Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 181143
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
443 AM MST THU DEC 18 2014

.SYNOPSIS...A SOMEWHAT MOIST WESTERLY FLOW WILL PREVAIL ACROSS
THE REGION THROUGH THURSDAY EVENING. A WEAK RIDGE WILL DEVELOP
EARLY FRIDAY ONLY TO BE FLATTENED BY AN INCREASINGLY MOIST
NORTHWEST FLOW AIMED AT NORTHERN UTAH FOR THE WEEKEND INTO EARLY
NEXT WEEK.


&&

.DISCUSSION...
.SHORT TERM (THROUGH 00Z MONDAY)...A VERY WEAK WESTERLY FLOW WITH
SUBTLE DISTURBANCES WILL PREVAIL ACROSS THE REGION TODAY INTO
TONIGHT. SATELLITE IMAGERY SHOWING CLEARING SKIES OVER WEST
CENTRAL AND NORTHWEST UTAH AT THIS TIME BUT BECAUSE THE AIR MASS
IS RELATIVELY MOIST ANY LITTLE DISTURBANCES IN THE WESTERLY FLOW
COULD EASILY DEVELOP CLOUDS ONCE AGAIN. HAVE PLAYED FOR PARTLY
CLOUDY SKIES FOR THE WESTERN VALLEYS TODAY BUT CONFIDENCE NOT VERY
HIGH THAT THEY WILL BE PARTLY CLOUDY. MOUNTAINS AND EASTERN
PORTIONS OF THE CWA SHOULD REMAIN MOSTLY CLOUDY AS MODELS SHOW A
WEAK DISTURBANCE MOVING THROUGH THIS AFTERNOON. A GRADUAL DECREASE
IN CLOUDS IS EXPECTED OVER MOST OF THE REGION TONIGHT...ESPECIALLY
OVER THE SOUTHEAST PART OF THE CWA. HAVE INCLUDED PATCHY FOG FROM
GREEN RIVER TO HANKSVILLE AND THE LAKE POWELL REGION FOR LATE
TONIGHT AND FRIDAY MORNING AS SKIES SHOULD HAVE THE BEST CHANCE OF
CLEARING DOWN THERE. IF SKIES CLEAR MORE THAN CURRENT FORECAST
THEN FOG WILL LIKELY FORM...ESPECIALLY IN AREAS PRONE TO HAVING
FOG SUCH THE MOUNTAIN VALLEYS...CACHE VALLEY AND POSSIBLY THE
WASATCH FRONT.

THE REASON FOR THE CLOUDS TO LIKELY DISSIPATE LATE TONIGHT IS
THAT A RIDGE IS FORECAST TO DEVELOP TEMPORARILY LATE TONIGHT INTO
FRIDAY. THIS RIDGE WILL BE SHORT LIVED OVER THE NORTH AS A MOIST
NORTHWEST FLOW DEVELOPS FROM THE EASTERN PACIFIC ACROSS OREGON AND
SOUTHEAST INTO NORTHERN UTAH BY LATE FRIDAY NIGHT AND WILL PERSIST
THROUGH NEXT MONDAY. PRECIPITATION WILL INCREASE IN INTENSITY
SATURDAY NIGHT INTO SUNDAY AS A DISTURBANCE MOVES ALONG THIS MOIST
FLOW. TEMPERATURES WILL BE COLD ENOUGH FOR A MIXTURE OF RAIN AND
SNOW IN THE NORTHWEST VALLEYS FRIDAY NIGHT AND SATURDAY BUT AS H7
TEMPERATURES WARM TO ABOUT -2 TO -3 DEGREES C BY SUNDAY MORNING
ALL VALLEYS SHOULD SEE JUST RAIN SATURDAY NIGHT AND SUNDAY. HEAVY
MOUNTAIN SNOWS ARE EXPECTED THROUGH THIS PERIOD FROM THE CENTRAL
WASATCH NORTHWARD AS WELL AS THE UINTA MOUNTAINS. THE GFS AND NAM
ARE SHOWING FROM 0.50 TO 1.25 INCHES OF PRECIPITATION BY SUNDAY
AFTERNOON OVER THE MOUNTAINS WITH MORE TO COME SUNDAY NIGHT AND
MONDAY.

THE SOUTHERN HALF OF THE CWA IS EXPECTED TO REMAIN DRY AS THIS
FIRE HOSE OF MOISTURE REMAINS AIMED AT NORTHERN UTAH AND SOUTHWEST
WYOMING. TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL TODAY THROUGH
SATURDAY BUT INCREASE ANOTHER 5 DEGREES SUNDAY AS SOUTH WINDS
BECOME ENHANCED WITH PASSAGE OF THE DISTURBANCE ACROSS NORTHERN
UTAH.


.LONG TERM (AFTER 00Z MONDAY)...GEFS ENSEMBLE MEAN SHOWS SIGNIFICANT
INTEGRATED WATER VAPOR TRANSPORT PERSISTING INTO NORTHERN UTAH
SUNDAY EVENING. THIS MOISTURE COUPLES WITH WARM AIR ADVECTION TO
EXTEND WEEKEND PRECIPITATION THROUGH MONDAY FOR THE NORTHERN
MOUNTAINS AND ADJACENT VALLEYS. SNOW LEVELS WILL RISE SUNDAY NIGHT
INTO MONDAY AFTERNOON...PROMOTING A RAIN/SNOW MIX IN THE MOUNTAIN
VALLEYS AND WHILE SNOW WILL CONTINUE IN THE MOUNTAINS ABOVE 7500
FEET.

A WEAK SHORTWAVE BRIEFLY SHUNTS THE MOISTURE TAP...THOUGH THE LATEST
06Z GFS RUN IS SOMEWHAT INSISTENT ON MAINTAINING NORTHERN MOUNTAIN
PRECIP THROUGH TUESDAY. AN ATMOSPHERIC RIVER REDEVELOPS ON CHRISTMAS
EVE...EJECTING FROM BLOSSOMING PACIFIC TROUGH. THOUGH MODELS DIFFER
ON NORTHERLY PLACEMENT OF THE LOW...CONSENSUS IS PRETTY SOLID FOR A
WORTHY PRECIP EVENT FOR NORTHERN UTAH ON CHRISTMAS DAY...WITH A
CONFIDENT INJECTION OF COLD AIR PUSHING SNOW LEVELS DOWN TO THE
VALLEY FLOORS.

&&

.AVIATION...SOUTHEAST WINDS WILL CONTINUE AT THE KSLC TERMINAL
THROUGH THE MORNING HOURS. CIGS WILL REMAIN PRIMARILY ABOVE 6000 FT
AGL...WITH A 20 PERCENT CHANCE OF DESCENDING TO THIS LEVEL UNTIL
ABOUT 14Z. VFR CONDITIONS SHOULD HOLD THROUGH THE TAF PERIOD.

&&

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

$$

PUBLIC...
AVIATION...

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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