Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 141016
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
416 AM MDT SUN SEP 14 2014

.SYNOPSIS...HIGH PRESSURE ALOFT ACROSS THE GREAT BASIN WILL
STRENGTHEN OVER THE REGION EARLY THIS WEEK. MOISTURE WILL SPREAD
NORTH INTO SOUTHERN UTAH EARLY WEDNESDAY...THEN CONTINUE NORTH
ACROSS THE ENTIRE AREA BY THURSDAY.

&&

.SHORT TERM (UNTIL 06Z THURSDAY)...THE LOW-AMPLITUDE UPPER RIDGE
CURRENTLY ACROSS THE GREAT BASIN WILL GRADUALLY STRENGTHEN OVER
THE NEXT 2-3 DAYS. THE AXIS OF THE RIDGE WILL SHIFT INTO EASTERN
UTAH OR WESTERN COLORADO BY WEDNESDAY. THIS SHIFT WILL ALLOW THE
DEEP-LAYER MOISTURE POOLED TO THE SOUTH OF UTAH TO WORK NORTH
INTO AND THROUGH MUCH OF NEVADA AND WESTERN UTAH MIDWEEK.

THE LATEST GOES IMAGERY PLACES PWAT VALUES OF /.75/ - /1.00/
INCHES ACROSS SOUTH-CENTRAL THROUGH EAST-CENTRAL UTAH EARLY THIS
MORNING. THIS MOISTURE WILL LIKELY FUEL AFTERNOON CONVECTIVE
CLOUDS ACROSS THE HIGHER TERRAIN OF SOUTHERN/EASTERN UTAH.
DIFFERENTIAL HEATING ALONE PROBABLY SUFFICIENT FOR ISOLATED
SHOWERS OR EVEN A THUNDERSTORM DURING THE AFTERNOON AND EARLY
EVENING. AN APPARENT SHORTWAVE EXITING THE CENTRAL SIERRAS AT TIME
MAY CHANGE THAT DYNAMIC A BIT LATE THIS AFTERNOON. THIS FEATURE
COULD ADD JUST ENOUGH DYNAMIC LIFT SUPPORT TO BOOST THE THREAT FOR
THUNDERSTORMS AS IT MOVES THROUGH NORTHERN/CENTRAL UTAH. NORTHERN
UTAH WILL LIKELY REMAIN DRY WITH SOME CLOUD COVER DUE TO THIS
SHORTWAVE MOVING THROUGH THE REGION.

SUBSIDENCE UNDERNEATH THE STRENGTHENING UPPER RIDGE SHOULD INHIBIT
DEEP CONVECTION THROUGH TUESDAY. MOISTURE TRAPPED UNDER THE RIDGE
WILL STILL GENERATE PLENTY OF CONVECTIVE CLOUD COVER...WITH
ISOLATED SHOWERS OR THUNDERSTORMS CONFINED TO MAINLY THE HIGHER
TERRAIN.

THE SHIFT OF THE UPPER RIDGE AXIS TO THE UTAH/COLORADO BORDER
REGION AND THE DEEPENING OF THE EASTERN PACIFIC TROUGH MIDWEEK
WILL FINALLY OPEN UP NEVADA AND WESTERN UTAH TO A MOISTURE SURGE
LATE IN THE WEEK. PWAT VALUES IN EXCESS OF /1.00/ INCHES WILL
REACH SOUTHWEST UTAH WEDNESDAY...THEN CONTINUE NORTH THROUGH
WEDNESDAY EVENING AND BEYOND. CONVECTION WITH LOCALLY HEAVY
RAINFALL SHOULD DEVELOP ACROSS SOUTHWEST UTAH ALONG THE LEADING
EDGE OF THE MOISTURE SURGE WEDNESDAY AFTERNOON...THEN STRETCH INTO
CENTRAL UTAH WEDNESDAY EVENING. NORTHERN UTAH WILL SEE ISOLATED
CONVECTION FORM UP LATE WEDNESDAY...WITH THE POTENTIAL FOR ORGANIZED
CONVECTION ACROSS NORTHWEST UTAH IF ANY SHORTWAVE ENERGY EJECTING
OUT OF THE EASTERN PACIFIC TROUGH WERE TO GRAZE THE AREA.

