000
FXUS65 KMSO 240314
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
ISSUED BY NATIONAL WEATHER SERVICE GREAT FALLS MT
914 PM MDT THU MAY 23 2013
.UPDATE...
UPDATED FORECAST IS OUT. ONLY REAL CHANGE WAS TO INCREASE POPS TO
100 PERCENT ALONG THE DIVIDE AND LOWER TEMPS IN BIT IN THE BUTTE
AREA. SNOW IS FALLING FOR MANY AREAS ALONG THE DIVIDE...SO CURRENT
WINTER HIGHLIGHTS LOOK GOOD. BRUSDA
&&
.AVIATION...ANOTHER WAVE OF MOISTURE AND LIFT WILL PUSH THROUGH THE
AREA TONIGHT BRINGING WIDESPREAD PRECIPITATION AND MVFR CONDITIONS
FROM KSMN TO KBTM. PRECIPITATION AT THESE LOCATIONS WILL INITIALLY
START AS RAIN BUT QUICKLY CHANGE TO SNOW. LOW CIGS/VIS IN BURSTS OF
HEAVIER SNOW WILL RESULT IN IFR CONDITIONS AT TIMES. CONDITIONS WILL
IMPROVE AFTER MIDNIGHT WITH PRECIPITATION ENDING FROM SOUTH TO
NORTH. BY MORNING CONDITIONS SHOULD BECOME VFR AT ALL TAF SITES. A
MOIST AND UNSTABLE AIRMASS WILL REMAIN OVER THE AREA FRIDAY
RESULTING IN SCATTERED AFTERNOON SHOWERS. LANGLIEB
&&
.PREV DISCUSSION... /ISSUED 300 PM MDT THU MAY 23 2013/
DISCUSSION...WESTERN MONTANA AND NORTH CENTRAL IDAHO ARE
CURRENTLY IN BETWEEN WEATHER FEATURES THIS AFTERNOON, WHICH HAS
ALLOWED US A BRIEF RESPITE FROM PRECIPITATION. THIS WILL BE SHORT
LIVED HOWEVER AS ANOTHER WAVE OF ENERGY IS EXPECTED TO ROTATE
AROUND THE LOW PRESSURE SYSTEM CURRENTLY SITTING IN THE PACIFIC
NORTHWEST. THIS WAVE HAS AN IMPRESSIVE AMOUNT OF LIFT ASSOCIATED
WITH IT AND THUS ANOTHER ROUND OF POTENTIALLY HEAVY WET SNOW IS
EXPECTED LATE THIS AFTERNOON THROUGH FRIDAY MORNING. THE LOCATIONS
WITH THE GREATEST LIKELIHOOD OF SEEING IMPACTFUL SNOW THIS EVENING
INCLUDE SOUTHWEST MONTANA (BUTTE, GEORGETOWN LAKE, ANACONDA,
MACDONALD PASS AND HOMESTAKE PASS), AND LEMHI COUNTY (LOST TRAIL
PASS, SALMON, GILMORE SUMMIT). LOCATIONS FURTHER NORTH ALONG THE
CONTINENTAL DIVIDE (WEST GLACIER, SWAN LAKE, CONDON, SEELEY LAKE)
WILL LIKELY SEE MORE SNOW DEVELOP OVERNIGHT INTO THE EARLY MORNING
HOURS. THE MAIN IMPACT FROM THIS NEXT ROUND OF SNOW WILL BE
SLUSHY/SLICK ROADWAYS, BREAKAGE OF TREE LIMBS WHICH HAVE ALREADY
BEEN WEAKENED BY TODAY`S SNOW, AND PERIODS OF VERY LOW VISIBILITY
DUE TO CONVECTIVE SHOWERS BRINGING SHORT LIVED PERIODS OF INTENSE
SNOWFALL. ADDITIONAL POWER OUTAGES ARE POSSIBLE. VARIOUS WINTER
WEATHER PRODUCTS WILL REMAIN IN EFFECT THROUGH FRIDAY MORNING.
THIS NEXT WAVE OF ENERGY WILL EXIT THE REGION TOMORROW MORNING,
BRINGING A SOMEWHAT DRIER PERIOD FOR THE MORNING. THIS WILL BE
AGAIN, SHORT-LIVED HOWEVER AS YET ANOTHER WAVE OF ENERGY ROTATES
AROUND THE LOW PRESSURE SYSTEM BRINGING ENHANCED SHOWERS ACROSS
ALL OF WESTERN MONTANA AND NORTH CENTRAL IDAHO. THE MAIN FOCUS OF
THESE SHOWERS DOES APPEAR TO BE ACROSS NORTHWEST MONTANA WHERE
ANOTHER ROUND OF SNOW SHOWERS IS POSSIBLE. FORECAST MODELS DO
INDICATE SNOW LEVELS BEGINNING TO RISE DURING THIS TIME SO
ACCUMULATING SNOW SHOULD NOT BE AS IMPACTFUL AS THE LATEST WAVES
MOVING THROUGH THE REGION.
