Winter Storm in Wyoming, December 6 to 8, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
303 PM MST THU DEC 6 2007

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
COLD FRONT EXTENDS FROM NORTHWEST TO SOUTHEAST WYOMING.  AREAS
OF SNOW CONTINUES ACROSS THE NORTH...AND WESTERN MOUNTAINS.
UPPER LOW MOVING INTO CALIFORNIA COAST WILL DEEPEN OVER THE GREAT
BASIN TONIGHT. COPIOUS PACIFIC MOISTURE EXTENDS FROM THE EASTERN
PACIFIC THROUGH CALIFORNIA...THE GREAT BASIN INTO WESTERN WYOMING.
THE COLD FRONT WILL PUSH SOUTH AS THE UPPER LOW AND MOISTURE MOVES
EAST AND NORTH. SNOW WILL BECOME WIDESPREAD ACROSS SOUTHERN
WYOMING LATE TONIGHT AND EARLY FRIDAY MORNING AND SPREAD RAPIDLY NORTH
INTO CENTRAL WYOMING. STRONG NORTH TO NORTHEAST WINDS WILL INCREASE
WITH THE SNOW WITH SIGNIFICANT WINTER STORM CONDITIONS DEVELOPING.
AREAS ACROSS NATRONA...FREMONT...SWEETWATER AND SOUTHERN LINCOLN COUNTY
MAY EXPERIENCE BLIZZARD CONDITIONS. AREAS ACROSS JOHNSON...HOT
SPRINGS AND SUBLETTE COUNTIES MAY REQUIRE SNOW ADVISORIES FOR
FRIDAY AND FRIDAY NIGHT. AT THIS TIME CONSIDER SNOWFALL AMOUNTS TO
BE ON THE CONSERVATIVE SIDE WITH THE WINTER STORM WATCH. IT IS
POSSIBLE FOR SNOWFALL AMOUNTS DOUBLE THE CURRENTLY FORECAST
AMOUNTS. WITH SO MUCH DEVELOPMENT LEFT TO OCCUR WITH THIS
STORM...DO NOT FEEL COMFORTABLE GOING WITH AMOUNTS NEAR 24 INCHES
BUT CASPER MOUNTAIN AND THE SOUTHERN WIND RIVER RANGE MAY GET
BLASTED.  TEMPERATURES WILL COOL SIGNIFICANTLY WITH BELOW ZERO TEMPERATURES
SATURDAY NIGHT. ROAD CLOSURES ARE HIGHLY LIKELY AS THIS WINTER STORM
GETS GOING. THIS IS EXPECTED TO HAVE SIGNIFICANT IMPACTS ACROSS
CENTRAL AND SOUTHERN WYOMING.

.LONG TERM...SUNDAY THROUGH THURSDAY

TAIL END OF DESERT SOUTHWEST LOW MAY KEEP SOME LIGHT SNOW ACROSS
SWEETWATER COUNTY INTO SUNDAY OTHERWISE IT SHOULD BE DRY AND COLD
BEHIND THE SIGNIFICANT SHORT TERM STORM SYSTEM. BRIEF SHORT WAVE
RIDGING MOVES IN SUNDAY NIGHT AHEAD OF WEAK CLIPPER BRUSHING THE
NORTH ON MONDAY AT LEAST WITH CURRENT 00Z GFS GUIDANCE WHICH IS
CONSISTENT WITH THE EURO MODEL. NEW 06Z GFS COMING IN ATTM HAS
DIFFERENT TIMING AND IS FURTHER WEST WITH THIS WAVE. WILL USE THE
00Z GFS RUN FOR THIS FORECAST PERIOD. RATHER DRY NW FLOW IS
EXPECTED TUESDAY AHEAD OF A POTENTIALLY MORE SIGNIFICANT WAVE ON
WEDNESDAY. FOR NOW HAVE JUST ADDED SOME LOWER GRADE POPS FOR
WEDNESDAY INTO WEDNESDAY NIGHT AND THURSDAY ACROSS THE NORTH AND
CENTRAL ZONES. TEMPERATURES SHOULD BE QUITE COLD SUNDAY AND SUNDAY
NIGHT BEHIND OUR FRIDAY/SATURDAY SYSTEM AND HAVE LOWERED
TEMPERATURES ACCORDINGLY WITH ROOM FOR FURTHER LOWERING IF SNOW
COVER SEEMS MORE IMMINENT. SOME MODERATION AFTER THAT AS LEE
TROUGHING DEVELOPS...ESPECIALLY FOR THE WIND CORRIDOR AND
EVENTUALLY SOME MORE CLOUD COVER AND WEDNESDAY SHORTWAVE.

