Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 290222
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
822 PM MDT THU APR 28 2016

.SYNOPSIS...THE UPPER LEVEL LOW PRESSURE SYSTEM APPROACHING THE
FOUR CORNERS REGION LATER TONIGHT WILL CONTINUE INTO THE CENTRAL
PLAINS STATES LATE FRIDAY. A SECOND STORM SYSTEM WILL FOLLOW THIS
WEEKEND...MAINTAINING COOL AND UNSETTLED CONDITIONS FOR MUCH OF
THE REGION.

&&

.DISCUSSION...
WATER VAPOR LOOP SHOWS AN EXPANSIVE CLOSED LOW CENTERED OVER FAR
NORTHERN ARIZONA. AMDAR 400-250MB WIND OBSERVATIONS PLACE A
CYCLONIC 100-125KT JET OVER THE DEEP SOUTHWEST CONUS INTO THE
SOUTHERN ROCKIES. GOES/HRRR/12Z KSLC RAOB INDICATE THE
PRECIPITABLE WATER VALUE RANGES FROM 0.15"-0.35" MOUNTAINS TO
0.50"-0.70" MOST VALLEYS.

WITH THE CLOSED LOW MAKING ITS WAY TOWARD THE FOUR CORNERS
OVERNIGHT...EXPECTING COLD POOL/DEFORMATION CONVECTION TO MAINLY
AFFECT THE SOUTHERN AND EASTERN ZONES. SREF INDICATES THUNDER
CHANCES WANE QUICKLY WITH SUNSET SO KEPT THAT IDEA FROM THE LAST
SHIFT.

HIGH ELEVATION...ABOVE 7500 FT...COULD SEE A QUICK 1-3" OF SNOWFALL
ACROSS THE BOOK CLIFFS...CENTRAL AND SOUTHERN MOUNTAINS.

OTHER STORY THIS EVENING AREA ENHANCED EASTERLY CANYON WINDS FROM
SALT LAKE COUNTY NORTH INTO THE CACHE...WITH A 10MB PRESSURE
GRADIENT FROM RIVERTON TO SALT LAKE CITY. HRRR-3KM ALONG WITH OUR
3KM WRFS INDICATE GUSTS SHOULD REMAIN FAIRLY STEADY JUST BELOW
ADVISORY CRITERIA. LOCALLY HIGHER GUSTS POSSIBLE NEAR FARMINGTON
AT TIMES.

&&

.PREVIOUS DISCUSSION...
THE UPPER LOW TRACKING EAST ALONG THE UTAH/ARIZONA BORDER WILL
SETTLE INTO THE FOUR REGION OVERNIGHT... THEN CONTINUE EAST INTO
THE CENTRAL PLAINS STATES BY LATE FRIDAY. SCATTERED CONVECTION
EAST OF THE ADVANCING LOW WILL LIKELY INCREASE A BIT IN AREAL
COVERAGE THROUGH THIS EVENING.

A SECOND AREA OF ORGANIZED PRECIP WILL LIKELY FORM IN THE STILL
DEFINABLE DEFORMATION AXIS ACROSS WEST-CENTRAL UTAH THROUGH EXTREME
SOUTHWEST WYOMING THIS EVENING. THIS DEFORMATION AXIS HAS BEEN
STRETCHED OUT ACROSS NORTHERN UTAH MUCH OF THE DAY. THIS AXIS IS
BEGINNING TO TILT ALONG THE SOUTHWEST TO NORTHEAST AXIS AS THE UPPER
LOW MOVES EAST ALONG OUR SOUTHERN BORDER. THE DEFORMATION WILL
WEAKEN CONSIDERABLY LATE TONIGHT...LEAVING SCATTERED CONVECTION
CLOSER TO THE LOW CENTER HEADING INTO FRIDAY MORNING.

A BRIEF LULL IN PRECIP WILL OCCUR FRIDAY AS A WEAK SHORTWAVE RIDGE
MOVES INTO THE AREA AHEAD OF A SECOND PACIFIC UPPER LOW SCHEDULED TO
ARRIVE OVER THE WESTERN GREAT BASIN SATURDAY. THIS NEXT FEATURE WILL
TAKE A MORE NORTH TO SOUTH TRACK THROUGH THE BASIN IN RESPONSE TO
STRONG RIDGING JUST OFF THE WEST COAST. THE GLOBAL MODELS HAVE
TRENDED TOWARDS TAKING THE LOW CENTER FURTHER TO THE WEST...WHICH
WOULD SIGNIFICANTLY REDUCE THE AMOUNT OF PRECIP STRETCHING EAST IN
WESTERN UTAH ON SATURDAY.

