Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 231230
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
530 AM MST TUE DEC 23 2014

.SYNOPSIS...A DRY NORTHERLY FLOW IS OVER THE AREA TODAY AS HIGH
PRESSURE BUILDS INTO THE GREAT BASIN. THE HIGH SHIFTS EAST
WEDNESDAY AHEAD OF A COLD WINTER STORM FOR CHRISTMAS DAY.

&&

.SHORT TERM (TIL 00Z SAT)...AN AMPLIFIED UPPER RIDGE IS ALONG THE
WEST COAST EARLY TODAY WITH A DRY NORTHERLY FLOW OVER THE CWA.
WINDS ALOFT ARE STILL FAIRLY STRONG ACROSS SOUTHERN UTAH THIS
MORNING AND COMBINED WITH A TIGHT SURFACE GRADIENT ARE CREATING
GUSTY NORTHEASTERLY GAP WINDS ACROSS WASHINGTON CO. WINDS HAVE
REMAINED JUST UNDER ADVISORY LEVELS SO FAR THIS MORNING BUT ARE
EXPECTED TO INCREASE SOMEWHAT FOR A TIME THROUGH MID MORNING
BEFORE DIMINISHING. SO HAVE LEFT THE WIND ADVISORY IN EFFECT.

A COOL MORNING AND STAGNANT CONDITIONS ACROSS THE NORTHERN AND
CENTRAL VALLEYS WILL KEEP MAX TEMPS ON THE COOL SIDE TODAY.

THE RIDGE SHIFTS EAST TONIGHT AND WED AHEAD OF A COLD TROF DIGGING
DOWN THE WEST COAST. INCREASING SWLY FLOW ALOFT AND A TIGHTENING
SOUTHERLY SURFACE GRADIENT ON WED SHOULD HELP MIX THE WESTERN
VALLEYS AND TEMPS SHOULD BUMP UP 10 DEGREES OR SO FROM TODAY AS
WARMER AIR ALOFT PARTIALLY MIXES DOWN. THERE IS A POTENTIAL FOR
TEMPS TO WARM EVEN MORE IF WE FULLY MIX BUT HIGHER CLOUDS WILL
ALSO BE INCREASING WED AND THIS WILL HOLD TEMPS BACK SOMEWHAT.

THE EC AND GFS ARE FINALLY IN PRETTY GOOD AGREEMENT ON THE
EVOLUTION OF THE WEST COAST TROF MOVING IT THRU THE GREAT BASIN
WED NIGHT AND THU. BOTH PUSH THE COLD FRONT INTO WRN UT BY 12Z AND
THRU THE CWA BY 18Z. THE AIRMASS WITH THIS TROF IS COLD ENOUGH AND
THE TROF IS DEEP ENOUGH FOR SNOW TO ALL VALLEY FLOORS OUTSIDE OF
THE FAR SOUTH AND IT IS FORECAST TO HAVE SUFFICIENT MOISTURE TO
PRODUCE SIGNIFICANT AMOUNTS OF SNOW.

SO WITH THE THREAT OF MAJOR TRAVEL IMPACTS ACROSS MUCH OF THE CWA
OCCURRING ON A MAJOR HOLIDAY HAVE GONE AHEAD AND ISSUED A WINTER
STORM WATCH FOR ALL MTNS AND THE WRN VALLEYS S TO CEDAR CITY
STARTING IN THE EARLY MORNING HOURS THU AND LASTING INTO FRI.

THE HEAVIEST SNOW AMOUNTS SHOULD BE UP AND DOWN THE ENTIRE I-15
CORRIDOR AND IN THE ADJACENT MTNS ON THU BUT ACCUMULATING SNOW IS
ALSO EXPECTED IN THE EAST AS THE FRONT BLOWS THRU THERE. GUSTY
NORTHWEST WINDS SHOULD ALSO FOLLOW THE FRONT INTO THE CWA AND
BLOWING AND DRIFTING SNOW WILL ADD TO THE TRAVEL IMPACTS.

THE UPPER TROF SPLITS THU NIGHT INTO FRI WITH A NORTHERN PORTION
MOVING OFF INTO THE PLAINS WHILE A SRN PORTION REMAINS OVER UT.
LINGERING SNOW IN THIS SRN PORTION OF THE TROF COULD PAD THE
TOTALS IN MAINLY THE NRN AND CENTRAL MTNS AND THE NWRN AND
W-CENTRAL VALLEYS THU NIGHT INTO FRI.

&&

.LONG TERM (AFTER 00Z SATURDAY)...VERY ACTIVE WEATHER PATTERN FOR
THE LONG TERM PORTION OF THE FORECAST...WITH A SIGNIFICANT PATTERN
SHIFT TO COLDER TEMPERATURES FOR THE REMAINDER OF 2014 IN STORE
EARLY NEXT WEEK.

AT 00Z SATURDAY...A TROUGH WILL REMAIN STRETCHED ACROSS THE WESTERN
UNITED STATES WITH A TRAILING SHORTWAVE DROPPING SOUTH ACROSS
NEVADA. THIS WILL HELP TO REINFORCE THE ALREADY PRESENT TROUGH.

AN UPSTREAM SHORTWAVE APPROACHING THE PACIFIC NORTHWEST SATURDAY
MORNING WILL HELP TO PUSH THE PREVIOUSLY MENTIONED TROUGH EASTWARD
AND AWAY FROM THE FORECAST AREA. THIS UPSTREAM TROUGH WILL THEN DIG
SOUTHWARD ACROSS THE WESTERN UNITED STATES...PULLING A VERY
COLD...CONTINENTAL AIRMASS SOUTHWARD FROM THE CANADIAN PRAIRIE
PROVINCES. THE ASSOCIATED COLD FRONT WILL CROSS THE AREA MONDAY
BRINGING EVEN COLDER TEMPERATURES TO THE STATE. ANY PRECIPITATION
WILL FALL AS SNOW FOR ALL BUT THE DIXIE AREA.

PUSHED POPS ABOVE CLIMO WITH THE PASSAGE OF THE COLD FRONT...BUT
HARD TO INCREASE TOO MUCH AS THIS SYSTEM IS FAIRLY MOISTURE STARVED
IN ITS CURRENT FORM. 00Z MODEL GUIDANCE WAS FAIRLY CONSISTENT WITH
THE EVOLUTION OF THE TROUGH...SO CONFIDENCE IN THE PATTERN CHANGE TO
COLDER TEMPERATURES IS HIGHER THAN AVERAGE. SOME OF THE
COLDEST...IF NOT THE COLDEST TEMPERATURES OF THE WINTER ARE POSSIBLE
BY TUESDAY MORNING.

&&

.AVIATION...NORTH TO NORTHWEST WINDS ARE EXPECTED TO CONTINUE
THROUGH THE DAY AT THE SLC TERMINAL.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
     MORNING FOR UTZ001>010-014>016-517-518.

     WIND ADVISORY UNTIL 1 PM MST THIS AFTERNOON FOR UTZ019-518.

WY...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
     MORNING FOR WYZ021.

&&

$$

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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