Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 231142
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
442 AM MST MON FEB 23 2015

.SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL INTENSIFY TO
THE WEST OF UTAH TODAY...THEN TRACK EAST SOUTHEAST ACROSS NORTHERN
ARIZONA ON TUESDAY. HIGH PRESSURE ALOFT WILL BRIEFLY RETURN TO
THE REGION TUESDAY NIGHT...FOLLOWED BY A COUPLE OF WEAK WEATHER
DISTURBANCES CROSSING THE REGION MIDWEEK.

&&

.SHORT TERM (THROUGH 12Z THURSDAY)...THE UPPER LOW CURRENTLY OVER
CENTRAL CALIFORNIA BECOMING BETTER ORGANIZED LATE TONIGHT.
INCREASINGLY STRONG UPWARD MOTION EVIDENT IN RAPIDLY COOLING
CLOUD TOPS AND EXPANDING AREA OF PRECIP IN TO THE EASTERN FLANK OF
THE LOW AT THIS TIME. GOOD BAROCLINIC STRUCTURE AND SOLID UPPER
LEVEL DIVERGENCE SHOULD MAINTAIN STRONG LIFT ACROSS SOUTHERN UTAH
INTO THIS EVENING. THIS RATHER BROAD AREA OF SYNOPTIC-SCALE LIFT
WILL PRIMARILY IMPACT SOUTHWEST AND SOUTH-CENTRAL UTAH THROUGH
TONIGHT TODAY AS THE CENTER OF THE UPPER LOW HOLDS BACK ACROSS
CALIFORNIA.

PRECIP WILL EXPAND NORTH AND EAST TONIGHT AS THE CENTER OF THE
UPPER LOW MOVES INTO SOUTHERN NEVADA THIS EVENING...THEN EAST-
SOUTHEAST ACROSS NORTHERN ARIZONA LATE TONIGHT/TUESDAY. LOOKING AT
A FAIRLY SHARP LINE BETWEEN HEAVY PRECIP AND DRY CONDITIONS
ACROSS CENTRAL UTAH AS THE UPPER LOW DEVELOPS A TIGHTER
CIRCULATION AS IT MOVES INTO NORTHWEST ARIZONA. THIS LINE WILL
DRIFT SOUTH WITH THE UPPER LOW DURING THE DAY TUESDAY.

AT THIS POINT THE GREATEST SNOW TOTALS WILL OCCUR ACROSS THE
SOUTHERN MOUNTAINS DUE TO THE LONGER DURATION CLOSER TO THE
CENTER OF THIS UPPER LOW. ADJACENT VALLEY LOCATIONS...ESPECIALLY
THE HIGHER VALLEY LOCATIONS OF SOUTHWEST AND SOUTH-CENTRAL
UTAH WILL CONTINUE TO RECEIVE PERIODS OF HEAVY SNOW THROUGH EARLY
TUESDAY MORNING.

A PROGRESSIVE SHORTWAVE RIDGE TRAILING THE EXITING UPPER LOW WILL
SHIFT SOUTH ACROSS THE FORECAST AREA TONIGHT. BEHIND THIS UPPER
RIDGE A FAST-MOVING AND WEAK SHORTWAVE WILL CROSS UTAH WEDNESDAY.
THIS FEATURE COULD GENERATE SOME LIGHT PRECIP...BUT MORE LIKELY
WILL BRING CLOUDS AND KEEP TEMPS DOWN A BIT ACROSS THE NORTH AND
EAST. A SECOND SHORTWAVE SCHEDULED TO MOVE THROUGH WEDNESDAY NIGHT
WILL BRING ADDITIONAL LIGHT PRECIP...CLOUDS AND STILL COOLER AIR
INTO THE STATE FOR THURSDAY.

&&

.LONG TERM (AFTER 12Z THURSDAY)...THE NEXT SHORTWAVE IN THE
NORTHWESTERLY STORM TRAIN IS FORECAST TO DROP INTO THE REGION
THROUGH THE DAY THURSDAY. THE ECMWF AND GFS ARE STILL IN
DISAGREEMENT ABOUT EXACTLY HOW STRONG THIS WAVE WILL BE WITH REGARDS
TO PRECIPITATION...BUT BOTH PAINT AT LEAST SOME QPF OVER NORTHERN
UTAH...SO HAVE INCREASED POPS THROUGH THIS PERIOD. THIS MOIST AND
SLIGHTLY UNSTABLE NORTHWESTERLY FLOW LOOKS TO LINGER OVER THE AREA
THROUGH THURSDAY NIGHT AND INTO FRIDAY.

GLOBAL MODELS STILL BRING THE LONGWAVE TROUGH DOWN INTO THE WESTERN
CONUS FRIDAY NIGHT THROUGH SATURDAY...WITH A VERY LARGE AREA OF
COLDER TEMPERATURES AND INCREASED CHANCE OF PRECIPITATION. AS FAR AS
UTAH IS CONCERNED...THERE IS STILL SOME UNCERTAINTY ABOUT WHETHER
THE ENTIRE STATE WILL GET A DECENT PRECIPITATION EVENT. THE 00Z
MODELS ALLOWED THE BEST ENERGY TO DIG TO THE SOUTH...WITH PRIMARILY
THE SOUTHERN HALF OF THE STATE GETTING EXTENDED
PRECIPITATION...SIMILAR TO THE EVENT CURRENTLY ONGOING AS OF THIS
WRITING. HAVE KEPT POPS ELEVATED ACROSS THE ENTIRE CWA FRIDAY NIGHT
THROUGH SUNDAY...BUT INCREASED POPS A BIT MORE ACROSS THE SOUTH TO
ACCOUNT FOR THIS NEW SOLUTION.

HEADING INTO THE BEGINNING OF NEXT WEEK...THE LARGE TROUGH IS
PROGGED TO EXIT THE REGION ON MONDAY...BUT YET ANOTHER TROUGH COULD
ENTER THE GREAT BASIN ON TUESDAY AND WEDNESDAY.

&&

.AVIATION...THE LARGEST WEATHER CONCERN AT THE SLC TERMINAL TODAY
WILL BE THE SURFACE WINDS. THESE WINDS HAVE THE POTENTIAL TO BE
GREATLY ERRATIC IN BOTH DIRECTION AND SPEED...AND COULD VARY GREATLY
ACROSS THE RUNWAYS. THE SOUTH END OF THE RUNWAY IS MOST LIKELY TO
EXPERIENCE EASTERLY WINDS...WITH GUSTS IN THE 20-30 KNOT RANGE
POSSIBLE. WHILE THESE EASTERLIES COULD EXPAND UP TO THE NORTH END OF
THE RUNWAY...WINDS THERE COULD SIMPLY REMAIN WESTERLY AT 5-10 KNOTS.
THESE WINDS WILL LIKELY BECOME LESS ERRATIC AND MORE NORTHERLY AFTER
18Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 8 AM MST TUESDAY FOR UTZ013-014-016-
     020-021-517-518.

     HIGH WIND WARNING UNTIL 11 AM MST THIS MORNING FOR UTZ002-003.

WY...NONE.
&&

$$

SHORT TERM...CONGER
LONG TERM/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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