Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 211121
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
421 AM MST FRI NOV 21 2014

.SYNOPSIS...A STORM SYSTEM CROSSING THE DESERT SOUTHWEST WILL
HAVE LITTLE IMPACT ON SOUTHERN UTAH TODAY. A STRONG NORTHWEST
FLOW WILL PUSH A COLD FRONT INTO NORTHERN UTAH SATURDAY AFTERNOON.
THIS COLD MOIST NORTHWEST FLOW WILL CONTINUE OVER THE AREA THROUGH
MONDAY...BEFORE HIGH PRESSURE STRENGTHENS ACROSS THE REGION FOR
MIDWEEK.

&&

.SHORT TERM (THROUGH 00Z TUESDAY)...A SHORTWAVE TROUGH IS NOTED IN
WATER VAPOR IMAGERY DIGGING SOUTHEAST THROUGH THE LOWER CO RIVER
VALLEY. THIS WAVE IS NOW EXPECTED TO TRACK FURTHER SOUTH THAN
PREVIOUSLY ADVERTISED...AND HAVE CUT BACK ON POPS ACROSS SOUTHERN
UT FOR THIS MORNING...ONLY LEAVING A SLIGHT CHANCE FOR HIGH
ELEVATION SHOWERS. OTHERWISE VERY LIGHT FLOW ALOFT TO THE NORTH OF
THIS SYSTEM IS EXPECTED TO DAY WITH PERIODS OF MID AND HIGH CLOUDS
CROSSING THE REGION. TEMPERATURES ARE EXPECTED TO CONTINUE TO
MODERATE ACROSS NORTHERN UT...ALTHOUGH A STABLE LAYER NEAR 800MB
WILL CONTINUE TO RESULT IN SOMEWHAT HAZY CONDITIONS ALONG THE
WASATCH FRONT.

THE MODELS REMAIN IN STRONG AGREEMENT WITH THE EVOLUTION OF THE
LARGE SCALE PATTERN ACROSS THE INTERIOR WEST DURING THE UPCOMING
WEEKEND INTO EARLY NEXT WEEK WITH NO REAL SURPRISES IN THE 00Z
MODEL SUITE. AS SUCH OVERALL CONFIDENCE REMAINS HIGH...AND ONLY
MINOR ADJUSTMENTS WERE MADE TO THE FORECAST THROUGH MONDAY.

STRONG MOISTURE ADVECTION IS FORECAST TO SPREAD ACROSS NORTHERN
UTAH EARLY SATURDAY...WITH A COLD FRONT SWEEPING THROUGH NORTHERN
UT LATE IN THE DAY...THEN SOUTHWARD THROUGH THE REMAINDER OF THE
STATE DURING THE EVENING. A PROLONGED PERIOD OF MOIST AND DEEPLY
UNSTABLE NORTHWEST FLOW WILL FOLLOW ACROSS NORTHERN UT...WHICH
WILL YIELD VERY FAVORABLE OROGRAPHIC FORCING FOR AREAS FAVORED IN
SUCH REGIMES. A LULL IN PRECIPITATION IS POSSIBLE DURING THE DAY
SUNDAY...BEFORE ANOTHER WAVE EMBEDDED WITHIN THIS FLOW ENHANCES
SNOWFALL ACROSS NORTHERN UT SUNDAY NIGHT INTO MONDAY.
PRECIPITATION IS EXPECTED TO WIND DOWN MONDAY AFTERNOON AS MID
LEVEL RIDGING BUILDS INTO THE GREAT BASIN.