&&

.AVIATION...

STORM SYSTEM CROSSING THE NORTHERN GREAT BASIN WILL BRING INCREASING
OVERRUNNING MOISTURE TO SOUTHERN AND CENTRAL WYOMING EARLY FRIDAY
THROUGH FRIDAY NIGHT. A COLD FRONT HAS MOVED SOUTHWARD ACROSS
NORTHERN WYOMING TODAY AND AT 21Z STRETCHED ACROSS THE BIGHORN BASIN
AND INTO NORTHERN NATRONA COUNTY. MVFR CIGS ALONG THE COLD FRONT
WILL PERSIST TONIGHT AT KCOD AND IFR CIGS WILL PERSIST AT KWRL.
WITH FRESH SNOWPACK AND LIGHT WINDS AT KWRL TONIGHT...FOG IS
EXPECTED TO FORM AFTER 10Z...LOWERING VSBYS TO ONE HALF OF A MILE AT
TIMES.
SNOW WILL BEGIN AT KRKS AT AROUND 05Z...AT KBPI AND KPNA AT AROUND
11Z AND KRIW...KLND AND KCPR AT AROUND 16Z. WINDS AHEAD OF THE
APPROACHING STORM WILL TURN TO THE NORTHEAST AND EAST AT LESS THAN
10 KT TONIGHT. EAST TO NORTHEAST WINDS WILL CONTINUE FRIDAY AT LESS
THAN 10 KT...BUT WILL INCREASE TO 12 TO 18 KT AT KCPR AND KRKS IN
THE AFTERNOON. WIDESPREAD IFR TO MVFR CONDITIONS ARE EXPECTED
FRIDAY...EXCEPT TO THE NORTH AND WEST OF THE STORM SYSTEM IN
KJAC...KWRL AND KCOD...WHERE MVFR CIGS IN LIGHT SNOW ARE POSSIBLE IN
THE AFTERNOON.

&&

.FIRE WEATHER...

AREAS OF SNOW AND STRONG WIND WILL INCREASE ACROSS THE AREA
THROUGH SATURDAY MORNING WITH COLDER TEMPERATURES AND HIGH HUMIDITY
EXPECTED. SNOWFALL OF 6 TO 12 INCHES...WITH LOCAL HIGHER AMOUNTS...
IS EXPECTED IN THE MOUNTAINS. WINTER STORM WATCHES ARE POSTED FOR
MOST OF SOUTHERN AND CENTRAL WYOMING FOR FRIDAY AND FRIDAY NIGHT.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY MORNING
FOR WYZ015-017-018-020-022.

WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING
FOR WYZ027>030.

WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY MORNING
FOR WYZ019.

&&

SHORT TERM...C.BAKER
LONG TERM...SKRBAC
AVIATION...SMITH
FIRE WEATHER...C.BAKER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
1243 PM MST THU DEC 6 2007

WYZ001>020-022>030-071200-
ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST-
BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS-
EAST SWEETWATER COUNTY-FLAMING GORGE-
GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS-
NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN-
NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS-
ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES-
SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN-
SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY-
TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN-
UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN-
WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST-
YELLOWSTONE NATIONAL PARK-
1243 PM MST THU DEC 6 2007

...WINTER STORM WATCH IN EFFECT FOR CENTRAL AND EASTERN FREMONT
COUNTY FROM 11 AM MST FRIDAY THROUGH 8 AM MST SATURDAY...

