Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 151012
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
412 AM MDT MON SEP 15 2014

.SYNOPSIS...HIGH PRESSURE WILL STRENGTHEN ACROSS THE INTERIOR WEST
THROUGH THE FIRST HALF OF THE WEEK. TROPICAL MOISTURE WILL SURGE
NORTHWARD INTO SOUTHERN UTAH WEDNESDAY...THEN CONTINUE NORTH
ACROSS THE ENTIRE AREA BY THURSDAY.

&&

.SHORT TERM (THROUGH 06Z FRIDAY)...THE UPPER RIDGE COVERING MUCH
OF THE WESTERN US WILL GAIN AMPLITUDE OVER THE NEXT COUPLE OF
DAYS. TROPICAL MOISTURE ASSOCIATED WITH HURRICANE ODILE WILL
REMAIN EFFECTIVELY PINNED BY THE RIDGE TO THE SOUTH OVER NORTHWEST
MEXICO/SOUTHERN ARIZONA THROUGH TUESDAY. THE SHIFT OF THE RIDGE
AXIS INTO WESTERN COLORADO COMBINED WITH THE DEEPENING TROUGH OFF
THE WEST COAST WILL ALLOW THIS TROPICAL MOISTURE TO SURGE NORTH
THROUGH THE DESERT SOUTHWEST AND INTO THE GREAT BASIN BEGINNING
MIDWEEK.

A WEAK SHORTWAVE MOVING EAST ACROSS NORTHERN UTAH EARLY THIS
MORNING IS GENERATING ENOUGH LIFT FOR WEAK CONVECTION ACROSS THE
NORTHERN THIRD OF THE STATE. MOST OF THIS CONVECTION WILL PRODUCE
LITTLE MORE THAN VIRGA OR VERY LIGHT SHOWERS BEFORE EXITING THE
AREA MID-MORNING.

MOISTURE TRAPPED UNDERNEATH THE BUILDING RIDGE WILL SPAWN
AFTERNOON CONVECTIVE CLOUD COVER TODAY AND TUESDAY. DIFFERENTIAL
HEATING COULD PRODUCE ENOUGH INSTABILITY FOR A FEW LIGHT SHOWERS
OR EVEN A STRAY THUNDERSTORM BOTH AFTERNOONS.

LOOKING AT AN INCREASING CHANCE FOR CONVECTION ACROSS SOUTHERN
UTAH LATE WEDNESDAY AS THE RIDGE AXIS SHIFTS OFF INTO WESTERN
COLORADO. A SUBSTANTIAL INCREASE IN BOTH AREAL COVERAGE AND
INTENSE FOR CONVECTIVE PRECIP WILL DEVELOP ON THURSDAY. ORGANIZED
CONVECTION COULD FORM UP ALONG THE LEADING EDGE OF THE TROPICAL
MOISTURE PLUME...WITH HEAVY CONVECTIVE RAIN TRAILING BACK INTO THE
CORE OF THE ADVANCING MOISTURE PLUME ACROSS SOUTHWEST UTAH.
WIDESPREAD RAIN SHOULD EXIST THURSDAY NIGHT AS THE TROPICAL MOISTURE
PLUME WILL COVER MUCH OF THE FORECAST AREA. WILL HAVE TO KEEP AN
EYE OUT FOR ORGANIZED HEAVY RAINS ASSOCIATED WITH ANY SHORTWAVE
ENERGY EJECTING NORTHEAST OUT OF THE ADVANCING WEST COAST UPPER
TROUGH.

&&

.LONG TERM (BEGINNING 06Z FRIDAY)...DESPITE THE DIFFERENCES BETWEEN
THE EC AND GFS ON THE EVOLUTION OF WHERE...WHEN AND IF A CLOSED LOW
SHOULD FORM OVER THE DESERT SOUTHWEST/EASTERN PACIFIC COME
FRIDAY...MOISTURE ASSOCIATED WITH ODILE SHOULD HAVE ALREADY REACHED
THE CWA ON THURSDAY. THE GFS IS MORE PROGRESSIVE WITH THE TROUGH
WITH THE CLOSED LOW NOT FORMING UNTIL THE TROUGH IS OVER CALIFORNIA
...THEN THE LOW MOVES INTO ARIZONA BEFORE LIFTING NORTHWARD ACROSS
UTAH SUNDAY INTO MONDAY IN A MUCH WEAKENED STATE. THE EC HAS THE LOW
FORMING OFF THE NORTHERN CALIFORNIA COAST THURSDAY EVENING AND THEN
MOVING DOWN THE COAST UNTIL SUNDAY MORNING BEFORE GRADUALLY
WEAKENING AS IT GETS PULLED NORTHWARD INTO THE PACIFIC NORTHWEST BY
THE NEXT UPSTREAM TROUGH. EACH SOLUTION IS PLAUSIBLE SO DID NOT
CHANGE MUCH IN THE GRIDS OTHER THAN KEEP CHANCE OR LOW CHANCE POPS A
LITTLE MORE WIDESPREAD FRIDAY AND SATURDAY AS THE UNCERTAINTY
WARRANTS THE POSSIBILITY.

&&

.AVIATION...SOUTHEAST WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH ABOUT 19-20Z THEN SHIFT TO THE NORTHWEST. VFR CONDITIONS
WILL PREVAIL THROUGH THE TAF PERIOD.

&&

.FIRE WEATHER...WELL ABOVE NORMAL TEMPERATURES BY 5 TO 10 DEGREES
WILL PREVAIL ACROSS THE REGION THROUGH WEDNESDAY. MINIMUM RELATIVE
HUMIDITY VALUES IN THE VALLEYS WILL BE IN THE MID TEENS TODAY AND
TUESDAY BUT INCH UPWARD WEDNESDAY AS MOISTURE BEGINS TO INCREASE.
THIS MOISTURE WHICH IS ASSOCIATED WITH HURRICANE ODILE WILL BE
BROUGHT NORTHWARD INTO THE EASTERN GREAT BASIN THURSDAY AND FRIDAY
DESPITE THE REMNANTS OF ODILE REMAINING FAR TO THE SOUTH IN ARIZONA.
WETTING RAINS ARE POSSIBLE THURSDAY AND FRIDAY BUT THEN SOME DRYING
IS EXPECTED TO OCCUR FROM NORTHWEST TO SOUTH OVER THE WEEKEND.

&&

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

&&

$$

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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