Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 010416
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1016 PM MDT TUE JUN 30 2015

.SYNOPSIS...STRONG HIGH PRESSURE ALOFT CENTERED ACROSS THE WESTERN
GREAT BASIN WILL SHIFT EAST TO THE FOUR CORNERS THIS WEEKEND.
SUFFICIENT MOISTURE WILL BE IN PLACE FOR AFTERNOON AND EVENING
THUNDERSTORMS THROUGH SATURDAY. INCREASING MOISTURE AND SOMEWHAT
COOLER TEMPERATURES WILL MOVE INTO THE REGION EARLY NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE CENTERED OVER UTAH.
AMDAR 400-250MB WIND OBSERVATIONS SHOW A 50-110KT ANTICYCLONIC JET
FROM ALONG THE PACIFIC NORTHWEST OVER THE NORTHERN ROCKIES AND
INTO THE MIDWEST. GOES/GPS/RAP/00Z SLC RAOB INDICATE THE
PRECIPITABLE WATER VALUE RANGES BETWEEN 0.50" NORTHEAST
MOUNTAINS...TO 1.00"-1.50" ACROSS WESTERN AND SOUTHERN VALLEYS.

RAP INDICATES WEAK WAVE SNUCK INTO THE RIDGE AXIS FROM NEVADA THIS
EVENING...WHICH SHOULD CONTINUE TO TREK EAST SOUTHEAST OVER NORTHERN
UTAH OVERNIGHT AS THE RIDGE REPOSITIONS ITSELF OVER NEVADA. BETWEEN
THIS TRIGGER AND COPIOUS INSTABILITY HAVE INDICATED SCATTERED
CONVECTION ACROSS THE NORTH AND ISOLATED OVER CENTRAL UTAH
OVERNIGHT...WHICH SITS WELL WITH RADAR TRENDS.

OTHERWISE UTILIZED COMBINATION OF PERSISTENCE AND LAMP GUIDANCE FOR
THE TEMPERATURE/DEWPOINT CURVE OVERNIGHT. BUMPED UP SKY GRIDS TO
ACCOUNT FOR ORGANIZED CONVECTION THIS EVENING.

&&

PREVIOUS DISCUSSION...

THE UPPER HIGH CURRENTLY POSITIONED ACROSS THE WESTERN GREAT BASIN
WILL BEGIN A SLOW EASTWARD SHIFT THROUGH THE REMAINDER OF THE WEEK.
TERRAIN-BASED CONVECTION THIS AFTERNOON APPEARS TO HAVE A LITTLE
GREATER AREAL COVERAGE...WITH SOME OF THIS ACTIVITY PRODUCING BRIEF
AND LOCALLY HEAVY RAINFALL.

THE WESTERN VALLEYS MAY BECOME INVOLVED WITH THIS CONVECTIVE
ACTIVITY THIS EVENING. THE NAM/GFS HAVE FOR A COUPLE OF MODELS RUNS
GRABBED ON TO A WEAK SHORTWAVE OVER EASTERN NEVADA WHICH ENDS UP
TRACKING SLOWLY EAST THROUGH WEST-CENTRAL UTAH THIS EVENING. THIS
SHORTWAVE WILL BE MOVING INTO A REGION OF FAIRLY HIGH CAPE VALUES.
THIS COMBINATION OF DYNAMIC SUPPORT AND PRIMED AIR MASS SHOULD LEAD
TO A PERIOD OF LOOSELY ORGANIZED CONVECTION ACROSS WEST-CENTRAL
THROUGH NORTHWEST UTAH THIS EVENING. GENERALLY WEAK SHEAR INDICATES
THAT STRONG CONVECTION IS UNLIKELY...THOUGH STRONG MICROBURST STILL
A GOOD BET THIS EVENING.

MODESTLY DRIER AIR /LOWER PWAT VALUES/ WILL WORK INTO THE REGION FOR
THE LATTER HALF OF THE WEEK. STILL LOOKING AT TERRAIN-BASED
CONVECTION BOTH DAYS...THOUGH THE AREAL COVERAGE WILL LIKELY BE
REDUCED WHEN COMPARED TO THE PRIOR COUPLE OF DAYS.

DRIER CONDITIONS CONTINUE THROUGH SATURDAY ACROSS THE FORECAST AREA
WITH THE RIDGE AXIS OVERHEAD. THIS WILL BRING A WARMING TREND IN
TEMPERATURES ON SATURDAY...WITH TEMPERATURES RISING TO AROUND 100F
ONCE AGAIN ALONG THE WASATCH FRONT.

GFS/EC CONTINUING TO SHOW THE RIDGE AXIS MOVING EAST
SUNDAY...RESULTING IN SOUTHERLY FLOW OVER THE AREA. THIS WILL DRAW
TROPICAL MOISTURE INTO THE AREA...BRINGING THE THREAT OF
SHOWERS/THUNDERSTORMS TO MUCH OF THE AREA. EARLIER GUIDANCE
INDICATED TROPICAL MOISTURE WOULD STICK AROUND INTO EARLY NEXT WEEK.
HOWEVER...MODELS NOW INDICATE MORE OF A WESTERLY COMPONENT TO THE
FLOW BY MONDAY AS ANOTHER PACIFIC NORTHWEST TROUGH FLATTENS THE
RIDGE. THIS WOULD ALLOW DRIER AIR TO MOVE BACK INTO AT LEAST
SOUTHERN AND WESTERN UTAH BY MONDAY AFTERNOON WITH THE DRYING TREND
INCREASING THROUGH DAY 7. FOR NOW...HAVE ONLY LOWERED POPS SLIGHTLY
BUT CURRENT FORECAST MAY BE TOO WET IF THE TREND IN GUIDANCE
HOLDS.

&&

.AVIATION...GUSTY NORTHWEST WINDS WILL CONTINUE AT THE SLC
TERMINAL THROUGH 05Z THEN GRADUALLY DECREASE BETWEEN 05Z AND 07Z.
WIND SHIFT TO SOUTH EXPECTED BY 07Z ALTHOUGH THIS MAT BE DELAYED BY
AN HOUR OR SO. THERE IS A 20 PERCENT CHANCE OF THUNDERSTORMS
IMPACTING THE TERMINAL THROUGH 09Z WITH GUSTY WINDS THE MAIN
THREAT.

&&

.FIRE WEATHER...THE STRONG HIGH PRESSURE OF THE PAST SEVERAL DAYS
WILL GRADUALLY SHIFT FROM THE WESTERN GREAT BASIN TO THE FOUR
CORNERS REGION BY THIS WEEKEND. FOR THE BALANCE OF THE WEEK
SUFFICIENT MOISTURE WILL EXIST TO SPAWN CONVECTION ACROSS THE
HIGHER TERRAIN DURING THE AFTERNOON AND EVENING HOURS...WITH SOME
OF THIS ACTIVITY SPILLING INTO THE WESTERN AND SOUTHERN VALLEYS
DURING THE LATE AFTERNOON AND EVENING HOURS. ONCE THE HIGH
PRESSURE SHIFTS TO THE FOUR CORNERS MOISTURE WILL INCREASE AS WILL
THE AREAL COVERAGE OF CONVECTION HEADING INTO EARLY NEXT WEEK. THE
INCREASE IN CLOUD COVER/PRECIP ALONG WITH MODESTLY COOLER AIR
ALOFT WILL LEAD TO TEMPERATURES FALLING BACK TO NEAR NORMAL LEVELS
BEGINNING SUNDAY.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

PUBLIC...ROGOWSKI/CONGER/TRAPHAGAN
FIRE WEATHER...CONGER
AVIATION...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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