Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 221641
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1041 AM MDT FRI MAY 22 2015

.SYNOPSIS...THE LOW PRESSURE SYSTEM OVER SOUTHERN CALIFORNIA
WILL TURN NORTHEAST AND TRACK NORTHEAST THROUGH THE SOUTHERN AND
EASTERN GREAT BASIN THIS WEEKEND.

&&

.DISCUSSION...THE UPPER LOW CURRENTLY OVER SOUTHERN CALIFORNIA
STILL ON TRACK TO TURN NORTHEAST AND SLOW CROSS SOUTHERN AND
EASTERN UTAH TONIGHT THROUGH SATURDAY EVENING. AHEAD OF THE UPPER
LOW AN AREA OF WEAK MOISTURE CONVERGENCE ACROSS NORTHERN UTAH HAS
PRODUCED WIDESPREAD CLOUD COVER AND POCKETS OF LIGHT PRECIP. THE
CONVERGENCE AREA WILL WEAKEN FURTHER THIS AFTERNOON AND WILL NOT
LIKELY BE THE SOURCE OF LIFT TO SUSTAIN PRECIP LATER TODAY.

MOSTLY CLEAR SKIES SOUTH BETWEEN THE UPPER LOW AND THE CONVERGENCE
ZONE SHOULD FILL IN QUICKLY WITH CONVECTIVE PRECIP AHEAD OF THE
ADVANCING UPPER LOW. TERRAIN-BASED CONVECTION HAS ALREADY FORMED
OVER THE SOUTHERN/CENTRAL MOUNTAINS...AND WILL CONTINUE TO
INCREASE IN AREAL COVERAGE AND INTENSITY SUPPORTED BY INCREASING
DYNAMIC LIFT AND WEAK UPPER DIVERGENCE NORTH OF THE LOW. THIS
CONVECTION WILL ALSO SPREAD NORTH ACROSS MUCH OF NORTHERN UTAH
DURING THE AFTERNOON. LOOKING AT THE POTENTIAL FOR HEAVY RAIN WITH
SOME OF THE STRONGER CONVECTIVE ELEMENTS. THE RELATIVELY SLOW
MOVEMENT OF THE STORMS WILL BRING THE POTENTIAL FOR LOCAL FLOODING
INTO PLAY FOR THE URBAN AREAS THIS AFTERNOON/EARLY EVENING.

A BROAD AREA OF SYNOPTIC-SCALE LIFT ASSOCIATED WITH THE UPPER LOW
WILL LEAD TO FAIRLY WIDESPREAD RAIN AND HIGH ELEVATION SNOWS OVER
THE WEEKEND. ON SATURDAY LOOKING AT THE HEAVIEST PRECIP IN CLOSE
PROXIMITY TO THE UPPER LOW AND THE ASSOCIATED COLD POOL ALOFT...
AND IN THE WARM ADVECTION WRAP AROUND BAND ACROSS FAR NORTHERN
THROUGH WEST-CENTRAL UTAH.

THE BIGGEST QUESTION MARK IN TERMS OF SIGNIFICANT PRECIP WILL BE
ALONG THE URBAN CORRIDOR OF NORTHERN UTAH. LOOKING AT ONLY A
BRIEF PERIOD OF NORTH-NORTHWEST WARM ADVECTION ON SATURDAY...
FOLLOWING BY WEAK EASTERLY COLD ADVECTION LATE AFTERNOON/EVENING.
THIS SWITCH IN THE THERMAL ADVECTION COULD DEVELOP A WEAK
DOWNSLOPE FLOW AND SIGNIFICANT REDUCE THE INTENSITY OF THE PRECIP.
FOR NOW WILL LOWER THE QPFS ACROSS THE URBAN CORRIDOR...THOUGH NOT
ENTIRELY END PRECIP AS THE LOCAL DOWNSLOPE FLOW WILL BE WEAK AND
ENOUGH SYNOPTIC-SCALE WILL STILL EXIST TO KEEP LIGHT PRECIP GOING
THROUGH EARLY SUNDAY.

SOUTHWEST UTAH COULD BECOME THE FOCUS FOR HEAVY PRECIP LATE
SATURDAY THROUGH EARLY SUNDAY. THE MOIST NORTHWEST WARM ADVECTION
PATTERN SETTING UP SHOULD GENERATE SUBSTANTIAL LIFT AND PRODUCE
AREAS OF MODERATE OR EVEN HEAVY PRECIP ALONG THE I-15 CORRIDOR AND
INTO THE MOUNTAINS TO THE EAST.

FOR MEMORIAL DAY MORE THAN ENOUGH RESIDUAL MOISTURE WILL EXIST FOR
SCATTERED CONVECTIVE PRECIP DURING THE DAY. THE SHORTWAVE RIDGE
SCHEDULED TO FOLLOW LATER IN THE DAY SHOULD BRING AN END TO MOST
PRECIP BY MONDAY EVENING.

&&

.AVIATION...CEILINGS WILL GENERALLY REMAIN ABOVE 6000 FT AGL
THROUGH THE DAY. SHOWERS DEVELOPING THIS AFTERNOON MAY BRING
CEILINGS TO OR BELOW THAT VALUE AT TIMES. SOUTHERLY WINDS ARE
EXPECTED TO PREVAIL...BUT SHOWERS COULD PRODUCE PERIODS OF GUSTY
AND/OR ERRATIC WINDS AT TIMES.

&&

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

$$

PUBLIC...CONGER
AVIATION...RUTZ/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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