246 
FXUS65 KSLC 311643
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1043 AM MDT SAT AUG 31 2013

.SYNOPSIS...A VERY MOIST AIRMASS WILL REMAIN IN PLACE ACROSS
SOUTHERN UTAH TODAY...WHILE DRIER AIR REMAINS ACROSS THE FAR
NORTH. A WEAK WEATHER SYSTEM WILL BRING THIS MOISTURE NORTHWARD
SUNDAY INTO LABOR DAY. HIGH PRESSURE WILL REDEVELOP OVER THE
REGION FOR THE MIDWEEK PERIOD. 


&&

.DISCUSSION...HIGH PRESSURE OVER NORTHERN NEW MEXICO CONTINUES TO
BE THE DOMINANT WEATHER FEATURE IN THE BIG PICTURE...WITH A STRONG
MONSOONAL RETURN FLOW SPREADING OVER THE SOUTHERN HALF OF THE
STATE. PWATS ACROSS THE SOUTH CONTINUE TO EXCEED 1.2 INCHES ALL
AREAS WITH EVEN DEEPER MOISTURE RESIDING ALONG THE UTAH/ARIZONA
BORDER. A PROGRESSIVE NORTHERN ROCKIES SHORT WAVE HAS ALLOWED
FURTHER DRYING ACROSS THE FAR NORTH AND DO NOT ANTICIPATE MUCH IN
THE WAY OF ACTIVE WEATHER ALONG THE WASATCH FRONT TODAY. 

MORNING MID LEVEL ANALYSIS INDICATES AN INVERTED TROUGH OVER
NORTHERN ARIZONA SPARKING DEEP CONVECTION ALONG THE NORTH RIM.
DEFORMATION AXIS DRAPED ACROSS THE SOUTHERN THIRD OF THE STATE
NOTICED IN WATER VAPOR...INTENSIFIED BY SAID TROUGH TO THE SOUTH.
BEST AREA OF UPPER DIVERGENCE COINCIDENT WITH THIS. DEW POINTS
ACROSS THE SOUTH REMAIN IN THE MID 50S TO LOW 60S AND MLCAPE
PROGGED TO INCREASE IN EXCESS OF 1000 J/KG THIS AFTERNOON
PROMOTING DEEP CONVECTION CAPABLE OF HEAVY RAIN IN THESE AREAS.
WITH A LIGHT EASTERLY COMPONENT TO THE FLOW ALOFT AND DEEPER
MOISTURE/INSTABILITY WORKING SOUTH CONVECTION SHOULD WORK DOWN
BASIN LATE IN THE DAY TODAY ENHANCING THE FLASH FLOOD
THREAT/POTENTIAL. SIGNIFICANT MID LEVEL CLOUD COVER NOTICED IN
SATELLITE ATTM IS EXPECTED TO THIN EARLY AFTERNOON ALLOWING STRONG
SURFACE HEATING AS A TRIGGER.

A FLASH FLOOD WATCH REMAINS IN PLACE FOR SOUTHWEST AND SOUTH
CENTRAL UTAH FOR THIS AFTERNOON AND EVENING. MADE ONLY
SUBTLE CHANGES TO POPS ALONG THE UT/NV BORDER AND THE LAKE POWELL
REGION...OTHERWISE NO OTHER UPDATES MADE OR PLANNED TO GOING
FORECAST. 

PREVIOUS DISCUSSION FOLLOWS...

THE MID LEVEL TROUGH OVER NORTHERN AZ IS FORECAST TO SLOWLY LIFT
NORTHWARD ACROSS THE FORECAST AREA BEGINNING SUNDAY ACROSS
SOUTHERN UT...AND CONTINUING INTO MONDAY OVER THE NORTH. AS SUCH
ANTICIPATE ANOTHER VERY ACTIVE CONVECTIVE DAY OVER SOUTHERN UT
SUNDAY AFTERNOON...WITH THE NORTH BECOMING MORE ACTIVE DURING THE
EVENING HOURS..AND LIKELY CONTINUING OVERNIGHT AS THIS WAVE
APPROACHES. HAVE INCREASED POPS OVER NORTHERN UT 10-20 PERCENT
SUNDAY AFTERNOON THROUGH SUNDAY NIGHT AND INTO MONDAY MORNING.

THUNDERSTORM COVERAGE ON LABOR DAY WILL BE DEPENDENT ON HOW
QUICKLY THIS WAVE MOVES NORTHWARD...AND THE MODELS AT THIS POINT
DO NOT SEEM TO HAVE A FIRM GRASP ON THIS. HAVE MAINTAINED A CHANCE
OF SHOWERS/THUNDERSTORMS INTO MONDAY AFTERNOON OVER MOST AREAS
WITH THE HIGHEST POPS IN THE NORTH. HOWEVER...IF THIS WAVE LIFTS
INTO ID BY EARLY AFTERNOON SUBSIDENCE WOULD LIKELY INHIBIT
ADDITIONAL CONVECTIVE DEVELOPMENT AREAWIDE.

IN THE WAKE OF THIS FEATURE...THE MID LEVEL RIDGE IS FORECAST TO
STRENGTHEN ACROSS THE REGION TUESDAY INTO WEDNESDAY. SUFFICIENT
MOISTURE WILL REMAIN TO SUPPORT A THREAT FOR SHOWERS AND
THUNDERSTORMS...HOWEVER WARMING ALOFT WILL LIKELY LIMIT
INSTABILITY...WITH CONVECTIVE ACTIVITY REMAINING LARGELY CONFINED
TO THE HIGHER TERRAIN. AN UPPER LOW WHICH IS FORECAST TO RESIDE
OFF THE PACIFIC COAST DURING THE FIRST HALF OF THE WEEK IS
FORECAST TO MOVE INLAND AND THROUGH THE NORTHERN ROCKIES LATE IN
THE UPCOMING WEEK. THIS LOOKS TO SUPPRESS THE RIDGE AXIS SOUTHWARD
AND ALLOW FOR A DRIER WESTERLY FLOW OVER NORTHERN UT.

&&

.AVIATION...LIGHT AND VARIABLE WINDS ARE EXPECTED TO CONTINUE AT
THE KSLC TERMINAL THROUGH 18/19Z BEFORE A PREVAILING NORTHWESTERLY
WIND SETS IN FOR THE AFTERNOON HOURS. EXPECTING A FEW TCU OVER THE
OQUIRRH MTNS AFTER 21Z BUT A DIRECT THUNDERSTORM IMPACT AT THE
KSLC TERMINAL IS NOT EXPECTED. A 20 PERCENT CHANCE EXISTS FOR A
SOUTHERLY ORIENTED OUTFLOW FROM THESE BUILDUPS HOWEVER.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...FLASH FLOOD WATCH THROUGH THIS EVENING FOR UTZ016-019>021-518. 

WY...NONE.
&&

$$

MERRILL/SEAMAN

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VISIT...
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