FOR THE HOLIDAY WEEKEND IT DOES APPEAR CONDITIONS WILL MODERATE
SLIGHTLY BACK TOWARDS MORE NORMAL CONDITIONS FOR THIS TIME OF
YEAR. THE THREAT OF PRECIPITATION WILL BE ON THE DECLINE ALTHOUGH
THEIR COULD BE SOME LINGERING SHOWERS?PARTICULARLY IN THE
AFTERNOONS. TEMPERATURES WILL RISE BACK TO NEAR NORMAL FOR THIS
TIME OF YEAR.
BY MONDAY ANOTHER TROUGH OF LOW PRESSURE IS EXPECTED TO PUMP
MOISTURE AND ENERGY BACK INTO THE REGION BRINGING PRECIPITATION
BACK INTO THE FORECAST. THIS COULD TRANSLATE INTO THUNDERSTORMS
ACROSS THE REGION BY TUESDAY AND WEDNESDAY.
&&
NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 9 AM MDT FRIDAY BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY POTOMAC/SEELEY
LAKE REGION...WEST GLACIER REGION.
ID... WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY EASTERN LEMHI
COUNTY.
&&
$$
000
FXUS65 KMSO 232343
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
ISSUED BY NATIONAL WEATHER SERVICE GREAT FALLS MT
543 PM MDT THU MAY 23 2013
UPDATED AVIATION SECTION
.DISCUSSION...WESTERN MONTANA AND NORTH CENTRAL IDAHO ARE
CURRENTLY IN BETWEEN WEATHER FEATURES THIS AFTERNOON, WHICH HAS
ALLOWED US A BRIEF RESPITE FROM PRECIPITATION. THIS WILL BE SHORT
LIVED HOWEVER AS ANOTHER WAVE OF ENERGY IS EXPECTED TO ROTATE
AROUND THE LOW PRESSURE SYSTEM CURRENTLY SITTING IN THE PACIFIC
NORTHWEST. THIS WAVE HAS AN IMPRESSIVE AMOUNT OF LIFT ASSOCIATED
WITH IT AND THUS ANOTHER ROUND OF POTENTIALLY HEAVY WET SNOW IS
EXPECTED LATE THIS AFTERNOON THROUGH FRIDAY MORNING. THE LOCATIONS
WITH THE GREATEST LIKELIHOOD OF SEEING IMPACTFUL SNOW THIS EVENING
INCLUDE SOUTHWEST MONTANA (BUTTE, GEORGETOWN LAKE, ANACONDA,
MACDONALD PASS AND HOMESTAKE PASS), AND LEMHI COUNTY (LOST TRAIL
PASS, SALMON, GILMORE SUMMIT). LOCATIONS FURTHER NORTH ALONG THE
CONTINENTAL DIVIDE (WEST GLACIER, SWAN LAKE, CONDON, SEELEY LAKE)
WILL LIKELY SEE MORE SNOW DEVELOP OVERNIGHT INTO THE EARLY MORNING
HOURS. THE MAIN IMPACT FROM THIS NEXT ROUND OF SNOW WILL BE
SLUSHY/SLICK ROADWAYS, BREAKAGE OF TREE LIMBS WHICH HAVE ALREADY
BEEN WEAKENED BY TODAY`S SNOW, AND PERIODS OF VERY LOW VISIBILITY
DUE TO CONVECTIVE SHOWERS BRINGING SHORT LIVED PERIODS OF INTENSE
SNOWFALL. ADDITIONAL POWER OUTAGES ARE POSSIBLE. VARIOUS WINTER
WEATHER PRODUCTS WILL REMAIN IN EFFECT THROUGH FRIDAY MORNING.
