Winter Storm in Utah, November 24 to 27, 2001

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
330 AM MST SAT NOV 24 2001

.SYNOPSIS...WEAK HIGH PRESSURE ALOFT WILL BE OVER THE AREA EARLY
TODAY.  A STRONG SOUTHWEST FLOW WILL BRING A WARM FRONT NORTHWARD
ACROSS UTAH THIS AFTERNOON AND EARLY EVENING.  A STRONG COLD FRONT
IS EXPECTED TO CROSS THE AREA LATE TONIGHT.

.DISCUSSION...ALL MODELS CONTINUE TO AGREE ON IDEA OF DEVELOPING
STORM. SHORTWAVE MOVING RAPIDLY EAST FROM CENTRAL PACIFIC BRINGS
GOOD MOISTURE AND MERGING WITH COLD SHORTWAVE DROPPING SOUTH FROM
THE GULF OF ALASKA.  THE MAIN PERIOD OF DEVELOPMENT IS JUST
BEGINNING WITH SURFACE PRESSURES BEGINNING TO PLUNGE NEAR THE
NORTHERN CA COAST.  THIS DEVELOPMENT CONTINUE THROUGH THIS AFTERNOON
WITH THE SURFACE LOW DEEPENING BY ABOUT 12-15 MB BETWEEN 06Z THIS
MORNING AND 00Z SATURDAY.  THE WHOLE SYSTEM CONTINUES EAST FAIRLY
RAPIDLY WITH THE ONLY REAL DISAGREEMENT BETWEEN MODELS BEING
TIMING.  AVN IS THE FASTEST AND PREFERRED.  EACH OF THE LAST 3 MODEL
CYCLES HAS MOVED THE TIMING UP AND EXTRAPOLATION SUGGESTS THE LATEST
AVN POSITIONS WILL BE FAIRLY GOOD AT 00Z. 06Z ETA ALSO CLOSED ABOUT
HALF OF THE GAP BETWEEN THE AVN AND 00Z ETA.

RESULT HERE IS RAPIDLY DEVELOPING STRONG SURFACE GRADIENT THIS
AFTERNOON BEHIND THE WARM FRONT THAT WILL SWING NORTH ACROSS THE
AREA.  IT NOW LOOKS LIKE MOST OF THE WARM FRONTAL PRECIPITATION WILL
BE WEST OF OUR AREA BUT SOME RELATIVELY LIGHT RAIN WILL MOVE THROUGH
THE NORTHWEST VALLEYS THIS AFTERNOON WITH SOME SNOW ABOVE 6000 FEET.
EXCEPTION TO THE LIGHT AMOUNTS WILL BE NEAR ENV WHERE SOUTHEAST FLOW
WILL PRODUCE UPSLOPE AND BRING HEAVIER RAIN.

COLD FRONT SHOULD REACH THE UT/NV BORDER ABOUT 06Z AND PASS THE
WASATCH FRONT ABOUT 09Z.  IT IS NEAR THE EAST EDGE OF OUR AREA BY
12Z. A STRONG BAND OF SNOW LIKELY WITH THE FRONT OVER THE MOUNTAINS
AND WEST WITH SOMEWHAT LIGHTER SNOW OVER THE EAST.  THEN A COLD
MOIST NORTHWEST FLOW CONTINUES THROUGH MONDAY.

WILL ISSUE A HIGH WIND WARNING FOR THE ZONES ALONG THE NV BORDER
FROM CDC NORTH FOR LATE THIS AFTERNOON AND TONIGHT AND FOR THE REST
OF THE WESTERN VALLEYS FOR TONIGHT.  WILL KEEP THE WINTER STORM
WATCH FOR THE MOUNTAINS FOR TONIGHT AND SUNDAY AND BACK IT OFF TO
LATE TONIGHT FOR THE WESTERN VALLEYS.  WONT ISSUE WSW UNTIL THE
ZONES ARE READY TO GO OUT HOPEFULLY NOT LONG AFTER 12Z.

WONT MESS WITH EXTENDED.  NEW MRF REASONABLY CONSISTENT WITH OLDER
IDEAS.  SOME DIFFERENCE IN HOW IT TREATS THE SHORTWAVE MOVING
RAPIDLY ACROSS THE AREA THURSDAY/FRIDAY BUT NOT CONFIDENCE THAT FAR
OUT NOT HIGH ANYWAY.

SLC 2885 CDC 2762 SANDERS

.SLC...HI WND WRNG LATE TDA/TNGT AND WNTR STRM WTCH LATE TNGT/SUN
       EXTREME WESTERN VALLEYS...UTZ005-015-016
    ...HI WND WRNG TNGT AND WNTR STRM WTCH LATE TNGT/SUN OTHER WRN
       VLYS XCPT DIXIE...UTZ001>004-014-IDZ024
    ...WNTR STRM WTCH MTNS AND MTN VLYS TNGT/SUN
       UTZ006>010-017-018-IDZ025