Winter Storm Warning 23, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
221 PM MDT SUN MAR 22 2009

SHORT TERM...TONIGHT THROUGH WEDNESDAY
CLASSIC EARLY SPRING STORM IS BEGINNING TO TAKE SHAPE JUST TO OUR
WEST. EXPLOSIVE DEVELOPMENT IS EXPECTED AS THIS SYSTEM MOVES INTO
WYOMING AND NRN COLORADO TONIGHT AND BEGINS TO INTERACT WITH AN
INCREASING MOIST ATMOSPHERE OVER THE WRN HIGH PLAINS. SLY WINDS IN
THE PLAINS HAVE CREATED SURGING DEW POINTS WITH LOWER 60S INTO
SRN KS AND 50S INTO CENTRAL NE AND UPPER 40S IN WRN NE. GULF IS
WIDE OPEN AND MOISTURE WILL CONTINUE TO INCREASE. THE COMBINATION
OF THIS JUICY AIR TO THE EAST AND ABNORMALLY COLD TROUGH OVER THE
GREAT BASIN ADDS UP TO RAPID CYCLOGENESIS TONIGHT OVER CENTRAL
WYOMING AND EVENTUALLY NERN COLORADO. MID LEVEL CIRCULATION WILL
MOVE RIGHT OVER RIVERTON TONIGHT BEFORE THE SYSTEM STRENGTHENS AND
STACKS OVER NERN COLORADO BY MORNING. COLD NLY SURGE WILL DEVELOP
AS THIS HAPPENS WHICH WILL TURN ANY RAIN OVER TO SNOW. STRONG MID
LEVEL FRONTOGENESIS...JET STREAK DYNAMICS...INCRG QG FORCING AND
EVEN SOME BRIEF ISENTROPIC UPGLIDE WILL PRODUCE MODERATE TO HEAVY
PCPN IN THE WARNED AREAS. EVEN THE WEST WILL SEE SOME MODERATE
ACCUMULATIONS AS CONVECTIVE SNOW SHOWERS THIS EVEN WITH EMBEDDED
THUNDERSNOW TRANSITIONS TO MORE STRATIFORM MONDAY MORNING IN
DEVELOPING NW FLOW. HAVE ALSO ADDED SOME ADVISORIES OUT WEST TO
COVER THIS...ESPECIALLY NW FAVORED AREAS INTO AT LEAST MONDAY
MORNING...IE ALPINE...THAYNE AND BEDFORD AREA. INTENSE SURFACE LOW
AND NLY COLD SURGE WILL PRODUCE SIGNIFICANT WINDS CREATING
BLIZZARD CONDITIONS IN JOHNSON COUNTY BY MORNING AND NEAR BLIZZARD
CONDITIONS ELSEWHERE AT TIMES... ESPECIALLY OPEN AREAS FROM
RIVERTON TO NORTH OF CASPER ALONG INTERSTATE 25. DEBATED A
BLIZZARD WARNING FOR THE CASPER ZONE BUT SINCE ANY BLIZZARD
CONDITIONS WILL LIKELY BE LIMITED TO THE OPEN AREA NORTH OF TOWN
WILL JUST HIT THIS IN THE STATEMENT. SNOWFALL AMOUNTS WILL BE HARD
TO MEASURE WITH ALL THE BLOWING AND DRIFTING BUT GENERAL IDEA OF 6
TO 12 FOR MANY AREAS STANDS WITH 10 TO 15 IN LANDER AND CASPER
WITH UP TO 18 INCHES NEAR CASPER MOUNTAIN. THE EAST THROUGH NORTH
FACING MOUNTAIN SLOPES OF CENTRAL WYOMING WILL SEE 1 TO 2 FEET
WITH MORE POSSIBLE ON CASPER MOUNTAIN WHERE OVER 2 FEET IS QUITE
POSSIBLE. JOHNSON COUNTY CAN EXPECT SUSTAINED NORTH WINDS OF 35 TO
45 MPH WITH GUSTS OF 50 TO 60 MPH CAUSING SERIOUS OR IMPOSSIBLE
TRAVEL. MANY OTHER AREAS WILL SEE NORTH WINDS OF 20 TO 35 MPH WITH
GUSTS OVER 40 MPH. AREAS NORTH OF CASPER WILL LIKELY SEE SUSTAINED
WINDS OF 25 TO 35 MPH WITH GUSTS OF 40 TO 50 MPH.

