Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 070935
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
335 AM MDT TUE JUL 7 2015

.SYNOPSIS...HIGH PRESSURE WILL REMAIN CENTERED OVER THE SOUTHERN
ROCKIES THROUGH MUCH OF THIS WEEK. ABUNDANT MOISTURE ALONG WITH
WEAK WEATHER DISTURBANCES MOVING THROUGH THE REGION WILL GENERATE
SHOWERS AND THUNDERSTORMS THROUGH MIDWEEK. A BROAD UPPER LOW
WILL MOVE THROUGH THE EASTERN GREAT BASIN LATE IN THE WEEK.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...
WATER VAPOR LOOP SHOWS A WEAK WAVE ACROSS SOUTHWEST
UTAH...OTHERWISE RIDGING DOMINATES THE GREAT BASIN...AHEAD OF A
CLOSED LOW OFF THE CALIFORNIA COAST. AMDAR 400-250MB WIND
OBSERVATIONS SHOW A 50-105KT WESTERLY JET FROM THE PACIFIC INTO
THE SOUTHWEST CONUS. GOES/GPS/RAP/00Z SLC RAOB INDICATE THE
PRECIPITABLE WATER VALUE RANGES BETWEEN 0.45" NORTHEAST
MOUNTAINS...TO 0.90"-1.35" ACROSS MOST VALLEYS.

ISOLATED CONVECTION STILL GOING ACROSS MAINLY CENTRAL AND
SOUTHERN UTAH AS A WAVE SPINS OVER SOUTHWEST UTAH. PLENTY OF
INSTABILITY TODAY AND GIVEN THE COMBINATION OF WEAK WAVE AND
TERRAIN CIRCULATIONS SHOULD HAVE LITTLE ISSUES DEVELOPING ISOLATED
TO SCATTERED CONVECTION ONCE AGAIN.

VALLEY DEWPOINTS ARE MAINLY IN THE 45F-55F RANGE...WITH BUFKIT
MODEL SOUNDINGS INDICATING A MODEST WARM RAIN LAYER...SUGGESTING
STRONGEST STORMS MAY AGAIN PROVIDE THREAT OF FLASH FLOODING FROM
LOCALLY HEAVY RAINFALL. HOWEVER LOOKING AT IR SATELLITE AM
CONCERNED ABOUT EXTENSIVE CLOUD COVER WHICH WOULD REDUCE
PRECIPITATION INTENSITY ON A BROADER SCALE...SO DECIDED AGAINST A
FLASH FLOOD WATCH.

TOMORROW IS A TRANSITION DAY AS THE UPSTREAM CLOSED LOW MAKES ITS
WAY INTO CENTRAL CALIFORNIA. INCREASING DRY SOUTHWESTERLY FLOW
WILL LIMIT CONVECTION ACROSS THE SOUTH AND PROVIDE THE OPPORTUNITY
FOR THE DEVELOPMENT OF GUSTY WINDS ACROSS A FEW SOUTHWESTERN
VALLEYS. FURTHER NORTH AND EAST WHERE CONVECTION DOES FORM...IT
WILL BE TRANSITIONING TO HIGHER BASED ACTIVITY.

INCREASING DIFFLUENCE ALOFT WILL SUPPORT SOME CONVECTIVE ACTIVITY
THURSDAY...YET MUCH OF IT SHOULD BE IN THE FORM OF DRY
THUNDERSTORMS AS THE COLUMN CONTINUES TO DRY. GUSTY SOUTHWEST
WINDS WILL CONTINUE TO SPREAD ACROSS THE STATE AHEAD OF THE CLOSED
LOW.

.LONG TERM (AFTER 12Z FRIDAY)...
THE PACIFIC TROUGH IS PROGGED TO CONTINUE TO PIVOT ACROSS THE
FORECAST AREA DURING THE DAY FRIDAY...WITH THE BEST SHORTWAVE
ENERGY MOVING INTO NORTHERN UTAH AND SOUTHWEST WYOMING DURING THE
AFTERNOON HOURS. LINGERING MOISTURE AND INSTABILITY OVER FAR
NORTHERN UTAH COULD KEEP A FEW SHOWERS GOING FRIDAY NIGHT/SATURDAY
MORNING.

