below average.

&&

.AVIATION...A ridge over the area today will keep showers and
thunderstorms down today with VFR conditions expected at all
terminals with just high clouds.

&&

.CLIMATE...Thursday and Friday will be much below normal for
temperatures. Right now Friday looks like the coolest day with
temperatures 15 to 20 degrees below normal, which is ironic since
it is also the summer solstice and the longest day of the year.
Looking at record cool high temperatures across the region, the
most likely station to set a new record cool daily high
temperature is Missoula. Records in Missoula go back to 1893, and
the record coolest June 21st occurred in 2003 when the
temperature only reached 56 degrees. The next coolest June 21st
was in 1963 when it only reached 58. To land in the coolest 10
June 21sts in the records the maximum temperature Friday can only
reach 63 degrees for Missoula.

Using Kalispell to represent most of northwest Montana, the
forecast high for Friday is in the mid 50s, which puts it about 10
degrees above the record cool high temperature of 44 degrees set
in 1916. Kalispell has records since 1899. Butte, with a forecast
high of 45 on Friday will come closer to its record cool maximum
daily temperature, which is 41 also set in 1916. Butte has records
back to 1899.

For central Idaho it was harder to find any climate stations that
have continuous records back that far. Surveying the data it
looks like much of that area will be within about 5-10 degrees of
record cool daily high temperatures on Friday. The current
forecast for Grangeville is in the upper 50s, which would likely
put them in the coolest 10 June 21sts. Grangeville has climate
data for summer from 1894 through 2014, so while the record is
incomplete there it is still extensive enough to put the cool
temperatures in context. The coolest start to summer there was 53
degrees measured in 1948.

With all this talk about how cool the afternoon temperatures will
be, you may be wondering about the low temperatures. The air mass
is definitely cool, but it is really the clouds and rain that
will hold the temperatures down during the day. But at night they
actually moderate the temperatures, so overnight lows will be
near normal to a few degrees below normal.

The summer solstice occurs at 8:54 AM PDT / 9:54 AM MDT on
Friday, June 21st 2019 and is the longest day of the year.

&&

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