THIS SYSTEM MOVES SLOWLY EAST OF THE AREA LATER MONDAY EVENING.
STILL SOME SIGNATURE THAT SNOW WILL LINGER AROUND LANDER AND FORT
WASHAKIE INTO THE EVENING IN CONVERGENT SIGNATURE AND THIS WILL HAVE
TO BE WATCHED. ANOTHER AREA WHERE SNOW WILL LINGER IN FROM NEAR
SOUTH PASS AND FARSON SOUTH TO NEAR ROCK SPRINGS WHERE OTHER SURFACE
TO H7 CONVERGENCE BOUNDARY MAY DEVELOP. OTHERWISE...GRADUAL
IMPROVEMENT OVERNIGHT BUT WITH STRONG WIND CONTINUING IN THE ERN
ZONES. NEXT SYSTEM APPROACHES RAPIDLY TUESDAY INTO TUESDAY NIGHT
WITH INCREASING CHANCES OF SNOW OUT WEST. IT APPEARS THIS MAY EVEN
TURNED INTO A CLOSED CIRCULATION NEAR OVER JUST TO OUR WEST JUST
BEYOND THE SHORT TERM. FOR NOW...HAVE INCREASED POPS OUT WEST TO
LIKELY AS EARLY AS TUESDAY THROUGH THE DAY WEDNESDAY AND INCREASED
THE POPS TO CHANCE EAST OF THE DIVIDE ON WEDNESDAY.

TIME TO PREPARE NOW FOR THIS UPCOMING EARLY MARCH SNOWSTORM...
BLIZZARD. TRAVELLERS...RANCHERS AND OTHERS WITH OUTDOOR INTERESTS
SHOULD PAY CLOSE ATTENTION TO THE WEATHER AND MAKE THE NECESSARY
PRECAUTIONS.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
FORECAST CHALLENGES CONTINUE IN THE EXTENDED WITH BOTH PCPN AND
TEMPS. LOOKS LIKE NWLY FLOW ALOFT WILL DOMINATE MOST OF THE
EXTENDED PERIOD OVER WEST CENTRAL WYOMING. JET ENERGY EXPECTED TO
DIG OVER WESTERN WYOMING DURING THE DAY ON WEDNESDAY. UPSLOPE FLOW
TO REESTABLISH ITSELF EAST OF THE DIVIDE BY WEDNESDAY AFTERNOON
AND EVENING. CLOUDS WILL INCREASE FOR SURE WITH A CHANCE FOR SNOW
THROUGH EARLY THURSDAY. AS A RESULT...BUMPED UP POPS A BIT BUT
LATER SHIFTS MAY WANT TO HIT POPS A BIT HARDER SPCLY OVER SE PARTS
OF RIVERTON CWA. THIS SHORT WAVE COULD END UP BEING STRONGER THAN
CURRENTLY ADVERTISED.

LIGHT SNOW OR FLURRIES THEN TO MOVE OUT OF FORECAST AREA ON THURSDAY
WITH SURFACE HIGH BUILDING IN. RESULT SHOULD BE CLEARING AND COLD FOR
THURSDAY NIGHT. IN FACT...TEMPS ACROSS ENTIRE CWA TO REMAIN BELOW
NORMAL INTO FRIDAY. WILL THEN GO WITH GFS SOLUTION FROM FRIDAY INTO
NEXT WEEKEND WITH THE AFOREMENTIONED NWLY FLOW ALOFT RESULTING IN
SCT SNOW SHOWERS OVER THE FAR NORTHWEST AND WESTERN MOUNTAINS OF
WYOMING...BUT MAINLY DRY AND BREEZY ELSEWHERE.

