Blizzard in Wyoming, February 1, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
317 AM MST THU FEB 01 2007

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT

9 AM UPDATE...COLD FRONT RAPIDLY ADVANCING SOUTH ACROSS WYOMING
A BIT QUICKER THAN ANTICIPATED.  NORTH TO NORTHEAST WINDS
HAVE INCREASED AS EXPECTED BEHIND THE FRONT CREATING BLOWING AND
DRIFTING CONDITIONS WITH SIGNIFICANT REDUCTIONS IN VISIBILITY...
ESPECIALLY AROUND BUFFALO.  SNOWFALL HAS ALSO BEGUN A BIT EARLIER
THAN EXPECTED. EXPECTING SOME AREAS TO REACH ADVISORY CRITERIA...SUCH
AS JOHNSON COUNTY...LANDER FOOTHILLS AND ADJACENT MOUNTAINS...AND
MUCH OF SWEETWATER COUNTY. WILL ISSUE ADVISORY FOR SNOWFALL AND THE
BLOWING AND DRIFTING CONDITIONS THROUGH 6 PM THIS EVENING.  MAY LAST
A BIT LONGER IN SWEETWATER COUNTY...AND WILL ADJUST THIS TIMING IN
THE AFTERNOON IF NEED BE.

INITIAL DISCUSSION...
NEXT STORM SYSTEM HEADING ACROSS MONTANA EARLY THIS MORNING. MODELS
IN GOOD AGREEMENT WITH MOVING THIS SYSTEM ACROSS THE STATE TODAY AND
BRINGING IN NORTH TO NORTHWEST FLOW FOR THE NEXT DAY OR TWO AFTER
FRONTAL PASSAGE. FRONT WILL MOVE FAIRLY FAST ACROSS THE STATE WITH A
QUICK 1 TO 2 INCHES OF SNOWFALL EXPECTED ACROSS THE VALLEYS AND 3 TO
6 INCHES OVER THE MOUNTAINS. SOME OF THE AREA FOOTHILLS COULD SEE 2
TO 4 INCHES BEFORE THE SYSTEM MOVES INTO COLORADO. BEHIND THIS SYSTEM
EXPECT VERY COLD TEMPERATURES WITH LOWS FRIDAY MORNING OF 20 TO 30
BELOW ZERO ACROSS THE WEST AND 10 TO 15 BELOW EAST OF THE DIVIDE.
WINDS TO BE ON THE BREEZY TO WINDY SIDE AHEAD AND BEHIND THE FRONT.
THIS SHOULD BRING SOME BLOWING AND DRIFTING SNOW OVER OUR FAVORED
LOCATIONS. NORTHERLY FLOW OVER THE STATE FRIDAY INTO SATURDAY WILL
CONTINUE CHANCES OF SNOW ACROSS THE NORTHWESTERN AND BIGHORN
MOUNTAINS. EXPECT TEMPERATURES TO REMAIN COLD OVER THE AREA FOR THE
NEXT FEW DAYS AS VALLEY INVERSIONS TRAP THE COLD AIR.

.LONG TERM...SUNDAY THROUGH THURSDAY
LONG RANGE MODELS SEEM TO BE AGREEMENT SUNDAY THROUGH TUESDAY WITH
RESPECT TO NW FLOW ALOFT. MOISTURE IN THE FLOW WILL BRING PERIODS OF
LIGHT SNOW TO THE WESTERN MTS AND BIGHORN MTS SUNDAY AND MONDAY WITH
LITTLE LESS ACTIVITY ON TUE. NOT MUCH PRECIP EXPECTED EAST OF THE
CONTINENTAL DIVIDE. THUS LOWERED PRECIP CHANCES MON AND TUE IN THESE
AREAS. HAVE OPTED FOR DRY FORECAST WED AND THU AS UPPER RIDGE GETS
NUDGED EASTWARD INTO ROCKY MTN REGION. THINKING IS THAT GFS IS TOO
FAST WITH WEATHER SYSTEM BLASTING THROUGH RIDGE BY NEXT THU
AFTERNOON. PLENTY OF TIME TO MONITOR IN COMING NIGHTS. AS FOR
TEMPS...700MB TEMPS ARE TO GRADUALLY WARM SUNDAY THROUGH WEDNESDAY.
THUS NORMAL AREAS THAT MIX WILL SEE WARMING AND THE MTS AS WELL.
THE SNOW COVERED BASINS WILL STILL HAVE TO OVERCOME INVERSION WHICH
WILL LIKELY SHARPEN WITH TIME. CURRENT TREND IN THE FORECAST LOOKED
GOOD AND MADE SOME LOCAL MODIFICATIONS BASED ON RECENT WEEKS OF THE
INVERSION.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...SNOW ADVISORIES THROUGH 6 PM
TODAY FOR WYOMING ZONES 8-11...15...17-19...28...30.

&&

SHORT TERM...HD/TWB
LONG TERM...RIW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
400 AM MST THU FEB 1 2007

WYZ001>020-022>030-021300-
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-
400 AM MST THU FEB 1 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

A STORM SYSTEM WILL HIT THE STATE DURING THE DAY TODAY AND LINGER
INTO THE EVENING ACROSS THE SOUTHERN SECTIONS WITH MOST AREAS SEEING
A PERIOD OF SNOWFALL. THE MOUNTAINS WILL LIKELY SEE 3 TO 6 INCHES.
THE LOWER ELEVATIONS WILL LIKELY SEE 1 TO 2 INCHES WITH UP TO 4
INCHES NEAR THE FOOTHILLS. STRONG NORTH WINDS OF 25 TO 35 MPH WITH
GUSTS TO 45 MPH ARE LIKELY TODAY AND TONIGHT WHICH WILL CAUSE AREAS
OF BLOWING AND DRIFTING SNOW AND BITTER COLD WIND CHILLS OF 20 TO 30
BELOW ZERO. CHECK THE LATEST ROAD AND WEATHER REPORT BEFORE
TRAVELLING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE VERY COLD AIR POURING DOWN INTO WYOMING WILL LIKELY MAKE FRIDAY
MORNING ONE OF THE COLDEST DAYS SO FAR THIS WINTER. LOWS FRIDAY
MORNING ACROSS THE WESTERN VALLEYS AND BASINS WILL LIKELY DIP TO 20
TO 30 BELOW ZERO...WITH LOWS OF 10 TO 20 BELOW ZERO ELSEWHERE.
ANOTHER COLD MORNING IS IN STORE FOR SATURDAY MORNING BUT THE
COMBINATION AND CLOUD COVER AND AREAS OF GUSTY WIND COULD HOLD SOME
OVERNIGHT LOWS ABOVE FRIDAY MORNINGS LOWS.

PLEASE BE PREPARED FOR BITTER COLD WEATHER CONDITIONS THROUGH
SATURDAY MORNING.

SPOTTER INFORMATION STATEMENT...

SPOTTERS SHOULD REPORT ANY SNOWFALL AMOUNTS TODAY AND TONIGHT.
SPOTTERS MAY ALSO WISH TO REPORT EXTREME COLD TEMPERATURES FRIDAY
MORNING. THANKS.

TRIW