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000
FXUS65 KMSO 052043
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
243 PM MDT THU MAY 5 2016

...A few strong thunderstorms late this afternoon and evening...

.DISCUSSION...Cirrus clouds are inhibiting heating and cumulus
development this early afternoon. Some clearing of this cirrus
shield is expected over the next few hours, which will aid in the
development of cumulus, showers, and thunderstorms. Right now it
appears the best potential for the strongest convection will be
over central Idaho and the southern Bitterroot, then move north-
northeast through Missoula between 4-6 pm and into the
Flathead/Mission, Seeley/Swan valleys, and along the Continental
Divide during the early to mid evening hours. The main impacts
from storms, aside from heavy rain and lightning, will be the
potential for gusty winds of 40-45 mph.

A second surge of showers/thunderstorms in central Idaho up
through northwest Montana is expected late this evening through
the overnight hours.

The next significant weather impact over the region will quickly
set up during the overnight hours. A strong surface high pressure
will dive south from Alberta and increase an easterly pressure
gradient across the Continental Divide. Northeast to east winds
will become pretty gusty across the Divide into the Flathead
valley overnight, then spreading southward through the day
Friday. Expect gusts over 30 mph in Kalispell for several hours
tonight and Friday. The BIGGEST IMPACT FROM EAST-NORTHEAST WINDS
FRIDAY WILL BE TO FLATHEAD LAKE. The windy conditions, especially
along the east and south side of the lake, will increase waves
and choppy conditions. Winds will diminish by Saturday morning.

Saturday through Sunday morning will be the nicest part of the
weekend, with plenty of sun and warm temperatures into the mid
and upper 70s under a ridge.

These conditions won`t last long as a trough of low pressure
entering from British Columbia will make its presence known
Sunday afternoon and evening. Moisture and instability will
increase ahead of the approaching front, helping to kick off
showers and thunderstorms across the region, with the best
potential for some strong storms in southwest Montana and Lemhi
county in Idaho.

A BIG CHANGE TO WET AND COOLER CONDITIONS IS LIKELY MONDAY,
PERSISTING THROUGH WEDNESDAY.

Expect temperatures to cool off 20 degrees from Sunday`s highs,
translating to cooler than normal conditions with highs only in
the 50s. A closed low actually develops within this trough and
will sit over the region through at least Tuesday. Unseasonably
cold temps can occur under such lows. While some much-welcomed
precip amounts are expected, snow levels are expected to lower to
4000-5000 feet. This is a big change, given all the warm temps we
have received over the last month. So...given the increasing
confidence for a change to cold and wet conditions, in addition
to possible mountain snow, folks with outdoor plans should monitor
the latest forecasts for any specifics with regards to potential
snowfall in higher elevations.

&&

.AVIATION...Isolated strong thunderstorms will impact the region
from roughly 05/2300Z through 06/0300Z, with KMSO and KGPI being
the two terminals most likely to be affected by thunderstorms. For
KMSO: gusty erratic outflow winds, heavy downpours (albeit
brief), and lightning has the best chance of impacting aviation
operations from 05/2300Z-06/0200Z. For KGPI: similar impacts
should be expected, however the best timeframe for impacts to
GPI`s terminal will range between 06/0000Z-06/0400Z. KBTM and KSMN
may see brief bouts of thundershower activity, however the
strongest will definitely be further north and west of these
locations. Once the cold front passes later tonight, expect a
strong easterly gradient to develop, bringing gusty east winds to
all terminals through the day Friday. Gusts up to 25-30 KTS will
be common.

&&

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

$$





000
FXUS65 KMSO 050950
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
350 AM MDT THU MAY 5 2016

...Thunderstorms this Afternoon...
...Increasing Winds Early Friday through Saturday...

