Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 241725
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1025 AM MST WED DEC 24 2014

.SYNOPSIS...HIGH PRESSURE OVER UTAH WILL SHIFT EAST AHEAD OF A
COLD WINTER STORM FOR CHRISTMAS DAY AND FRIDAY. UNSETTLED WEATHER
WILL CONTINUE INTO THE WEEKEND AND EARLY NEXT WEEK.

&&

.DISCUSSION...THE UPPER TROUGH POSITIONED OF THE PACIFIC NORTHWEST
COAST THIS MORNING WILL CONTINUE SOUTHEAST INTO THE GREAT BASIN
FOR CHRISTMAS DAY. THIS OPEN TROUGH WILL FORM INTO A CLOSED MID-
LEVEL FEATURE OVER THE GREAT BASIN...THEN SLOWLY GRIND SOUTHEAST
TO THE FOUR CORNERS REGION BY EARLY FRIDAY.

THE LEADING SURFACE COLD FRONT WILL REACH FAR NORTHWEST UTAH LATE
THIS EVENING...THEN SWEEP ACROSS THE ENTIRE FORECAST AREA BY EARLY
CHRISTMAS AFTERNOON. A TIGHT LOW-LEVEL BAROCLINIC ZONE BEHIND THE
SURFACE FRONT INDICATES THAT STRONG LIFT WILL EXIST ALONG THE
FRONTAL BOUNDARY...LEADING TO DECENT CONVECTION ACROSS NORTHWEST
THROUGH WEST-CENTRAL UTAH LATE TONIGHT/EARLY CHRISTMAS MORNING.
ANY RAIN WILL QUICKLY TURN TO SNOW BEHIND THE FRONT...WITH
SUBSTANTIAL SNOW ACCUMULATIONS THROUGH THE MORNING HOURS.

THE COLD FRONT...THOUGH STILL FAIRLY STRONG...WILL LOSE A BIT OF
ITS PUNCH AS THE THERMAL GRADIENT RELAXES A BIT OVER SOUTHERN AND
EASTERN UTAH. STILL LOOKING AT SIGNIFICANT ACCUMULATIONS
ASSOCIATED WITH THE FRONT...THOUGH MOST OF THIS WILL FOCUS ALONG
THE I-15/I-70 CORRIDORS AND ACROSS THE HIGHER CENTRAL/SOUTHERN
UTAH TERRAIN.

A PERIOD OF STEADY SNOW WILL EXISTS ACROSS MUCH OF NORTHERN UTAH
AND SOUTHWEST WYOMING AS MOIST WARM ADVECTION WRAP AROUND PRECIP
FORMS IN ASSOCIATION WITH THE CLOSED MID-LEVEL FEATURE MOVING INTO
SOUTHERN UTAH. THIS THERMALLY DRIVEN LIFT WILL PEAK DURING THE
AFTERNOON/EARLY EVENING HOURS UP NORTH...THEN SHIFT FURTHER SOUTH
WITH THE UPPER LOW DURING THE LATE AFTERNOON AND EVENING HOURS. A
SWITCH TO EASTERLY COLD ADVECTION ACROSS THE NORTH SHOULD BRING A
DECREASE IN SNOW LATE THURSDAY NIGHT...ESPECIALLY TO THE WEST OF
THE WASATCH RANGE ALONG THE URBAN CORRIDOR.

ONLY CHANGE TO THE CURRENT SUITE OF WARNINGS/ADVISORIES MAY BE FOR
THE EASTERN VALLEYS ON CHRISTMAS. PROXIMITY OF THE UPPER LOW
MOVING TOWARDS THE FOUR CORNERS WOULD BRING ABOUT THE POSSIBILITY
OF SIGNIFICANT ACCUMULATING SNOWS...ESPECIALLY WHERE TERRAIN
ORIENTATION IS MOST FAVORABLE. WILL CONSIDER ADDITIONAL HIGHLIGHTS
IN THE AFTERNOON FORECAST PACKAGE.

&&

.AVIATION...A SIGNIFICANT WINTER STORM WILL IMPACT THE SLC TERMINAL
EARLY THURSDAY MORNING INTO FRIDAY MORNING. A STRONG COLD FRONT IS
EXPECTED TO CROSS THE TERMINAL BETWEEN 08-09Z TONIGHT...BRINGING
GUSTY NORTHWEST WINDS...ACCUMULATING SNOW AND LIFR CONDITIONS FOR
THE REMAINDER OF THE MORNING. SNOWFALL INTENSITIES ARE EXPECTED TO
DECREASE THURSDAY AFTERNOON BUT PERIODIC IFR/LIFR CONDITIONS ARE
EXPECTED TO CONTINUE INTO THE OVERNIGHT HOURS. 2 TO 5 INCHES OF SNOW
ACCUMULATION IS EXPECTED ON UNTREATED SURFACES.

A 60 PERCENT CHANCE EXISTS THAT SOUTHERLY WIND GUSTS AHEAD OF THE
FRONT WILL EXCEED 30 MPH AT TIMES AFTER 22Z TODAY.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING FROM 2 AM THURSDAY TO NOON MST FRIDAY FOR
     UTZ001>004-006>010-014>016-517-518.

     WINTER WEATHER ADVISORY FROM 2 AM THURSDAY TO NOON MST FRIDAY
     FOR UTZ005.

WY...WINTER STORM WARNING FROM 2 AM THURSDAY TO NOON MST FRIDAY FOR
     WYZ021.

&&

$$

PUBLIC...CONGER
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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