Flash Flood Warning 8, NWS Salt Lake City, UT

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UTAH
400 PM MDT TUE JUL 13 1999

SYNOPSIS...DEEP TROPICAL MOISTURE CONTINUES TO MOVE UP INTO UTAH
FROM THE SOUTH.  THE NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS
SOUTHERN AND CENTRAL UTAH WILL DECREASE TONIGHT AND THEN REDEVELOP
WEDNESDAY.  THE MOISTURE WILL MAKE IT UP INTO NORTHERN UTAH
TONIGHT.  SCATTERED SHOWERS AND THUNDERSTORMS SHOULD DEVELOP
WEDNESDAY THEN ACROSS THE NORTH.  A COLD FRONT MOVES INTO NORTHWEST
UTAH LATE WEDNESDAY.  GUSTY SOUTH-SOUTHWEST WINDS WILL DEVELOP
ACROSS MOST OF THE STATE WEDNESDAY AHEAD OF THAT FRONT.  BY THURSDAY
THIS FRONT SHOULD STALL NEAR A DELTA-DUCHESNE LINE.  THE AIRMASS
WILL THEN SLOWLY DRY AND STABILIZE FROM THE WEST THURSDAY INTO THE
WEEKEND.  COOLER TEMPERATURES AND MUCH HIGHER HUMIDITIES WILL OCCUR
INTO THURSDAY.

DISCUSSION...ADDED MOST OF CENTRAL UTAH TO THE FLASH FLOOD WATCH AND
EXTENDED THE EXPIRATION TIME UNTIL MIDNIGHT.  PW VALUES OF OVER AN
INCH HAVE MOVED UP INTO SOUTHWEST AND CENTRAL UTAH THIS AFTERNOON.
AN UPPER LEVEL LOW AND H2 JET STREAK WILL ENHANCE THE DYNAMIC LIFT
TONIGHT.  SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO THIS EVENING
BUT WILL BECOME MORE ISOLATED AFTER MIDNIGHT.  THE EXCEPTION WILL BE
WHERE THE DYNAMIC LIFT REMAINS ASSOCIATED WITH THE UPPER LOW/H2 JET
STREAK.  THERE IS THE POTENTIAL TO HAVE AN MCS SOMEWHERE IN SOUTHERN
AND CENTRAL UTAH THROUGH THE NIGHT.  WILL LET THE EVENING SHIFT SEE
HOW THINGS UNFOLD TO DETERMINE IF THE WATCH NEEDS TO EXPIRE EVEN
LATER TONIGHT.  EXPECT MORE OF THE SAME WEDNESDAY ACROSS SOUTHERN
AND CENTRAL UTAH AND ANOTHER FLASH FLOOD WATCH WILL LIKELY BE NEEDED
DESPITE THE INCREASING LOW LEVEL FLOW.  TRAINING OF STORMS WILL
BECOME MORE OF CONCERN FOR WEDNESDAY AFTERNOON.  GUSTY SOUTH-
SOUTHWEST WINDS WILL SURFACE TOMORROW ACROSS MUCH OF THE STATE AS
THE GRADIENT TIGHTENS OUT AHEAD OF AN APPROACHING COLD FRONT.  WINDS
WERE ADDED TO MOST ZONES TO COVER FOR THIS.  BY THURSDAY DRYING
BEGINS TO DEVELOP FROM THE WEST.  THE FLOW AT MID LEVELS TURNS MORE
WESTERLY AS WELL.  THIS WILL BEGIN TO DECREASE THE CHANCE OF SHOWERS
AND THUNDERSTORMS IN THE WESTERN VALLEYS.  THE CENTRAL MOUNTAINS AND
EASTERN UTAH SHOULD REMAIN ACTIVE ON THURSDAY AS THE MOISTURE WILL
BE SLOW TO EXIT.  I TRIED TO SHOW THIS TREND WITH THE POPS IN THE
CURRENT FORECAST.

NORTHERN UTAH WILL BEGIN TO HAVE MOISTURE MOVE UP FROM THE SOUTH
THIS EVENING.  NUDGED POPS UP A BIT FOR TONIGHT.  MAIN AREAS THAT
COULD SEE SOME STORMS THIS EVENING ARE THE SOUTHERN WASATCH FRONT
AND OUT NEAR THE NEVADA BORDER.  DEEPER MOISTURE WILL MAKE IT UP
INTO EXTREME SOUTHEAST IDAHO BY WEDNESDAY MORNING.  THE CHANCE OF
SHOWERS AND THUNDERSTORMS THEREFORE WILL INCREASE ACROSS THE NORTH
THE NEXT 24 HOURS.  HEAVY RAINFALL WILL BE POSSIBLE WITH ANY STORMS
WEDNESDAY.  I INCREASED THE POPS ACROSS NORTHERN UTAH TOMORROW AND
TOMORROW NIGHT AS WELL.  VERTICAL SPEED SHEAR STILL LOOKS MARGINAL
FOR SEVERE THUNDERSTORMS TOMORROW.  WILL LET THE MID SHIFT REASSESS
THIS.  THE COLD FRONT SHOULD MOVE INTO NORTHWEST UTAH LATE TOMORROW
AFTERNOON...THROUGH THE SALT LAKE AREA BY LATE EVENING...AND THEN
STALL NEAR A DELTA-DUCHESNE LINE BY SUNRISE THURSDAY.  THE AIRMASS
WILL DRY AND STABILIZE TO THE NORTH OF THIS STALLED FRONT THURSDAY.

IN THE EXTENDED...MONSOONAL MOISTURE WILL BE SLOW TO LEAVE EASTERN
UTAH AND WE HAVE LEFT A MENTION OF THUNDERSTORMS INTO SATURDAY FOR
THE CENTRAL AND EASTERN MOUNTAINS.  OTHERWISE THE AIRMASS WILL
GRADUALLY DRY AND WARM FROM THE WEST INTO THE WEEKEND.

SLC 4771 CDC +983 MAIER

.SLC...FLASH FLOOD WATCH TIL 06Z MOST OF CENTRAL AND SOUTHERN UTAH.