Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 192232
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
432 PM MDT TUE AUG 19 2014

.SYNOPSIS...CYCLONIC FLOW ACROSS THE NORTH COMBINED WITH A WEAK
WEATHER SYSTEM TO THE SOUTH  WILL MAINTAIN AN UNSETTLED PATTERN
THROUGH THE REMAINDER OF THE WEEK. A COLDER TROUGH LOOKS TO IMPACT
MAINLY THE NORTH THIS WEEKEND.

&&

.DISCUSSION...THE CLOSED UPPER LOW ON THE CALIFORNIA COAST
CONTINUES TO SLOWLY TRANSITION SOUTHEAST PER AFTERNOON SATELLITE
IMAGERY. ATTENDANT JET NOW NOSING INTO SOUTHWESTERN UTAH WITH
THE LEFT EXIT REGION PROVIDING ADDITIONAL LIFT TO THE DEEPLY
MOIST AIRMASS IN PLACE. BEST DIVERGENT FLOW ALOFT COINCIDENT WITH
THIS YIELDING BEST LIFT ACROSS CENTRAL AND EASTERN UTAH ATTM. JET
COUPLING THAT WAS OCCURRING EARLIER TODAY HAS SINCE WANED WITH
NORTHERN BRANCH JET STREAK SLIDING FURTHER TO THE NORTH AND
EAST...THUS DYNAMIC LIFT HAS DIMINISHED SOME AND THIS WAS NOTED IN
WARMING OF CLOUD TOPS PER IR IMAGERY EARLIER TODAY.

LOTS OF RAIN ACROSS SOUTHERN AND CENTRAL UTAH TODAY WHERE EXISTING
FLASH FLOOD WATCH REMAINS IN PLACE. BULK OF ACTIVITY THUS FAR HAS
BEEN STRATIFORM WITH EMBEDDED CONVECTION...ESPECIALLY SOUTHERN
AND SOUTHEASTERN PORTIONS WHERE THE LCL IS VERY LOW AT 750M PER
SPC MESO ANALYSIS. INSTABILITY HAS NOT BEEN OVERLY IMPRESSIVE BUT
MUCAPE NEAR OR JUST OVER 500 J/KG...MOSTLY BELOW THE FREEZING
LEVEL...COMBINED WITH AFOREMENTIONED LIFT HAS BEEN SUFFICIENT TO
GENERATE LOCALLY HEAVY RAIN AND UNDERESTIMATION ALONG THE FRINGES
OF KICX DUE TO WARM RAIN PROCESSES. LOW LEVEL UPSLOPE FLOW AIDED
PRECIP EFFICIENCY AS WELL ACROSS THE GRAND STAIRCASE.

AS THE LOW CONTINUES TO SHIFT EAST OVER THE NEXT FEW HOURS
ASSOCIATED LIFT WILL CONTINUE TO SHIFT EAST ALLOWING THE TAPERING
TREND IN PRECIP THAT HAS BEGAN ACROSS THE WEST TO SHIFT EAST OVER
MOST AREAS EARLY EVENING.

LOOKING UPSTREAM...CONVECTION OVER NORTHEASTERN NEVADA HAS
SPARKED NICELY AS HRRR INDICATED WOULD OCCUR EARLIER TODAY. WHAT
NOW IS A SUBTLE TROUGH AXIS ALONG THE UT/NV BORDER IS FORECAST TO
TIGHTEN OVERNIGHT...NEVADA CONVECTION CURRENTLY ON THE WESTERN
FRINGE OF THIS WILL TRANSITION EAST WITH THIS WHILST MOVING INTO A
MORE DEEPLY MOIST ENVIRONMENT. HRRR INDICATES SCATTERED CONVECTION
MOVING BACK INTO THE WASATCH FRONT AT OR JUST AFTER MIDNIGHT THEN
SHIFTING EAST...LIKE THIS IDEA DUE TO ADDED LIFT ALONG TIGHTENING
AXIS.

THE BROAD PACIFIC TROUGH REMAINS FORECAST TO SETTLE INTO SOCAL BY
THIS TIME TOMORROW...FILLING SLIGHTLY. AIRMASS OVER THE FORECAST
AREA WILL DRY SOME BUT REMAIN SUFFICIENT FOR AIRMASS STORMS OVER
TERRAIN AND NEIGHBORING VALLEYS TOMORROW THROUGH THURSDAY. THE LOW
WILL CONTINUE FILLING THROUGH THAT TIME BEFORE BECOMING MORE OF AN
OPEN WAVE TRACKING SOUTH BY FRIDAY.

A LARGE SCALE PATTERN CHANGE REMAINS ON TAP LATE WEEK THROUGH THE
WEEKEND. 12Z GFS LINING UP BETTER WITH THE ECMWF LATCHING ONTO THE
MORE AMPLIFIED SOLUTION OF A MEAN LONGWAVE TROUGH ACROSS THE
NORTHERN ROCKIES/PACNW. PATTERN LOOKS QUITE FALL-LIKE FOR THE TIME
BEING AT LEAST. SAID AMPLIFIED SOLUTION GRAZES THE FAR
NORTH...SURGING A WELL DEFINED COLD FRONT THROUGH NORTHERN UTAH
MIDDAY SATURDAY. UPPED POPS ACROSS THE NORTH TO MOSTLY SCATTERED
WITH AND BEHIND THIS FRONT...LOWERED TEMPS ACROSS THE NORTH AS
WELL AS H7 VALUES FORECAST TO FALL IN THE +3 TO +4 RANGE SATURDAY
NIGHT THROUGH SUNDAY.

HIGH PRESSURE DOES NOT LOOK TO REESTABLISH ITSELF UNTIL POSSIBLY
MIDWEEK OF NEXT WEEK.

&&

.AVIATION...EXPECT SOUTHERLY WINDS TO CONTINUE AT THE SLC TERMINAL
THROUGHOUT THE DAY. SHOWERS MAY CAUSE WINDS TO BECOME ERRATIC AT
TIMES. CEILINGS WILL OCCASIONALLY FALL TO NEAR 6000 FEET AGL FOR
MUCH OF THE AFTERNOON AND EVENING.

&&

.FIRE WEATHER...DEEP MOISTURE WILL REMAIN IN PLACE OVER THE FIRE
DISTRICT TONIGHT. SHOWERS AND THUNDERSTORMS WILL BECOME LESS
NUMEROUS THROUGH THIS EVENING BUT WILL LOCALLY CONTINUE THROUGH THE
NIGHT. THE AIRMASS WILL DRY SOMEWHAT WEDNESDAY BUT ENOUGH MOISTURE
WILL REMAIN WEDNESDAY INTO THURSDAY FOR MAINLY AFTERNOON AND EVENING
MOUNTAIN THUNDERSTORMS. WINDS START TO INCREASE FRIDAY AHEAD OF A
COLD FRONT THAT WILL CROSS UTAH SATURDAY THROUGH SUNDAY MORNING. THE
FRONT WILL BE ACCOMPANIED BY SHOWERS AND THUNDERSTORMS ACROSS THE
NORTH. AFTERNOON HUMIDITY WILL BEGIN TO FALL INTO THE TEENS SUNDAY
AS DRIER AIR SPREADS IN BEHIND THE COLD FRONT AND REMAIN LOW INTO
THE FIRST PART OF THE WEEK.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...FLASH FLOOD WATCH UNTIL 10 PM MDT THIS EVENING FOR UTZ010-
     012>014-016-019>021-517-518.

WY...NONE.
&&

$$

MERRILL/KRUSE/WILENSKY


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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