THIS NEXT WAVE OF ENERGY WILL EXIT THE REGION TOMORROW MORNING,
BRINGING A SOMEWHAT DRIER PERIOD FOR THE MORNING. THIS WILL BE
AGAIN, SHORT-LIVED HOWEVER AS YET ANOTHER WAVE OF ENERGY ROTATES
AROUND THE LOW PRESSURE SYSTEM BRINGING ENHANCED SHOWERS ACROSS
ALL OF WESTERN MONTANA AND NORTH CENTRAL IDAHO. THE MAIN FOCUS OF
THESE SHOWERS DOES APPEAR TO BE ACROSS NORTHWEST MONTANA WHERE
ANOTHER ROUND OF SNOW SHOWERS IS POSSIBLE. FORECAST MODELS DO
INDICATE SNOW LEVELS BEGINNING TO RISE DURING THIS TIME SO
ACCUMULATING SNOW SHOULD NOT BE AS IMPACTFUL AS THE LATEST WAVES
MOVING THROUGH THE REGION.
FOR THE HOLIDAY WEEKEND IT DOES APPEAR CONDITIONS WILL MODERATE
SLIGHTLY BACK TOWARDS MORE NORMAL CONDITIONS FOR THIS TIME OF
YEAR. THE THREAT OF PRECIPITATION WILL BE ON THE DECLINE ALTHOUGH
THEIR COULD BE SOME LINGERING SHOWERS?PARTICULARLY IN THE
AFTERNOONS. TEMPERATURES WILL RISE BACK TO NEAR NORMAL FOR THIS
TIME OF YEAR.
BY MONDAY ANOTHER TROUGH OF LOW PRESSURE IS EXPECTED TO PUMP
MOISTURE AND ENERGY BACK INTO THE REGION BRINGING PRECIPITATION
BACK INTO THE FORECAST. THIS COULD TRANSLATE INTO THUNDERSTORMS
ACROSS THE REGION BY TUESDAY AND WEDNESDAY.
&&
.AVIATION...ANOTHER WAVE OF MOISTURE AND LIFT WILL PUSH THROUGH THE
AREA TONIGHT BRINGING WIDESPREAD PRECIPIPITATION AND MVFR CONDITIONS
FROM KSMN TO KBTM. PRECIPITATION AT THESE LOCATIONS WILL INITIALLY
START AS RAIN BUT QUICKLY CHANGE TO SNOW. LOW CIGS/VIS IN BURSTS OF
HEAVIER SNOW WILL RESULT IN IFR CONDITIONS AT TIMES. CONDITIONS WILL
IMPROVE AFTER MIDNIGHT WITH PRECIPITATION ENDING FROM SOUTH TO
NORTH. BY MORNING CONDITIONS SHOULD BECOME VFR AT ALL TAF SITES. A
MOIST AND UNSTABLE AIRMASS WILL REMAIN OVER THE AREA FRIDAY
RESULTING IN SCATTERED AFTERNOON SHOWERS. LANGLIEB
&&
NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 9 AM MDT FRIDAY BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM MDT
FRIDAY POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY EASTERN LEMHI
COUNTY.
&&
$$
000
FXUS65 KMSO 232048
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
ISSUED BY NATIONAL WEATHER SERVICE GREAT FALLS MT
248 PM MDT THU MAY 23 2013
.DISCUSSION...WESTERN MONTANA AND NORTH CENTRAL IDAHO ARE
CURRENTLY IN BETWEEN WEATHER FEATURES THIS AFTERNOON, WHICH HAS
ALLOWED US A BRIEF RESPITE FROM PRECIPITATION. THIS WILL BE SHORT
LIVED HOWEVER AS ANOTHER WAVE OF ENERGY IS EXPECTED TO ROTATE
AROUND THE LOW PRESSURE SYSTEM CURRENTLY SITTING IN THE PACIFIC
NORTHWEST. THIS WAVE HAS AN IMPRESSIVE AMOUNT OF LIFT ASSOCIATED
WITH IT AND THUS ANOTHER ROUND OF POTENTIALLY HEAVY WET SNOW IS
EXPECTED LATE THIS AFTERNOON THROUGH FRIDAY MORNING. THE LOCATIONS
WITH THE GREATEST LIKELIHOOD OF SEEING IMPACTFUL SNOW THIS EVENING
INCLUDE SOUTHWEST MONTANA (BUTTE, GEORGETOWN LAKE, ANACONDA,
MACDONALD PASS AND HOMESTAKE PASS), AND LEMHI COUNTY (LOST TRAIL
PASS, SALMON, GILMORE SUMMIT). LOCATIONS FURTHER NORTH ALONG THE
CONTINENTAL DIVIDE (WEST GLACIER, SWAN LAKE, CONDON, SEELEY LAKE)
WILL LIKELY SEE MORE SNOW DEVELOP OVERNIGHT INTO THE EARLY MORNING
HOURS. THE MAIN IMPACT FROM THIS NEXT ROUND OF SNOW WILL BE
SLUSHY/SLICK ROADWAYS, BREAKAGE OF TREE LIMBS WHICH HAVE ALREADY
BEEN WEAKENED BY TODAY`S SNOW, AND PERIODS OF VERY LOW VISIBILITY
DUE TO CONVECTIVE SHOWERS BRINGING SHORT LIVED PERIODS OF INTENSE
SNOWFALL. ADDITIONAL POWER OUTAGES ARE POSSIBLE. VARIOUS WINTER
WEATHER PRODUCTS WILL REMAIN IN EFFECT THROUGH FRIDAY MORNING.
