Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 202211
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
411 PM MDT MON APR 20 2015

.SYNOPSIS...HIGH PRESSURE ALOFT WILL BUILD EAST INTO THE GREAT
BASIN ON TUESDAY. A LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST WILL MOVE INLAND TUESDAY...THEN TURN NORTH AND
IMPACTS MUCH OF SOUTHERN...CENTRAL AND WESTERN UTAH MIDWEEK.

&&

.SHORT TERM (THROUGH 00Z FRIDAY)...THE UPPER RIDGE CURRENTLY OVER
THE WEST COAST STATES WILL MOVE EAST INTO THE WESTERN GREAT BASIN
OVERNIGHT...THEN SETTLE INTO UTAH ON TUESDAY. AT THE SAME TIME AN
UPPER LEVEL LOW PRESSURE SYSTEM JUST OFF THE SOUTHERN CALIFORNIA
COAST WILL MOVE INLAND EARLY TUESDAY...THEN TURN NORTH INTO
EXTREME SOUTHERN NEVADA LATE TUESDAY NIGHT/WEDNESDAY. THIS UPPER
LOW WILL IMPACT PORTIONS OF SOUTHERN...CENTRAL AND WESTERN UTAH
MIDWEEK.

CONVECTIVE CLOUD COVER ONCE AGAIN DEVELOP[ED ACROSS THE HIGHER
TERRAIN OF NORTHEAST THROUGH SOUTHERN UTAH. THIS CONVECTION
LACKING ANY IDENTIFIABLE DYNAMIC FEATURE TO SUPPORT DEEP LIFT
PRODUCED AT BEST ISOLATED LIGHT SHOWERS THIS AFTERNOON. CONVECTION
SHOULD END QUICKLY EARLY THIS EVENING WITH THE LOSS OF DAYTIME
HEATING. IN GENERAL LOOKING AT A SIMILAR DAY TUESDAY AS TODAY. THE
EXCEPTION TO THIS MAY OCCUR ACROSS THE SOUTHWEST/CENTRAL MOUNTAIN
ZONES AS SOME MOISTURE AHEAD OF THE ADVANCING UPPER LOW WORKS
NORTH THROUGH THAT PORTION OF THE FORECAST AREA. DEEP CONVECTION
STILL UNLIKELY AS THE DYNAMIC SUPPORT FOR LIFT REMAINS REMOVED
FROM THE STATE.

THE CONTINUED NORTHWARD ADVANCE OF MOISTURE ALONG WITH THE UPPER
LOW POSITIONED OVER FAR SOUTHERN NEVADA SHOULD PRODUCE AN
INCREASING TREND IN CONVECTION FROM TUESDAY NIGHT THROUGH WEDNESDAY
NIGHT. THE KEY TO LOCATING ORGANIZED SHOWERS/ISOLATED THUNDERSTORMS
WILL BE TO DETERMINE WHERE THE DEFORMATION ZONE ALONG THE NORTH
THROUGH NORTHEAST FLANK OF THE UPPER LOW SETS UP. EARLY WEDNESDAY
THE GFS/ECMWF PLACES THIS FEATURE OVER CENTRAL UTAH...THEN
ADVANCES IT NORTHWARD INTO NORTHERN UTAH LATE WEDNESDAY
AFTERNOON/EVENING. HAVE BOOSTED POPS/QPFS A BIT NEAR THIS
BOUNDARY...THOUGH NOT LOOKING FOR STRONG CONVECTION OR HEAVY RAIN
AT THIS TIME.

A SHORTWAVE MOVING EAST THROUGH THE NORTHERN ROCKIES WILL GRAZEFAR
NORTHERN UTAH THURSDAY. MOISTURE LEFT OVER FROM THE EARLIER
CONVECTION WILL LIKELY FUEL ADDITIONAL SHOWERS/STORMS ACROSS THE
NORTH. THE WEAK DYNAMIC LIFT AND WEAK SHEAR NOT EXPECTED TO
PRODUCE STRONG CONVECTION OUTSIDE OF NEAR THE IDAHO BORDER DURING
THE AFTERNOON.

.LONG TERM (AFTER 00Z FRIDAY)...GLOBAL MODELS ARE FINALLY STARTING
TO CONVERGE ON A SOMEWHAT CONSISTENT SOLUTION...THOUGH SUBTLE TO
NOT SO SUBTLE DIFFERENCES REMAIN. TO START THE LONG TERM FORECAST
PERIOD...A SHORTWAVE WILL BE CROSSING THE BAJA CALIFORNIA AREA.
SUFFICIENT MOISTURE...LIFT AND INSTABILITY SHOULD BE IN PLACE
AHEAD OF THIS TROUGH TO CONTINUE THE THREAT OF THUNDERSTORMS INTO
LATE THURSDAY EVENING ACROSS THE CWA.

YET ANOTHER TROUGH WILL APPROACH THE NORTHERN CALIFORNIA COAST EARLY
FRIDAY. THIS TROUGH WILL PROGRESS INTO THE WESTERN GREAT BASIN BY
FRIDAY AFTERNOON AND WILL LIKELY PROVIDE ENOUGH LIFT FOR ANOTHER
ROUND OF CONVECTION FRIDAY AFTERNOON/EVENING. BUMPED UP POPS AS
CONFIDENCE HAS INCREASED WITH THE TIMING OF THESE FEATURES FRIDAY
AFTERNOON/EVENING. THIS TROUGH WILL CONTINUE TO SLOWLY MOVE ACROSS
THE GREAT BASIN/DESERT SOUTHWEST THROUGH SATURDAY. THERE IS A
RELATIVE LARGE RANGE OF SOLUTIONS AS TO THE EXACT PATH OF THIS
TROUGH AFTER FRIDAY AFTERNOON. REGARDLESS...EXPECT THE THREAT OF
CONVECTION TO REDEVELOP SATURDAY AFTERNOON/EVENING...BUT COVERAGE
IS LESS CERTAIN THAN EARLIER PERIODS.

BY LATE SATURDAY...THIS TROUGH IS FORECAST BY A RELATIVELY LARGE
SEGMENT OF THE GUIDANCE TO FINALLY EJECT EASTWARD...WITH RIDGING
DEVELOPING ACROSS THE CWA FOR THE REMAINDER OF THE WEEKEND AND INTO
EARLY NEXT WEEK.

&&

.AVIATION...NORTHWEST WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH THE EVENING...SWITCHING TO SOUTHEAST BETWEEN 03-05Z.

&&

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

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...KRUSE

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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