AVIATION...
PREVAILING VFR CONDITIONS WILL RAPIDLY DETERIORATE THIS EVENING OVER
WESTERN WYOMING AND AFTER APPROXIMATELY 04Z MONDAY OVER CENTRAL
PORTIONS OF THE STATE. A MAJOR PACIFIC STORM SYSTEM WILL MOVE
TOWARD THE REGION THIS EVENING...BRINGING NUMEROUS RAIN AND MOUNTAIN
SNOW SHOWERS TO WESTERN WYOMING THIS EVENING AND WIDESPREAD RAIN AND
MOUNTAIN SNOW TO CENTRAL AREAS BETWEEN ABOUT 06Z AND 09Z MONDAY. THE
RAIN WILL CHANGE TO SNOW AFTER ABOUT 09Z MONDAY IN THE CENTRAL
BASINS. WIDESPREAD IFR WITH AREAS OF LIFR CONDITIONS IN MODERATE TO
HEAVY SNOW ARE EXPECTED EAST OF THE DIVIDE FROM ABOUT 09Z THROUGH AT
LEAST 18Z MONDAY. SCATTERED IFR WITH ISOLATED LIFR CONDITIONS IN
SNOW SHOWERS ARE ANTICIPATED ELSEWHERE.

FIRE WEATHER...
MAJOR WINTER STORM TO IMPACT MUCH OF THE AREA TONIGHT THROUGH MONDAY.
SNOW SHOWERS AND EVEN THUNDERSTORMS WILL HIT THE AREA THROUGH THIS
EVENING BEFORE THE STORM GAINS FURTHER STRENGTH AND CREATES
WIDESPREAD SNOW AND STRONG WIND. THE STRONG WIND WILL BE MAINLY
EAST OF THE DIVIDE WHERE BLIZZARD CONDITIONS ARE EXPECTED FROM
NORTH OF CASPER TO BUFFALO. OTHER AREAS IN CENTRAL WYOMING WILL
ALSO SEE STRONG NORTH WIND AND PLENTY OF SNOW.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM MDT
MONDAY FOR WYZ030.

WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT MONDAY
FOR WYZ005-007-009-015-017>019.

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON MDT
MONDAY FOR WYZ012-023-024-027-028.

BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO 9 PM MDT MONDAY FOR
WYZ010-011.

WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON MDT MONDAY
FOR WYZ002-003.

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM MDT
MONDAY FOR WYZ001.

WINTER STORM WARNING FROM 3 AM TO 9 PM MDT MONDAY FOR WYZ020-022.

&&

SHORT TERM...SKRBAC
LONG TERM...KPL
AVIATION...CHURCH
FIRE WEATHER...SKRBAC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
428 AM MDT SUN MAR 22 2009

WYZ001>020-022>030-222200-
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-
428 AM MDT SUN MAR 22 2009

...AN ASSORTMENT OF WINTER WEATHER HIGHLIGHTS COVER MUCH OF WEST
CENTRAL WYOMING LATE TONIGHT THROUGH MONDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY

ISOLATED TO WIDELY SCATTERED SHOWERS WILL SPREAD ACROSS
WYOMING TODAY. A FEW RUMBLES OF THUNDER ARE ALSO
POSSIBLE THIS AFTERNOON ALONG WITH GUSTY SOUTHWEST WINDS.

.DAYS TWO THROUGH SEVEN...TONIGHT THROUGH SATURDAY

A STRONG PACIFIC STORM SYSTEM IS STILL EXPECTED TO MOVE INTO
THE REGION TONIGHT AND MONDAY. MUCH COLDER AIR WILL MOVE INTO WEST
CENTRAL WYOMING AND CLOUDS WILL BE ON THE INCREASE. THIS SYSTEM
WILL BRING MODERATE TO HEAVY SNOW POTENTIAL EAST OF THE CONTINENTAL
DIVIDE WHERE A SIGNIFICANT SNOWSTORM IS POSSIBLE...ESPECIALLY ACROSS
JOHNSON AND NATRONA COUNTIES BY MONDAY. THE COMBINATION OF SNOW AND
WIND WILL SEVERELY HAMPER TRAVEL AND OTHER OUTDOOR ACTIVITIES
THROUGH MONDAY EVENING.

SNOWFALL AMOUNTS OF 6 TO 12 INCHES ARE POSSIBLE WITH 1 TO 2 FEET FROM
CASPER MOUNTAIN TO THE EAST SLOPES OF THE WIND RIVER MOUNTAINS.
PLEASE SEE THE LATEST WINTER STORM STATEMENTS FROM THE NATIONAL
WEATHER SERVICE IN RIVERTON FOR MORE DETAILS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY...BUT BE PREPARED FOR A
SUDDEN CHANGE IN THE WEATHER TONIGHT.

TEAM RIVERTON