Winter Storm in Utah, November 22 to 24, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
953 PM MST THU NOV 21 2013

.SYNOPSIS...AN UPPER LOW DEVELOPING OVER SOUTHERN CALIFORNIA WILL
KEEP MOISTURE OVER CENTRAL AND SOUTHERN UTAH THROUGH THE
WEEKEND...AND WILL GENERATE AN EASTERLY FLOW OVER NORTHERN UTAH.

&&

.DISCUSSION...A MULTI-FACETED WINTER STORM EVENT IS UNDERWAY
ACROSS THE FORECAST AREA...AND WILL CONTINUE THROUGH THE NEXT 36
TO 48 HOURS.

ACROSS NORTHERN UTAH...A SIGNIFICANT DOWNSLOPE WIND EVENT IS
UNDERWAY...RESULTING FROM A COMBINATION OF STRONG LOW LEVEL COLD
ADVECTION EMANATING FROM WYOMING...VERY STRONG EASTERLY 700MB
FLOW...AND A TIGHT PRESSURE GRADIENT. THIS HAS RESULTED IN WIND
GUSTS AS HIGH AS 80 MPH THUS FAR ACROSS DAVIS COUNTY...AND
ANTICIPATE THESE STRONG WINDS WILL CONTINUE OVERNIGHT AS THE
DIURNAL CYCLE BECOMES MORE FAVORABLE. WINDS MAY ABATE A BIT LATE
FRIDAY MORNING INTO EARLY FRIDAY AFTERNOON...HOWEVER THE
INGREDIENTS WILL REMAIN SUPPORTIVE OF ANOTHER ROUND OF STRONG
WINDS LATE FRIDAY AFTERNOON INTO FRIDAY NIGHT ACROSS THESE SAME
AREAS. EARLIER SHIFT EXTENDED THE HIGH WIND WARNING AND THIS LOOKS
GOOD.

FURTHER SOUTH...THE UPPER LOW SPINNING ALONG THE SOUTHERN CA COAST
HAS DEVELOPED A SUBSTANTIAL MOISTURE TAP...AND THIS WILL REMAIN IN
PLACE THROUGH THE DAY FRIDAY AS THE PARENT LOW MOVES VERY LITTLE.
ADDITIONALLY...COLD AIR HAS SURGED SOUTH ACROSS SOUTHWEST UT...AND
SHOULD SPILL INTO THE EASTERN VALLEYS AS WELL OVERNIGHT. WITH THIS
LOW LEVEL COLD AIR IN PLACE ANTICIPATE SNOW LEVELS AT LEAST DOWN
TO 5 KFT IF NOT LOWER THROUGH THE WEEKEND. CURRENTLY BANDS OF SNOW
ARE LIFTING NORTH ACROSS SOUTHWEST UT EASTWARD INTO THE SOUTHERN
MOUNTAINS...AND ANTICIPATE THIS WILL CONTINUE OVERNIGHT.

WITH THE UPPER LOW MOVING VERY LITTLE OVER THE NEXT 24-36 HOURS A
PERSISTENT DIFFLUENT PATTERN COUPLED WITH STRONG MOISTURE
ADVECTION INTO SOUTH CENTRAL AND SOUTHWEST UTAH WILL PROVIDE A
VERY FAVORABLE SETUP FOR HEAVY SNOWFALL ACROSS SOUTHERN UT EAST OF
I-15...PARTICULARLY AREAS SUCH AS ESCALANTE AND CAPITOL REEF
NATIONAL PARK. CURRENTLY HAVE WINTER WEATHER ADVISORIES IN EFFECT
FOR THESE AREAS...AND THIS IS PROBABLY SUFFICIENT FOR THE WESTERN
VALLEYS...BUT MAY NEED TO BE UPGRADED ACROSS THE HIGHER TERRAIN
AND AREAS FURTHER EAST.

UPDATED EARLIER TO REMOVE POPS ACROSS NORTHERN UT AS PRECIPITATION
HAS DISSIPATED. NO ADDITIONAL UPDATES PLANNED THIS EVENING.

&&

.AVIATION...SURFACE WINDS ARE THE PRIMARY OPERATIONAL CONCERN AT
KSLC. THE PREDOMINANT WIND OVERNIGHT THROUGH FRIDAY IS EXPECTED TO
REMAIN SOUTHWEST...HOWEVER OCCASIONAL SURGES OF EASTERLY FLOW WILL
LIKELY REACH THE TERMINAL RESULTING IN TEMPORARY GUSTY EAST TO
SOUTHEAST WINDS. ADDITIONALLY...THE INCREASING EASTERLIES ALOFT
COULD RESULT IN LOW LEVEL WIND SHEAR OVERNIGHT INTO FRIDAY MORNING
DURING PERIODS OF SOUTHWESTERLY SURFACE WINDS.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY UNTIL 5 PM MST SATURDAY ABOVE 5000 FEET
     FOR UTZ013-020.

