Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 011144
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
444 AM MST SUN FEB 1 2015

.SYNOPSIS...HIGH PRESSURE ALOFT WILL REMAIN POSITIONED ALONG THE
WEST COAST THROUGH MIDWEEK. A MOIST WEST NORTHWEST FLOW WILL
DEVELOP ACROSS THE NORTHERN GREAT BASIN FOR THE FIRST HALF OF
THE WEEK.

&&

.SHORT TERM (THROUGH 00Z THURSDAY)...THE PATTERN ACROSS THE
EASTERN PACIFIC CONSISTS OF A DEEP VORTEX BETWEEN 150W-160W WITH A
DOWNSTREAM RIDGE ALONG THE WEST COAST. THIS PATTERN WILL CHANGE
LITTLE THROUGH THE MIDDLE OF THE UPCOMING WEEK.

A SERIES OF SHORTWAVES EJECTING OUT OF THE EASTERN PACIFIC VORTEXWILL
SERVE TO KEEP THE WEST COAST RIDGE LOW AMPLITUDE WITH A MOIST
WEST-NORTHWEST FLOW ACROSS THE INTERIOR WEST. THESE EMBEDDED
SHORTWAVES WILL HAVE THE GREATEST IMPACT OVER THE NORTHERN ROCKIES
WHERE THE BEST COLD AIR AND DYNAMIC LIFT WILL CONCENTRATE.

NORTHERN UTAH WILL BE ON THE SOUTHERN END OF THESE PASSING
SHORTWAVES. MOIST LOW-LEVEL WARM ADVECTION AHEAD OF THESE
FEATURES WILL DRIVE ENOUGH LIFT FOR LIGHT PRECIP. PRECIP WILL
INCREASE IN INTENSITY AND AREAL COVERAGE AS COLD ADVECTION AND
WEAK DYNAMIC LIFT DEVELOP WITH THE PASSING SHORTWAVES.

PROLONGED...BUT NOT CONTINUOUS PRECIP BETWEEN LATE TONIGHT THROUGH
WEDNESDAY COULD LEAD TO SIGNIFICANT HIGH ELEVATION SNOW ALONG THE
WASATCH RANGE. THE NORTHERN WASATCH RANGE WILL LIKELY SEE THE
GREATEST TOTALS...THOUGH A NUMBER OF AREAS ALONG THE ENTIRE RANGE
COULD BE LOOKING AT A FOOT OR MORE OF NEW SNOW THROUGH MIDWEEK.
ADJACENT VALLEY LOCATIONS FOR THE MOST PART WILL RECEIVE RAIN OR A
RAIN/SNOW MIX THROUGH THE DURATION OF THE EVENT.

&&

.LONG TERM (AFTER 00Z THURSDAY)...THE MOIST NORTHWEST FLOW WILL
LIKELY LINGER IN THE FAR NORTHERN PORTIONS OF THE CWA HEADING INTO
WEDNESDAY NIGHT...BUT SHOULD BE SHUNTED OFF TO THE NORTH AND EAST BY
THURSDAY MORNING AS THE WEST COAST RIDGE SHIFTS OVER THE GREAT
BASIN. MODELS HAVE BEEN CONSISTENT IN SAYING THAT THIS RIDGE BRINGS
STRONG WARM ADVECTION AND INCREASING SOUTHWEST FLOW ALOFT OVER THE
AREA THURSDAY AND MOST OF FRIDAY...LEADING TO CONSIDERABLY WARMER
THAN NORMAL TEMPERATURES FOR EARLY FEBRUARY.

THE RIDGE IS PROGGED TO FLATTEN THROUGH THE LATTER HALF OF
FRIDAY...ALLOWING A MOIST ZONAL FLOW TO RE-ESTABLISH ITSELF OVER THE
NORTHERN HALF OF THE CWA. THE MAJOR UNCERTAINTY AT THE MOMENT IS HOW
LONG THIS INCREASED THREAT OF PRECIPITATION LASTS ACROSS THE NORTH.
THE 00Z RUN OF THE ECMWF MAKES IT A PRETTY QUICK SHOT...WITH THE
RIDGE AMPLIFYING AGAIN BY LATE SATURDAY. THE GFS KEEPS THE MOISTURE
AROUND ANOTHER 12-24 HOURS THROUGH SUNDAY AFTERNOON. CURRENT
FORECAST IS TILTED SLIGHTLY TOWARD THE ECMWF TIMING...WITH THE
DETAILS FOR SUNDAY AND ONWARD REMAINING LOW CONFIDENCE. EVEN WITH
MODELS INDICATING THE CHANCE OF A SHORTWAVE TROUGH MOVING THROUGH
THE REGION MONDAY/TUESDAY...THE PERSISTENT PATTERN OF A MEAN RIDGE
OVER THE WEST SHOWS NO REAL SIGNS OF BREAKING DOWN THROUGH DAY 10.

&&

.AVIATION...WINDS AT THE SLC TERMINAL ARE EXPECTED TO SWITCH TO THE
NORTHWEST BETWEEN 18Z AND 20Z...WITH A 30 PERCENT CHANCE THAT
SOUTHERLIES PERSIST PAST 20Z. CEILINGS WILL LOWER THROUGH
TODAY...BUT SHOULD REMAIN ABOVE 7000FT THROUGH AT LEAST 03Z MONDAY.
THERE IS ALSO A 30 PERCENT CHANCE OF MVFR VISIBILITIES IN HAZE
THROUGH THE TAF PERIOD.

$$

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

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...SCHOENING

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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