SNOW FORECASTS AND THE GOING WINTER STORM WATCH STILL LOOK IN GOOD
SHAPE ACROSS THE WASATCH AND WESTERN UINTAS. VALLEY SNOWFALL
TOTALS ARE MORE UNCERTAIN...AND THIS IS THE PORTION OF THE
FORECAST WHERE CONFIDENCE REMAINS LOWER. INITIALLY SNOW LEVELS
WILL LIKELY BE SLOW TO FALL TO THE VALLEY FLOORS BEHIND THE
SURFACE FRONT...WITH SNOW LIKELY NOT BEGINNING ACROSS THE VALLEYS
UNTIL MID TO LATE SATURDAY EVENING. AS SUCH MUCH OF THE QPF EARLY
IN THE EVENT WILL LIKELY FALL AS RAIN. PERIODS OF LIGHTER
PRECIPITATION WILL FOLLOW SATURDAY NIGHT INTO EARLY SUNDAY...AND
AGAIN SUNDAY NIGHT INTO EARLY MONDAY...WITH SOME ENHANCEMENT
ALONG THE BENCHES AND POSSIBLY SOUTHEAST OF THE GSL. AT THIS POINT
IT APPEARS ADVISORY LEVEL SNOWFALL AMOUNTS ARE MOST LIKELY ALONG
THE VALLEY FLOORS...WITH HIGHER AMOUNTS NOT OUT OF THE QUESTION
ALONG THE BENCHES.

&&

.LONG TERM (AFTER 00Z TUESDAY)...RIDGE BEGINS TO BUILD INTO UTAH
ACCORDING TO BOTH THE EC AND GFS ALTHOUGH THE GFS HOLDS UNTO A WEAK
DISTURBANCE IN THE NORTHWEST FLOW ACROSS EXTREME NORTHERN UTAH
TUESDAY AFTERNOON. THERE IS DECENT WARM ADVECTION FORECAST BY THE
GFS SO LEFT SOME SLIGHT CHANCE IN THE NORTHERN VALLEYS AND CHANCE IN
THE MOUNTAINS. THIS MAY STILL BE OVER DONE IF THE EC IS CORRECT
WHICH SHOWS NO PRECIP BETWEEN 00Z TUESDAY AND 00Z WEDNESDAY. THE
700MB TEMPS MODERATE QUITE RAPIDLY FROM -12C AT SLC 00Z TUESDAY TO
-4C BY 00Z WEDNESDAY. SO SURFACE TEMPS SHOULD MODERATE AS WELL BUT
NOT TO THEIR FULL POTENTIAL DUE TO A LIKELY CLOUD COVER ALONG THE
WASATCH FRONT AND MOUNTAINS. FARTHER SOUTH ACROSS CENTRAL AND
SOUTHERN UTAH DRY CONDITIONS ARE EXPECTED THROUGH THE REMAINDER OF
THE WEEK AS BOTH THE EC AND GFS HAVE A RIDGE IN PLACE. TEMPERATURES
WILL BE SLIGHTLY ABOVE NORMAL.

SINCE THE EC WENT TOWARDS THE GFS SOLUTION AND NOW BOTH HAVE A RIDGE
IN PLACE FOR THE MID WEEK PERIOD HAVE REMOVED POPS OR REDUCED THEM
SIGNIFICANTLY. CONFIDENCE HOWEVER IN THE THURSDAY AND FRIDAY PERIOD
IS LOW DUE TO THE EC HAVING SUCH A LARGE SWING FROM PREVIOUS RUNS.
DECIDED TO LEAN TOWARDS THE GFS FOR THIS PERIOD WHICH WILL HAVE NEAR
OR SLIGHTLY ABOVE NORMAL TEMPERATURE WISE AND BELOW CLIMO FOR POPS.

&&

.AVIATION...NO OPERATIONAL WEATHER CONCERNS AT THE SLC TERMINAL
THROUGH THE TAF PERIOD UNDER VFR CONDITIONS. WIND WILL REMAIN
LIGHT...BUT A SHIFT FROM THE SOUTH TO THE NORTHWEST IS EXPECTED
BETWEEN 18 AND 19Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE MONDAY NIGHT
     FOR UTZ007>009.

WY...NONE.
&&

$$

SEAMAN/STRUTHWOLF

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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