ONCE THE UPPER LOW SETTLES INTO THE SOUTHERN GREAT BASIN/DESERT
SOUTHWEST LATE IN THE WEEKEND WILL SEE AN INCREASE IN AREAL COVERAGE
OF PRECIP ACROSS MAINLY THE SOUTHERN HALF OF UTAH ON SUNDAY. THIS
PRECIP WILL LIKELY CONTINUE BEYOND THE SHORT RANGE FORECAST PERIOD.

POTENTIAL EXISTS FOR A SIGNIFICANT DOWNSLOPE/CANYON WIND EVENT ALONG
THE WASATCH FRONT/CACHE VALLEY SATURDAY NIGHT/SUNDAY. NEAR 700MB
EASTERLY COLD ADVECTION OUT OF WYOMING WITH SPEEDS RUNNING AROUND 30
TO 40 KTS AND A FAVORABLE NORTHEAST SURFACE PRESSURE GRADIENT WILL
ALMOST CERTAINLY CREATE STRONG CANYON WINDS ALONG THE WASATCH
FRONT/CACHE VALLEY. POTENTIAL DOES EXIST FOR A GENERAL DOWNSLOPE
WIND EVENT WITH TIGHT THETA SURFACE PACKING NEAR THE RIDGETOPS
SATURDAY EVENING WHICH COLLAPSES DOWN THE WEST SLOPES LATE SATURDAY
NIGHT/EARLY SUNDAY. WIND HIGHLIGHTS APPEAR LIKELY WITH EITHER AN
HIGH END ADVISORY OR HIGH WIND WARNING POSSIBLE.

AFTER MORE THAN A WEEK OF UNSETTLED WEATHER WITH A NEAR-CONSTANT
PROGRESSION OF CLOSED LOWS DRIFTING THROUGH THE AREA...IT APPEARS
THERE IS A BREAK ON THE HORIZON STARTING NEXT WEEK. BY SUNDAY
NIGHT...EXTENDED MODELS ARE IN AGREEMENT THAT A CLOSED LOW WILL BE
FILLING AND WEAKENING OVER UTAH. LINGERING MOISTURE AND SLIGHT
INSTABILITY COULD BE ENOUGH FOR A FEW SHOWERS HERE AND THERE MONDAY
AFTERNOON...BUT OTHERWISE THINGS SHOULD BE DRYING OUT STARTING
MONDAY ACROSS UTAH AND SOUTHWEST WYOMING.

GRADUAL RIDGING BEGINS ACROSS THE GREAT BASIN TUESDAY. THE GFS MODEL
DOES INDICATE DAILY AFTERNOON INSTABILITY OVER THE HIGHER TERRAIN OF
UTAH...AS IS TYPICAL FOR THIS TIME OF YEAR. EACH DAY LOOKS
PROGRESSIVELY DRIER AND WARMER...SO EXPECTING MAYBE A FEW SHOWERS
OVER THE HIGHER TERRAIN MONDAY AND TUESDAY GIVING WAY TO JUST A FEW
CUMULUS CLOUDS BY LATER IN THE WEEK.

THE AXIS OF THE RIDGE PUSHES THROUGH AROUND MIDWEEK...BRINGING
TEMPERATURES AROUND 5-10 DEGREES ABOVE AVERAGE. HOWEVER...THE NEXT
ACTIVE PERIOD IS NOT FAR BEHIND. CURRENT IDEA IN THE EXTENDED MODELS
IS TO BRING YET ANOTHER CLOSED LOW THROUGH CALIFORNIA AND INTO THE
GREAT BASIN BY THE END OF THE WORK WEEK...MEANING COOL AND UNSTABLE
CONDITIONS COULD RETURN BY THE END OF THE WORKWEEK AND INTO NEXT
WEEKEND.

&&

.AVIATION...EASTERLY CROSSWINDS WILL CONTINUE TO IMPACT PORTIONS
OF THE SLC TERMINAL RUNWAYS THROUGH AT LEAST 04Z...WITH PERIODIC
EASTERLIES POSSIBLE THROUGH 14Z. OTHERWISE...WINDS SHOULD GENERALLY
TREND TO THE SOUTH-SOUTHEAST AROUND 03Z-05Z. THERE IS A 20 PERCENT
CHANCE THAT CEILINGS COULD DROP BELOW 7000FT OVERNIGHT...BUT IN
GENERAL A BREAK FROM THE SHOWERY ACTIVITY IS EXPECTED THROUGH AT
LEAST 18Z.

&&

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

$$

PUBLIC...ROGOWSKI/CONGER/VAN CLEAVE
AVIATION...SCHOENING

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)


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