Freeze Warning 3, NWS Riverton, WY

330 
WWUS75 KRIW 061055
NPWRIW

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE RIVERTON WY
455 AM MDT TUE SEP 6 2016

...FREEZING TEMPERATURES WILL CONTINUE EARLY THIS MORNING...

.A CLEAR SKY AND LIGHT WIND WILL KEEP TEMPERATURES BELOW FREEZING PAST
SUNRISE THIS MORNING. IF HEADING OUTDOORS THIS MORNING...DRESSING
IN LAYERS IS STRONGLY ENCOURAGED.

WYZ013-023-061500-
/O.CON.KRIW.FZ.W.0003.000000T0000Z-160906T1500Z/
JACKSON HOLE-STAR VALLEY-
INCLUDING THE CITIES OF...JACKSON...AFTON...ALPINE...
STAR VALLEY RANCH...THAYNE
455 AM MDT TUE SEP 6 2016

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM MDT THIS MORNING...

* TEMPERATURE...25 TO 30.

* IMPACTS...SENSITIVE PLANTS MAY NEED TO BE COVERED OR TAKEN 
  INDOORS. THOSE GOING OUTDOORS IN THE MORNING SHOULD DRESS IN 
  LAYERS TO PROTECT THEMSELVES FROM THE COLD. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR
HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER
SENSITIVE VEGETATION.

&&

$$

WYZ025-026-061500-
/O.CON.KRIW.FZ.W.0003.000000T0000Z-160906T1500Z/
UPPER GREEN RIVER BASIN FOOTHILLS-UPPER GREEN RIVER BASIN-
INCLUDING THE CITIES OF...PINEDALE...LA BARGE...BIG PINEY...
FARSON
455 AM MDT TUE SEP 6 2016

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM MDT THIS MORNING...

* TEMPERATURE...25 TO 30...EXCEPT AROUND 20 NEAR BONDURANT.

* IMPACTS...SENSITIVE PLANTS MAY NEED TO BE COVERED OR TAKEN 
  INDOORS. THOSE GOING OUTDOORS IN THE MORNING SHOULD DRESS IN 
  LAYERS TO PROTECT THEMSELVES FROM THE COLD. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR
HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER
SENSITIVE VEGETATION.

&&

$$

WYZ016-061500-
/O.CON.KRIW.FZ.W.0003.000000T0000Z-160906T1500Z/
UPPER WIND RIVER BASIN-
INCLUDING THE CITY OF...DUBOIS
455 AM MDT TUE SEP 6 2016

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM MDT THIS MORNING...

* TEMPERATURE...30 TO 32.

* IMPACTS...SENSITIVE PLANTS MAY NEED TO BE COVERED OR TAKEN 
  INDOORS. THOSE GOING OUTDOORS IN THE MORNING SHOULD DRESS IN 
  LAYERS TO PROTECT THEMSELVES FROM THE COLD. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR
HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER
SENSITIVE VEGETATION.

&&

$$

TEAM RIVERTON

Area Forecast Discussion
National Weather Service Riverton WY
1058 AM MDT MON SEP 5 2016