...WINTER STORM WATCH IN EFFECT FOR MUCH OF SWEETWATER COUNTY FROM 5
AM MST FRIDAY THROUGH 8 AM MST SATURDAY...

...WINTER STORM WATCH IN EFFECT FOR THE GREEN MOUNTAIN AND
RATTLESNAKE RANGES FROM 8 AM FRIDAY THROUGH 8 AM MST SATURDAY...

...WINTER STORM WATCH IN EFFECT FOR NATRONA COUNTY FROM 11 AM MST
FRIDAY THROUGH 8 AM MST SATURDAY...

...WINTER STORM WATCH IN EFFECT FOR SOUTH LINCOLN COUNTY FROM 5 AM
MST FRIDAY THROUGH 8 AM MST SATURDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

SNOW WILL BE FOUND ACROSS THE WESTERN MOUNTAINS AND IN PORTIONS OF
THE BIG HORN BASIN THIS AFTERNOON...WITH AN ADDITIONAL 1 TO 2 INCHES
EXPECTED BY THIS AFTERNOON. STRONGER WINDS WILL BE PRESENT ACROSS THE
WEST AS WELL...THOUGH WILL BE THE STRONGEST OVER THE ABSAROKA AND
WIND RIVER MOUNTAIN RANGES. SNOWFALL TO TAPER OFF DURING THE EVENING
HOURS TONIGHT...THOUGH THERE WILL STILL BE SOME LIGHT SNOW SHOWERS
OVER WESTERN WYOMING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A STRONG WINTER STORM IS EXPECTED TO MOVE INTO THE NORTHERN
GREAT BASIN LATE TONIGHT AND SPREAD INTO SOUTH CENTRAL WYOMING ON
FRIDAY. SNOW WILL SPREAD NORTH THROUGH THE MORNING HOURS OF FRIDAY...
AND WILL IMPACT SWEETWATER AND SOUTH LINCOLN COUNTY IN THE PRE-DAWN
HOURS...AND INTO EASTERN AND CENTRAL FREMONT...AND NATRONA COUNTIES
BY FRIDAY AFTERNOON. SNOW...POSSIBLY HEAVY AT TIMES...WILL CONTINUE
INTO THE MORNING HOURS OF SATURDAY. SNOWFALL ACCUMULATIONS OF 5 TO 8
INCHES ARE ANTICIPATED ACROSS THE LOWER ELEVATIONS OF THE WATCH AREA
BY SATURDAY MORNING...WITH 12 INCHES POSSIBLE OVER CASPER MOUNTAIN
AND THE HIGHER ELEVATIONS IN SOUTHERN WYOMING. ADDITIONALLY...
SUBLETTE COUNTY MAY SEE 3 TO 5 INCHES OF SNOWFALL BY SATURDAY
MORNING. THE EXACT DETAILS OF THIS STORM SYSTEM IS STILL UNCERTAIN SO
STAY TUNED FOR FUTURE WATCHES...WARNINGS AND ADVISORIES. THIS STORM
WILL CREATE SNOWPACKED ROADWAYS WITH SIGNIFICANT BLOWING AND DRIFTING
OF SNOW ALSO POSSIBLE...INCLUDING INTERSTATE 80 THROUGH SWEETWATER
COUNTY...INTERSTATE 25 THROUGH NATRONA COUNTY AND ROUTES 287 AND 28
IN FREMONT COUNTY. MOTORISTS SHOULD EXPECT HAZARDOUS DRIVING
CONDITIONS...AND VERIFY ROAD CONDITIONS BEFORE LEAVING.  STAY TUNED
FOR DAILY UPDATES ON THIS WEATHER SCENARIO.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS TODAY AND TONIGHT.
THANK YOU.

TEAM RIVERTON