     HIGH WIND WARNING UNTIL NOON MST SATURDAY FOR UTZ002-003.

     WIND ADVISORY UNTIL NOON MST SATURDAY FOR UTZ001.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST SATURDAY FOR UTZ517-518.

     WIND ADVISORY UNTIL NOON MST FRIDAY FOR UTZ012-013.

     WINTER WEATHER ADVISORY UNTIL 11 AM MST FRIDAY FOR UTZ015-016.

WY...NONE.
&&

SEAMAN

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
500 PM MST THU NOV 21 2013

UTZ001>016-019>021-517-518-WYZ021-230000-
CACHE VALLEY/UTAH PORTION-NORTHERN WASATCH FRONT-
SALT LAKE AND TOOELE VALLEYS-SOUTHERN WASATCH FRONT-
GREAT SALT LAKE DESERT AND MOUNTAINS-WASATCH MOUNTAIN VALLEYS-
WASATCH MOUNTAINS I-80 NORTH-WASATCH MOUNTAINS SOUTH OF I-80-
WESTERN UINTA MOUNTAINS-WASATCH PLATEAU/BOOK CLIFFS-
WESTERN UINTA BASIN-CASTLE COUNTRY-SAN RAFAEL SWELL-
SANPETE/SEVIER VALLEYS-WEST CENTRAL UTAH-SOUTHWEST UTAH-
UTAHS DIXIE AND ZION NATIONAL PARK-SOUTH CENTRAL UTAH-
GLEN CANYON RECREATION AREA/LAKE POWELL-CENTRAL MOUNTAINS-
SOUTHERN MOUNTAINS-SOUTHWEST WYOMING-
500 PM MST THU NOV 21 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN TWO THIRDS OF
UTAH AND SOUTHWEST WYOMING.

.DAY ONE...THIS AFTERNOON AND TONIGHT

VERY STRONG EASTERLY WINDS ARE EXPECTED ALONG THE WASATCH FRONT
THROUGH TONIGHT...WITH GUSTS IN EXCESS OF 70 MPH EXPECTED FROM
WEBER COUNTY SOUTH TO NORTHEASTERN SALT LAKE COUNTY. STRONG EAST
TO NORTHEASTERLY WINDS GUSTING TO 55 MPH ARE ALSO EXPECTED THROUGH
TONIGHT IN THE CACHE VALLEY AND ALONG ROUTE 6 BETWEEN PRICE AND
GREEN RIVER IN EASTERN UTAH.

SNOW WILL CONTINUE TO IMPACT TRAVEL OVER MUCH OF CENTRAL AND
SOUTHERN UTAH ABOVE 5000 FEET THROUGH TONIGHT...INCLUDING ALONG
I-15 AND I-70. SNOW LEVELS COULD LOWER INTO THE SOUTHWESTERN
VALLEYS TONIGHT AND ACCUMULATING SNOW MAY IMPACT ALL ROUTES IN
THESE AREAS OVERNIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE STRONG EAST TO NORTHEAST WINDS ARE EXPECTED TO GRADUALLY
DIMINISH IN ALL AREAS LATE FRIDAY MORNING...BUT REDEVELOP ALONG
THE WASATCH FRONT AND CACHE VALLEY LATE FRIDAY AFTERNOON...AND
CONTINUE FRIDAY NIGHT INTO EARLY SATURDAY.

ACCUMULATING SNOW IS ALSO EXPECTED TO CONTINUE ACROSS MOST OF
SOUTHERN UTAH ABOVE 5000 FEET THROUGH SATURDAY. THIS SNOW MAY BE
PARTICULARLY HEAVY NEAR ESCALANTE AS WELL AS AREAS NEAR BOULDER
MOUNTAIN AND THE HENRY MOUNTAINS.

DRIER WEATHER WITH A WARNING TREND WILL RETURN FOR THE FIRST PART
OF NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR INFORMATION ON POTENTIAL TRAVEL IMPACTS VISIT...
HTTP://WWW.UDOTTRAFFIC.UTAH.GOV/ROADWEATHERFORECAST.ASPX