Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 062207
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
407 PM MDT MON JUL 6 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 06Z THU)...TWO FEATURES TO NOTE THIS
AFTERNOON...A SLOW MOVING AND WEAK SHORT WAVE TRANSLATING EAST
ACROSS THE UT/ID BORDER AND A WEAK DISTURBANCE WITHIN AN
INCREASINGLY MOIST RETURN FLOW ON THE WESTERN PERIPHERY OF THE
HIGH OVER CENTRAL UTAH. BOTH HAVE INITIATED CONVECTION THIS
AFTERNOON BUT THE FORMER WILL SOON BE A NON PLAYER IN THE COMING
HOURS...THOUGH SOME CELLS HAVE PRODUCED LOCALLY HEAVY RAIN AND
WILL SO FOR A FEW MORE HOURS OVER THE FAR NORTH. SHORT TERM FOCUS
SHIFTS TO THE LATTER WHICH IS NOW BEGINNING TO IMPINGE ON THE
SOUTHERN WASATCH FRONT FROM THE SOUTH.

SCATTERED TO NUMEROUS SHOWERS/STORMS HAVE DEVELOPED OVER
SOUTHERN/CENTRAL UTAH TODAY WITH SOME PRODUCING LOCALLY HEAVY
RAINFALL. JUST RECEIVED A REPORT OVER THE LAST HOUR FROM CEDAR
CITY OF .75 INCHES OF RAIN IN A HALF HOUR...THIS FROM A RATHER
BENIGN LOOKING STORM STRUCTURALLY-WISE. IN THE NEAR TERM WILL
CLOSELY MONITOR POTENTIAL FOR LOCALLY HEAVY RAINFALL AND
ASSOCIATED FLASH FLOODING IF OVER PRONE AREAS. EXPECT COVERAGE OF
STORMS WILL INCREASE TO ROUGHLY UTAH/SLC COUNTY THIS EVE.
INCREASED TO SCATTERED STORM COVERAGE VALLEYS THAT FAR NORTH.

BEING A WEAK AND SLOW MOVING DISTURBANCE...OPTED TO INCREASE
OVERNIGHT CLOUD COVER AND RETAIN NOCTURNAL SHOWERS ACROSS THE
SOUTHERN HALF OF THE AREA TONIGHT INTO THE MORNING HOURS. PWAT
IN EXCESS OF 1 INCH AND WEAK FORCING SHOULD PROVIDE ENOUGH
JUICE/LIFT TO MAINTAIN THESE DURING THE COOL HOURS MUCH LIKE THIS
MORNING.

EXPECTING ALL BUT THE CENTRAL WASATCH FRONT/NORTHWEST DESERTS TO
SEE ANOTHER ROUND OF SCATTERED TO NUMEROUS CONVECTION TOMORROW AS
SIMILAR MOISTURE/INSTABILITY PROFILES WILL EXIST AND YET ANOTHER
WEAK RETURN FLOW WAVE WILL BE PRESENT. POPS INCREASED AS SUCH.

FOCUS WEDNESDAY SHIFTS TO EVOLUTION AND TRACK OF THE CLOSED LOW
OFF THE CALI COAST...WHICH AT THAT TIME WILL BE COMING ON SHORE. A
DRYING SOUTHWESTERLY FLOW ALOFT LOOKS TO PUNCH INTO THE SOUTHWEST
ALLOWING A NET DECREASING PWAT TREND TO SURGE NORTHEAST.
CONVECTION IS STILL EXPECTED TO OCCUR OVER THE NORTHERN 2/3RDS OF
THE AREA WEDNESDAY AFTERNOON AS THE BULK OF DRYING WILL OCCUR
ALOFT...BUT COVERAGE WILL LIKELY BE LESS EXPANSIVE AND HIGHER
BASED.

.LONG TERM (AFTER 06Z THURSDAY)...THE CLOSED PACIFIC LOW WILL MOVE
INLAND INTO CALIFORNIA LATE WEDNESDAY INTO THURSDAY. OUT AHEAD OF
THIS LOW...DRIER AIR WILL MOVE INTO UTAH IN THE SOUTHWEST
FLOW...WITH PRECIPITABLE WATER VALUES DROPPING BELOW HALF AN INCH IN
MANY LOCATIONS.

THAT SAID...MODELS HAVE INCREASED THE SPEED OF THIS
PACIFIC WAVE SO THAT IT NOW MOVES INTO THE EASTERN GREAT BASIN
THURSDAY AFTERNOON RATHER THAN THURSDAY NIGHT OR FRIDAY. EVEN WITH
LIMITED MOISTURE...THIS VIGOROUS WAVE SHOULD BE ENOUGH TO INITIATE
SOME HIGH BASED CONVECTION THURSDAY AFTERNOON ACROSS THE WESTERN
HALF OF UTAH. WITH THESE INGREDIENTS COMING TOGETHER...HAVE ADDED A
MENTION OF GUSTY THUNDERSTORM WINDS INTO THE FORECAST FOR THURSDAY
AFTERNOON AND EVENING. HAVE ALSO INCREASED THE SYNOPTIC SCALE WINDS
A BIT IN THE FORECAST...AS SOUTHERLIES SHOULD INCREASE SOME ON
THURSDAY AND FRIDAY AS THE SURFACE LOW PASSES TO THE NORTH.

THE AIRMASS DRIES EVEN MORE ON FRIDAY AND SATURDAY AFTER THE
SHORTWAVE PASSES...SO HAVE MAINTAINED THE DRYING AND SLOW WARMING
TREND HEADING INTO THE WEEKEND. THE NEXT QUESTION IS WHEN DEEPER
MOISTURE RETURNS AND HOW QUICKLY. THE GFS STARTS BRINGING IN
MOISTURE FROM THE SOUTH ON SUNDAY...WITH PRECIPITABLE WATER VALUES
QUICKLY EXCEEDING ONE INCH. THE ECMWF IS SLOWER WITH THIS MOISTURE
RETURN...BUT HAVE TRENDED THE FORECAST TOWARD THE IDEA OF INCREASED
CONVECTION MOVING IN FROM THE SOUTH SUNDAY AND MONDAY FOR NOW.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED AT THE KSLC TERMINAL THROUGH
THE TAF PERIOD. NORTHWEST WINDS AT 2200 UTC ARE EXPECTED TO SWITCH
TO THE SOUTH BY 2300 UTC AS OUTFLOW FROM CONVECTION MOVES THROUGH.
THERE IS A 30 PERCENT CHANCE THAT ADDITIONAL OUTFLOW WINDS FROM
CONVECTION IN THE AREA WILL IMPACT THE TERMINAL BETWEEN 0000-0400
UTC. THERE IS ALSO SLIGHT CHANCE THAT A THUNDERSTORM WILL DIRECTLY
IMPACT THE TERMINAL DURING THIS TIME FRAME.

&&

.FIRE WEATHER...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL
BE THE RULE THROUGH TOMORROW. 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.

AN ABRUPT PATTERN SHIFT IS CURRENTLY ADVERTISED DURING THE MIDDLE OF
THE WEEK. A DRY AND GUSTY SOUTHWESTERLY FLOW DEVELOPS TRENDING
HUMIDITY LOWER...BEGINNING WEDNESDAY AFTERNOON ACROSS THE FAR
SOUTHWEST VALLEYS. CONVECTION WILL STILL BE AROUND...THOUGH WETTING
RAIN BECOMES LESS OF A POSSIBILITY AS ACTIVITY BECOMES HIGHER
BASED.

&&

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

$$

MERRILL/SCHOENING/GRAHAM


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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