Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 141148
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
448 AM MST SUN DEC 14 2014

.SYNOPSIS...A WEAKENING STORM SYSTEM WILL SLOWLY MOVE OUT OF THE
REGION TODAY. HIGH PRESSURE WILL RETURN FOR MONDAY WITH
ADDITIONAL WEAK SYSTEMS CROSSING THE AREA THROUGH MIDWEEK.


&&

.SHORT TERM (THROUGH 00Z WEDNESDAY)...AN UPPER LEVEL SHEAR AXIS
COUPLED WITH A COLD POOL ALOFT AND A MOIST LOW LEVEL AIRMASS HAS
ALLOWED AREAS OF SNOW TO PERSIST THROUGH THE OVERNIGHT HOURS
ACROSS NORTHERN UT. THIS SNOWFALL APPEARS TO HAVE BEEN ENHANCED IN
PART BY THE RELATIVELY WARM WATERS OF THE GREAT SALT LAKE...WITH
RADAR ALSO SUGGESTING SNOW SHOWERS DOWNWIND OF UTAH LAKE ACROSS
AREAS SOUTH OF PROVO OVERNIGHT. THIS UPPER SHEAR AXIS WILL REMAIN
IN PLACE BUT WEAKEN THROUGH THE DAY. AS SUCH HAVE INCLUDED
SCATTERED SNOW SHOWERS ACROSS THE NORTHERN VALLEYS WITH MORE
WIDESPREAD COVERAGE ACROSS THE HIGHER TERRAIN. ADDITIONAL
ACCUMULATION IS EXPECTED TO REMAIN LIGHT...AND AS SUCH HAVE
CANCELED THE GOING WINTER WX ADVISORY FOR THE WESTERN UINTAS.

FURTHER SOUTH...LOW LEVEL MOISTURE COUPLED WITH CLEARING SKIES
OVERNIGHT WILL ALLOW FOR PATCHY FOG THIS MORNING ACROSS THE
SOUTHERN AND EASTERN VALLEYS.

MID LEVEL RIDGING IS FORECAST TO BRIEFLY BUILD ACROSS THE REGION
LATE TONIGHT INTO THE DAY MONDAY...DOWNSTREAM FROM ANOTHER MID
LEVEL TROUGH WHICH IS FORECAST TO APPROACH THE COAST DURING THIS
TIMEFRAME. THE 00Z/06Z MODEL SUITE IS IN GENERAL AGREEMENT
LIFTING A PLUME OF WARM AIR/MOISTURE ADVECTION ACROSS CENTRAL AND
PERHAPS NORTHERN UT MONDAY NIGHT INTO EARLY TUESDAY. AS SUCH HAVE
INCREASED POPS 20-30 PERCENT ACROSS THESE AREAS.

&&

.LONG TERM (AFTER 00Z WEDNESDAY)...A MESSY WEATHER PATTERN IS
SETTING UP FOR THE TUESDAY NIGHT THROUGH THURSDAY TIME FRAME. A
BROAD WEAK TROUGH WITH MULTIPLE DISTURBANCES WILL MOVE ACROSS THE
REGION. TO COMPLICATE THE FORECAST THE GLOBAL MODEL SOLUTIONS DIFFER
IN TIMING AND STRENGTH. THE GFS OPERATIONAL RUN SHOWS A WEAK SYSTEM
OUTRUNNING THE MAIN TROUGH TUESDAY NIGHT AFFECTING MAINLY WESTERN
PORTIONS OF THE CWA WHILE THE EC DOES NOT HAVE THIS FEATURE.
THEREFORE HAVE BACKED OFF A LITTLE ON THE POPS ACROSS EASTERN
PORTIONS SINCE THE EC APPEARS TO HAVE SUPPORT OF THE GFS ENSEMBLE
MEAN.

THE EC BRINGS A MORE CONSOLIDATED TROUGH ACROSS THE CWA DURING THE
DAY WEDNESDAY WHILE THE GFS HAS ITS SECOND TROUGH HANGING BACK AND
MOVING THROUGH THURSDAY MORNING. OVERALL IDEA OF A TROUGH MOVING
THROUGH THE REGION LOOKS REASONABLE SO INCREASE POPS BETWEEN 00 AND
12Z THURSDAY. THIS MAY NEED TO BE PUSHED BACK OR MOVED UP BY 6-12
HRS...BUT WANTED TO GET SOME LIKELY SNOW MENTIONED IN THE FORECAST
FOR THE MOUNTAINS. BOTH THE GFS AND EC BUILD A RIDGE BEHIND THIS
TROUGH FOR FRIDAY ALTHOUGH THE GFS IS SLIGHTLY SLOWER AND NOT AS
STRONG. ALTHOUGH THE MOUNTAINS WILL REALIZE A 5-10 DEGREE WARMING
BETWEEN THURSDAY AND FRIDAY THE VALLEYS MAY ONLY SEE A COUPLE OF
DEGREES DUE TO A LIKELY INVERSION IN PLACE. THE WARMING WILL LIKELY
BE MORE OF A RESULT OF PARTLY CLOUDY SKIES OR EVEN MOSTLY SUNNY
SKIES COME FRIDAY VERSES CLOUDY SKIES EXPECTED THURSDAY.

ANOTHER STORM SYSTEM MOVES IN SATURDAY AFTERNOON OR LATER DEPENDING
ON MODEL OF CHOICE. THE SLOWER GFS IS STRONGER AND SLOWER WITH THE
TROUGH COMING IN SATURDAY AFTERNOON AND CLOSING OFF OVERHEAD
SATURDAY EVENING BEFORE DRIFTING SOUTH INTO NORTHERN ARIZONA BY
SUNDAY AFTERNOON. THE EC BRINGS A TROUGH INTO NORTHERN UTAH ABOUT
MIDDAY AND THEN CLOSES IT OFF AS IT LIFTS INTO WYOMING...BUT IT TOO
THEN DRIFTS SOUTH SOUTHWEST SUNDAY ACROSS THE CWA. PROBABLY NOT MUCH
OF A WEATHER MAKER BUT HAVE LOW POPS TO COVER THE FACT THAT A TROUGH
IS IN THE VICINITY OF THE CWA.


&&

.AVIATION...NORTHWEST WINDS WILL PREVAIL AT THE SLC TERMINAL THROUGH
TODAY. CIGS SHOULD REMAIN BETWEEN BKN035 AND BKN060 THROUGH ABOUT
22Z BUT COULD EASILY POP UP TO OR ABOVE BKN070 AS EARLY AT MIDDAY.
CONFIDENCE LOW IN THIS CIG FORECAST. WINDS WILL LIKELY SHIFT TO
SOUTHEAST BETWEEN 03 AND 04Z TONIGHT.


&&

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