Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 221106
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
506 AM MDT WED APR 22 2015

.SYNOPSIS...HIGH PRESSURE ALOFT OVER THE GREAT BASIN WILL SLOWLY
SHIFT EAST OF THE STATE LATER TODAY...WHILE A LOW PRESSURE SYSTEM
OVER SOUTHERN CALIFORNIA SENDS MOISTURE NORTH ACROSS UTAH. MOISTURE
WILL CONTINUE TO INCREASE THROUGH SATURDAY BEFORE AN UPPER TROUGH
SWEEPS A COLD FRONT THROUGH THE AREA.

&&

.SHORT TERM (THROUGH 12Z SATURDAY)...MORNING WATER VAPOR IMAGERY AND
RAP ANALYSIS SHOWS A RIDGE OVER NORTHERN UTAH AND EXTENDING INTO
IDAHO AND WESTERN MONTANA WHILE A CLOSED LOW CONTINUES TO SPIN OVER
SOUTHERN CALIFORNIA. A BAND OF CLOUDS ASSOCIATED WITH SOME LIGHT
PRECIPITATION IS EVIDENT ACROSS SOUTHERN UTAH ALONG A DEFORMATION
AXIS...WHILE SKIES ARE CURRENTLY MOSTLY CLEAR ACROSS THE NORTH. THE
DEFORMATION AXIS WILL LIFT NORTH THROUGH THE DAY AND INTO THE
EVENING HOURS AS THE LOW WEAKENS AND EJECTS PIECES OF IT THROUGH THE
AREA. EXPECT SHOWERS TO DEVELOP INTO NORTHERN UTAH AND SOUTHWEST
WYOMING LATER TODAY AS A RESULT. ENOUGH INSTABILITY WILL BE PRESENT
TO ALLOW A FEW THUNDERSTORMS TO DEVELOP WITH DAYTIME HEATING.

TEMPERATURES WILL REMAIN RATHER WARM THROUGHOUT THE AREA...ALTHOUGH
SOUTHERN UTAH WILL BE A BIT COOLER THAN YESTERDAY WITH CLOUD COVER
EXPECTED TO REMAIN IN PLACE FOR MUCH OF THE DAY. TEMPERATURES WILL
GRADUALLY TREND COOLER THROUGH THE END OF THE WEEK AS MOISTURE
INCREASES OVER THE AREA.

WHAT IS LEFT OF THE LOW OVER SOUTHERN CALIFORNIA WILL BE REINFORCED
AS THE SOUTHERN BRANCH OF A SPLITTING STORM MERGES WITH IT LATE
TONIGHT. THIS LOW WILL THEN OPEN UP AND TRACK EAST ACROSS ARIZONA
TOMORROW...WHILE THE NORTHERN BRANCH WAVE GRAZES NORTHERN UTAH. WITH
MOISTURE INCREASING...THE PRESENCE OF THIS SPLIT SYSTEM SHOULD ALLOW
FOR AN INCREASING CHANCE OF PRECIPITATION OVER THE AREA TOMORROW.

SOUTHWEST FLOW THURSDAY NIGHT INTO FRIDAY AHEAD OF THE NEXT
APPROACHING TROUGH IS PROGGED TO BRING PWATS TO OVER A HALF INCH
OVER WESTERN UTAH BY FRIDAY AFTERNOON. THIS MOISTURE COMBINED WITH
THE LIFT AHEAD OF THE TROUGH SHOULD PROVIDE GOOD COVERAGE OF SHOWERS
OVER MUCH OF THE FORECAST AREA. ALTHOUGH THE TROUGH IS PROGGED TO
WEAKEN AS IT CROSSES UTAH IN FAVOR OF A STRONGER UPSTREAM SYSTEM...A
SHALLOW COLD FRONT IS EXPECTED TO PUSH INTO NORTHERN UTAH. SHOWERS
ARE EXPECTED TO PERSIST FRIDAY NIGHT BUT WITH PARTICULAR FOCUS ALONG
THE BOUNDARY WHICH IS EXPECTED TO STALL ALONG WEST-CENTRAL THROUGH
NORTHEAST UTAH.

