Winter Storm in Utah, January 27 to 29, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1041 PM MST SAT JAN 26 2013

.SYNOPSIS...A BROAD PACIFIC NORTHWEST TROUGH WILL PUSH A COLD
FRONT INTO AND THROUGH THE FORECAST AREA SUNDAY. HIGH PRESSURE IS
EXPECTED TO RETURN FOR THE MIDDLE TO LATTER PART OF THE WEEK.

&&

.DISCUSSION...SATELLITE IMAGERY SHOWS THE VORTICITY MAX THAT SPAWN
WIDESPREAD VALLEY RAIN/MOUNTAIN SNOW ACROSS SOUTHERN UTAH HAS
MOVED INTO NORTHWEST NEW MEXICO LATE THIS EVENING. THE WIDESPREAD
PRECIP IN THE WRAP AROUND BAND TO THE NORTH AND WEST OF THIS
FEATURE WILL EXIT UTAH LATER TONIGHT. ALLOWED THE WINTER WEATHER
ADVISORY FOR THE SOUTHERN MOUNTAINS TO EXPIRE AS ANY ADDITIONAL
SNOW AT HIGHER ELEVATIONS WILL BE MINIMAL. AN EXTENSIVE LOW CLOUD
FIELD TRAILING THIS EXITING STORM WILL BEGIN TO THIN OUT A BIT
ACROSS SOUTHWEST UTAH LATER TONIGHT. PATCHY FOG THIS EVENING COULD
RAPIDLY DEVELOP LATE TONIGHT...WITH AREAS OF DENSE FOG POSSIBLE BY
SUNDAY MORNING.

THE NEXT STORM SYSTEM TO IMPACT UTAH WILL REACH NORTHERN UTAH
SUNDAY. THE UPPER LEVEL TROUGH CURRENTLY OVER THE PACIFIC
NORTHWEST STATES WILL ENTER UTAH AS AN ELONGATED FEATURE
EXTENDING FROM THE NORTHERN ROCKIES ALL THE WAY INTO THE DESERT
SOUTHWEST LATE SUNDAY/SUNDAY NIGHT. THE ASSOCIATED SURFACE COLD
FRONT WILL REACH NORTHWEST UTAH SUNDAY MORNING...THEN EXIT TOE
STATE TO THE EAST LATE SUNDAY NIGHT.

CONVECTION...INCLUDING ISOLATED THUNDERSTORMS...HAS DEVELOPED ALONG
AND WELL AHEAD OF THE FRONT THIS EVENING. THIS CONVECTIVE EVIDENCE
OF DEEP LIFT ALONG WITH THE MODELS TREND TOWARDS STRONGER
FRONTOGENESIS SUGGESTS THIS FRONT WILL BE RATHER ACTIVE AS IT MOVES
THROUGH THE REGION SUNDAY. FAVORABLE JET SUPPORT ALSO INDICATES
GOOD DIVERGENCE ALOFT TO SUPPORT DEEP WINTER-TIME CONVECTION.
LOOKING AT A PERIOD OF INTENSE POST-FRONTAL SNOW...FOLLOWED BY
STEADIER SNOWFALL UNTIL THE MID-LEVEL TROUGH PASSAGE EARLY MONDAY.

THE LATEST GFS MAINTAIN A SOLUTION WHERE A DECENT SECONDARY SYSTEM
FOLLOWS ON MONDAY NIGHT/TUESDAY. STRONG AND MOIST WARM ADVECTION
WILL ENHANCE SNOW AGAIN UP NORTH MONDAY NIGHT...WITH PERIODS OF
HEAVY SNOW POSSIBLE UNTIL THIS SECOND SYSTEM PASSES TUESDAY
NIGHT. THE LATEST ECMWF IS NOT A STRONG AS THE GFS...BUT ALSO
OFFERS UP A DECENT SHOT OF PRECIP DURING THE SAME PERIOD.

UPDATE ISSUE EARLIER FOR AREAS OF FOG UP NORTH. REMAINDER OF THE
FORECAST LOOKS FINE FOR NOW.

THIS STRONG FRONT WILL LEND MORE SUPPORT TO THE SCOURING OUT OF
THE REMAINING VALLEY INVERSIONS ACROSS THE REGION SUNDAY
AFTERNOON/NIGHT.

&&

.AVIATION...CIGS AT KSLC ARE EXPECTED TO REMAIN PREDOMINANTLY IN THE
400-600 FT RANGE OVERNIGHT...BUT WILL SCATTER OUT AT TIMES. THERE IS
A 40 PERCENT CHANCE DENSE FOG DEVELOPS OVERNIGHT IF THIS STRATUS
LAYER SCATTERS OUT FOR LONGER THAN BRIEF PERIODS. SOUTHERLY WINDS
WILL INCREASE AROUND MIDDAY SUNDAY AHEAD OF AN APPROACHING COLD
FRONT...WHICH IS EXPECTED TO REACH THE TERMINAL DURING THE 20-22Z
TIMEFRAME. PERIODS OF HEAVY SNOW ARE POSSIBLE ALONG AND BEHIND THE
FRONT INTO SUNDAY EVENING.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY FROM 11 AM SUNDAY TO NOON MST MONDAY FOR
     UTZ001>005.

     WINTER WEATHER ADVISORY FROM 11 AM SUNDAY TO NOON MST MONDAY FOR
     UTZ006>009.

WY...NONE.
&&

PUBLIC...CONGER
AVIATION...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
322 PM MST SAT JAN 26 2013

UTZ001>016-019>021-517-518-WYZ021-272230-
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-
322 PM MST SAT JAN 26 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

VALLEY RAIN AND MOUNTAIN SNOW WILL CONTINUE TO SPREAD ACROSS
SOUTHERN UTAH THROUGH THIS EVENING. ACCUMULATING SNOWFALL IS
EXPECTED ACROSS THE SOUTHERN AND CENTRAL MOUNTAINS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

AN APPROACHING COLD FRONT WILL ENTER NORTHWEST UTAH BY SUNDAY
AFTERNOON...THEN SWEEP THROUGH THE ENTIRE STATE BY EARLY MONDAY.
RAIN AND SNOW SHOWERS WITH ISOLATED THUNDERSTORMS ALONG AND AHEAD
OF THE FRONT WILL TURN QUICKLY TO ALL SNOW BEHIND THE FRONT.
WIDESPREAD ACCUMULATING SNOW IS POSSIBLE...WITH THE HEAVIEST SNOW
ACROSS NORTHERN UTAH. SEVERAL INCHES OF SNOW ARE POSSIBLE IN THE
VALLEYS...WITH THE POTENTIAL FOR HEAVY SNOW IN THE NORTHERN
MOUNTAINS.

THE COLD FRONT WILL SERVE A DUAL PURPOSE IN THAT THE COLDER
TEMPERATURES AND WINDS THAT IT BRINGS WILL FINALLY SCOURER OUT
THE VALLEY INVERSIONS ACROSS THE NORTH. FOG AND HAZE SHOULD CLEAR
OUT...AND LIKELY NOT RETURN TO ANY GREAT DEGREE NEXT WEEK.

A SERIES OF WEAK WEATHER DISTURBANCES WILL GRAZE NORTHERN UTAH
DURING THE WEEK. NONE OF THESE ARE EXPECTED TO BRING MUCH SNOW...
BUT WILL BRING ADDITIONAL COLD AIR TO THE REGION.

.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