Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 192212
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
412 PM MDT TUE MAY 19 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL CONTINUE TO ELONGATE AND
SHEAR APART OVER NORTHERN UTAH AND SOUTHWEST WYOMING TONIGHT. THE
NEXT STORM SYSTEM WILL ARRIVE LATE IN THE WEEK AND IMPACT MUCH OF
UTAH THROUGH THE HOLIDAY WEEKEND.

&&

.SHORT TERM (THROUGH 18Z FRIDAY)...UPPER LOW CURRENTLY OVER THE
EASTERN GREAT BASIN/CENTRAL ROCKIES CONTINUES TO ELONGATE AND
SHEAR...WITH A RETROGRADING NEAR H5 CIRCULATION OVER NORTHERN
NEVADA AND THE PRIMARY UPPER LOW NOW OVER CENTRAL WYOMING. A
DEVELOPING BUT FAIRLY WEAK DEFORMATION CONTINUES TO TAKE FORM ALONG
THE UT/ID BORDER ON INTO WESTERN WYOMING BETWEEN THESE CIRCULATION
CENTERS.

SCATTERED CONVECTION HAS BEEN THE RULE OF THUMB TODAY ACROSS THE
AREA WITHIN A MOIST AND CONDITIONALLY UNSTABLE ENVIRONMENT. SBCAPE
HAS BEEN MOST PRONOUNCED ACROSS FAR EASTERN UTAH TIDE CLOSEST TO
THE SOUTHERN BRANCH JET /500-1000 J PER KG/ AND HAVE NOTED SOME
DEEPER AND MORE ORGANIZED DEVELOPMENT THERE...BUT LARGELY
CONVECTION HAS BEEN RELATIVELY SHALLOW WITH BRIEF MODERATE RAIN
BEING THE NORM.

AREAL COVERAGE OF CONVECTION IS EXPECTED TO DISSIPATE MOST RAPIDLY
ACROSS THE SOUTH THIS EVE AS COMBINATION OF SOME MID LEVEL DRYING
FROM THE SOUTH AND LOSS OF SOLAR SHOULD BOTH DRY/STABILIZE THE
ENVIRONMENT. BULK OF THE NOCTURNAL ACTIVITY SHOULD TIE CLOSER TO
THE AFOREMENTIONED DEFORMATION ACROSS FAR NORTHERN UTAH AFTER
MIDNIGHT...THOUGH SHOWERS SHOULD LARGELY BE ON THE LIGHT SIDE AS
FORCING DOES NOT APPEAR TO BE OVERLY ROBUST.

HEIGHTS WILL BUILD FROM THE SOUTHEAST TOMORROW AS SHORT WAVE
RIDGING BEGINS TO BUILD IN AHEAD OF THE NEXT LOW CLOSING/DIGGING
SOUTHEAST ALONG THE CALI COAST. ALTHOUGH THE AIRMASS IS EXPECTED
TO CONTINUE DRYING ALOFT FROM THE SOUTH...RESIDUAL LOW LEVEL
MOISTURE COMBINED WITH TERRAIN DRIVEN UPDRAFTS SHOULD ONCE AGAIN
PROMOTE SCATTERED CONVECTION ALONG THE MOUNTAIN SPINES AND POINTS
DOWNSTREAM IN CENTRAL/NORTHERN UTAH. ADDITIONAL LIFT THURSDAY /WITHIN
AN INCREASINGLY DIFFLUENT REGION ALOFT/ DOWNSTREAM OF THIS LOW IS
EXPECTED TO DO LARGELY THE SAME ACROSS THE AREA...COUNTERACTING
FURTHER DRYING OF THE AIRMASS. POTENTIAL FOR INCREASED AREAL
COVERAGE OF STORMS WILL GRADUALLY INCREASE EARLY FRIDAY MORNING AS
THIS NEXT LOW BEGINS CHURNING IN FROM THE SOUTHWEST BRINGING
LOWERING HEIGHTS AND INCREASED MOISTURE TO THE AREA.

.LONG TERM (AFTER 18Z FRIDAY)...GLOBAL MODELS IN AGREEMENT ABOUT
NUDGING THE CLOSED LOW NORTHEASTERLY THROUGH THE STATE ON
FRIDAY...THOUGH THE GFS LAGS A BIT. THIS LAG WOULD KEEP THE CENTER
OF THE CIRCULATION...AND SUBSEQUENT MOISTURE...HUGGING THE SW REGION
OF THE CWA WELL INTO FRIDAY EVENING. TIMING ASIDE...A GOOD CHUNK OF
THE CWA SHOULD HAVE SHOWERS BY FRIDAY AFTERNOON. THE EC PERSISTS IN
CAREENING AN ENSUING LOW INTO THE GREAT BASIN BY SATURDAY...THOUGH
LATEST RUN PLUNGES THE FEATURE THROUGH NEVADA BEFORE WRAPPING IT
AROUND THE SW CORNER OF UTAH. THIS CHANGE IN PROGRESSION WOULD KEEP
MUCH OF SUNDAY PRECIPITATION FOCUSED ON THE SOUTHERN PORTION OF THE
CWA. THE GFS BY THIS POINT BRINGS A MILD RIDGE WITH A SUBSIDENT
DRYING ENVELOPE AS THE LOW GETS BOOTED EAST OF THE CWA. EITHER OF
THESE POSSIBILITIES WOULD SUGGEST AT LEAST A SLIGHT DECREASE OF POPS
IN THE NORTHERN VALLEYS FOR SUNDAY.

GFS ENSEMBLE PLOT BECOMES A SCATTERED PLATE OF SPAGHETTI STRANDS BY
MONDAY...WITH A SOMEWHAT COMMON THEME IN THE EC AND GFS OF A SLIGHT
WARMING AND DRYING TREND IN THE EARLY WEEK...THOUGH RESIDUAL
MOISTURE STILL LIKELY TO PESTER NORTHERN LOCALES AND HIGHER TERRAIN
WITH INTERLUDES OF SHOWERS ON MONDAY AND TUESDAY AFTERNOON.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE EVENING AT THE
SLC TERMINAL. CIGS ABOVE 6000 FT AGL SHOULD PREVAIL...BUT PASSING
SHOWERS MAY BRIEFLY DROP CIGS BELOW THAT VALUE THROUGH ABOUT 02Z.
NORTHWEST WINDS ARE EXPECTED TO SHIFT TO THE SOUTHEAST BETWEEN 03Z
AND 05Z...BUT NEARBY SHOWERS MAY RESULT IN PERIODS OF GUSTY AND/OR
ERRATIC WINDS INTO THE EARLY EVENING.

&&

.FIRE WEATHER...THE COOL AND MOIST CONDITIONS OF THE PAST SEVERAL
DAYS WILL YIELD TO A SLIGHT WARMING AND DRYING TREND FOR WEDNESDAY
AND THURSDAY AS A WEAK HIGH PRESSURE RIDGE BUILDS INTO THE REGION.
WIDESPREAD THUNDERSTORMS WILL STILL LIKELY BLOSSOM EACH
AFTERNOON...WITH GUSTY OUTFLOW WINDS POSSIBLE WITH THE STRONGEST
ACTIVITY. A LARGE LOW PRESSURE SYSTEM IS EXPECTED TO BRING A RETURN
OF COOL TEMPERATURES AND PRECIPITATION TO MUCH OF THE REGION ON
FRIDAY...PERSISTING INTO THE WEEKEND.

&&

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

$$

MERRILL/VERZELLA/TRAPHAGAN


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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