.SHORT TERM...Today through Wednesday night

Main circulation is now over the southern Idaho/MT line as our CWA
sits underneath the disorganized baroclinic leaf. Convection over
the area continues with forcing from southwest difluent flow and
left front quad dynamics. The most prominent streak of thunderstorms
continue at the time of this writing on a track from eastern
Sweetwater County, across eastern Fremont County and into western
Natrona County, where a few earlier rounds of convection Sunday had
already dumped between one quarter to a half inch of rain in some of
those areas to locally over an inch according to radar estimates and
rain gage reports. In fact, many areas of the north half of the CWA
have reported close to one half inch of precip in the last 24
hours with YNP receiving anywhere from a few hundredths to locally
one quarter of an inch. The vort/circulation asct with the long
wave trough should swing by just to the northwest of YNP by 12z
this morning along with the troughpa. After the passage of the
trough/vort max, showers will become more focused across northern
WY later this morning in the form of frequent shower activity. The
cold air originating over the Gulf of Alaska will get a good shove
southeast toward Wyoming on the back side of the trough as it
exits to the northeast, allowing the snow level to drop to about
8k over NW WY and to between 9000 and 9500 feet over the Wind
River/Big Horn/Salts/WY Range by sunrise this morning. However,
the northwest mountains and YNP stand the best chance of receiving
additional wrap around rain/snow cold air cu showers today,
especially in areas that favor nw flow. The northern Star valley
could even experience rain/high elevation snow bands in the
favored nw flow if the showers make it that far south. Any snow
accumulations this morning will be on the light side since we have
already experienced the bulk of the precip from this particular
weather system. Patchy fog is expected to form in the Wind River
Basin this morning under clearing skies and damp ground. North of
there, showers and clouds will likely inhibit fog formation. In
addition to the scattered showers and isolated afternoon
thunderstorms in northern Wyoming today, we could see a narrow
strip of shower activity from Sweetwater County to Casper today as
the models want to spit out dew showers in that area, probably
due to the right entrance region of the exiting jet max today.
Some showers will linger this evening in the north and east
central zones as another reinforcing sfc boundary slides in from
the northeast with a deck of stratocu spilling in from Johnson Co
south into Natrona County this evening. High temperatures today
will be a tad bit milder in the northwest today with a bit less in
the way of clouds/precip but still on the cool side with highs
mainly in the 50s and 60s. Elsewhere, at the lower elevations, it
will be cool with highs in the 60s and 70s.

Will issue a freeze watch for the far west valleys and basins for
tonight/tuesday morning.

On Tuesday, the next shortwave riding down the backside of the long
wave trough will arrive late in the day resulting in a late show of
convection/thunderstorms from late afternoon into the evening,
mainly across the Big Horn Mtns and the lower elevations of Johnson
and Natrona counties as well as across the Wind Rivers, Absaroka
Mtns, and Casper Mtn, with the strongest activity in Johnson Co
where the best CAPES will be. This activity should last well into
Tuesday evening.

By Wednesday, we could see critical fire weather conditions taking
shape across Sweetwater County with west winds increasing to 20 to
30 mph along with the min RH down into the mid teens as the flow
becomes more zonal. Temperatures will gradually warm through mid
week.

.LONG TERM...Thursday through Monday

Synopsis...a cold front will spread some showers and
isolated thunderstorms into the north Thursday afternoon and
Thursday night. Windy and mild conditions will prevail on Thursday
across southern Wyoming. Dry weather with cooler temperatures
prevail on Friday behind the cold front. Milder and dry conditions
expected on Saturday with breezy to windy conditions across the
south half of Wyoming. A cold front is forecast to push into
northern Wyoming late Sunday and across the area Sunday night.
Much colder conditions with rain and mountain snow are possible
across north and central Wyoming Sunday night and Monday.

Discussion...ECMWF and GFS in good overall agreement through the
first part of the weekend, and then show increasing spread with
system digging digging into the northern Rockies Sunday and
Monday.

Longwave pattern on Thursday consists of upper high near
40N/145W with broad trough across the northern tier of the U.S.
Upper low currently off the SW Alaskan coast is expected to slide
SE into northern Montana Thursday, turning east into the northern
plains Thursday night. Only spotty showers/isolated thunderstorms
are expected to make it into northern Wyoming with this system
Thursday afternoon and night. Temperatures will be 5-8F cooler
behind the cold front on Friday across the north and central.

Fire weather conditions will become elevated once again on Saturday
with gusty west winds, a return to above normal temperatures and low
relative humidity across southern and central Wyoming.

An upper low currently over the Kamchatka peninsula is expected
to begin its journey eastward; into the Gulf of Alaska on Friday,
diving down front side of eastern Pacific ridge into the
Rockies/Great Basin late Sunday and Monday. ECMWF deterministic is
more progressive with this system, but both ECMWF and GFS ensemble
means hold a significant degree of troughing back across the
Great Basin, favoring the GFS deterministic solution of a good
portion of this system's energy dropping south along or west of
the divide, into the Great Basin. Confidence is still low this far
out, but this could shape up to be a significant rain, mountain
snow event Sunday night and Monday along and east of the
Continental Divide. GFS H7 temperatures are forecast to be -3c to
-4c east of the divide Monday morning, translating to snow levels
between 6500 and 7000 feet. Forecast goes with chance PoPs
spreading south Sunday night and Monday with highs in the 50s
across the north and central on Monday as a start for Day 8...yes,
it is still officially Summer.

