Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 312254
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
354 PM MST SAT JAN 31 2015

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH
TONIGHT. A MOIST WEST NORTHWEST FLOW WILL DEVELOP ACROSS THE
NORTHERN GREAT BASIN MONDAY AND CONTINUE INTO WEDNESDAY.

&&

.DISCUSSION...THE SHORT WAVE RIDGE CROSSING UT FROM THE NORTH AT
THIS TIME IS GENERATING STRONG DRYING AND SUBSIDENCE WITH CLEARING
SKIES ACROSS THE CWA. AN AREA OF STRATUS WILL LINGER ALONG AND
WEST OF THE I-15 CORRIDOR FROM ABOUT PROVO SOUTH INTO THE NIGHT
BUT SHOULD DISSIPATE AFTER MIDNIGHT. PRECIP HAS COME TO AN END
ACROSS THE CWA AND ALLOWED THE REMAINING WINTER WEATHER HIGHLIGHT
TO EXPIRE.

A FAIRLY TIGHT NORTHERLY SURFACE GRADIENT IS IN PLACE ACROSS THE
CWA THIS AFTN AND WILL PERSIST ACROSS CENTRAL AND SRN UT TONIGHT.
THIS SHOULD BRING ENOUGH MIXING TO THESE AREAS TO SUFFICIENTLY
DRY LOWER LEVELS AND PRECLUDE MUCH FOG DEVELOPMENT TONIGHT. LEFT A
MENTION IN SOME AREAS TO ALLOW FOR LOCAL GROUND FOG IF THE WINDS
DROP OFF SOONER. ALSO HAVE A MENTION OF FOG IN THE COLDER NRN
VALLEYS.

THE UPSTREAM RIDGE JUST OFF THE COAST TODAY CROSSES THE CWA ON SUN
AND FLATTENS RAPIDLY SUN NIGHT AS A WEAK WAVE PASSES MAINLY TO OUR
NORTH. THIS WAVE DOES PUSH SOME MOISTURE INTO FAR NRN UT BRINGING
A THREAT OF LIGHT PRECIP.

THIS PATTERN OF AN INCREASINGLY MOIST WNWLY FLOW OVER NRN UT
CONTINUES THRU TUE WITH A CONTINUED CHANCE OF VALLEY RAIN AND MTN
SNOW FROM ABOUT SLC NORTH. DONT EXPECT ENOUGH MTN ACCUMULATION
FROM THESE WEAK WAVES TO WARRANT ANY HIGHLIGHTS AND VALLEY PRECIP
SHOULD STAY AS RAIN.

&&

.LONG TERM (AFTER 00Z WEDNESDAY)...SIGNIFICANT MODEL DIFFERENCES
PLAGUE THE BEGINNING OF THE LONG TERM FORECAST PERIOD. THE 06Z GFS
AND 00Z EC AND THE 12Z GFS AND 12Z EC REMAINED OUT OF SYNC IN A
SIMILAR MANNER...WITH THE GFS CONTINUING TO DEPICT A HIGHER
AMPLITUDE RIDGE OVER THE EASTERN PACIFIC/PACIFIC COAST THAN THE EC.
THE MAIN IMPACT FROM THIS HIGHER AMPLITUDE RIDGE IS THE GFS HAS A
MORE SIGNIFICANT SYSTEM DIGGING INTO THE EASTERN GREAT BASIN AND
ROCKY MOUNTAIN STATES. THE EC...WITH THE LOWER AMPLITUDE
RIDGE...BRINGS A WEAKER BRUSH-BY SYSTEM THROUGH THE INTERMOUNTAIN
REGION WHICH PRIMARILY IMPACTS AREAS NORTH OF UTAH.

LOOKING AT ENSEMBLE DATA FROM THE GEFS...GFS AND CANADIAN...MUCH OF
THE GUIDANCE SUPPORTS A HIGHER AMPLITUDE RIDGE OVER THE EASTERN
PACIFIC/PACIFIC COAST. GIVEN THIS DATA...DECIDED TO CONTINUE THE
TREND OF LEANING TOWARD THE GFS. THIS WOULD BRING A STRONGER AND
COLDER SYSTEM INTO THE CWA TUESDAY NIGHT INTO WEDNESDAY WITH A
HIGHER THREAT OF PRECIPITATION THAN THE EC SOLUTION WOULD
INDICATE.

FOLLOWING THIS SYSTEM...A LARGE RIDGE IS EXPECTED TO BUILD INTO THE
WESTERN UNITED STATES WITH LITTLE CHANCE OF PRECIPITATION EXPECTED
WEDNESDAY THROUGH FRIDAY. MUCH OF THE LONGER RANGE MODEL GUIDANCE
INDICATES A MORE ZONAL PATTERN WILL DEVELOP NEXT WEEKEND...SOMEWHAT
INCREASING THE THREAT OF PRECIPITATION ACROSS NORTHERN UTAH.

&&

.AVIATION...NORTH TO NORTHWEST WINDS WILL CONTINUE AT THE SLC
TERMINAL THROUGH THE EVENING. EXPECT WINDS TO SHIFT TO THE SOUTH TO
SOUTHEAST BETWEEN 06-09Z.

&&

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

WY...NONE.
&&

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...KRUSE

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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