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000
FXUS65 KSLC 182101
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
301 PM MDT SAT MAY 18 2013

.SYNOPSIS...NEXT COLDER SYSTEM WILL CROSS THE REGION TONIGHT
THROUGH MONDAY MORNING. HIGH PRESSURE WILL BRIEFLY RETURN ON
TUESDAY THEN SHIFT EAST WEDNESDAY.

&&

.DISCUSSION...UPPER TROUGH CONTINUES TO SHIFT EAST OVER THE
EASTERN GREAT BASIN THIS AFTERNOON AND WILL EXIT THE STATE
TONIGHT. PRETTY IMPRESSIVE AMOUNTS OF PRECIPITATION FELL THIS
MORNING OVER NORTHERN UTAH WITH THE BAND THAT STRETCHED ALONG THE
WASATCH FRONT. BRIGHAM CITY HAD JUST UNDER TWO INCHES OF WATER WITH
MANY LOCATIONS RECEIVING WELL OVER AN INCH. SCATTERED RAIN SHOWERS
ARE NOW DEVELOPING ALONG WITH ISOLATED THUNDERSTORMS. A FEW
LIGHTNING STRIKES HAVE BEEN DETECTED AND WILL MOST LIKELY CONTINUE
INTO THE EVENING HOURS. INCREASING CLOUDS ACROSS THE SOUTHWEST
PORTION OF THE STATE HAVE GIVEN RISE TO SHOWERS. THESE SHOWERS
ARE MOVING EAST AROUND THE BOTTOM OF THE EXITING TROUGH. ISOLATED
THUNDERSTORMS ARE ALSO POSSIBLE WITH THESE SHOWERS ESPECIALLY
OVER HIGHER TERRAIN.

THE COLDER SECONDARY SHORT WAVE IS EXPECTED TO DROP INTO THE
NORTHERN GREAT BASIN AFTER MIDNIGHT. NEWER MODEL HINTS THAT BEST
THREAT FOR PRECIPITATION WITH THIS FEATURE WILL BE CENTRAL UTAH.
PREVIOUS MODEL SUGGESTED NORTHERN UTAH. WILL LEAVE PREVIOUS POPS
OVER THE NORTH UNCHANGED...BUT WILL INCREASE POPS OVER CENTRAL
PORTION OF THE STATE AND OVER THE CENTRAL AND SOUTHERN MOUNTAINS
THROUGH THE DAY SUNDAY. SNOW LEVELS WITH THIS SYSTEM WILL BE A
LITTLE LOWER THAN THIS MORNING BUT STILL DO NOT EXPECT
SIGNIFICANT IMPACTS OVER ANY OF THE MAJOR PASSES. A CONTINUED
THREAT OF PRECIPITATION WILL LINGER OVER THE NORTHERN CWA INTO
MONDAY UNDER WRAP AROUND MOISTURE AS THE SYSTEM PULLS OFF TO THE
EAST.

RIDGING WILL THEN BUILD BACK INTO THE GREAT BASIN...AT LEAST FOR A
FEW DAYS...BRINGING A WARMER AND DRIER AIRMASS. THE RIDGE SHIFTS
EAST TUESDAY NIGHT AS A DEEP COLD CLOSED LOW FORMS OVER THE
PACIFIC NORTHWEST STATES AND DROPS SLOWLY SOUTHEAST. MODELS
CONTINUE TO STRUGGLE WITH THE DETAILS ON HOW THIS LOW EVOLVES
BUT THE OVERALL IDEA OF KEEPING A WARM DRY SOUTHWEST FLOW OVER THE
CWA WITH THE COLD AIR STAYING MOSTLY TO OUR WEST SEEMS LIKELY.
EXPECT THAT IMPULSES WILL BREAK OFF THE PARENT LOW AND SWING
THROUGH THE STATE FROM TIME TO TIME AND A COLD FRONT COULD SEE-SAW
BACK AND FORTH ACROSS THE NORTHWEST PORTION OF THE STATE. STILL
TOO EARLY TO TRY AND GUESS AT TIMING OF THESE FEATURES.

&&

.AVIATION...CIGS THE PRIMARY OPERATIONAL CONCERN AT THE KSLC
TERMINAL THROUGH THE REMAINDER OF THE AFTERNOON. ALTHOUGH CLOUD
COVER IS THINNING SOME PERIODIC CIGS OVERHEAD WILL LOWER TO 6000FT
AGL AT TIMES WITH PASSING SHOWERS. THESE PASSING SHOWERS COMBINED
WITH SURFACE GRADIENT AND TIME OF DAY WILL ALSO PROMOTE NORTHWEST
WINDS NEAR OR GREATER THAN 8 KNOTS THROUGH THIS EVENING...THOUGH
OCCASIONAL LIGHT AND VARIABLE CONDITIONS REMAIN POSSIBLE FOR BRIEF
PERIODS.

SOME LIGHTNING STRIKES HAVE BEEN NOTED OVER THE LAKE OVER THE LAST
FEW HOURS...BUT ONLY A 20 PERCENT CHANCE EXISTS THAT A CELL WILL
IMPACT THE TERMINAL TODAY.

&&

.FIRE WEATHER...A SERIES OF STORM SYSTEMS WILL KEEP A COOL AND WET
PATTERN IN PLACE INTO MONDAY. DOWNSLOPE/CANYON WINDS WILL GUST
ACROSS PRONE AREAS ACROSS THE STATE AT TIMES THROUGH MONDAY NIGHT AS
REINFORCING COOLER AIR ARRIVES. IT COULD BE DRY AND BREEZY ENOUGH TO
PRESENT LOCAL CRITICAL FIRE WEATHER CONDITIONS IN DIXIE ON MONDAY.

SHOWERS DIMINISH IN COVERAGE THIS AFTERNOON THROUGH TONIGHT. THEN
THE NEXT SYSTEM WILL BRING ANOTHER ROUND OF WETTING RAIN (SNOW ABOVE
7.5KFT) TO NORTHERN AND CENTRAL UTAH SUNDAY. A THIRD SYSTEM WILL
MAINLY AFFECT EASTERN UTAH MONDAY.

THE PATTERN SHIFTS AS A RIDGE BUILDS IN TUESDAY AND WEDNESDAY. A
WARMING AND DRYING TREND WILL TAKE PLACE WITH MOISTURE RECOVERIES AT
NIGHT BEGINNING TO LAG.

SOUTHWEST WINDS BEGIN TO DEVELOP TUESDAY NIGHT AS A LARGE STORM
SYSTEM DEVELOPS OVER THE PACIFIC NORTHWEST. THESE WINDS INCREASE AND
BECOME STRONG AND GUSTY WEDNESDAY THROUGH SATURDAY. AT THE SAME
TIME...DAYTIME HUMIDITY LEVELS BECOME VERY DRY...5-12% ACROSS MOST
VALLEYS...MAKING FOR WIDESPREAD CRITICAL FIRE WEATHER CONDITIONS IF
ANY FUELS ARE CRITICAL.

&&

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

&&

$$

PUBLIC.........YOUNG
FIRE WEATHER...ROGOWSKI
AVIATION.......MERRILL

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)