THIS NEXT WAVE OF ENERGY WILL EXIT THE REGION TOMORROW MORNING,
BRINGING A SOMEWHAT DRIER PERIOD FOR THE MORNING. THIS WILL BE
AGAIN, SHORT-LIVED HOWEVER AS YET ANOTHER WAVE OF ENERGY ROTATES
AROUND THE LOW PRESSURE SYSTEM BRINGING ENHANCED SHOWERS ACROSS
ALL OF WESTERN MONTANA AND NORTH CENTRAL IDAHO. THE MAIN FOCUS OF
THESE SHOWERS DOES APPEAR TO BE ACROSS NORTHWEST MONTANA WHERE
ANOTHER ROUND OF SNOW SHOWERS IS POSSIBLE. FORECAST MODELS DO
INDICATE SNOW LEVELS BEGINNING TO RISE DURING THIS TIME SO
ACCUMULATING SNOW SHOULD NOT BE AS IMPACTFUL AS THE LATEST WAVES
MOVING THROUGH THE REGION.
FOR THE HOLIDAY WEEKEND IT DOES APPEAR CONDITIONS WILL MODERATE
SLIGHTLY BACK TOWARDS MORE NORMAL CONDITIONS FOR THIS TIME OF
YEAR. THE THREAT OF PRECIPITATION WILL BE ON THE DECLINE ALTHOUGH
THEIR COULD BE SOME LINGERING SHOWERS?PARTICULARLY IN THE
AFTERNOONS. TEMPERATURES WILL RISE BACK TO NEAR NORMAL FOR THIS
TIME OF YEAR.
BY MONDAY ANOTHER TROUGH OF LOW PRESSURE IS EXPECTED TO PUMP
MOISTURE AND ENERGY BACK INTO THE REGION BRINGING PRECIPITATION
BACK INTO THE FORECAST. THIS COULD TRANSLATE INTO THUNDERSTORMS
ACROSS THE REGION BY TUESDAY AND WEDNESDAY.
&&
.AVIATION...THE LATEST SURGE OF MOISTURE AND DYNAMICS WILL BE
SWEEPING NORTHWARDS INTO CANADA THIS AFTERNOON. CONDITIONS WILL
ONLY IMPROVE TEMPORARILY AS YET ANOTHER SPOKE OF ENERGY POWERED BY
A STRONG JET STREAK WILL MOVE INTO LEMHI COUNTY AND SOUTHWEST
MONTANA LATER THIS AFTERNOON. KSMN AND KBTM WILL BE MOST IMPACTED
WITH LOW CEILINGS AND LIMITED VISIBILITIES THROUGH MUCH OF THE
NIGHT. THE CONTINENTAL DIVIDE WILL BE OBSCURED ALL THE WAY TO THE
CANADIAN BORDER. THE IDAHO PANHANDLE AND FAR NORTHWEST CORNER OF
MONTANA WILL SEE IMPROVED CONDITIONS THROUGH MUCH OF THE NIGHT, IN
RELATIVE COMPARISON TO LOCATIONS TO THE EAST. WHILE CONDITIONS ARE
EXPECTED TO IMPROVE FOR FRIDAY, THE ATMOSPHERE WILL BE MOIST AND
UNSTABLE ENOUGH FOR CLOUD AND SHOWER DEVELOPMENT BY AFTERNOON.
&&
NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 9 AM MDT FRIDAY BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM MDT
FRIDAY POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 9 AM MDT FRIDAY EASTERN LEMHI
COUNTY.
&&
$$
000
FXUS65 KMSO 231808
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
ISSUED BY NATIONAL WEATHER SERVICE GREAT FALLS MT
1208 PM MDT THU MAY 23 2013
.DISCUSSION...THE FIRST ROUND OF HEAVY WET SNOW WHICH MOVED ALONG
THE CONTINENTAL DIVIDE THIS MORNING IS SLOWLY EXITING THE REGION.
SNOW AMOUNTS UP TO A FOOT HAVE BEEN REPORTED ACROSS AREAS SUCH AS
ANACONDA IN SOUTHWEST MONTANA, WHICH WAS THE HARDEST HIT AREA.
