Severe Thunderstorm Warning 83, NWS Salt Lake City, UT

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
245 PM MDT THU SEP 13 2001

SYNOPSIS...AN UPPER LEVEL SYSTEM WILL MOVE ACROSS SOUTHERN IDAHO
TONIGHT. A DRIER...STABLE AIR MASS WILL BE OVER THE AREA FRIDAY.
MOISTURE MOVING NORTH THROUGH ARIZONA WILL BEGIN TO SPREAD INTO
SOUTHWEST UTAH SATURDAY THEN OVER THE REMAINDER OF SOUTHERN UTAH BY
SUNDAY.

DISCUSSION...UPPER LOW NEAR SOUTHWEST CORNER OF ID WILL CONTINUE
SLOWLY EAST-NORTHEAST TO BE OVER EASTERN MT BY THIS TIME TOMORROW.
GOOD DYNAMICS ONLY BRUSH THE EXTREME NORTHERN PORTION OF THE AREA
TONIGHT BUT IT WILL KEEP THINGS QUITE ACTIVE OVER THE ZONES THAT
TOUCH THE ID BORDER.  FAIRLY STRONG VERTICAL SHEAR IN THAT AREA AND
WHEN COUPLED WITH THE DYNAMICS WILL ALLOW SOME OF THE STORMS TO
APPROACH SEVERE LEVELS.  SUFFICIENT MOISTURE OVER SOUTHEAST
PORTION OF THE AREA TO KEEP SOME ACTIVITY THIS EVENING FROM THE
MOUNTAINS EASTWARD.  BUT IT SHOULD BE STRONGLY DIURNAL AND FADE
QUICKLY THIS EVENING.

BY TOMORROW A MUCH DRIER AND VERY STABLE AIR MASS SHOULD HAVE SPREAD
ACROSS THE STATE.  WILL KEEP A SLIGHT CHANCE IN THE MOUNTAINS NEAR
BEAR LAKE BUT OTHERWISE IT LOOKS LIKE PROBABLY JUST SOME FLAT
CUMULUS IN THE AFTERNOON.  ON SATURDAY MOISTURE WORKING NORTH ALONG
THE LOWER COLORADO RIVER VALLEY WILL SPREAD INTO SOUTHWEST UT IN THE
AFTERNOON.  MODELS ALSO SHOW IMPRESSIVE INSTABILITY CENTERED OVER
SOUTHERN NV SATURDAY EVENING THAT WILL ALSO IMPACT THE SOUTHWEST.
SO WILL BRING A CHANCE OF THUNDERSTORMS BACK INTO THE SOUTHWEST LATE
SATURDAY AND SATURDAY NIGHT.  THAT WILL SPREAD ACROSS THE REST OF
THE SOUTH ON SUNDAY AND THE LATEST MODEL RUNS SUGGEST IT COULD
SPREAD UP TO THE SOUTHERN WASATCH FRONT.  WONT GO QUITE THAT FAR
YET...ONLY TO ABOUT A U24-PUC LINE.

AVN IS CONTINUING THE IDEA THAT SHOWED UP IN LAST NIGHTS MRF OF A
TROF DROPPING INTO NORTHWEST UT MON NIGHT.  THE ETA IS IN GOOD
AGREEMENT ON THE POSITION/INTENSITY OF THIS WAVE AT THE END OF ITS
60HR RUN.  THIS SOLUTION ISNT TERRIBLY FAR FROM WHAT LAST NIGHTS
UKMET SHOWED.  THE 12Z UKMET SEEMS TO MOVE A LITTLE TOWARD THE
DEEPER OF THE MRF/AVN SO WILL ACCEPT THE IDEA FOR NOW.  THAT WOULD
BRING A FAIRLY STRONG COLD FRONT INTO NORTHWEST UT MONDAY EVENING.
MOST OF THE PRECIPITATION WITH THIS SYSTEM WILL PROBABLY STAY OVER
AND WEST OF THE NORTHERN MOUNTAINS BUT SCATTERED SHOWERS ARE
POSSIBLE IN NORTHEAST UT TUESDAY IF THE LOW TRACK THAT WAY.  WONT
GET CARRIED AWAY ON THIS YET AND WONT GO AS COOL AS THE 120HR AVN
WOULD SUGGEST.   BUT WILL STILL HAVE TUESDAY 10-15 DEGREES BELOW
AVERAGE AT SLC TUE.  THE SOUTH WILL STAY DRY BUT MAY COOL A BIT
TUESDAY.  WEDNESDAY/THURSDAY SHOULD BE DRY WITH WESTERLY FLOW AND
SLOW WARMING OF TEMPERATURES.

SLC 4--1 CDC ---2 SANDERS

.SLC...NONE.