Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 101507
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
907 AM MDT THU APR 10 2014

.SYNOPSIS...A MILD WESTERLY FLOW ALOFT WILL PREVAIL THROUGH THE
REMAINDER OF THE WEEK. A PAIR OF WEAK SYSTEMS WILL AFFECT THE
REGION DURING THE UPCOMING WEEKEND.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A LAST DISTURBANCE OVER THE
NORTHERN ROCKIES...AHEAD OF AN EXPANSIVE RIDGE BUILDING INTO THE
WESTERN CONUS. AMDAR 400-250MB WIND OBSERVATIONS REVEAL A CYCLONIC
75-125KT JET FROM BRITISH COLUMBIA ACROSS THE NORTHERN ROCKIES.
MEANWHILE A WESTERLY 75-125KT JET EXTENDED FROM SOUTHERN
CALIFORNIA TOWARD THE FOUR CORNERS. GOES/GPS/RAP/12Z RAOB INDICATE
THE PRECIPITABLE WATER VALUE RANGES BETWEEN 0.16" AND 0.48".

TRANQUIL CONDITIONS WITH A RIDGE ALOFT BUILDING IN. WITH A WEAK
BOUNDARY MOVING THROUGH LAST NIGHT WILL BE A BIT COOLER TODAY...BUT
STILL QUITE NICE.

UPDATED TO REMOVE MORNING SHOWER WORDING IN THE NORTHERN WASATCH.
ANY CHANGES TO TEMPERATURES...SKY...AND WIND WERE VERY MINOR. REST
UNCHANGED.

PREVIOUS DISCUSSION FOLLOWS...

THE WEAK FRONTAL BOUNDARY WORKING INTO NRN UT HAS GENERATED A FEW
CLOUDS AND POSSIBLY A FEW SPRINKLES NEAR THE ID BORDER PER KMTX
RADAR. DONT SEE MUCH MORE THAN THIS DEVELOPING TODAY BUT KEPT A VERY
LOW POP IN THE NRN WASATCH FOR THIS MORNING TO COVER THIS THREAT.

THE ONLY OTHER IMPACT OF THIS WEAK FRONT WILL BE TO COOL NRN CWA
TEMPS A FEW DEGREES. THE SOUTH WILL REMAIN WARM OR POSSIBLY EVEN A
BIT WARMER THAN YESTERDAY AS HIGH CLOUDS WILL BE MOVING OUT OF THE
CWA NOT LONG AFTER SUNRISE AND EXPECT A MOSTLY SUNNY DAY.

WEAK SHORT WAVE RIDGING WILL KEEP THE CWA DRY AND MOSTLY CLEAR
TONIGHT WITH HIGHER CLOUDS ADVANCING INTO THE CWA FROM THE SW ON FRI
AS THE WEAK CLOSED LOW IN THE ERN PAC STARTS TO MOVE INLAND. THIS
FEATURE SETS UP A DEFORMATION ZONE ACROSS THE CWA AS IT PASSES TO
OUR SOUTH BRINGING A THREAT OF WEAK HIGH BASED CONVECTIVE SHOWERS ON
SAT LINGERING INTO SAT EVE ACROSS THE SOUTH.

THE OOZ GFS AND EC HAVE HELD FAST TO THEIR RESPECTIVE SOLUTIONS FOR
THE NRN BRANCH SHORT WAVE FOR SAT NIGHT/SUN WITH THE EC INDICATING A
FAIRLY SHARP COLD TROF AND TRACKING THE COLDEST AIR ALOFT OVER NRN
UT WHILE THE GFS CONTINUES TO INDICATE THIS TROF WILL BE MORE OF A
GRAZING FEATURE WITH ONLY THE LOW LEVEL COLD AIR REACHING THE
CWA...AND NOT AS COLD AS THE EC. THE EC SOLUTION WOULD BRING AT
LEAST A CHANCE OF PRECIP TO A GOOD PORTION OF THE CWA AND WOULD BE
COLD ENOUGH FOR SNOW TO THE NRN VALLEY FLOORS.

WOULD EXPECT MOST LIKELY OUTCOME WILL BE SOMEWHAT OF A COMPROMISE
BETWEEN THESE SOLUTIONS BUT DID NOT ALTER POPS AND TEMPS MUCH DUE TO
THE CONTINUED UNCERTAINTY.

MODELS DIFFER SIGNIFICANTLY AFTER 00Z MONDAY. GFS CONTINUES TO
DEPICT A BRUSH BY SYSTEM WHICH WOULD KEEP A FEW SHOWERS GOING OVER
THE NORTHERN MOUNTAINS. ECMWF CONTINUES TO SHOW A MUCH MORE WELL
DEFINED TROUGH STATEWIDE. INHERITED THE GFS SOLUTION AND SEE NO
REASON TO CHANGE THIS FAR OUT. EITHER WAY THIS SYSTEM IS FOLLOWED
RAPIDLY BY A RIDGE WHICH WILL ESSENTIALLY SHUT OFF PRECIPITATION
THROUGH TUESDAY MORNING. WARM ADVECTION WILL ALLOW WARMING OF TEMPS
TO BEGIN THE WEEK. RIDGE WILL FLATTEN AS NEXT UPSTREAM SYSTEM HEADS
FOR THE CWA. THIS SYSTEM LIKE THE PREVIOUS IS NOT HANDLED WELL BY
THE MODELS. THE GFS SEEMS TO BE THE MORE ROBUST MODEL WITH A SERIES
OF WEAK SHORT WAVES TUESDAY AFTERNOON THROUGH THURSDAY. TWEAKED POPS
TO MATCH SURROUNDING AREAS BUT BASICALLY CHANGED THEM LITTLE.
SOMEWHAT COOLER TEMPERATURES ARE ALSO EXPECTED.

&&

.AVIATION...OUTSIDE OF A WIND SWITCH BETWEEN 17-18Z...OPERATIONAL
WEATHER CONCERNS WILL REMAIN MINIMAL AT THE KSLC TERMINAL THROUGH
THE VALID TAF PERIOD. LIGHT AND VARIABLE TO LIGHT SOUTHEAST WINDS
ARE EXPECTED TO SWITCH TO THE NORTHWEST EARLIER THAN NORMAL
TODAY...WITH SPEEDS INCREASING TO ABOVE 7 KNOTS PRIOR TO 18Z.

&&

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

$$

PUBLIC...ROGOWSKI/WILENSKY/YOUNG
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)



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