WHILE WE WILL GET A BRIEF RESPITE FROM PRECIPITATION, ANOTHER WAVE
OF ENERGY IS EXPECTED TO ROTATE AROUND THE LOW PRESSURE SYSTEM
CURRENTLY SITTING IN THE PACIFIC NORTHWEST. THIS WAVE HAS AN
IMPRESSIVE AMOUNT OF LIFT ASSOCIATED WITH IT AND THUS ANOTHER
ROUND OF POTENTIALLY HEAVY WET SNOW IS EXPECTED LATE THIS AFTERNOON
THROUGH FRIDAY MORNING. THE LOCATIONS WITH THE GREATEST LIKELIHOOD
OF SEEING IMPACTFUL SNOW THIS EVENING INCLUDE SOUTHWEST MONTANA
(BUTTE, GEORGETOWN LAKE, ANACONDA, MACDONALD PASS AND HOMESTAKE
PASS), AND LEMHI COUNTY (LOST TRAIL PASS, SALMON, GILMORE SUMMIT).
LOCATIONS FURTHER NORTH ALONG THE CONTINENTAL DIVIDE (WEST
GLACIER, SWAN LAKE, CONDON, SEELEY LAKE) WILL LIKELY SEE MORE SNOW
DEVELOP OVERNIGHT. THE MAIN IMPACT FROM THIS NEXT ROUND OF SNOW
WILL BE SLUSH/SLICK ROADWAYS, AND BREAKAGE OF TREE LIMBS WHICH
HAVE ALREADY BEEN WEAKENED BY TODAY`S SNOW. ADDITIONAL POWER
OUTAGES ARE POSSIBLE. VARIOUS WINTER WEATHER PRODUCTS WILL REMAIN
IN EFFECT THROUGH FRIDAY MORNING.
&&
.AVIATION...THE LATEST SURGE OF MOISTURE AND DYNAMICS WILL BE
SWEEPING NORTHWARDS INTO CANADA THIS AFTERNOON. CONDITIONS WILL
ONLY IMPROVE TEMPORARILY AS YET ANOTHER SPOKE OF ENERGY POWERED BY
A STRONG JET STREAK WILL MOVE INTO LEMHI COUNTY AND SOUTHWEST
MONTANA LATER THIS AFTERNOON. KSMN AND KBTM WILL BE MOST IMPACTED
WITH LOW CEILINGS AND LIMITED VISIBILITIES THROUGH MUCH OF THE
NIGHT. THE CONTINENTAL DIVIDE WILL BE OBSCURED ALL THE WAY TO THE
CANADIAN BORDER. THE IDAHO PANHANDLE AND FAR NORTHWEST CORNER OF
MONTANA WILL SEE IMPROVED CONDITIONS THROUGH MUCH OF THE NIGHT, IN
RELATIVE COMPARISON TO LOCATIONS TO THE EAST. WHILE CONDITIONS ARE
EXPECTED TO IMPROVE FOR FRIDAY, THE ATMOSPHERE WILL BE MOIST AND
UNSTABLE ENOUGH FOR CLOUD AND SHOWER DEVELOPMENT BY AFTERNOON.
&&
NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 9 AM MDT FRIDAY BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM MDT
FRIDAY BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM MDT
FRIDAY POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM MDT
FRIDAY EASTERN LEMHI COUNTY.
&&
$$
000
FXUS65 KMSO 230958
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
358 AM MDT Thu May 23 2013
.DISCUSSION...The area of heaviest precipitation that produced
heavy snow this morning and resulted in power outages across
parts of southwest Montana overnight has since moved north and is
presently over the Bob Marshall/Scapegoat Wilderness areas. It
seems likely that Seeley Lake is experiencing their heaviest
snowfall, but do not anticipate more than 1 to 2 inches of snow
through daybreak resulting in little if any impact. However this
may not be the case over southwest Montana where snow continues to
fall in Butte, Anaconda and up towards Georgetown Lake. Given the
continued snow, already known impacts and in anticipation of a
challenging morning commute have issued a Winter Weather Advisory
that is in effect till 10am. Main impacts will be the weight of
any additional snowfall on area vegetation, power lines and
continued slushy roadways. Things should start to improve shortly
after sunrise.