&&

.AVIATION...THE SLC TERMINAL WILL EXPERIENCE VFR CONDITIONS
THROUGH THE TAF PERIOD. SOUTHEAST WINDS ARE EXPECTED TO SWITCH
TO THE NORTHWEST BETWEEN 20 AND 21Z.

&&

.FIRE WEATHER...A GRADUAL BUILDING OF THE RIDGE ACROSS THE REGION
THROUGH WEDNESDAY WILL BRING WARM TEMPERATURES AND GENERALLY DRY
CONDITIONS WITH THE EXCEPTION OF WEAK CONVECTION OVER THE HIGHER
TERRAIN EACH AFTERNOON. RELATIVE HUMIDITIES WILL LOWER INTO THE MID
TEENS EACH AFTERNOON THROUGH TUESDAY BUT WILL BEGIN TO INCREASE OVER
THE SOUTH BY WEDNESDAY AFTERNOON AS A DEEP MOISTURE SURGE
APPROACHES. WETTING RAINS ARE EXPECTED ACROSS MOST OF THE DISTRICT
THURSDAY INTO FRIDAY BEFORE SOME DRYING OCCURS NEXT WEEKEND.

&&

.LONG TERM (AFTER 06Z THURSDAY)...DESPITE THE DIFFERENCES BETWEEN THE
EC AND THE GFS ON THE EVOLUTION OF THE TROUGH AS IT MOVES ACROSS THE
WEST THURSDAY AND FRIDAY...THEY BOTH BRING DEEP MOISTURE ASSOCIATED
WITH ODILE NORTHWARD INTO THE WESTERN PORTIONS OF THE CWA THURSDAY
MORNING. THE DEEP MOISTURE REMAINS THROUGH LATE THURSDAY NIGHT
BEFORE DRYING BEGINS ACROSS THE NORTHWEST. THE GFS INDICATES PWAT OVER
0.75 OF AN INCH WILL PREVAIL ACROSS THE AREA FROM 06Z THURSDAY
UNTIL 06Z FRIDAY. WITHIN THIS TIME MOST OF WESTERN AND SOUTHERN
VALLEYS WILL HAVE PWAT GREATER THAN 1.00 INCH WITH ISOLATED 1.25
INCHES. THE PW FORECAST FOR SLC IS ABOUT 1.10 INCHES WHICH IS
ROUGHLY 2.5 STANDARD DEVIATIONS ABOVE NORMAL. HAVE INCREASED POPS
EARLY THURSDAY OVER THE WESTERN VALLEYS AS THE EC AND GFS ARE NOW
A LITTLE FASTER IN BRINGING IN THE MOISTURE. TIMING OF WHEN TO
DECREASE THE PRECIPITATION FROM THE NORTHWEST IS A LITTLE
CHALLENGING SINCE THE EC AND GFS HAVE DIFFERENT SOLUTIONS ON HOW
THE TROUGH EVOLVES. THE EC LEAVES THE SOUTHERN PORTION OF THE
TROUGH OFF THE CALIFORNIA COAST WHICH ALLOWS THE NORTHERN PORTION
OF THE TROUGH TO SWEEP THROUGH A LITTLE FASTER THEN THE GFS WHICH
HOLDS THE TROUGH TOGETHER. THE GFS 500 MB TEMP IS 4 DEGREES C
COLDER THEN THE EC IS COME FRIDAY AFTERNOON WHICH WOULD ARGUE TO
KEEP INSTABILITY SHOWERS LINGERING THROUGH THE DAY OVER A LARGE
CHUNK OF THE CWA WHILE THE EC BEING WARMER AND FASTER WITH THE
TROUGH HAS LESS POPS. HAVE LEANED TOWARD THE GFS FOR NOW.

&&


.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...RED FLAG WARNING FROM 2 PM TO 8 PM MDT SUNDAY WYZ277

&&

$$

CONGER/STRUTHWOLF

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)



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