Severe Thunderstorm Warning 61, NWS Salt Lake City, UT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
220 PM MST SAT NOV 27 2004

.SYNOPSIS...A LARGE AND VERY COLD PACIFIC STORM SYSTEM WILL MOVE
ACROSS NORTHERN UTAH TONIGHT AND THEN SETTLE OVER SOUTHEAST UTAH BY
LATE SUNDAY. THIS SYSTEM WILL MOVE AWAY FROM THE REGION ON MONDAY.

&&

.DISCUSSION...WIDESPREAD SNOW CONTINUES OVER MUCH OF CENTRAL AND
NORTHERN UTAH...WITH A HOLE OVER THE SL VALLEY WHERE DOWNSLOPE FLOW
APPEARS TO BE DOMINATING FOR NOW AFTER A BRIEF PERIOD OF SNOW THIS
MORNING. MODERATE TO OCCASIONAL HEAVY SNOW PAST FEW HOURS FROM THE
CASTLE VALLEY TO OGDEN AND LOGAN AND INTO SW WYOMING (1-4 INCHES)
INCLUDING ALL MOUNTAINS (5-11 INCHES SO FAR AND HEAVIEST IN THE
NORTHERN WASATCH) IN BETWEEN. FRONTAL BAND AT THE SURFACE EXTENDS
FROM SOUTHWEST UTAH...WHERE A DEEPENING SURFACE LOW EXISTS...AND
NORTHWARD TO ABOUT SLC. THIS WILL CONTINUE TO SHIFT EAST THIS
AFTERNOON AND EVENING AS COLD AIR ADVECTION ALOFT AND UPPER LOW
SUPPORT SWINGS THROUGH. HEAVY PRECIP WILL OCCUR ALONG AND BEHIND
THIS BOUNDARY (INCLUDING SALT LAKE VALLEY) AS IT MOVES INTO
SOUTHEAST UTAH TONIGHT. COOLING TOPS NOW OCCURRING IN CENTRAL UTAH
WHERE BEST DIVERGENCE IS OCCURRING AND WILL CONTINUE THIS EVENING.
ALOFT 700-500 MB LOW IS MOVING ACROSS FAR NORTHERN UTAH AND WILL
REACH SW WYOMING TONIGHT AND PARK. THIS WILL DEVELOP A SURFACE
REFLECTION UNDER IT. THIS NORTHERN PORTION IS THE POSITIVELY TILTED
END OF THE MEAN UPPER TROF AXIS THAT EXTENDS BACK INTO CENTRAL
CALIFORNIA. STRONG VORT MAX CROSSING LAKE TAHOE WILL DIVE SOUTHEAST
ALONG THE JET STREAK AND BEGIN TO DIG THE UPPER TROF TO THE SOUTH
AND PULL ENERGY SOUTHWARD LATE TONIGHT AND ON SUNDAY. JET ENERGY ON
THE EAST SIDE OF THE SYSTEM REACHES 150 KT FROM W-E OVER SOUTHERN
UTAH INTO COLORADO ON SUNDAY WHILE THE CLOSED OFF UPPER LOW CENTER
SLIDES SOUTH IN EASTERN UTAH.

ALL THE ABOVE SUPPORTS PERIODS OF HEAVY SNOW IN THE CENTRAL AND
NORTH THIS AFTERNOON SHIFTING SOUTHWARD OVERNIGHT. OROGRAPHIC WINDS
ABRUPTLY SHIFT TO THE NW EARLY THIS EVENING AND REACH SOUTHWARD INTO
SW UTAH. LOCALIZED HEAVY SNOW WILL OCCUR FROM THE SOUTHERN WASATCH
FRONT AND MOUNTAINS TO SW UTAH IN THE VALLEYS AND TERRAIN. IN
ADDITION WITH 700 MB TEMPS LOWERING TO -14C BY SUNDAY MORNING AND
-32F AT 500 MB ALONG WITH NW-N FLOW THIS SETS THE STAGE FOR LAKE
ENHANCED SNOW AND LAKE EFFECT. UNSTABLE AIR MASS WILL ALSO SUPPORT
GENERAL SNOW SHOWERS AND SQUALLS ON SUNDAY...WHILE THE LOW CLOSES
OFF IT WILL ALSO SEND WRAP AROUND PRECIP INTO EASTERN UTAH WHICH
WILL BE ENHANCED IN THE UINTA MOUNTAINS. WE WILL KEEP NUMEROUS
WARNINGS AND ADVISORIES FOR MOST LOCALES INTO SUNDAY MORNING...MAY
NEED TO CONTINUE A FEW INTO THE AFTERNOON.