.DISCUSSION...An approaching frontal system is bringing showers
and isolated thunderstorms through north-central Idaho and
northwest Montana this morning. These showers will continue to
spread north-northeast through the morning. By early afternoon,
daytime heating will increase the instability over the area, and
another round of showers and thunderstorms are expected to develop
and last through the evening hours. Storms could become scattered
to numerous, and bring gusty winds and frequent lightning. Brief
heavy rain and hail are also possible in stronger storms. These
storms are likely to disrupt outdoor plans. Those that see/hear
thunderstorms should plan to take shelter.

The focus of showers and thunderstorms will shift southward for
Friday and Saturday, resulting in lingering precipitation for
north-central Idaho and southwest Montana during this time. In
addition, a strong pressure gradient will strengthen over the area
due to a cool, surface high pressure east of the Continental
Divide. Therefore, east winds will increase across northwest
Montana early Friday morning, and strengthen across the rest of
western Montana and into Lemhi County by Friday afternoon. These
breezy winds can disrupt boating activities on area lakes,
especially Flathead Lake, as choppy conditions grow. Exposed
north-south roadways could experience strong crosswinds at times.
Winds will decrease by Saturday.

The models are indicating another low pressure system move down
out British Columbia on Sunday night into Monday. This low
pressure system will bring another round of widespread
precipitation and cooler temperatures. Maximum temperatures on
Monday appear to be running around 5 degrees below normal for this
time of year.

The low is anticipated to slowly progress across southern Idaho
into Wyoming Tuesday into Wednesday. The position of the low will
cause wrap around precipitation which will mainly impact the
Continental Divide down into southwest Montana. Temperatures will
remain below normal on Tuesday with a slight warming on Wednesday.
The models diverge on a solution for the latter part of the week,
so little changes were made to the current forecast.

&&

.AVIATION...Showers with isolated thunderstorms are streaming
through north-central Idaho and northwest Montana this morning,
with light showers in the vicinity of KGPI. Another round of
showers and thunderstorms will develop across the area around
05/2100Z and last through the evening, bringing a thunderstorm
chances to KGPI, KMSO, and KBTM. The primary threat with stronger
storms will be gusty winds and frequent lightning, with periods of
brief heavy rain and hail possible. Stronger showers will also
quickly lower ceilings, briefly obstructing terrain and
visibility. An increase in easterly winds will begin for KGPI and
KBTM after 06/0400Z, and KMSO generally after 06/0600Z.

&&

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

$$





000
FXUS65 KMSO 042044
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
244 PM MDT WED MAY 4 2016

.DISCUSSION...High clouds and continued warm temperatures are the
main story for today`s weather. A stray mountain shower is
possible as cumulus form on the terrain this afternoon, but little
moisture will make it to the ground. Expect light winds through
sunset and overnight.

On Thursday a frontal system will provide the forcing for
widespread thunderstorms, some of which may be strong. Storms
will begin forming around noon, and continue through the evening
hours. Gusty winds and lightning will be the primary threats, but
brief heavy rains and hail are possible in the stronger cells.
There will be more instability tomorrow than with previous systems
this spring, so stay weather aware if you have outdoor plans. Warm
temperatures will continue one more day before cooler air moves in
overnight into Friday.

Friday and Saturday a close upper low pressure system will be
trekking its way across the southwest U.S. and Great Basin. It`s
possible some wrap around moisture from this low will make its way
into Lemhi county and southwest Montana. If it does expect
generally light amounts. The biggest potential impact for Fri and
Sat will be the development of EAST WINDS across western Montana.
A strong surface high pressure in central Montana will produce
increasing pressure gradients for easterly winds. This is a
favorable pattern for Flathead Lake to receive some enhancement of
these east winds and impact the lake with some INCREASING WAVES each
day.

The pattern becomes a little more active starting Sunday and
Monday. A weather disturbance will push its way through the region
bringing scattered rain showers.

Tuesday and Wednesday next week some models are hinting at cooler
temperatures and showery conditions with a trough developing over
the region. However, there is quite a bit of uncertainty with
this solution.

