Flash Flood Warning 18, NWS Salt Lake City, UT

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UTAH
1020 AM MDT WED JUL 28 1999

SYNOPSIS...A MOIST AIRMASS WILL REMAIN OVER UTAH THROUGH THURSDAY.
A MORE WESTERLY FLOW OVER NORTHERN UTAH FRIDAY WILL RESULT IN SOME
DRYING OVER THE NORTHWEST.

DISCUSSION...VERY MOIST AIRMASS WILL REMAIN IN PLACE OVER THE
FORECAST AREA THROUGH THURSDAY.  EXPECT A LOT OF DIURNAL CONVECTIVE
ACTIVITY TO CONTINUE.  STABILITY FORECASTS CONTINUE TO SUGGEST
SOUTHERN UT WILL BE MORE UNSTABLE THAN THE NORTH BUT THE MAIN IMPACT
FROM THAT IS TO DELAY THE DEVELOPMENT OVER THE NORTH A EXTRA COUPLE
OF HOURS AND TO SLIGHTLY REDUCE THE AREAL COVERAGE...ESPECIALLY IN
THE VALLEY AREAS.  MODELS CONTINUE TO INDICATE THAT REMNANTS OF A
CIRCULATION THAT HAS BEEN OVER WESTERN MEXICO THE LAST COUPLE OF
DAYS WILL MOVE NORTH AND BE NEAR THE UT/AZ BORDER ABOUT THU
AFTERNOON.  IF THIS HAPPENS IT SHOULD RESULT IN AN ENHANCED AREA OF
ACTIVITY OVER SOUTHWEST UT THU AFTERNOON/EVENING.  HOWEVER THIS TYPE
OF FEATURE NOTORIOUSLY HARD TO PREDICT ACCURATELY MAKING ME
RELUCTANT TO REFLECT THAT IDEA IN THE PUBLIC FORECASTS YET.  BUT IF
TONIGHTS RUNS CONTINUE THE TREND AND SATELLITE DATA SUPPORTS THE
IDEA THE MIDNIGHT CREW MAY WANT TO BEEF UP THE SOUTHWEST FOR
TOMORROW.  MAY BE A BIT OF DRYING OVER THE NORTH ON FRIDAY BEHIND A
WEAK SHORTWAVE THAT IS MOVING ACROSS EARLY IN THE DAY.  THE FLOW
TURNS WESTERLY BRIEFLY BUT BY AFTERNOON IS GOING SOUTHERLY AGAIN
ALREADY.  SO WILL LOWER PROBABILITIES IN THE NORTHWEST A BIT FRI BUT
ANY BREAK IS LIKELY TO BE SHORT LIVED.

WILL LEAVE FLASH FLOOD WATCH AS IT IS FOR NOW.  RADAR
INDICATES SOME AREA MAY BE GETTING CLOSE TO HAVING FLOOD PROBLEMS
WITH SOME ESTIMATES NEAR 2 INCHES IN THE SOUTHWEST. LITTLE ACTIVITY
IN THE SOUTHEAST YET BUT THATS FAIRLY COMMON DURING THE EARLY
AFTERNOON AND STILL EXPECT TO SEE THINGS FIRE UP THERE BY LATE
AFTERNOON/EVENING.

NEW AVN LOOKS LIKE THE HIGH IS CENTERED FARTHER NORTH AND EAST EARLY
SAT THAN PREVIOUS EXTENDED MODELS.  THIS WOULD ALLOW CONVECTION
PRETTY MUCH AREA-WIDE AGAIN BY SATURDAY AFTERNOON AND WITH LITTLE
CHANGE THROUGH THE REMAINDER OF THE EXTENDED PERIOD.  SO EXPECT
SCATTERED DIRUNAL ACTIVITY TO CONTINUE WITH A SLIGHTLY GREATER
COVERAGE OVER THE SOUTH THAN IN THE NORTH.

SLC 4443 CDC 5554 SANDERS

.SLC...FLASH FLOOD WATCH NOON TIL MIDNIGHT FOR MOST OF SOUTHERN UTAH.