UPPER LOW SLIDES FURTHER SOUTH AND INSTABILITY SNOW SHOWERS WILL
GRADUALLY END SUNDAY NIGHT...WHILE WRAP AROUND BANDS PULL EAST.
PARTIAL CLEARING WILL ALLOW FOR COLDEST TEMPS OF THE SEASON WHILE
COLDEST 700 MB AIR OF NEAR -16C SETTLES OVER UTAH. COLD AIR
ADVECTION NE FLOW ALSO WILL BRING WINDY CONDITIONS TO PARTS OF SW
UTAH SUNDAY NIGHT INTO MONDAY MORNING WITH A TIGHT N-S GRADIENT AND
35-40 KNOTS OF WIND AT 700 MB LEVEL. WE KEEP CHANCE FOR PRECIP INTO
MONDAY FOR MAINLY SOUTHEAST UTAH AS THE PROXIMITY OF CLOSED UPPER
LOW AT THE ARIZONA AND NEW MEXICO BORDER SENDS PRECIP INTO THIS
REGION. WARMING ALOFT OVER NORTHERN UTAH WILL SQUASH INSTABILITY TO
A SHALLOW DEPTH. UPPER RIDGING IN THE WAKE OF THE LOW WILL BRING A
WARMING TREND TO MOST LOCALES BUT SNOW COVERED NORTHERN VALLEYS WILL
STRUGGLE UNDER THE DEVELOPING INVERSION NEXT WEEK. NEXT SHORT WAVE
IS PROGGED BY THE 12Z GFS TO MOVE INTO NEVADA ON WEDNESDAY AND CROSS
UTAH ON THURSDAY. THIS CONTINUES TO BE HANDLED DIFFERENTLY BY OTHER
MODELS AND GFS RUNS...CLOSING OFF THE WEST AND NOT CAUGHT UP IN THE
WESTERLIES OR EVEN A RATHER DEEP TROF OVER UTAH. LIMITED CHANGES IN
THE EXTENDED BUT DO INDICATE CHANCE OF PRECIP AND COOLING ON
THURSDAY. SHORT WAVE RIDGE PROGGED TO FOLLOW THIS SYSTEM AHEAD OF A
POSSIBLY STRONGER UPPER TROF APPROACHING THE PACIFIC COAST.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WARNINGS AND ADVISORIES IN EFFECT THROUGH SUNDAY AM MOST
     MOUNTAINS AND WESTERN VALLEYS...SEE SLCWSWSLC.
WY...SNOW ADVISORY THROUGH SUNDAY AM.
ID...SNOW ADVISORY THROUGH TONIGHT.

&&

TARDY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
535 AM MST SAT NOV 27 2004

IDZ024-025-UTZ001>021-WYZ021-281300-
CACHE VALLEY/IDAHO PORTION-CACHE VALLEY/UTAH PORTION-CASTLE COUNTRY-
CENTRAL AND SOUTHWEST MOUNTAINS-
GLEN CANYON RECREATION AREA/LAKE POWELL-
GREAT SALT LAKE DESERT AND MOUNTAINS-HENRY MOUNTAINS-
NORTHERN WASATCH FRONT-SALT LAKE AND TOOELE VALLEYS-SAN RAFAEL SWELL-
SANPETE/SEVIER VALLEYS-SOUTH CENTRAL UTAH-SOUTHERN WASATCH FRONT-
SOUTHWEST UTAH-SOUTHWEST WYOMING-UTAHS DIXIE AND ZION NATIONAL PARK-
WASATCH MOUNTAIN VALLEYS-WASATCH MOUNTAINS I-80 NORTH-
WASATCH MOUNTAINS SOUTH OF I-80-WASATCH MOUNTAINS/IDAHO PORTION-
WASATCH PLATEAU/BOOK CLIFFS-WEST CENTRAL UTAH-WESTERN UINTA BASIN-
WESTERN UINTA MOUNTAINS-
535 AM MST SAT NOV 27 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EXTREME SOUTHEAST
IDAHO...SOUTHWEST WYOMING AND THE WESTERN TW0-THIRDS OF UTAH.

.DAY ONE...TODAY

A VERY COLD WINTER STORM WILL INTENSIFY OVER THE AREA THIS AFTERNOON
AND EVENING. HEAVY SNOW IS EXPECTED IN MANY AREAS AND WARNINGS AND
ADVISORIES HAVE BEEN ISSUED. PLEASE CHECK THE LATEST WINTER WEATHER
MESSAGE FROM SALT LAKE CITY /SLCWSWSLC/ FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE WINTER STORM WILL CONTINUE TO IMPACT THE AREA THROUGH SUNDAY AND
POSSIBLY INTO MONDAY.

.SPOTTER INFORMATION STATEMENT...

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