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000
FXUS65 KSLC 152205
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
405 PM MDT WED MAY 15 2013

.SYNOPSIS...A WEAK UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS
SOUTHERN UTAH THROUGH THIS EVENING. BEHIND THIS SYSTEM A STRONGER TROUGH
WILL MOVE INTO THE GREAT BASIN LATE IN THE WEEK...FOLLOWED BY A
STILL COLDER SYSTEM OVER THE WEEKEND. HIGH PRESSURE WILL RETURN
BY THE MIDDLE OF NEXT WEEK.



&&

.DISCUSSION...UPPER LEVEL DISTURBANCE CURRENTLY MOVING ACROSS
SOUTH CENTRAL UTAH THIS AFTERNOON PER WATER VAPOR IMAGERY. LITTLE
CONVECTIVE ACTIVITY WITH THE LOW...BUT IS CONTRIBUTING TO
INSTABILITY PRODUCING CONVECTION OVER SOUTHWEST WYOMING AND THE
HIGHER TERRAIN OF NORTHERN UTAH. MOISTURE IS CONCENTRATED AT MID
AND UPPER LEVELS SO DO NOT EXPECT MUCH RAIN TO HIT THE
GROUND. GUSTY WINDS SEEM TO BE THE BIGGEST THREAT THROUGH THE
EARLY EVENING. EXPECTING CONVECTIVE ACTIVITY TO WIND DOWN WITH THE
LOSS OF DAYTIME HEATING.

SOUTHERLY FLOW WILL INCREASE TOMORROW AHEAD OF THE FIRST IN A
SERIES OF STORM SYSTEMS THAT WILL IMPACT THE AREA THROUGH EARLY
NEXT WEEK. BREEZY CONDITIONS ARE POSSIBLE PRIMARILY SOUTH OF THE
STALLED FRONTAL BOUNDARY OVER NORTHERN UTAH...PARTICULARLY OVER
SOUTHWEST UTAH. ENOUGH MOISTURE AND INSTABILITY WILL EXIST FOR
SOME MORE ISOLATED STORMS OVER NORTHERN UTAH...BUT SOUTHERN UTAH
WILL REMAIN QUITE DRY...LIMITING CONVECTIVE ACTIVITY.

EC/GFS PUSH THE INITIAL STORM SYSTEM AND ASSOCIATED COLD FRONT THROUGH
LATE THURSDAY NIGHT THROUGH FRIDAY. ECMWF IS A BIT FASTER MOVING
THE FRONT THROUGH AND ALSO GIVES THE SYSTEM MORE OF A TILT. THOUGH
THE SYSTEM APPEARS TO BE LACKING IN MOISTURE IN BOTH
SOLUTIONS...ENOUGH INSTABILITY WILL EXIST FOR SOME DECENT
CONVECTION...ESPECIALLY IN THE VICINITY OF THE FRONTAL BOUNDARY.
TEMPS WILL DROP NOTICEABLY WITH THE BOUNDARY...WITH MAXES RUNNING
VERY CLOSE TO SEASONAL NORMS IF NOT A LITTLE BELOW BY SATURDAY.
THIS IS A BIG CHANGE COMPARED TO THE 15-20F ABOVE CLIMO HIGHS
OBSERVED THE PAST FEW DAYS.

THE SECOND STORM SYSTEM IN THE SERIES IS PROGGED TO MOVE IN RIGHT
BEHIND THE INITIAL WAVE SATURDAY NIGHT/SUNDAY MORNING...BRINGING A
REENFORCING SHOT OF COLD AIR AND CONTINUED UNSETTLED
CONDITIONS...ESPECIALLY FOR NORTHERN UTAH. 12Z ECMWF AND GFS STILL
DIFFER SOME WITH THE SYSTEM...WITH THE ECMWF CONTINUING TO BRING
THE SYSTEM FARTHER SOUTH...MOVING COLD POOL ENERGY OVER THE
FORECAST AREA SUNDAY. IN THE FARTHER NORTH GFS SOLUTION...THE BEST
COLD POOL INSTABILITY REMAINS NORTH AND EAST OF THE AREA. LATEST
GEM MORE CLOSELY FOLLOWS THE GFS AND HAS FOR THE PAST FEW
RUNS...SO HAVE NOT GONE TOO BULLISH ON POPS FOR THIS PERIOD.

ALL GLOBAL MODELS BRING HIGH PRESSURE BACK OVER THE GREAT BASIN
FOR MONDAY NIGHT/TUESDAY AND KEEP IT IN PLACE THROUGH
MIDWEEK...BRINGING A WARMING AND DRYING TREND. IN THE
EXTENDED...SOME INDICATION OF ANOTHER PACIFIC STORM SYSTEM MOVING
IN FOR THE END OF THE WORK WEEK...BUT MODELS STILL DISAGREE ON THE
DETAILS.

&&

.AVIATION...NORTHERLY WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH THE EVENING...WITH OCCASIONAL GUSTS FROM ISOLATED SHOWERS
MOVING THROUGH THE AREA. CEILINGS ARE EXPECTED TO REMAIN ABOVE 7000
FEET AGL THROUGH THE TAF PERIOD. WINDS SHOULD SWITCH TO SOUTHEAST
AROUND 03-04Z.

&&

.FIRE WEATHER...A STORM SYSTEM WILL MOVE ONTO THE WEST
COAST THURSDAY AND ACROSS THE GREAT BASIN FRIDAY. WINDS AHEAD OF
THIS APPROACHING STORM WILL INCREASE ACROSS ALL VALLEYS THURSDAY
AND REMAIN STRONG OVER SOUTH CENTRAL AND EASTERN UTAH THROUGH
FRIDAY. RELATIVE HUMIDITIES BELOW 15 PERCENT WILL ACCOMPANY THESE
WINDS WHICH WILL ACCELERATE THE CURING OF THE FINE FUELS WHICH ARE
STILL IN THE GREEN UP PHASE. SHOWERS AND THUNDERSTORMS WILL
ACCOMPANY THE COLD FRONT FRIDAY AFTERNOON ACROSS MAINLY THE
NORTHWESTERN HALF OF THE STATE AND THEN LINGER IN THE UNSTABLE AIR
MASS ACROSS THE NORTHERN TWO THIRDS OF THE AREA SATURDAY. ALTHOUGH
A GOOD RECOVERY IN RH IS EXPECTED...THE RAIN SHOWERS ARE EXPECTED
TO BE GENERALLY LIGHT...WITH RAINFALL AMOUNTS OF LESS THAN 0.25 OF
AN INCH. ISOLATED AMOUNTS OF 0.75 OF AN INCH ARE POSSIBLE IN THE
MOUNTAINS OF NORTHERN UTAH.

&&

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

$$

PUBLIC...TRAPHAGAN
FIRE WEATHER...STRUTHWOLF
AVIATION...VERZELLA

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)