The focused area of precipitation will gradually work its way
north throughout the day and eventually into Canada this
afternoon. Dramatic cooling and drying has been observed behind
the precipitation and a clearing trend this morning is likely
across southwest and west central Montana. However another
disturbance, clearly visible on satellite data off the Oregon
coast, will rotate through the Great Basin and up into southwest
Montana later this afternoon. This wave and its attendant upper
level jet streak will interact with an already moist atmosphere
that will be slowly growing more unstable due to daytime heating
to produce another round of showers and thunderstorms. Models have
gradually be trending west with this convective precipitation,
spreading it from Lemhi County, Idaho northeast basically along
the Divide through this evening. Key threats and potential impacts
will be very heavy rainfall and perhaps some pea sized hail. There
will be a brief break in the train of waves pushing off the larger
Pacific Northwest low pressure system late Thursday night into
early Friday. However by Friday afternoon/Saturday early morning
models are suggesting that a portion of the main low may break
away and move quickly through northwest Montana. This will shift
colder air once again into Montana along with another round of
precipitation. However precipitation and snowfall amounts should
be significantly less than those experienced over the past twenty-
four hours with snow likely limited to locations above 5000ft.
The northwestern United States will remain under an upper level
low that will keep rotating moisture and instability into western
Montana and north central Idaho. This will keep a chance of
showers in the forecast for Saturday and through the rest of the
forecast period. Temperatures will remain slightly below normal.
&&
.AVIATION...A low pressure system will keep a chance of showers
over the region. This system will have the greatest impact on KGPI
and KBTM. In addition, snow showers will obscure the mountains and
passes along the Continental divide.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 10 AM MDT this morning
Butte/Blackfoot Region.
ID...None.
&&
$$
Dickerson/Kolata
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000
FXUS65 KMSO 222047
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
247 PM MDT Wed May 22 2013
.DISCUSSION...Several impacts are expected this evening. First, a
very unstable atmosphere will linger over southwest Montana into early
this evening. The low level wind environment is such that a few
storms could be strong into early this evening from Butte to
Anaconda and northward to Seeley Lake and Ovando.
Second, a cold front is moving across western Montana this
afternoon and evening with a quite cold air mass for this time of
year wedging into the area. Snow levels are lowering to near
valley levels from Hamilton to Missoula northward across northwest
Montana. However, we are currently forecasting the precipitation
to remain mainly in the form of rain except above about 4000 feet
and in the lower valleys of far northwest Montana from Thompson
Falls to Hot Springs and near Libby. This is one part of the
forecast that our confidence is not high...meaning there is a
small possibility of the rain temporarily changing to snow in some
of the other valleys, such as Mission, Missoula, Bitterroot, Flathead,
and Seeley/Swan.
The third overnight concern is the moderate to heavy
precipitation. The cold front is expected to stall near the
continental divide resulting a prolonged period of moderate to
heavy showers especially from about Drummond northward across
Seeley Lake, the Mission Valley, Flathead Valley, Eureka, Swan
Valley, and Glacier Park. Some areas should see more than one inch
of precipitation tonight causing local ponding of water and stream
rises. However, with the precipitation changing to snow in the
mountains with lowering snow levels this evening, the bigger
streams and rivers should not see a major reaction. In other
words, the precipitation goes to snow pack rather than runoff.
Fourth, but also very important is overnight temperatures in west
central Idaho. A cold air mass has shifted into Idaho. Partial
clearing is expected tonight from Grangeville to Orofino. As such,
temperatures should fall to near or a little below the freezing
point in many valley locations. Those that have started their
gardens and sensitive outside plants may want to protect tonight.
Another weather disturbance should brush western Montana late
Thursday and Thursday night. However, some of the more recent
forecast guidance is trending towards a more eastward shift of the
main precipitation core east of the divide. At this point we have
only trended down the precipitation forecast some for Thursday
night.
A series of weather disturbances are expected to shift across
northern Idaho and western Montana Saturday, Sunday and Monday.
This should translate into occasional showers. Despite the
occasional precipitation, temperatures should moderate to near
normal values over the weekend into Memorial Day.
&&
.AVIATION...A low pressure system will maintain through the
Pacific Northwest for the next couple of days. Widespread rain
and snow will keep lowered ceilings and visibility. Obscured
mountains and passes due to snow and cloud cover will be common
through tonight. Snow levels have lowered to many of the valley
locations of northwest Montana and western Idaho this afternoon
and snow levels continue to lower throughout the region. Moderate
to heavy rain and snow showers with embedded thunderstorms should
be expected through this evening. Locations between KSMN, KBTM and
KMSO have the most instability and thunderstorms will be in the
vicinity through this evening. Drier air will move into north
central Idaho overnight and precipitation will decrease. Rain and
snow will continue through much of western Montana and along the
divide through much of Thursday. Saturated surface conditions may
also lead to early morning fog development Thursday morning.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 6 AM MDT Thursday Lower Clark Fork
Region.
