Severe Thunderstorm Warning 34, NWS Salt Lake City, UT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
310 PM MDT TUE JUL 20 2004

.SYNOPSIS...WESTERLY FLOW ALOFT WILL BUILD INTO THE AREA AND REMAIN
IN PLACE INTO THE WEEKEND.  THIS WILL BRING DRIER AIR INTO THE
REGION...ESPECIALLY OVER SOUTHERN UTAH.

&&

.DISCUSSION...THE UPPER FLOW OVER THE WEST CONTINUES TO BECOME MORE
ZONAL AS A RESULT OF THE TROUGH MOVING OUT OF THE PACIFIC NORTHWEST
AND ACROSS THE NORTHERN ROCKIES. THE UPPER HIGH THATS BEEN PUMPING
MOISTURE NORTHWARD INTO THE FORECAST AREA AROUND ITS WESTERN EDGE IS
GRADUALLY FLATTENING AND ALLOWING SLIGHTLY DRIER AIR TO MOVE IN FROM
THE WEST. STILL ENOUGH MOISTURE AND INSTABILITY TO HELP TODAYS
ACTIVITY HOWEVER.

WESTERLY FLOW BRINGING WEAK DYNAMICS INTO THE AREA FROM THE WEST.
ONE SUCH PIECE IS MOVING EAST THROUGH NEVADA AND IS THE SOUTHERN
EXTENT OF A BROADER SHORTWAVE THAT EXTENDS NORTH INTO MONTANA.
TROUGH APPEARS TO BE SHEARING OUT AS IT MOVES EAST.
REGARDLESS...THIS ENERGY IS HELPING TO FIRE CONVECTION OVER EASTERN
AND NORTHEASTERN NEVADA AND EXTREME WESTERN UTAH.  THE ETA PICKS UP
ON THIS FEATURE AND MOVES IT EAST OVER THE NEXT 12 HRS...ALSO
BRINGING IN WEAK NORTHWEST FLOW AT LOW LEVELS BEHIND IT.  THIS LOW
LEVEL CONVERGENCE AND WEAK UPPER DYNAMICS IS PROGGED TO BE OVER
ROUGHLY THE NORTHWEST QUARTER OF UTAH THIS EVENING.  ATMOS STILL
PRETTY UNSTABLE WITH GOES LIS AROUND -4 TO -5...CONFIRMING THE
ETAS EARLIER MODEL SOUNDING FOR SLC THIS AFTERNOON.  SO EVEN THOUGH
THERES QUITE A BIT OF SUNSHINE OVER THE NORTHERN HALF OF UTAH RIGHT
NOW...EXPECT THINGS TO FILL IN...ESPECIALLY IF WE CAN SQUEEZE A FEW
MORE DEGREES OUT THIS AFTERNOON AND AS ACTIVITY OVER NEVADA MOVES
EAST.  THE SOUTHERN MOUNTAINS HAVE BEEN GOING PRETTY GOOD LAST FEW
HOURS THANKS TO DEEPER MOISTURE.  GOES PWS REMAIN OVER AN INCH
THERE.  THE CENTRAL MOUNTAINS HAVE BEEN QUIET TODAY...LIKELY DUE TO
SOME BACK EDGE SUBSIDENCE BEHIND LAST NIGHTS WAVE THATS MOVING
INTO WYOMING RIGHT NOW.  SO EXPECT THE SOUTH TO KEEP GOING INTO AT
LEAST EARLY THIS EVENING...WITH CELLS DRIFTING NORTHEAST OFF THE
HIGHER TERRAIN AND INTO THE SOUTHEAST VALLEYS BEFORE DIMINISHING
AFTER SUNSET.  THE NORTHERN HALF OF THE FORECAST AREA WILL GET GOING
LATER...AND MAY EVEN GO A LITTLE PAST MIDNIGHT.  WILL LIKELY SEE
SOME OUTFLOWS AROUND IN THE NORTH LIKE LAST NIGHT SINCE MOST
MOISTURE IS STILL AT MID LEVELS.

THE HIGH CONTINUES ITS GRADUAL MOVE SOUTH AND WEST TOMORROW TO
POSITION ITSELF OVER NORTHERN BAJA BY THURSDAY MORNING.  PWS
DECREASE TO AROUND A HALF AN INCH OVER THE SOUTHWEST...TO AROUND .75
IN THE EAST AND SOUTHEAST...AND JUST ABOVE THAT ON AN E-W AXIS ALONG
NORTHERN UTAH.  AS A RESULT SHOULD SEE OVERALL LESS CONVECTION
TOMORROW.  EXCEPTION WILL BE ALONG WEAK W-E STATIONARY BOUNDARY THAT
SETS UP ACROSS CENTRAL UTAH TOMORROW TO FOCUS SOME CONVECTION OVER
AND SLIGHTLY NORTH OF THERE.  BUT WITH OVERALL DRIER AIRMASS DONT
EXPECT ANYTHING TOO HEAVY WITH WHAT DOES FORM.  THE PATTERN REPEATS
ITSELF THURSDAY WITH THE ETA STILL SHOWING WEAK LOW LEVEL
CONVERGENCE ACROSS CENTRAL UTAH.  THE WEAK NORTHWEST FLOW WILL HELP
KEEP HIGHS/LOWS IN THE NORTH AROUND NORMAL FOR THIS TIME OF YEAR.

UPPER FLOW PATTERN FRI-SUN IS GENERALLY WESTERLY AND GRADUALLY
TURNING NORTHWESTERLY AS ENERGY DROPS INTO THE NORTHERN PLAINS AND
THE UPPER RIDGE BUILDS TO OUR WEST.  MID LEVEL MOISTURE PERSISTENTLY
REMAINS OVER THE NORTH DURING THIS TIME OTHERWISE OTHER AREAS ARE
RELATIVELY DRY.  WENT WITH CLIMATOLOGY FOR POPS...BASICALLY HIGHER
TERRAIN WITH AFTERNOON HEATING...ESPECIALLY IN THE NORTH.

UPPER HIGH BY MONDAY IS CENTERED OVER SOUTHERN CALIFORNIA...AND
MOISTENS UP ACCORDING TO THE GFS.  THERMAL RIDGE PUMPS UP BY THIS
TIME TO HELP WARM US UP.  OTHERWISE LEFT PREVIOUS PACKAGE FOR
MON-TUE UNCHANGED.  FOR NOW AFTERNOON MOUNTAIN CONVECTION DRIFTING
OFF TO THE SOUTHEAST IN NORTHWEST FLOW.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...

UT...NONE.
WY...NONE.
ID...NONE.

&&

JACKSON