000
FXUS65 KSLC 160307
AFDSLC

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

.SYNOPSIS...A WEAK UPPER LEVEL DISTURBANCE WILL MOVE INTO COLORADO
TONIGHT. 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...WATER VAPOR LOOP SHOWS A CLOSED LOW OPENING UP AS IT
MOVES INTO WESTERN COLORADO. ACARS 400-250MB WIND OBSERVATIONS SHOW
A 60-105KT WESTERLY JET ALONG THE CANADIAN BORDER. RAP...GOES...GPS
SENSORS...AND 00Z SLC RAOB INDICATE PRECIPITABLE WATER VALUES IN THE
0.20"-0.85" RANGE ACROSS THE REGION.

15Z SHORT RANGE ENSEMBLES INDICATE INSTABILITY WILL SLOWLY DIMINISH
ACROSS NORTHERN UTAH OVERNIGHT...THOUGH RADAR TRENDS HAVE SHOWN A
BETTER DOWNWARD TREND DURING THE PAST HOUR. THE PASSAGE OF THE MAIN
FEATURE IS LIKELY A MAIN CONTRIBUTOR TO DIMINISHING SHOWERS. KEPT
IDEA OF ISOLATED (SCATTERED ALONG NEVADA BORDER) SHOWERS DIMINISHING
BY MIDNIGHT ACROSS THE NORTH.

INCREASED CLOUD COVER PER IR SATELLITE UPSTREAM. BUMPED UP GUSTS
ACROSS SOUTHERN UTAH (SYNOPTIC) AND WESTERN UTAH (OUTFLOW).
OTHERWISE VERY MINOR CHANGES TO TEMPERATURES OVERNIGHT. REST
UNCHANGED.

PREVIOUS DISCUSSION FOLLOWS...
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
REINFORCING 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...EAST NORTHEAST WINDS WILL CONTINUE AT THE SLC
TERMINAL THROUGH THE EARLY 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 04-06Z.

&&

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

$$

PUBLIC...ROGOWSKI/TRAPHAGAN
AVIATION...ROGOWSKI

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