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000
FXUS65 KSLC 161755
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1155 AM MDT THU MAY 16 2013

.UPDATE...UPDATED AVIATION DISCUSSION

&&

.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 FRONT ASSOCIATED WITH DEEPENING TROUGH OVER
THE EASTERN PACIFIC NEARLY STATIONARY AND APPEARS TO BE DRAPED
FROM ROUGHLY BRIGHAM CITY TO DUGWAY PER SURFACE OBS/ANALYSIS. NOT
EXPECTING MUCH PROGRESSION OF THIS FEATURE OVER THE NEXT 18-24
HOURS THOUGH WILL LIKELY SEE IT SAG SLIGHTLY SOUTHEAST OVER THAT
TIME. SAID TROUGH WILL CONTINUE TO CARVE SOUTH ALONG THE PACIFIC
COAST BEFORE CHURNING THROUGH THE GREAT BASIN STATES LATE TOMORROW
ON THROUGH THE WEEKEND BRINGING UNSETTLED WEATHER AND SIGNIFICANT
COOLING TO THE AREA.

12Z KSLC SOUNDING CONTINUES TO REFLECT HIGH BASED THUNDERSTORM
POTENTIAL THIS AFTERNOON/EVE WITH ANTICIPATED FOCUS ALONG AND JUST
SOUTH/EAST OF THE SURFACE FRONT. DRY SUB-CLOUD LAYER BELOW 600MB
WILL PROMOTE MICROBURST WINDS WITH THE MORE DEVELOPED CELLS ACROSS
THE NORTH...THIS THE PRIMARY SHORT TERM CONCERN TO SENSIBLE WEATHER.

WHAT LOOKS TO BE ISOLATED CONVECTION ACROSS THE THE NORTH TODAY
WILL BECOME MORE WIDESPREAD TOMORROW AFTERNOON AS THE UPPER TROUGH
NOW OVER 130W TURNS INLAND WITH PRIMARY SHORT WAVE RIDING ALONG
SURFACE BOUNDARY TOMORROW EVENING/OVERNIGHT. POTENTIAL EXISTS FOR
ISOLATED STRONG CONVECTION ALONG AND EAST OF THE BOUNDARY AT THAT
TIME AS MARGINAL MOISTURE...GOOD SHEAR AND FORCING COINCIDE. OUTSIDE
OF THIS FORCING LOOKS TO PROMOTE WIDESPREAD SHOWERS WITHIN POST
FRONTAL ENVIRONMENT ACROSS THE WEST THROUGH THE OVERNIGHT HOURS
WELL INTO SATURDAY. PRIMARY FORECAST CHALLENGE OF THIS SHIFT TO
FOCUS ON THIS AS WELL AS TRAILING WAVE THAT KEEPS THINGS ACTIVE
THROUGH SUNDAY. BOTTOM LINE...TRENDING MUCH COOLER WITH UNSETTLED
CONDITIONS LASTING THROUGH THE WEEKEND.

GOING FORECAST ON TRACK AND HAVE MADE NO UPDATES ATTM. PREVIOUS
DISCUSSION FOCUSING ON MEDIUM RANGE BELOW.

A TRAILING SHORT WAVE BRINGS EVEN COLDER AIR INTO THE GREAT BASIN
SAT NIGHT THRU SUN WITH ADDITIONAL PRECIP AND SNOW LEVELS LOWERING
TO AROUND 7000 FT FOR A TIME SUN MORNING. DONT EXPECT MUCH IF ANY
IMPACT FROM THIS SNOW ON ANY OF THE MAIN TRANSPORTATION ROUTES.

RIDGING FOLLOWS THIS WAVE MON INTO TUE WITH THE AIRMASS WARMING BACK
UP TO ABOVE NORMAL LEVELS. MODELS DIVERGE AFTER THIS ON HOW FAST
THEY SWING INLAND A DEEP COLD CLOSED LOW THAT DEVELOPS OVER THE
PACNW MON NIGHT INTO TUE. THE EC WANTS TO KEEP THE SYSTEM ALONG THE
COAST WHILE THE GFS MOVES IT TO SWRN ID BY WED AFTN. LEANED
TOWARDS THE WARMER EC IN THE FORECAST AS IT IS STARTING TO GET
LATE ENOUGH IN THE SPRING WHERE IT IS MORE DIFFICULT TO BRING A
COLD TROF INLAND AND THE GFS CAME AROUND TO THE EC SOLUTION FOR
THIS WEEKENDS EVENT.



&&

.AVIATION...WIND SHIFT BOUNDARY STALLED VERY NEAR THE KSLC
TERMINAL THIS MORNING. LIGHT NORTHWEST ARE EXPECTED TO CONTINUE THROUGH
EARLY AFTERNOON...ALTHOUGH THERE IS A 30 PERCENT CHANCE THAT
SOUTHERLY WINDS COULD RETURN BETWEEN 18-21Z. AFTER 20-21Z...OUTFLOW
FROM SHOWERS AND THUNDERSTORMS OVER THE OQUIRRHS WILL LIKELY
AFFECT THE TERMINAL THROUGH AT LEAST 00Z...RESULTING IN GUSTY AND
ERRATIC WINDS. THERE IS A 20 PERCENT CHANCE OF A THUNDERSTORM
DIRECTLY IMPACTING THE TERMINAL BETWEEN 20-00Z. A COLD FRONT WILL
CROSS THE TERMINAL THIS EVENING MAINTAINING NORTH WINDS THROUGH
THE OVERNIGHT HOURS.

&&

.FIRE WEATHER...STRENGTHENING SOUTHWEST FLOW WILL BRING WINDY
CONDITIONS TO MUCH OF CENTRAL AND SOUTHWEST UTAH THIS AFTERNOON AND
EVENING...WHERE HUMIDITIES ARE EXPECTED TO FALL INTO THE 10 TO 15
PERCENT RANGE. FUELS HAVE BEEN DEEMED NON-CRITICAL ACROSS THIS
AREA...SO NO HIGHLIGHTS ARE CURRENTLY IN EFFECT. A COLD FRONT WILL
SLOWLY CROSS UTAH FROM NORTHWEST TO SOUTHEAST TONIGHT THROUGH
FRIDAY. A MUCH COOLER AIRMASS WILL FOLLOW THE FRONT FOR THE
WEEKEND...WITH WETTING RAINS AND HIGH ELEVATION SNOW FRIDAY THROUGH
SATURDAY ACROSS THE NORTHERN HALF OF UTAH. COOL TEMPERATURES WILL
REMAIN OVER THE AREA THROUGH THE WEEKEND BEFORE A WARMING TREND
ENSUES EARLY NEXT WEEK.

&&

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

$$

PUBLIC...MERRILL
FIRE WEATHER...SEAMAN
AVIATION...GRAHAM

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)