Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 121125
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
425 AM MST FRI FEB 12 2016

.SYNOPSIS...HIGH PRESSURE OVER UTAH TODAY WILL WEAKEN AS A COUPLE
OF WEAK WEATHER DISTURBANCES CROSS NORTHERN UTAH THIS WEEKEND.
HIGH PRESSURE ALOFT WILL REBOUND ACROSS THEN REGION EARLY NEXT
WEEK.

&&

.SHORT TERM (UNTIL 00Z TUESDAY)...THE PERSISTENT UPPER RIDGE
ACROSS THE GREAT BASIN WILL HANG ON FOR ONE MORE DAY TODAY...THEN
WEAKEN AS A COUPLE OF SHORTWAVES MOVE EAST-SOUTHEAST ACROSS THE
NORTHERN ROCKIES/NORTHERN GREAT BASIN THIS WEEKEND.

THE FOG...URBAN HAZE AND STRATUS THAT HAS BEEN LOCKED IN ACROSS
THE NORTHERN THROUGH WEST-CENTRAL VALLEYS THE PAST SEVERAL DAYS
WILL FOR THE MOST PART REMAIN IN PLACE THROUGH EARLY SATURDAY. THE
BIGGEST CHANGE WILL BE SOME EROSION OF THE STRATUS AROUND THE
PERIMETER TODAY...ALONG WITH SIGNIFICANTLY LESS AREAL COVERAGE OF
DENSE FOG THROUGH EARLY SATURDAY MORNING.

THE FIRST WEEKEND SHORTWAVE WILL FOCUS ON THE NORTHERN ROCKIES
SATURDAY. THIS FEATURE WILL LIKELY KEEP THE LOW-LEVEL COLD
ADVECTION TOO FAR TO THE NORTH TO HAVE ANY SIGNIFICANT IMPACT ON
THE STRONG VALLEY INVERSIONS ACROSS NORTHERN/WESTERN UTAH. SUSPECT
THAT THE MAIN CHANGE IF ANY FROM THIS FIRST FEATURE WILL BE TO
NUDGE SOME OF THE STRATUS SOUTH AND EAST OUT OF THE NORTHWEST
DESERT WITH A LITTLE LESS AREAL COVERAGE OF DENSE FOG SATURDAY
MORNING.

AMPLIFICATION OF THE UPPER RIDGE NEAR 130W SUNDAY WILL DRIVE A
SECOND SHORTWAVE ON A SOUTHEAST TRAJECTORY ACROSS NORTHERN AND
EASTERN UTAH. THIS FEATURE WILL BRING SUBSTANTIALLY COLDER AIR
ALOFT AND FAIRLY WIDESPREAD BUT MOSTLY LIGHT PRECIP INTO NORTHERN
UTAH...WHICH IN TURN COULD END UP WEAKENING OR BREAKING DOWN
ENTIRELY MOST VALLEY INVERSIONS BY SUNDAY NIGHT. MOIST LOW-LEVEL
WARM ADVECTION DEVELOPING BEHIND THE EXITING SHORTWAVE WILL
MAINTAIN SOME LIGHT PRECIP ACROSS THE NORTH AND FURTHER ERODE ANY
LINGERING VALLEY INVERSIONS ON MONDAY.

THE CLEARING OUT OF THE WEST-CENTRAL UTAH VALLEYS WILL DEPEND
LARGELY ON THE TRAJECTORY OF THE SUNDAY SHORTWAVE. IF THIS FEATURE
REMAINS TOO FAR TO THE NORTH AND EAST PER THE ECMWF...THEN THE
LOW-LEVEL COLD ADVECTION MAY NOT BE SUFFICIENT TO DISLODGE THE
STRONG INVERSIONS CURRENTLY IN PLACE. THE GFS SOLUTION WOULD
BRING SLIGHTLY STRONGER LOW-LEVEL COLD ADVECTION...THOUGH IT
WOULD STILL REMAIN A COIN FLIP AS TO WHETHER THE INVERSIONS WOULD
BREAK DOWN ON MONDAY. FOR NOW WILL GO WITH THE GFS SOLUTION AND
PUSH THE FOG AND SURFACE VERY COLD AIR OUT AND BRING MODESTLY
WARMER TEMPS TO THE AREA HEADING INTO EARLY NEXT WEEK.

.LONG TERM (AFTER 00Z TUESDAY)...ON THE FRONT SIDE OF A BUILDING
RIDGE ONCE AGAIN...700MB TEMPERATURES BEGIN A WARMING TREND BACK
ABOVE 0C. WHILE THE RIDGE OF HIGH PRESSURE AND WARMER TEMPERATURES
WILL BE SHORT LIVED...PEAKING AROUND 4C BY LATE WEDNESDAY/EARLY
THURSDAY...A BETTER ALIGNED TROUGH FEATURE WILL IMPACT THE AREA BY
THURSDAY AND INTO THE WEEKEND...BRINGING PRECIP CHANCES BACK TO
UTAH. GLOBAL FORECAST MODELS CONTINUE TO BE MOSTLY IN SYNC EXCEPT
FOR EXACT TIMING OF THE TROUGH FOR NEXT THURSDAY INTO FRIDAY. A
SLIGHT SPLITTING NATURE OF THE PATTERN LOOKS PROBABLE.

THE WIND PATTERN LOOKS TO QUICKLY SWITCH FROM A NORTHWESTERLY TO A
SOUTHWESTERLY BY MID WEEK...HELPING TO KEEP THE ATMOSPHERE MIXED
ENOUGH TO HOPEFULLY DAMPEN DOWN THE INVERSION BUILDING PROCESS.

&&

.AVIATION...FOR THE SLC TERMINAL TODAY...EXPECTING IFR CONDITIONS IN
FOG/HAZE AND LOW STRATUS TO PERSIST THROUGH ABOUT 20Z TO 21Z BEFORE
HAZE SCATTERS OUT. 40 PERCENT CHANCE OF SEEING LIFR CONDITIONS
BEFORE 16Z. LIGHT SOUTHERLY WINDS TO SWING NORTHERLY BY 17Z.

&&

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

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...DEWEY

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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