Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 201038
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
438 AM MDT WED AUG 20 2014

.SYNOPSIS...THE AIRMASS OVER THE FORECAST AREA WILL SLOWLY DRY
TODAY...THOUGH CONDITIONS WILL REMAIN UNSETTLED OVER THE NEXT FEW
DAYS. A COLD TROUGH WILL MOVE ACROSS NORTHERN UTAH OVER THE
WEEKEND.

&&

.DISCUSSION...A MOIST AIRMASS REMAINS OVER THE FORECAST AREA THIS
MORNING...WITH SATELLITE DERIVED PWS AROUND 1.0 INCH OVER MOST
LOCATIONS. UTAH IS CURRENTLY IN BETWEEN TWO PIECES OF A SPLIT
STORM SYSTEM. THE SOUTHERN END IS A CLOSED LOW JUST OFF THE
CALIFORNIA COAST AND THE NORTHERN END IS A BROAD TROUGH OVER THE
PACIFIC NORTHWEST. SHORTWAVE ENERGY OVER NORTHERN UTAH ON THE
SOUTH END OF THAT TROUGH HAS ALLOWED A BROAD AREA OF SHOWERS WITH
EMBEDDED THUNDERSTORMS TO DEVELOP. THESE SHOWERS ARE CURRENTLY
EXITING THE WASATCH FRONT AND MOVING INTO THE HIGHER TERRAIN TO
ITS EAST AS WELL AS SOUTHWEST WYOMING.

CURRENT THINKING IS THAT PRESENT SHOWER ACTIVITY WILL DECREASE IN
COVERAGE BY MID-MORNING AS THE SHORTWAVE MOVES OUT OF NORTHERN
UTAH...RESULTING IN A RELATIVE LULL IN PRECIPITATION.
HOWEVER...AIRMASS OVER THE AREA REMAINS QUITE UNSTABLE BETWEEN THE
TROUGH AND THE LOW. DESPITE MODELS CONTINUING TO SHOW A DRYING
TREND WITH PWS DECREASING TO AS LOW AS 0.6 BY LATE THIS
AFTERNOON...ENOUGH MOISTURE WILL REMAIN FOR AFTERNOON CONVECTION
FOCUSED OVER THE HIGHER TERRAIN. ENOUGH FLOW EXISTS TO ALLOW THIS
ACTIVITY TO DRIFT INTO ADJACENT VALLEYS.

PATTERN LOOKS TO EVOLVE SLOWLY THURSDAY AND FRIDAY AS THE SOUTHERN
LOW MOVE ACROSS CALIFORNIA AND ARIZONA AND THE STRONGER SECOND
PIECE OF THE NORTHERN TROUGH MOVES ONSHORE. LATEST GFS TAKES THE
SOUTHERN LOW INTO SOUTHEAST UTAH BY FRIDAY AFTERNOON...PROVIDING
ADDITIONAL INSTABILITY...WHILE THE EC KEEPS THAT SYSTEM OVER
ARIZONA. REGARDLESS...ENOUGH MOISTURE AND INSTABILITY WILL REMAIN
TO ALLOW FOR A CONTINUED THREAT OF CONVECTION.

EC/GFS SHOW THE PACIFIC NORTHWEST TROUGH MOVING ACROSS NORTHERN
UTAH FRIDAY NIGHT THROUGH EARLY SUNDAY. THE ASSOCIATED COLD FRONT
MOVES THROUGH NORTHERN UTAH FRIDAY NIGHT/SATURDAY MORNING AND
THROUGH CENTRAL AND SOUTHERN UTAH BY SATURDAY EVENING. 700 MB
TEMPS IN THE +10C TO +12C RANGE FRIDAY ARE PROGGED TO DROP TO AS
LOW AS +4C TO +5C OVER NORTHERN UTAH SATURDAY WITH LESS COOLING
OVER SOUTHERN UTAH. A BROAD AREA OF PRECIP WOULD ACCOMPANY THE
SYSTEM SATURDAY...FOCUSED ON NORTHERN AND CENTRAL UTAH. RAISED
POPS SOME FOR THIS PERIOD BUT MODEL RUN-TO-RUN CONSISTENCY HAS
BEEN POOR TO THIS POINT.

BEHIND THE TROUGH...MODELS INDICATE A BRIEF DRYING AND WARMING
TREND BEFORE SHOWING ANOTHER TROUGH MOVING THROUGH NORTHERN UTAH
MONDAY NIGHT AND TUESDAY.

&&

.AVIATION...IN GENERAL...SOUTHEAST WINDS WILL PREVAIL AT THE SLC
TERMINAL THROUGH MID MORNING BUT WILL INTERMITTENTLY BE ERRATIC DUE
TO SHOWERS. SOUTH WINDS WILL INCREASE AFTER 17Z AND REMAIN ELEVATED
THROUGH THE AFTERNOON. HOWEVER...THERE IS A 20 PERCENT CHANCE OF
WINDS SHIFTING TO THE NORTHWEST AFTER 22Z. CIGS ARE EXPECTED TO
CLIMB ABOVE 7000 FEET AGL BY 13Z BUT THERE IS A 40 PERCENT CHANCE
THEY WILL IMPROVE EARLIER.

&&

.FIRE WEATHER...SOME OF THE MOISTURE FROM THE MONSOONAL SURGE WILL
REMAIN  ACROSS THE REGION THROUGH THE NEXT SEVERAL DAYS AS A TROUGH
DEVELOPS OVER THE PACIFIC NORTHWEST AND THEN SWINGS THROUGH UTAH
SATURDAY. MINOR DISTURBANCES BETWEEN NOW AND SATURDAY WILL KICK OFF
CONVECTION BOTH DAY AND NIGHT THROUGH FRIDAY PRODUCING ISOLATED
WETTING RAINS ACROSS THE SOUTH AND WIDELY SCATTERED WETTING RAINS
ACROSS THE NORTH. RELATIVE HUMIDITY LEVELS WILL BE ELEVATED DURING
THE NEXT FEW DAYS AS WELL. THE TROUGH DEVELOPING OVER THE PACIFIC
NORTHWEST WILL INTERACT WITH THE MOISTURE THATS REMAINS OVER THE
NORTHERN HALF OF THE REGION ON SATURDAY LIKELY PRODUCING WIDESPREAD
RAIN. TEMPERATURES WILL BE COOLER DURING THE NEXT SEVERAL DAYS...
ESPECIALLY SATURDAY DUE TO THE COLD FRONT AND PRECIPITATION. DRYING
WILL RETURN SUNDAY INTO MONDAY BUT ANOTHER TROUGH MAY INCREASE
CHANCES OF SHOWERS TUESDAY.

&&

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

$$

PUBLIC...TRAPHAGAN
AVIATION/FIRE WX...STRUTHWOLF

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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