&&

.AVIATION.../18Z ISSUANCE/

VFR conditions will prevail for most terminal sites through the
forecast period. The main concern will be isolated showers...mainly
across the northwest and northern mountains today. Also, there is
the possibility that some relatively high based isolated, convection
could impact areas between KRKS-KCPR between 22Z and 03Z Tuesday
associated with an upper jet streak. After 03Z, as a clipper front
moves south through eastern/central WY with some local MVFR ceilings
possibly impacting Johnson, Natrona or Fremont Counties after 06Z
Tuesday along with possibly some light rain showers near KCPR. Wind
shear will also be possible at/near KWRL from 04--9Z.

&&

.FIRE WEATHER...

Cooling temperatures this morning may result in some
snowfall over the northwestern zones and fires. Shower activity
should generally diminish by this afternoon, though some isolated
shower activity will redevelop over northern Wyoming late Tuesday
afternoon and evening. Temperatures will likely dip below freezing
in many locations in the far west valleys and basins of Wyoming
tonight and into Tuesday morning. Warming and mostly dry conditions
anticipated through Wednesday, with humidity decreasing across the
area. The combination of increasing west winds and minimum relative
humidity in the mid teens may result in critical fire weather
conditions for fire weather zone 279 on Wednesday afternoon and
early evening.

&&

.RIW Watches/Warnings/Advisories...
Freeze Watch from late tonight through Tuesday morning for
WYZ013-016-023-025-026.

&&

SHORT TERM...Lipson
LONG TERM...AEM
AVIATION...BRAUN
FIRE WEATHER...Lipson

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
333 AM MDT MON SEP 5 2016

WYZ001>020-022>030-061100-
YELLOWSTONE NATIONAL PARK-ABSAROKA MOUNTAINS-CODY FOOTHILLS-
NORTH BIG HORN BASIN-SOUTHWEST BIG HORN BASIN-
SOUTHEAST BIG HORN BASIN-OWL CREEK AND BRIDGER MOUNTAINS-
BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST-
NORTHEAST JOHNSON COUNTY-SOUTHEAST JOHNSON COUNTY-
TETON AND GROS VENTRE MOUNTAINS-JACKSON HOLE-
WIND RIVER MOUNTAINS WEST-WIND RIVER MOUNTAINS EAST-
UPPER WIND RIVER BASIN-WIND RIVER BASIN-LANDER FOOTHILLS-
GREEN MOUNTAINS AND RATTLESNAKE RANGE-
NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN-STAR VALLEY-
SALT RIVER AND WYOMING RANGES-UPPER GREEN RIVER BASIN FOOTHILLS-
UPPER GREEN RIVER BASIN-SOUTH LINCOLN COUNTY-
ROCK SPRINGS AND GREEN RIVER-FLAMING GORGE-EAST SWEETWATER COUNTY-
333 AM MDT MON SEP 5 2016

...FREEZE WATCH FOR THE WESTERN VALLEYS AND BASINS FOR LATE
TONIGHT THROUGH TUESDAY MORNING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL
WYOMING.

.DAY ONE...TODAY AND TONIGHT

SOME PATCHY FOG IS EXPECTED IN THE WIND RIVER BASIN THIS MORNING.
SCATTERED SHOWERS AND ISOLATED AFTERNOON THUNDERSTORMS ARE
EXPECTED MAINLY IN NORTHERN WYOMING TODAY AND THIS EVENING.
TEMPERATURES WILL LIKELY DIP TO BELOW FREEZING IN THE WESTERN
VALLEYS AND BASINS LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

TUESDAY...TEMPERATURES WILL LIKELY DIP TO BELOW FREEZING IN THE
WESTERN VALLEYS AND BASINS TUESDAY MORNING. WIDELY SCATTERED
THUNDERSTORMS ARE EXPECTED IN NORTHERN AND EAST CENTRAL WYOMING
LATE TUESDAY AFTERNOON AND EVENING.

WEDNESDAY AND THURSDAY...ELEVATED FIRE WEATHER CONDITIONS SOUTH
WITH WINDY, DRY AND WARM CONDITIONS.

SATURDAY...ELEVATED FIRE WEATHER CONDITIONS SOUTH AND CENTRAL WITH
BREEZY TO WINDY, WARM AND DRY CONDITIONS EXPECTED.

.SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT
ANY SNOWFALL OR RAINFALL AMOUNTS. THANK YOU.

TEAM RIVERTON