Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 232211
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
311 PM MST FRI JAN 23 2015

.SYNOPSIS...A VERY WEAK SYSTEM WILL SLIDE SOUTH ACROSS UTAH
THROUGH TONIGHT. STRONG HIGH PRESSURE WILL BUILD INTO THE WESTERN
STATES SATURDAY THROUGH EARLY NEXT WEEK.

&&

.SHORT TERM (THRU 00Z TUE)...THE WEAK SHORT WAVE DROPPING SOUTH
THRU THE CWA TODAY CONTINUES TO BRING SOME LOWER CLOUDINESS TO
THE NRN ZONES AND HAS BROUGHT A LITTLE LIGHT SNOW TO THE UINTA
MTNS AND N SLOPE FOOTHILLS IN SWRN WY.

THE CLOUDS WILL GRADUALLY DISSIPATE THROUGH THIS EVENING AS THE
SYSTEM SHIFTS OUT OF THE AREA.

THE NORTHERLY SURFACE GRADIENT HAS TIGHTENED UP ACROSS THE SOUTH
THIS EVE THEN RELAXES AGAIN AFTER 12Z TOMORROW. LOCAL GUSTY NELY
WINDS THRU THE GAPS IN SWRN UT HAVE DEVELOPED AND SHOULD PERSIST
INTO EARLY SAT BUT SPEEDS SHOULD STAY BELOW ADVISORY LEVELS.

CLEARING SKIES TONIGHT WILL ALLOW NRN VALLEY INVERSIONS TO BECOME
A LITTLE BETTER DEVELOPED AND EXPECT THESE TO PERSIST THRU MON.
OVERRUNNING MOISTURE AT THE NOSE OF THE BUILDING RIDGE IS FORECAST
TO CROSS THE NORTH SATURDAY INTO SAT NIGHT. EXPECTED SOME LOW AND
MID LEVEL CLOUDINESS FROM THESE BUT NO PRECIP.

STILL FORECAST TO GET VERY WARM ALOFT WITH 700 MB TEMPS OF +3C
OVER SLC AT 00Z MON AND +6C AT 00Z TUE IN THE LATEST GFS. THIS IS
UNSEASONABLY WARM AND THE HIGHER ELEVATIONS WILL RESPOND THE
MOST. VALLEY INVERSIONS ARE EXPECTED TO REMAIN IN PLACE WITH
DETERIORATING URBAN AIR QUALITY BUT TEMPS IN THE INVERSION SHOULD
STILL REACH THE 40S ALONG THE WASATCH FRONT DUE TO THE VERY WARM
AIR ALOFT.

CLOUDS INCREASE FROM THE SOUTH LATE MON AS A MOIST UPPER LEVEL
TROF STARTS TO LIFT NORTH TOWARDS THE GREAT BASIN.

&&

.LONG TERM (AFTER 00Z TUESDAY)...AN EJECTING SHORTWAVE IS EXPECTED
TO BE NEAR THE SOUTHERN CALIFORNIA COAST AT THE BEGINNING OF THE
LONG TERM FORECAST PERIOD. SIGNIFICANTLY ELEVATED PRECIPITABLE WATER
VALUES WILL BE PRESENT WITH THIS SHORTWAVE AS IT MOVES NORTHWARD DUE
TO THE BREAKDOWN OF THE REX BLOCKING PATTERN. AS THE TROUGH PASSES
VEGAS...THE 12Z GFS INDICATES PW VALUES WILL APPROACH THE 99TH
PERCENTILE.

TIMING ASSOCIATED WITH THIS SHORTWAVE IS RELATIVELY SIMILAR WITH
BOTH THE 12Z GFS AND 12Z EC. BOTH MODELS BRING THE SHORTWAVE ACROSS
SOUTHERN CALIFORNIA AND INTO NEVADA DURING THE DAY TUESDAY AND THEN
ACROSS UTAH LATER TUESDAY INTO EARLY WEDNESDAY. EXPECT A FAIRLY
LARGE AREA OF PRECIPITATION ACROSS SOUTHERN UTAH BY EARLY
TUESDAY...REACHING CENTRAL AND NORTHERN UTAH TUESDAY MORNING/EARLY
AFTERNOON. GIVEN THE ABNORMALLY HIGH MOISTURE VALUES WITH THIS
SYSTEM...EXPECT THE MODELS ARE PROBABLY UNDERDONE IN REGARDS TO
AREAL COVERAGE OF PRECIPITATION.

FOLLOWING THE PASSAGE OF THE SHORTWAVE...ANOTHER CUT OFF LOW MOVES
INTO THE A VERY SIMILAR POSITION THAT THE PREVIOUS SHORTWAVE
VACATED...AND ANOTHER REX BLOCKING PATTERN IS FORECAST TO DEVELOP
LATE IN THE WEEK INTO NEXT WEEKEND. IF THIS PATTERN REDEVELOPS...THE
LIKELIHOOD OF SIGNIFICANT PRECIPITATION ACROSS MUCH OF THE CWA WOULD
BE MINIMAL.

&&

.AVIATION...OCCASIONAL CEILINGS NEAR 5500-6000 FEET AGL WILL REMAIN
POSSIBLE AT THE SLC TERMINAL THROUGH ABOUT 00-02Z. NORTH TO
NORTHWEST WINDS WILL CONTINUE BEFORE SWITCHING TO THE SOUTHEAST
BETWEEN 02-04Z.

&&

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

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...KRUSE

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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