Flash Flood Watch 1, NWS Salt Lake City, UT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
337 AM MST SAT JAN 5 2008

.SYNOPSIS...STRONG MOIST PACIFIC STORM WILL MOVE THROUGH
THE REGION THIS WEEKEND AND INTO MONDAY.

&&

.DISCUSSION...WIDESPREAD PRECIPITATION OCCURRING ACROSS NORTHERN
AND SOUTHWEST UTAH AS THE STRONG PACIFIC SYSTEM AND COLD FRONT
ENTER WESTERN UTAH. SNOW HAS BEEN HEAVY IN THE NORTHERN AND SW
MOUNTAINS WILL LOCALLY HEAVY RAIN IN SOUTHWEST UTAH WITH SNOW
LEVELS ARE RUNNING NEAR 6500 FEET. COLD FRONT AND TRAILING MID
LEVEL BAROCLINIC ZONE ON TRACK TO CROSS NORTHERN UTAH THIS MORNING
AND THEN SHIFT INTO CENTRAL UTAH THIS AFTERNOON AND EVENING.
STRONG TO SEVERE WINDS HAVE DECREASED SOMEWHAT IN THE NORTH BUT
REMAIN IN WARNING CRITERIA. STRONG 50-60 KNOT 700 MB FLOW WILL
BE SHUNTED TO THE SOUTHEAST THIS MORNING. BESIDES THE CURRENT WINDS
THE MAIN ISSUE TODAY WILL BE RAIN CHANGING TO SNOW AND HEAVY FOR
A PERIOD IN THE NORTHERN VALLEYS...INCLUDING THE SANPETE VALLEY
AND UINTA BASIN. ALSO HEAVY RAIN WILL CONTINUE IN THE SOUTHWEST
THIS MORNING AND THEN BECOME MORE INTERMITTENT THIS AFTERNOON.
THUS THE POTENTIAL FOR SIGNIFICANT RUNOFF IS THERE AND WE WILL
ADDRESS WITH A FLASH FLOOD WATCH OVER MAINLY ZION PARK. WILL ALLOW
WIND WARNINGS TO TRANSITION INTO WINTER STORM THOUGH A PERIOD OF
RAIN WILL OCCUR THIS MORNING BEFORE SNOW LEVELS CRASH TO THE
VALLEY FLOOR IN THE NORTH.

WITH THE COLD FRONT THIS MORNING MODEL SOUNDINGS PROG STEEPENING
LAPSE RATES RATHER QUICKLY. MEAN FLOW SHIFTS TOWARDS WEST LATER
THIS MORNING AND INTO THE AFTERNOON AND DECREASES SIGNIFICANTLY.
STRONG JET CORE FORECAST TO DIVE ACROSS SOUTHWEST AND CENTRAL UTAH
TODAY. THUS BAROCLINIC ZONE HAS GOOD SUPPORT THROUGH THE AFTERNOON
AS IT DROPS SOUTHWARD AND SHOULD SLOW OVER CENTRAL UTAH THIS
EVENING WHILE BECOMING WARM AIR ADVECTION AHEAD OF THE NEXT
PACIFIC WAVE TONIGHT. WARM AIR ADVECTION SNOW WILL LIKELY SPREAD
INTO NORTHERN UTAH LATE TONIGHT WHILE MEAN FLOW INCREASES FROM THE
SOUTHWEST. A SECONDARY COLD FRONT WILL ARRIVE ON SUNDAY WHICH WILL
BRING ANOTHER BAND OF HEAVY SNOWFALL...FOCUSED FROM THE WASATCH
FRONT AND THEN SPREADING ACROSS THE UINTA BASIN AND INTO SOUTHWEST
UTAH I-15 CORRIDOR DURING SUNDAY EVENING. HAVE EXTENDED WARNINGS
FOR THIS PERIOD OF SNOW AND ADDED A WATCH TO PART OF CENTRAL UTAH.
DUE TO BREAK IN SNOWFALL TONIGHT HAVE NOT EXTENDED THE CENTRAL AND
NORTHERN WASATCH FRONT BUT AT LEAST SOLID ADVISORY FOR SUNDAY...AND
DUE TO SUB ADVISORY SNOW TODAY IN WEST CENTRAL AND SOUTHWEST UTAH
HAVE NOT ISSUED HIGHLIGHTS TODAY BUT WARNING CRITERIA NEAR
FILLMORE ON SUNDAY A GOOD PROBABILITY WITH NORTHWEST FLOW BANKING
INTO THE MOUNTAINS SUNDAY EVENING SO ADDED A WATCH. CURRENT THINKING
IS SNOW ADVISORY ON SUNDAY AND SUNDAY EVENING FOR SOUTHWEST UTAH
I-15 CORRIDOR. THIS FRONTAL ZONE WILL EXTEND ACROSS THE CASTLE
COUNTRY AND COLD UINTA BASIN INTO SUNDAY EVENING BEFORE ENDING.
HAVE SIGNIFICANTLY RAISED WEATHER CHANCES IN THE NORTH ON SUNDAY.