&&

.AVIATION...High level clouds will continue to stream over the
area this afternoon and overnight ahead of tomorrow`s frontal
system. KBTM will see some gusts to around 20 knots, but other
areas should keep light and variable winds. Mountain-based
cumulus can be seen on satellite imagery, and these will continue
to form over the terrain until after sunset. Although some may
turn to light showers, terminals in valleys should stay dry for
the most part. A lightning strike or two in the vicinity of KMSO
and KGPI cannot be totally ruled out, but looks unlikely.
Thunderstorms are likely for tomorrow afternoon.

&&

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

$$





000
FXUS65 KMSO 042044
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
244 PM MDT WED MAY 4 2016

.DISCUSSION...High clouds and continued warm temperatures are the
main story for today`s weather. A stray mountain shower is
possible as cumulus form on the terrain this afternoon, but little
moisture will make it to the ground. Expect light winds through
sunset and overnight.

On Thursday a frontal system will provide the forcing for
widespread thunderstorms, some of which may be strong. Storms
will begin forming around noon, and continue through the evening
hours. Gusty winds and lightning will be the primary threats, but
brief heavy rains and hail are possible in the stronger cells.
There will be more instability tomorrow than with previous systems
this spring, so stay weather aware if you have outdoor plans. Warm
temperatures will continue one more day before cooler air moves in
overnight into Friday.

Friday and Saturday a close upper low pressure system will be
trekking its way across the southwest U.S. and Great Basin. It`s
possible some wrap around moisture from this low will make its way
into Lemhi county and southwest Montana. If it does expect
generally light amounts. The biggest potential impact for Fri and
Sat will be the development of EAST WINDS across western Montana.
A strong surface high pressure in central Montana will produce
increasing pressure gradients for easterly winds. This is a
favorable pattern for Flathead Lake to receive some enhancement of
these east winds and impact the lake with some INCREASING WAVES each
day.

The pattern becomes a little more active starting Sunday and
Monday. A weather disturbance will push its way through the region
bringing scattered rain showers.

Tuesday and Wednesday next week some models are hinting at cooler
temperatures and showery conditions with a trough developing over
the region. However, there is quite a bit of uncertainty with
this solution.

&&

.AVIATION...High level clouds will continue to stream over the
area this afternoon and overnight ahead of tomorrow`s frontal
system. KBTM will see some gusts to around 20 knots, but other
areas should keep light and variable winds. Mountain-based
cumulus can be seen on satellite imagery, and these will continue
to form over the terrain until after sunset. Although some may
turn to light showers, terminals in valleys should stay dry for
the most part. A lightning strike or two in the vicinity of KMSO
and KGPI cannot be totally ruled out, but looks unlikely.
Thunderstorms are likely for tomorrow afternoon.

&&

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

$$





000
FXUS65 KMSO 040946
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
346 AM MDT WED MAY 4 2016

...Strong Storms Possible Thursday, then Breezy Winds Friday...

.DISCUSSION...

High pressure will begin to breakdown today but for most areas the
only noticeable difference from previous days will be an increase
in high and mid level clouds. A few showers and thunderstorms will
be possible, mainly across the higher terrain during the
afternoon/evening hours. Otherwise, temperatures will again be
15-20 degrees above normal leading many creeks and rivers to run
swift and higher than normal due to accelerated snowmelt.

Models are still in agreement that showers and thunderstorms will
increase Thursday as a cold front approaches the Northern Rockies
Thursday afternoon and evening. Storms that do develop could
become strong at times, resulting in frequent lightning, erratic
strong winds, brief heavy rain, and the potential for small hail.

Showers will linger into Friday, though thunderstorm chances will
decrease as the low pressure system shifts southward. In addition,
easterly winds will develop in the wake of the system, leading to
increasingly breezy winds Friday morning and afternoon for mainly
western Montana. Cooler temperatures can be expected during this
transition period Friday.

High pressure will rebuild over the weekend which will allow drier
conditions with near normal temperatures to return. By early next
week, forecast models generally agree that the region will be
under a northwest flow. This pattern would lead to seasonable
temperatures and occasional shower activity.