WINTER WEATHER ADVISORY until 6 AM MDT Thursday Kootenai/Cabinet
Region.
ID...None.
&&
$$
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000
FXUS65 KMSO 221010
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
410 AM MDT Wed May 22 2013
.DISCUSSION...While the forecast heavy rain and high elevation
snow is still on track for today through the end of the week, a
few changes to the forecast have been made, albeit small changes.
It seems that the cold air intrusion may not be as impactful as
previously forecast, although enough cold air will still be in
place to cause accumulating snowfall in the high terrain across
the Northern Rockies. Snowfall amounts continue to be a question,
as placement of precipitation and cold air will ultimately impact
who gets what, and where. There is good confidence that Glacier
National Park, the Whitefish range, Mission mountains, and the Bob
Marshall Wilderness should see the most snowfall, with the bulk of
this snow falling above 7000 feet. Lighter amounts are possible
between roughly 5000 feet and 7000 feet. Below 5000 feet, most all
locations will see rainfall throughout the day, with precip
continuing well into the day Thursday, and much of Friday as well
(especially across NW Montana). Those with plans to be outdoors,
especially if you are traveling to Glacier National Park, or over
Lookout and Marias Pass, should prepare for inclement, rapidly
changing conditions.
Forecast models continue to shift both the path of the closed upper
level low pressure system circulation and the subsequent location
of the heaviest precipitation on Friday. The consensus of today`s
model suite in comparison to the past two days of model data would
present the heaviest precipitation along the Continental Divide,
and perhaps even into northwest Montana Friday morning. Then on
Friday afternoon, a second wave rotating around the main upper
level low will help initiate showers and thunderstorms first
across central Idaho, spreading across western Montana into Friday
evening. Key impacts will likely be heavy rainfall and perhaps
some lightning associated with the strongest thunderstorms.
Saturday should be a rather nice day with temperatures warming to
near normal. However, there will be a continued threat for some
scattered afternoon showers. But then on Sunday, models bring in
yet another atmospheric disturbance to help produce more
widespread showers and some thunderstorms across the Northern
Rockies. The GFS depicts a slower timing with the passage of that
disturbance lasting into Monday as well. Beyond Monday, the
forecast becomes increasingly complex and highly volatile to
change. But the overall theme will be continued chances for
showers and thunderstorms, with temperatures no warmer than normal
and likely below normal throughout the week.
&&
.AVIATION...Rain with embedded thunderstorms continue to stream
across central Idaho and across west central and NW Montana this
morning. Precipitation will continue to fill in as the day
unfolds, with heavy rain affecting all terminals. This will cause
periodically lowered ceilings and visibility, with gusty winds
also increasing by this afternoon. By nightfall, high mountain
terrain will begin to receive snowfall, especially across NW
Montana. Mountains will become shrouded in thick cloud cover and
falling snow, with elevations below 5000 feet will receive rain,
or a rain/snow mix through Thursday morning.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Allegretto/Dickerson
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000
FXUS65 KMSO 212043
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
243 PM MDT Tue May 21 2013
...Gusty winds with thunderstorms this afternoon and evening...
...Much colder air to produce snow over Lookout Pass and even
Libby and Yaak...
...Rain and high elevation snow through Friday...
.DISCUSSION...The first in a series of cold fronts is passing
through eastern Oregon and Washington this afternoon. Warm
afternoon temperatures and the cold front passage will bring
showers and thunderstorms through north central Idaho and western
Montana beginning this afternoon. Gusty winds will initially be
the main threat with thunderstorms through this evening.
Much colder air will follow the cold front especially into north
central Idaho and northwest Montana. There is a good chance that rain
will change to snow in northwest Montana Wednesday morning.
Locations of main concern for snow are in the vicinity of Libby
and Yaak and over Lookout Pass. Accumulations are not expected
initially but may begin to accumulate through Wednesday morning.
Precipitation will enhance in the afternoon on Wednesday and there
is the potential for slushy accumulations especially over Lookout
Pass. At this time snow is not forecast for Kalispell, and
locations to the south, but if the low track changes snow may
become possible.
A low pressure system aloft should direct surges of moisture
northward across mainly western Montana Thursday into Friday.