THE FINAL IN THE SERIES OF WAVES ARRIVES SUNDAY NIGHT AND MONDAY
ACROSS NORTHERN UTAH. THIS BRINGS THE COLDEST AIR MASS FROM 700
TO 500 MB...AND SHOULD BE ASSOCIATED WITH ANOTHER WIND SHIFT TO
NORTHWEST BY MONDAY AFTERNOON...AND -16C AIR MASS AT THIS LEVEL.
SNOWFALL COULD BE A COUPLE TO FEW INCHES IN THE VALLEYS AND HIGH
END SNOW ADVISORY IN THE CENTRAL AND NORTHERN MOUNTAINS.

SHORT WAVE RIDGE PROGGED FOR MONDAY NIGHT AND TUESDAY. ANOTHER
SYSTEM DEVELOPS WARM AIR ADVECTION ON TUESDAY AND MOISTENS THE
AIR MASS IN NORTHERN UTAH. SOUTHERLY FLOW WILL WARM THE NORTHERN
VALLEYS AS WELL AS AIR MASS WARMING WHICH WILL BRING HIGHER SNOW
LEVELS. COLD FRONT FORECAST FOR TUESDAY NIGHT AS THE SHORT WAVE
TROUGH PASSES THROUGH PER ECMWF AND GFS RUNS...AND LINGERING POST
FRONTAL SNOW SHOWERS ON WEDNESDAY...ESPECIALLY IN THE NORTHERN
MOUNTAINS. TRACK OF SHORT WAVE TROUGH SUPPORTS SNOW SPREADING
DOWN THE I-15 CORRIDOR INTO SOUTHWEST UTAH AND AFFECTING
PARTS OF THE EASTERN VALLEYS AS WELL WITH SNOW SHOWERS INTO
SOUTHEAST UTAH.

A SIMILAR WAVE IS FORECAST FOR THURSDAY INTO FRIDAY SO HAVE PLACED
HIGHER WEATHER CHANCES FOR THE NORTH. 00Z ECMWF DIGS THIS SYSTEM
INTO THE DESERT SOUTHWEST ON FRIDAY.

&&

.HDYRO...STRONG UPSLOPE AND HEAVY PRECIPITATION OCCURRING IN
SOUTHWEST UTAH AND WILL CONTINUE THROUGH THIS MORNING. SNOW
LEVEL 6500 TO 7000 FEET AND HEAVY RAIN ALREADY PAST FEW
HOURS IN ENTERPRISE AND ZNP WITH 0.3 TO 0.8 INCHES. UPPER TROUGH
MOVE OVERHEAD THIS MORNING SUPPORTS MORE HEAVY RAIN AND RUNOFF
WILL BECOME SIGNIFICANT THIS MORNING. HAVE ISSUED WATCH FOR
FLASH FLOOD PRONE AREAS OF THE SOUTHWEST. PRECIPITATION TAPERS
TO SHOWERS THIS AFTERNOON AND SNOW LEVELS BEGIN TO LOWER.

&&

.AVIATION...MODERATE SOUTHERLY WINDS WILL CONTINUE AT THE KSLC
TERMINAL UNTIL A COLD FRONT MOVES THROUGH BETWEEN 12Z OR 13Z THIS
MORNING. RAIN WILL ACCOMPANY THE FRONT BUT A CHANGE OVER TO SNOW IS
EXPECTED BY 14Z ALTHOUGH THERE IS A 30 PERCENT CHANCE THAT A CHANGE
OVER WILL HOLD OFF UNTIL 15Z. IFR OR LOWER CONDITIONS ARE EXPECTED
TO PREVAIL THROUGH 21Z. HOWEVER...THERE IS A 20 PERCENT CHANCE THAT
THE SNOW AND LIFR CONDITIONS COULD END BY 19Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...HEAVY SNOW WARNING UNTIL 5 PM SUNDAY FOR UTZ011.

