Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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872
FXUS65 KSLC 152223
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
423 PM MDT FRI MAY 15 2015

.SYNOPSIS...A SLOW MOVING LOW PRESSURE SYSTEM WITH SEVERAL EMBEDDED
WEATHER DISTURBANCES WILL MOVE ACROSS THE REGION TONIGHT THROUGH
SATURDAY. A WEAK RIDGE WILL MOVE IN SUNDAY INTO MONDAY BUT ANOTHER
SYSTEM IS EXPECTED LATER MONDAY INTO TUESDAY.


&&

.SHORT TERM (THROUGH 06Z TUESDAY)...SATELLITE SHOWING LARGE
CIRCULATION OVER THE WESTERN CONUS WITH SEVERAL LOBES OF ENERGY
ROTATING AROUND THE CENTER OF LOW WHICH APPEARS TO BE OVER
CENTRAL NEVADA. ONE LOBE IS OVER NORTHERN UTAH THAT IS ASSOCIATED
WITH THE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. THIS LOBE
WILL MOVE INTO SOUTHERN IDAHO BY EARLY EVENING. THE NEXT LOBE IS
OVER WEST CENTRAL ARIZONA WHICH IS LIFTING NORTHEAST. THIS WILL
INCREASE THE SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE
SOUTHEAST PORTION OF THE CWA THIS EVENING.

WRAP AROUND MOISTURE IN WEAK WARM ADVECTION PATTERN IS EXPECTED
TO MOVE IN ACROSS NORTHWESTERN UTAH SATURDAY AFTERNOON BASED ON
THE 12Z GFS AND NAM RUNS BUT THE 18Z RUNS HAVE MOVED THE TIMING OF THIS
MOISTURE INCREASE TO BETWEEN 10-15Z SATURDAY. THE MOST RECENT
RAP13 ALSO SUPPORTS THIS EARLIER SPEED SO WILL PASS ALONG TO
EVENING SHIFT THAT AN UPDATE MIGHT BE NECESSARY TO MOVE UP THE
TIMING. TEMPS ARE EXPECTED TO REMAIN COOL ACROSS THE NORTHERN CWA
UNDER THE PRECIP SHIELD SATURDAY.

SOUTHERN UTAH SHOULD SEE A LOT LESS ACTIVITY SATURDAY AS THE CORE
OF THE LOW WILL BE OVER NORTHERN UTAH. THE SOUTHERN TIER NEAR THE
ARIZONA BORDER SHOULD SEE AN INCREASE IN WESTERLY WINDS WITH GUSTS
TO NEAR 40 MPH POSSIBLE LATE AFTERNOON.

THE LOW EXITS INTO WYOMING SUNDAY LEAVING A RIDGE OVER THE REGION
SUNDAY INTO MONDAY. HOWEVER ENOUGH RESIDUAL MOISTURE IN THE AIR
MASS FOR A CHANCE OF SHOWERS OVER MAINLY NORTHERN UTAH AND HIGHER
TERRAIN. HAVE BACKED OFF ON THE POPS BUT LEFT THE CHANCE FOR NOW. THE
NEXT SYSTEM WILL MOVE IN MONDAY AFTERNOON WITH GOOD DIFFLUENCE
EXPECTED TO DEVELOP OVER SOUTHERN UTAH BY MONDAY AFTERNOON SO HAVE
INCREASED POPS. WIDESPREAD PRECIP EXPECTED TO MOVE NORTHWARD
MONDAY EVENING SO HAVE INCREASE POPS INTO NORTHERN UTAH AS WELL
FOR THE EVENING.


.LONG TERM (AFTER 06Z TUESDAY)...ANOTHER SERIES OF RELATIVELY BROAD
UPPER LEVEL LOWS WILL IMPACT THE EASTERN GREAT BASIN THROUGH THE
LONG TERM FORECAST PERIOD. THE UPPER LEVEL LOW APPROACHING THE
CALIFORNIA COAST MONDAY AFTERNOON WILL TRANSITION TO A NEGATIVELY
TILTED TROUGH AS IT CROSSES THE DESERT SOUTHWEST INTO UTAH TUESDAY.
THIS WILL CONTINUE TO BRING THE UNSETTLED CONDITIONS ACROSS THE
STATE INTO TUESDAY.

THIS TROUGH WILL TRANSITION INTO THE NORTHERN HIGH PLAINS LATER
TUESDAY...LEAVING A DEFORMATION AXIS ACROSS NORTHERN UTAH THAT WILL
REMAIN IN PLACE THROUGH MUCH OF THE DAY WEDNESDAY. CURRENT FORECAST
MAY CONTINUE PRECIPITATION TOO FAR SOUTH AND WEST AS SUBSIDENCE MAY
SHUT OFF PRECIPITATION CHANCES FOR CENTRAL AND SOUTHERN UTAH TUESDAY
AFTERNOON. LOWERED THESE AREAS A BIT AND FUTURE SHIFTS MAY NEED TO
ADJUST FURTHER IF MODELS REMAIN CONSISTENT.

YET ANOTHER BROAD UPPER LEVEL WILL DEVELOP OFF THE WEST COAST AS A
FAIRLY STRONG SHORTWAVE DIGS SOUTHWARD OFF THE WESTERN UNITED
STATES. THIS UPPER LEVEL LOW WILL EVENTUALLY EJECT EASTWARD LATER
THURSDAY INTO FRIDAY. BOTH THE 12Z EC AND THE 12Z GFS EJECT A MODEST
WAVE AHEAD OF THE PARENT LOW ACROSS THE CWA THURSDAY
AFTERNOON/EVENING. THIS UPPER LEVEL LOW WILL GRADUALLY MOVE ACROSS
THE SOUTHWEST FRIDAY INTO THE WEEKEND. GIVEN THIS PATTERN...KEPT THE
ABOVE CLIMO POPS AND NEAR TO SLIGHTLY BELOW CLIMO TEMPERATURES.
CONFIDENCE IN TIMING FEATURES THURSDAY INTO FRIDAY IS LOW.

&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE
EVENING. CIGS ARE EXPECTED TO REMAIN ABOVE 6000 FT AGL BUT COULD
BRIEFLY DROP TO OR BELOW THAT LEVEL IN PASSING SHOWERS. SOUTHERLY
WINDS SHOULD PREVAIL THROUGH THE EVENING...BUT THERE IS A 40 PERCENT
CHANCE OF GUSTY AND/OR ERRATIC WINDS WITH SHOWERS IN THE VICINITY OF
THE TERMINAL THROUGH THE EARLY EVENING.

&&

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

$$

SHORT TERM...STRUTHWOLF
LONG TERM...KRUSE
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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