&&

.AVIATION...Increasing mid to high level clouds are expected
today. Isolated showers are possible this afternoon for the
terrain. Otherwise, expect VFR conditions with generally light
winds for TAF sites. The exception will be for KBTM, where
occasional afternoon wind gusts could reach 15-20 kts at times.


&&

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

$$





000
FXUS65 KMSO 032004
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
204 PM MDT TUE MAY 3 2016

.DISCUSSION...High pressure will keep sublime spring conditions
with and above normal high temperatures (15-20 degrees) in place
through Wednesday. Overnights temperatures will be quite warm in
the mountains, further continuing the melt of our dwindling snow
pack (presently 60%-80% or normal). However, valley temperatures
are going to remain comparatively crisp and seasonably cool. Some
additional cumulus clouds are likely to sprout Wednesday
afternoon, but surmount to little more than periodic shade.

Thursday will be another warm day, with an increasingly
destabilizing atmosphere across all of the Northern Rockies ahead
of a cold front expected later that night. The front will bring
about an increased potential for thunderstorms, likely to develop
later in the afternoon and through the early evening hours, as
they typically do. Given the amount of instability being shown in
models, there is a growing threat that storms that develop could
cause gusty winds (in excess of 30+ mph), along with frequent
lightning, brief heavy rain, and/or small hail. Mostly all of
western Montana and central Idaho will be under the gun for
storms, so keep an eye to the sky Thursday afternoon and prepare
for a potentially stormy evening.

By Friday, the cold front will have exited the region, but
lingering easterly winds will develop in the wake of the low
pressure system still over the region. The will keep showers
possible through the day as well, though thunder chances will be
much less. Expect cooler temperatures and a breezy east wind to
affect western Montana, although cooler temps may also be felt
across north central Idaho as well.

The weekend looks rather quiet as high pressure rebuilds, helping
keep conditions dry and temperatures near normal for this time of
year. Forecast confidence takes a decided nose dive as we head
into next week, though there is just a little bit more consistency
with the latest suite of long range forecast models this morning.
Generally speaking, it appears the Northern Rockies will fall
under a fairly progressive NW flow aloft. This would support
temperature near normal temperatures and chances for afternoon
showers and/or thunderstorms.

&&

.AVIATION...High pressure will continue to result in stable
conditions with generally light winds and limited cloud cover.
Any aviation impacts will likely only come from temperatures 10-15
degrees about average resulting in high density altitudes.

&&

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

$$





000
FXUS65 KMSO 030938
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
338 AM MDT TUE MAY 3 2016

.DISCUSSION...Bright, sunny skies will again be common today as a
ridge of high pressure remains overhead. Temperatures will be
pleasantly warm with highs ranging from 15-20 degrees above
normal. These warm temperatures will set the stage for another
gradual rise in creeks and rivers from snow melt as the week
progresses.

Precipitation chances will be minimal through mid week. Increasing
mid level moisture on Wednesday will allow for isolated to
scattered showers/thunderstorms mainly over the higher terrain,
but minimal instability will keep storms rather weak.

Moisture and instability will increase Thursday to bring the
potential for widespread showers and thunderstorms. Though there
is still some uncertainty, ingredients are becoming more
favorable for the possibility of a few strong storms to develop
that could bring very gusty erratic winds to localized areas.

Showers and thunderstorms will extend into Friday, though the
focus of precipitation shifts farther south. In addition, a
backdoor cold front will set up along the Continental Divide
Friday and result in breezy east winds across the area. Winds will
stay breezy through Saturday for north-central ID and southwest MT
as the surface high pressure tracks southward. Precipitation will
begin to taper off for the rest of the area by Saturday, though
some isolated showers could develop through the rest of the
weekend.

Forecast models continue to allow for the potential of a
relatively cool and showery pattern early next week but
confidence is low at this point.

&&

.AVIATION...High pressure will continue to result in stable
conditions with generally light winds and limited cloud cover.
Any aviation impacts will likely only come from temperatures 10-15
degrees about average resulting in high density altitudes.

&&

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

$$





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