There are at least two significant waves of precipitation. The
first arrives Wednesday night and then a stronger wave hitting
Thursday night and Friday. There is some uncertainty regarding the
location of the heaviest precipitation with the GFS further west
over the Bitterroots northward across the Flathead and the NAM and
ECMWF a bit further east over the continental divide from Wisdom
northward across Bob Marshall and Glacier Park. One way or the
other, Glacier Park southward to McDonald Pass should see
significant precipitation. Snow levels should generally be around
5000 to 6000 feet. However, at night or within heavier shower
cores, the snow level may briefly go down to valley floors, such
as Seeley Lake, Swan Lake and in the vicinity of the Park. In the
higher terrain, heavy snow is expected with 1 to 2 feet possible
in the terrain of Glacier Park by Friday.
Besides the moisture from the weather system over Montana, the
other concern is the very cool air mass that will settle over
northern Idaho and western Montana. Partial clearing may occur
Wednesday night, Thursday night and Friday night allowing areas of
frost. Locations that may be most susceptible to frost include
Grangeville, Pierce, Libby, and Thompson Falls.
The main low pressure system should shift northward into Canada
Friday. However, another trough of low pressure and relatively
cool and unsettled air mass should settle over the region for the
Memorial Weekend.
&&
.AVIATION...High resolution model data show isolated showers and
thunderstorms this afternoon, but by this evening a more defined
line of thunderstorms is forecast to form. Showers with isolated
thunderstorms are already developing ahead of the cold front that
is passing through Washington and Oregon. The main threats with
thunderstorms will be very gusty winds and small hail. As the sun
sets this evening and thunderstorms die off, rainfall will spread
across central Idaho and then western Montana overnight tonight.
Snow levels will lower behind the cold front tonight with snow
possible to the valley floors of northwest Montana. Low cloud
decks and visibility will be common during the day Wednesday.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
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000
FXUS65 KMSO 210947
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
347 AM MDT Tue May 21 2013
...Thunderstorms possible this afternoon/evening...
...Persistent rainfall, in addition to high terrain snowfall, expected
Wednesday and Thursday...
.DISCUSSION...The first half of today should begin fairly
pleasant, which will be rather deceiving since the evening and
overnight hours will be quite a departure from this morning`s
weather. Cloud cover will steadily increase, with winds kicking up
across all of western Montana and central Idaho. As the winds help
to mix out the atmosphere, temperatures will warm to near 80
degrees in many valley locations this afternoon. The atmosphere
will then destabilize and allow a scenario ripe for thunderstorms,
some potentially strong and damaging, especially across Lincoln
County in northwest Montana. This will be the favored region for
thunderstorm development, however most of the Northern Rockies
could see a storm or two through this evening.
Tonight, the cut off low pressure system advertised in previous
forecasts to bring heavy rainfall to the region will begin more
fully impact central Idaho. Rain will spread across west central
Montana Wednesday morning, and very literally remain stationary
through Thursday as well. By later in the day Thursday, rain will
finally shift north into Alberta.
During the Wednesday-Thursday time frame, over one inch of rainfall
has the potential to fall across Glacier Park and surrounding
terrain, while the rest of Flathead County and Lincoln County
could see between 0.75 and 1.00 inch of rainfall. In addition, 2 to
4 inches of snowfall could coat the higher terrain across
northwest Montana, as temperatures and snow levels take a
significant dive.
Forecast models are struggling with how to handle each push of
energy ejecting off the parent coastal cut off low pressure system
beginning Thursday night and continuing through the weekend. Thus
have made only minimal changes to the overall forecast which had
above normal chances for precipitation continuing through the
weekend. In addition to periodic chances for showers, there will
also be at least a slight chance for thunderstorms each afternoon.
But the flow remains modest at best and with abundant moisture
around expect the key impact (aside from lightning) to be
occasional moderate rainfall, which could hamper weekend plans.
Temperatures will show a gradual warming trend with values working
their way back up to around normal for late May.
Some model consistency remains regarding the dissipation of that
stubborn cut off low with models each showing it expanding into a
broad, coastal trough by the start of next week. This should
promote a continued gradual warming trend but also keep a steady
stream of Pacific moisture moving across the Northern Rockies.
&&
.AVIATION...Clear skies and calm winds will be present this
morning, but the Northern Rockies will see a change as today
progresses. Cloud cover will thicken and lower, with south to
southeast winds increase, some gusts to 30 to 35 mph through this
evening. Thunderstorm potential will also increase this afternoon
and evening, especially for KGPI and northwest Montana airfields.
Thunderstorms that do develop could be locally strong, causing
very gusty winds and small hail. As the sun sets this evening and
thunderstorms die off, rainfall will spread across central Idaho
and then western Montana overnight tonight. Low cloud decks and
visibility will be common during the day Wednesday.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Dickerson/Allegretto
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