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AREA FORECAST DISCUSSION

 
 FXUS65 KSLC 272350
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
450 PM MST FRI FEB 27 2015

.SYNOPSIS..A DEVELOPING WINTER STORM SYSTEM WILL AFFECT MUCH OF
THE SOUTHERN AND CENTRAL GREAT BASIN THIS WEEKEND. A SECOND STORM
WILL FOLLOW THE WEEKEND STORM EARLY NEXT WEEK.

&&

.SHORT TERM (THROUGH 00Z TUESDAY)...A STORM SYSTEM CURRENTLY SLIDING
SOUTH ALONG THE WEST COAST IS PUMPING UP A WEAK SHORTWAVE RIDGE
ACROSS EASTERN NEVADA...WHICH SHOULD SHIFT INTO UTAH THIS EVENING.
IN THE MEANTIME...AIRMASS OVER UTAH RETAINING ENOUGH MOISTURE AND
WITH A NEARLY 20C DIFFERENCE BETWEEN 500 AND 700MB...ENOUGH
INSTABILITY TO GENERATE A FEW SHOWERS OVER THE AREA. THESE SHOWERS
ARE EXPECTED TO DECREASE IN COVERAGE AFTER SUNSET.

THE AFOREMENTIONED STORM SYSTEM IS STILL PROGGED TO SPLIT AND BECOME
ELONGATED NORTHEAST TO SOUTHWEST...SLOWING ITS PROGRESSION IN THE
PROCESS. THE RESULT WILL BE AN EXTENDED PERIOD OF UNSETTLED WEATHER
FOR THE FORECAST AREA LATE TONIGHT THROUGH THE EARLY PART OF NEXT
WEEK. HOWEVER...MODELS SINCE LAST NIGHT HAVE TRENDED TOWARDS A
COMPLEX EVOLUTION INVOLVING SEVERAL DIFFERENT FEATURES AND FORCING
MECHANISMS AFFECTING DIFFERENT PARTS OF MOSTLY SOUTHERN AND CENTRAL
UTAH THROUGH MONDAY.

FIRST...SOUTH WINDS INCREASING OVER ARIZONA AHEAD OF THE STORM
SYSTEM WILL CONVERGE INTO WEAKER FLOW OVER UTAH TONIGHT AND EXPECTED
TO FIRE UP A BAND OF PRECIPITATION ACROSS FAR SOUTHERN UTAH. MODELS
THEN SHOW AN EMBEDDED SHORTWAVE DISTURBANCE EJECTING OUT ACROSS UTAH
TOMORROW...SPREADING THIS AREA OF PRECIPITATION NORTH TO AROUND THE
I-80 CORRIDOR. AFTERWARDS A DEFORMATION AXIS...MORE PROMINENT IN THE
GFS/NAM THAN IN THE EC...EXTENDING FROM WEST-CENTRAL UTAH THROUGH
THE UINTA MOUNTAINS AS THE TROUGH CONTINUES TO STRETCH OUT...IS
PROGGED TO ALLOW A BAND OF PRECIPITATION TO SETTLE ACROSS THAT AREA
TOMORROW NIGHT INTO SUNDAY WHILE PRECIPITATION DECREASES ACROSS
SOUTHERN UTAH. THIS BAND WILL WEAKEN DURING THE DAY SUNDAY. BY
SUNDAY NIGHT...AN UPSTREAM TROUGH DIVING INTO THE AREA WILL CAUSE
THE PATTERN TO AMPLIFY BEFORE THE STORM GETS SHOVED EAST ACROSS THE
DESERT SOUTHWEST. THIS WILL PUMP THE SOUTHERLIES BACK UP INTO UTAH
AND LIFT A WARM FRONT UP FROM THE SOUTH ALONG WITH ANOTHER ROUND OF
PRECIPITATION FOR THE SOUTHERN AND EASTERN PORTIONS OF THE FORECAST
AREA.

GIVEN THE DILEMMA WITH THE MULTIPLE FEATURES AND LINGERING
UNCERTAINTY REGARDING THE EVOLUTION OF THE STORM...HAVE OPTED TO
ADDRESS JUST THE FIRST ROUND OF PRECIPITATION...TONIGHT INTO
TOMORROW NIGHT...WITH WINTER WEATHER HIGHLIGHTS. THIS WILL MAINLY
AFFECT PORTIONS OF SOUTHERN AND CENTRAL UTAH. THE WINTER STORM WATCH
FOR THE CENTRAL AND SOUTHERN MOUNTAINS IS NOW AN ADVISORY...AND
ADJACENT VALLEYS TO THE SOUTH AND EAST WHERE THE SOUTH FLOW IS
FAVORABLE HAVE BEEN ADDED TO THE ADVISORY AS WELL. ALTHOUGH SNOW
WILL BE POSSIBLE DOWN TO THE VALLEY FLOORS...FOCUS WILL BE ON
ELEVATIONS ABOVE AROUND 5000FT WHERE THE BULK OF THE ACCUMULATING
SNOW WILL OCCUR. IF MODELS ARE CORRECT WITH THE DEFORMATION AXIS AND
THE WARM FRONT...ADDITIONAL ZONES MAY EVENTUALLY NEED TO BE ADDED
AND/OR HIGHLIGHTS EXTENDED.

CANYON WINDS ALONG THE WASATCH FRONT STILL A POSSIBILITY BOTH
TONIGHT AND TOMORROW NIGHT GIVEN THE EASTERLY PRESSURE GRADIENT
ACROSS SOUTHWEST WYOMING AND NORTHEAST UTAH. HOWEVER...MODELS
CONTINUE TO LOOK LESS PROMISING FOR A SIGNIFICANT EVENT DUE TO
WEAKENING SUPPORT AT 700MB. EXPECT JUST SOME LOCALLY ENHANCED FLOW
OUT OF THE CANYONS TONIGHT AND A BIT STRONGER TOMORROW NIGHT. THESE
WINDS ARE NOT EXPECTED TO BECOME STRONG ENOUGH TO CAUSE SIGNIFICANT
ISSUES.

&&

.LONG TERM (AFTER 00Z TUESDAY)...MODELS CONTINUE TO BE IN GOOD
AGREEMENT IN BRINGING ANOTHER SHORTWAVE TROUGH SOUTH FROM CANADA
MONDAY NIGHT AND TUESDAY. ALONG WITH ANOTHER ROUND OF RAIN AND
SNOW...IT WILL ALSO BRING ANOTHER REINFORCING SHOT OF COLDER AIR.
THE COLDEST TEMPERATURES LOOK TO BE ON WEDNESDAY. THE MOUNTAINS OF
NORTHERN AND CENTRAL UTAH COULD SEE A BRIEF SHOT OF HEAVY SNOW WITH
THIS QUICK MOVING SYSTEM. BEYOND WEDNESDAY...MODELS CONTINUE TO
BRING A BUILDING RIDGE OF HIGH PRESSURE WHICH WOULD BRING WARMING
TEMPERATURES AND DRY CONDITIONS THROUGH AT LEAST NEXT WEEKEND.

&&

.AVIATION...ISOLATED SHOWERS WILL CONTINUE TO MOVE THROUGH THE SLC
TERMINAL THROUGH EARLY EVENING. CEILINGS NEAR THESE SHOWERS MAY
LOWER BRIEFLY BELOW 7000FT AGL...OTHERWISE THEY WILL REMAIN AROUND
9000-10000 FEET AGL OR CLOUDS MAY SCATTER OUT AT TIMES.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM MST
SUNDAY FOR UTZ012-013-020-517-518.

WY...NONE.
&&




CHENG/SOLUM

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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