.LONG TERM (AFTER 12Z SATURDAY)...QUITE GOOD AGREEMENT IN MEDIUM
RANGE GUIDANCE REGARDING EVOLUTION AND TRACK OF THE UPPER LEVEL
TROUGH THAT WILL BE RESIDING OVER THE PACNW STATES LATE WEEK. RAPID
RIDGE AMPLIFICATION SPREADING EAST FROM 140W-130W FRIDAY NIGHT AND
ASSOCIATED JET RIDING ATOP WILL DRIVE THIS FEATURE SOUTHEAST INTO
THE GREAT BASIN AS AN OPEN WAVE SATURDAY...BEFORE CLOSING IT OFF
OVER THE 4 CORNERS REGION SUNDAY. PLENTIFUL RESIDUAL MOISTURE IN
PLACE COMBINED WITH PRESENCE OF A DECAYING SURFACE BOUNDARY DRAPED
ACROSS CENTRAL UTAH SHOULD PROVIDE INITIAL FOCUS OF PRECIP ACROSS
CENTRAL PORTIONS OF THE AREA EARLY SATURDAY...BUT ALL GLOBAL
GUIDANCE POINT TO RAPID EXPANSION AND INCREASED INTENSITY OF PRECIP
TO MOST ALL AREAS FOR THE AFTERNOON AND EVENING HOURS AS LARGE SCALE
LIFT WITHIN A CONDITIONALLY UNSTABLE AIRMASS TAKES PLACE. MODEST CAA
FROM THE NORTHWEST WILL TREND H7 TEMPS DOWN TO ROUGHLY -7 C BY
SUNDAY MORNING ALLOWING SNOWLEVEL TRENDS TO FALL TO AROUND 6000 FT
SATURDAY NIGHT INTO SUNDAY MORNING...ACCUMULATING MOUNTAIN SNOWFALL
IS EXPECTED BUT NET IMPACT SHOULD REMAIN ON THE LOW SIDE. HAVE
CONTINUED TO INCREASE POPS...SIGNIFICANTLY SO FOR SATURDAY
NIGHT...LOWER SNOW LEVELS AND INCREASE QPF THIS FORECAST.

AS THE UPPER LOW CLOSES OFF SUNDAY GUIDANCE ONCE AGAIN SUGGESTS
DEVELOPMENT OF WEAK UPGLIDE ACROSS THE EAST...THIS LIKELY TO
MAINTAIN AT LEAST SCATTERED PRECIP FROM SOUTHWEST WYOMING SOUTH
THROUGH THE SWELL. INCREASED POPS ALONG THOSE LINES.

AFOREMENTIONED WEST COAST RIDGING WILL BUILD INTO THE EASTERN GREAT
BASIN LATE SUNDAY INTO NEXT WEEK ALLOWING STABLE AND DRY CONDITIONS
TO TAKE HOLD. A MARKED AND STEADY WARMING TREND IS NOTED IN
GLOBALS...H7 TEMPS CLIMBING TO OR JUST ABOVE +7 C BY THURSDAY...THIS
ALLOWING WELL ABOVE NORMAL TEMPS ONCE AGAIN BY MIDWEEK.

&&

.AVIATION...OPERATIONAL WEATHER CONCERNS WILL REMAIN MINIMAL AT THE
KSLC TERMINAL TODAY. LIGHT SOUTHEAST SURFACE WINDS ARE EXPECTED TO
SWITCH TO THE NORTHWEST BETWEEN 18-20Z PER NORM. CLOUD COVER WILL BE
ON THE RISE THIS AFTERNOON...WITH SOME SHOWERS DEVELOPING GENERALLY
EAST OF THE TERMINAL THIS AFTERNOON AND EVENING. CIGS ARE EXPECTED
TO REMAIN WELL ABOVE 6000FT AGL HOWEVER.

&&

.FIRE WEATHER...A WEAK UPPER LOW OVER SOUTHERN CALIFORNIA WILL
CONTINUE TO SPIN MOISTURE INTO THE DISTRICT TODAY ALLOWING ISOLATED
TO WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP BY
THIS AFTERNOON. THE MOST LIKELY AREAS FOR THESE WILL BE ALONG THE
MOUNTAIN SPINE FROM THE SOUTHERN MOUNTAINS NORTHEAST TO THE
UINTAS...BUT WETTING RAIN POTENTIAL WILL REMAIN ON THE LOW SIDE.
BRIEF GUSTY WINDS AND LIGHT PRECIP WILL BE THE MOST LIKELY OUTCOME
FROM ANY PASSING CELLS. SURFACE RH TRENDS WILL CONTINUE TO GRADUALLY
INCREASE ACROSS THE AREA DUE TO SAID INCREASE OF MOISTURE. AS THE
LOW SLOWLY MOVES EAST THROUGH THE DESERT SOUTHWEST TONIGHT THROUGH
FRIDAY THE CHANCE OF SHOWERS/STORMS WILL INCREASE SLIGHTLY EACH DAY
MOST ALL AREAS.

A STRONGER STORM SYSTEM IS EXPECTED TO TRACK IN FROM THE NORTHWEST
SATURDAY. WIDESPREAD WETTING RAINS AND ACCUMULATING MOUNTAIN SNOW
LOOK TO OCCUR...WITH SNOW LEVELS POSSIBLY LOWERING TO AROUND 6000FT
BY SATURDAY NIGHT.

&&

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

$$

CHENG/MERRILL

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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