BEHIND THE EXITING SYSTEM...A DRIER SW FLOW IS EXPECTED TO REMAIN
OVER THE FORECAST AREA BETWEEN THE RIDGE CENTERED OVER TEXAS AND
ANOTHER PACIFIC TROUGH. LATEST EC KEEPS THE EXITING SYSTEM STRONGER
THAN WHAT IS INDICATED IN THE GFS SOLUTION...CAUSING SOME SLIGHT
DIFFERENCES IN THE DIRECTION OF THE FLOW ALOFT OVER THE FORECAST
AREA. THUS...THE GFS BRINGS SOME MOISTURE INTO SOUTHEAST UTAH
SATURDAY. THIS MOISTURE IS THEN PROGGED TO SPREAD NORTHWARD SUNDAY
AS THE PACIFIC NORTHWEST TROUGH APPROACHES THE COAST...CAUSING THE
FLOW ALOFT TO BECOME MORE SOUTHERLY. MEANWHILE...DUE TO DIFFERENCES
IN THE POSITIONS OF THESE TWO TROUGHS...THE FLOW STAYS MORE
CONSISTENTLY SOUTHWESTERLY...KEEPING A MUCH DRIER AIRMASS OVER THE
FORECAST AREA. HAVE KEPT IN SOME SLIGHT CHANCE/CHANCE POPS OVER THE
UPCOMING WEEKEND DUE TO THE GFS SOLUTION. HOWEVER...DUE TO LACK OF
RUN-TO-RUN CONSISTENCY CONFIDENCE IS LOW IN EITHER SOLUTION.

GFS KEEPS THE PACIFIC NORTHWEST STORM SYSTEM WELL NORTH OF THE AREA
EARLY NEXT WEEK...BRINGING DRIER AIR BACK IN. THOUGH THE SYSTEM GETS
CLOSER TO THE FORECAST AREA IN THE EC SOLUTION...THE AIRMASS REMAINS
MOSTLY DRY. AS A RESULT...HAVE SHOWN A TREND TOWARD DECREASING POPS
INTO DAY 7.

&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE
MORNING. SOUTHEAST WINDS ARE EXPECTED TO SHIFT TO THE NORTHWEST
BETWEEN 17Z AND 19Z.

&&

.FIRE WEATHER...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL
BE THE RULE AGAIN TODAY. NEW LIGHTNING STARTS ARE THE PRIMARY
CONCERN...WITH SOME STORMS PROVIDING AN OPPORTUNITY FOR A WETTING
RAIN. THE CONVECTIVE COVERAGE WILL KEEP TEMPERATURES DOWN AND
HUMIDITY UP A BIT.

WEDNESDAY SHOULD BE A TRANSITION DAY WITH DRIER AIR MOVING IN ALOFT
FROM THE SOUTH. ACTIVITY ACROSS SOUTHERN UTAH SHOULD BE MORE
ISOLATED AND HIGHER BASED AS A RESULT. LOCALLY GUSTY WINDS MAY
DEVELOP BY AFTERNOON ACROSS THE SOUTHWEST.

THURSDAY AND FRIDAY WILL BRING ISOLATED CONVECTION TO MAINLY
NORTHERN UTAH WITH GUSTY WINDS AND LIGHTNING. DRIER CONDITIONS
WILL SETTLE INTO THE REGION THROUGH THE UPCOMING WEEKEND. PERIODS
OF GUSTY SOUTHWEST WINDS WILL PERSIST WITH HUMIDITY FALLING BELOW
CRITICAL LEVELS.

&&

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

$$

SHORT TERM/FIRE WEATHER...ROGOWSKI
LONG TERM/AVIATION...TRAPHAGAN

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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