     HIGH WIND WARNING UNTIL 5 AM SATURDAY FOR UTZ003.

     WINTER STORM WARNING UNTIL 6 PM SATURDAY FOR UTZ001-UTZ002-
     UTZ003.

     WIND ADVISORY UNTIL 5 AM SATURDAY FOR UTZ002-UTZ004.

     WINTER STORM WARNING UNTIL 5 PM SUNDAY FOR UTZ004.

     WINTER STORM WARNING UNTIL 6 PM SUNDAY FOR UTZ007-UTZ008-UTZ009-
     UTZ010-UTZ517-UTZ518.

     WINTER STORM WARNING UNTIL 5 PM SUNDAY FOR UTZ006.

     HIGH WIND WARNING UNTIL 8 AM SATURDAY FOR UTZ015-UTZ016.

     SNOW AND BLOWING SNOW ADVISORY UNTIL 6 PM SATURDAY FOR UTZ005.

     WINTER STORM WATCH FROM 6 AM SUNDAY TO 9 PM SUNDAY FOR UTZ014-
     UTZ015.

     WIND ADVISORY UNTIL 8 AM SATURDAY FOR UTZ014.

     SNOW ADVISORY UNTIL 5 PM SUNDAY FOR UTZ012.

     FLASH FLOOD WATCH UNTIL NOON SATURDAY FOR UTZ019.

WY...WINTER STORM WARNING UNTIL 5 PM SUNDAY FOR WYZ021.

&&

PUBLIC...TARDY

AVIATION...STRUTHWOLF

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

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
325 PM MST FRI JAN 4 2008

UTZ001>016-019>021-517-518-WYZ021-051330-
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-
325 PM MST FRI JAN 4 2008

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

.DAY ONE...TONIGHT

VERY STRONG SOUTHERLY WINDS WILL CONTINUE ACROSS THE MOUNTAINS AND
WESTERN VALLEYS OF UTAH THROUGH TONIGHT. THESE WINDS ARE AHEAD OF A
STRONG COLD FRONT WHICH WILL REACH EXTREME NORTHWEST UTAH LATE
TONIGHT. MOUNTAIN LOCATIONS WILL SEE WIND GUSTS WELL ABOVE 70 MPH ON
THE EXPOSED RIDGES THROUGH TONIGHT. STRONG WINDS WILL ALSO EFFECT
THE WESTERN VALLEYS THROUGH TONIGHT. NUMEROUS HIGH WIND WARNINGS AND
WIND ADVISORIES ARE IN EFFECT FOR THE MOUNTAINS AND WESTERN VALLEYS.

PRECIPITATION WILL INCREASE TONIGHT AS THE COLD FRONT APPROACHES.
WINTER STORM WARNINGS WILL BEGIN IN THE MOUNTAINS TONIGHT AS HEAVY
SNOW DEVELOPS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A MAJOR WINTER STORM WILL AFFECT MUCH OF UTAH ON SATURDAY. HEAVY
SNOWS ARE EXPECTED IN THE MOUNTAINS AND MANY VALLEY AREAS. NUMEROUS
WINTER WEATHER WARNINGS AND ADVISORIES ARE IN EFFECT FOR SATURDAY.

THE MAIN PACIFIC STORM WILL MOVE THROUGH UTAH SUNDAY THROUGH MONDAY.
SNOW WILL CONTINUE ACROSS MUCH OF THE STATE...WITH MUCH COLDER
TEMPERATURES EARLY NEXT WEEK. THE NEXT PACIFIC STORM WILL AFFECT
MAINLY THE NORTHERN HALF OF THE STATE LATE TUESDAY THROUGH
WEDNESDAY. A SUBSEQUENT COLD PACIFIC STORM MAY FOLLOW FOR LATE IN
THE WEEK.

.SPOTTER INFORMATION STATEMENT...

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

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

GIBSON