000
FXUS65 KSLC 162215
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
415 PM MDT THU MAY 16 2013

.SYNOPSIS...AN UPPER TROUGH WILL DEEPEN ALONG THE WEST COAST TODAY
THEN CROSS THE GREAT BASIN FRIDAY THROUGH EARLY SATURDAY. A
COLDER SYSTEM WILL CROSS THE REGION SATURDAY NIGHT AND SUNDAY.
HIGH PRESSURE WILL RETURN FOR THE FIRST PART OF NEXT WEEK.




&&

.DISCUSSION...SURFACE COLD FRONT BECAME MORE EVIDENT IN SURFACE
OBS THIS AFTERNOON...CLEARLY MAKING A SLIGHT SOUTHEAST SHIFT
THROUGH THE SALT LAKE VALLEY OVER THE LAST 6 HOURS. ATTM BOUNDARY
EXTENDS FROM POINT OF THE MOUNTAIN WEST TO ROUGHLY IBAPAH PUT
FURTHER SOUTHWARD MOVEMENT SHOULD BE NEAR NIL. ISOLATED
CONVECTION EXISTS ALONG AND EAST OF THIS BOUNDARY...BUT
STORMS/LIGHTNING HAVE BEEN ISOLATED TO SOUTHWEST WYOMING WHERE
BEST CAPE EXISTS. SAID FRONT IS EXPECTED TO STALL TONIGHT THEN
RETREAT BACK NORTH TOMORROW MORNING AS THE DEEPENING PACIFIC
TROUGH TO OUR WEST FURTHER AMPLIFIES AND TURNS INTO THE WESTERN
GREAT BASIN STATES.

VERY WARM AND BREEZY CONDITIONS WILL CONTINUE ACROSS THE SOUTHERN
2/3RDS OF THE AREA THIS AFTERNOON INTO AND THROUGH FRIDAY IN THE PRE-
FRONTAL ENVIRONMENT. TEMPS WILL REMAIN ABOVE CLIMO IN THOSE AREAS
WHILST NORTH OF THE FRONT EXPECTING CLOSER TO SEASONAL CONDITIONS
OVER THE NEXT 24 HOURS.

GOOD AGREEMENT IN GUIDANCE WITH TRACK AND EVOLUTION OF
AFOREMENTIONED PACIFIC TROUGH. NEAR H7 BAROCLINIC ZONE WILL
TIGHTEN OVER THE FAR NORTHWEST TONIGHT WITH SHOWERS BECOMING MORE
WIDESPREAD AROUND AND NEAR UT/NV/ID TRIPLE POINT. THIS TREND WILL
CONTINUE THROUGH FRIDAY WITH CONVECTION...POTENTIALLY
STRONG...ALONG AND EAST OF THE SURFACE FRONT AND MORE STRATOFORM
TYPE PRECIP EXISTING IN THE POST FRONTAL ENVIRONMENT. DOWNSTREAM
PROGRESSION OF THE FRONT WILL FINALLY MAKE A MORE ROBUST MOVE EAST
TOMORROW AFTERNOON THROUGH THE NIGHT PASSING THROUGH MOST ALL AREAS
SATURDAY...TROUGH BECOMING NEGATIVELY TILTED OVERHEAD AT THAT TIME.
PERIOD OF MOST WIDESPREAD AND LIKELY SOAKING RAINFALL...SNOW
LEVELS LOWERING TO NEAR 8000FT...WILL OCCUR SATURDAY MORNING AS
MID LEVEL AXIS PASSES THROUGH. INCREASED POPS TO LIKELY OR HIGHER
FOR MANY AREAS ACROSS THE NORTH AS THIS OCCURS.

SECONDARY WAVE WITHIN W-NW FLOW ALOFT ARRIVES SUNDAY MORNING
BRINGING EVEN COLDER AIR AND ANOTHER SHOT OF WIDESPREAD PRECIP
ACROSS THE NORTHERN HALF. SNOW LEVELS EXPECTED TO LOWER TO NEAR
OR SLIGHTLY BELOW 7000FT AT THAT TIME WITH ACCUMULATIONS ON COLDER
SURFACES ABOVE. CURRENT GRIDS HAVE 6 INCHES AT ALTA BY THE END OF
THE DAY...THOUGH IMPACT IS EXPECTED TO BE MINIMAL ON THE HIGHER
MOUNTAIN ROADWAYS.

BOTTOM LINE FOR THE WEEKEND...MUCH COOLER WITH TEMPS AT OR BELOW
CLIMO WITH SHOWERS/STORMS FOCUSED ACROSS THE NORTHERN HALF. QUITE
UNSETTLED.

EARLY NEXT WEEK RIDGING WILL AMPLIFY QUITE RAPIDLY IN WAKE OF
DEPARTING TROUGH. TEMPS TO REBOUND AS SUCH WITH ABOVE NORMAL
CONDITIONS ONCE AGAIN THROUGH AT LEAST MIDWEEK...LIKELY LONGER.
GLOBAL MODELS CONTINUE TO ADDRESS FORMATION OF A STRONG CLOSED LOW
OVER THE PACNW MID/LATE WEEK...AND 12Z RUNS A BIT CLOSER REGARDING
BIG PICTURE POSITION SLIGHTLY MORE INLAND AS EARLIER RUNS OF GFS
INDICATED. NOT QUITE READY TO GET INTO DETAILS AS OF YET AS
WAITING TO SEE MORE CONSISTENCY BOTH RUN TO RUN AND MODEL TO
MODEL...BUT THIS FURTHER INLAND POSITION WOULD COOL THE WEST DOWN
QUITE A BIT. DID HEDGE TEMPS IN THAT DIRECTION SLIGHTLY.

&&

.AVIATION...ANTICIPATE NORTH-NORTHWEST WINDS TO CONTINUE AT THE KSLC
TERMINAL THROUGH THE EVENING HOURS. HOWEVER...THERE IS A 30 PERCENT
CHANCE FOR GUSTY AND ERRATIC WINDS AT THE TERMINAL THROUGH 02Z FROM
OUTFLOW BOUNDARIES ASSOCIATED WITH CONVECTION IN THE AREA.
ANTICIPATE THE SWITCH TO SOUTHEAST DRAINAGE WINDS WILL BE DELAYED UNTIL
AFTER 10Z...WITH A 40 PERCENT CHANCE THEY WILL STAY NORTH THROUGH
THE PERIOD. CEILINGS WILL SLOWLY LOWER OVERNIGHT BUT ARE EXPECTED TO
REMAIN WELL ABOVE 6000FT AGL.

&&

.FIRE WEATHER...A COLD FRONT STALLED ACROSS NORTHERN UTAH WILL
REMAIN IN PLACE THROUGH FRIDAY...BEFORE CROSSING THE REMAINDER OF
THE AREA FRIDAY NIGHT INTO SATURDAY. AHEAD OF THIS FRONT GUSTY
SOUTHWEST WINDS AND LOW DAYTIME HUMIDITY CAN BE EXPECTED OVER
SOUTHERN AND EASTERN UTAH...WHILE COOLER...SHOWERY CONDITIONS ARE
EXPECTED OVER THE NORTH. THE PARENT LOW PRESSURE SYSTEM WILL CROSS
THE AREA FRIDAY NIGHT INTO SATURDAY...BRINGING THE BEST CHANCE FOR
PRECIPITATION ACROSS THE AREA. BEHIND THIS SYSTEM  A WARMING TREND
IS EXPECTED EARLY NEXT WEEK...ALONG WITH AN INCREASE IN SOUTH WINDS.

&&

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

$$

MERRILL/SEAMAN/GRAHAM


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