Flash Flood and Heavy Snow in Utah, November 12, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
445 AM MST FRI NOV 12 2004

.SYNOPSIS...AN UPPER LEVEL LOW PRESSURE AREA OVER THE GREAT BASIN
TODAY WILL SLOWLY SHIFT SOUTH THROUGH ARIZONA OVER THE WEEKEND.

&&

.DISCUSSION...OLD LOW CENTER NEAR THE WESTERN UINTA BASIN BECOMING A
LOBE THAT WILL ROTATE WEST AROUND NEW CENTER FORMED BY SHORTWAVE
DIGGING SOUTHEAST THROUGH CA. THAT WILL SHIFT THE BULK OF THE
DYNAMIC LIFT FROM THE NORTHERN PORTION OF THE AREA TO SOUTHWEST UT
BY THIS AFTERNOON/EVENING. HOWEVER PLENTY OF MOISTURE WITH AT LEAST
WEAK INSTABILITY IN THE AFTERNOON TO KEEP SCATTERED SHOWERS OVER
MOST OF THE NORTH.

THE NEW LOW CENTER SAGS SOUTH INTO ARIZONA SATURDAY PULLING MOST OF
THE DYNAMIC SUPPORT WITH IT.  HOWEVER STILL GOOD OROGRAPHIC LIFT FOR
THE SOUTHEAST SLOPES OF THE SOUTHERN MOUNTAINS TONIGHT AND SATURDAY.
SNOWFALL WILL BE CLOSE TO LOW END ADVISORY AMOUNTS DURING THAT TIME
BUT CURRENTLY DONT EXPECT SUFFICIENT SNOW TO BE WIDESPREAD ENOUGH
TO NEED AN ADVISORY.  BUT THE DAY CREW CAN REASSESS THAT FOR THE
AFTERNOON PACKAGE.

THE NEW LOW SUFFERS THE SAME FATE AS OUR CURRENT CIRCULATION...BEING
MOSTLY ABSORBED BY ANOTHER STRONG SHORTWAVE THAT DIGS SOUTHEAST
ACROSS CA SATURDAY. MOST OF ITS ENERGY ROTATES WEST THROUGH SOUTHERN
UT SATURDAY NIGHT BUT A PORTION EJECTS TO THE NORTHEAST KEEPING SOME
SHOWERS GOING AS FAR NORTH AS THE UINTA MOUNTAINS.

A SHORTWAVE RIDGE MOVES PAST MONDAY.  THEN THE NEXT PACIFIC SYSTEM
SLIDES PAST...HAVING SPLIT WELL OFF SHORE.  BUT THE RIDGE OVER THE
NORTHWEST THAT HAS CONTRIBUTED TO THE BLOCKING PATTERN IS FORECAST
TO BE GONE ALLOWING THE WESTERLIES TO PUSH ACROSS THE NORTHERN
INTERMOUNTAIN REGION.  THAT PUSHES A WEAK LOW LEVEL BOUNDARY ACROSS
ABOUT THE NORTHERN THIRD OF UT TUESDAY.

UP TO THAT POINT THERE IS FAIRLY GOOD AGREEMENT IN THE
MODELS...ALTHOUGH THERE IS SOME VARIABILITY IN TIMING OF THE TUESDAY
FEATURE.  THEN THE GFS CONTINUES TO POINT TOWARD A PATTERN
READJUSTMENT WITH A RIDGE POSITION DEVELOPING IN THE EASTERN
PACIFIC. IT STILL RESULTS IN A SPLIT PATTERN OVER THE WEST...BUT
WITH THE SPLIT BEING A PORTION OF THE POLAR WESTERLIES INSTEAD OF
SOMETHING THAT HAS BEEN DRIFTING THROUGH THE MID LATITUDES FOR A
WHILE.  THAT BRINGS A COLDER AND MORE PROGRESSIVE TROF ACROSS THE
AREA STARTING ABOUT FRIDAY.

HOWEVER OTHER GLOBAL MODELS...PARTICULARLY THE EUROPEAN
MODELS...ARENT AS EAGER TO GIVE UP ON THE SPLIT IN THE EASTERN
PACIFIC. BUT THEY AGREE THAT THE BLOCKING HIGH WILL GO AWAY SO SOME
CHANGE IN THE RECENT BLOCKY SPLITTY PATTERN APPEARS A GOOD BET.
MOST OF THE IMPACT OF THE CHANGES WILL BE JUST BEYOND THE CURRENT
FORECAST PACKAGE SO THE DAY CREW CAN WRESTLE WITH HOW TO HANDLE IT
DEPENDING ON HOW THE 12Z MODEL RUNS LOOK.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
ID...NONE.

&&

SANDERS