Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 181621
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1021 AM MDT MON AUG 18 2014

.SYNOPSIS...SOUTHERLY FLOW AHEAD OF AN UPPER LEVEL LOW ALONG THE
CALIFORNIA COAST WILL SPREAD DEEP MOISTURE BACK INTO THE REGION
LATE MONDAY AND TUESDAY. A DRYING TREND IS EXPECTED FOR THE LATTER
HALF OF THE WEEK.

&&

.DISCUSSION...TWO PRIMARY FEATURES TO NOTE ON THE BIG
PICTURE...RIDGE IN THE VICINITY OF THE 4 CORNERS WITH AXIS OVER
NORTHERN AZ/NM AND AN UPPER LOW SPINNING OFF THE NORCAL COAST.
MORNING WATER VAPOR INDICATES A SLIGHT EASTWARD SHIFT OF THE
RIDGE WITH A RETURN FLOW SHORT WAVE DRIVING AN MCV ACROSS
SOUTHWESTERN ARIZONA...THIS AS THE LOW CONTINUES TO GRADUALLY
TRANSITION SOUTH OFF THE CALI COASTLINE.

A FEW SHOWERS WERE NOTED ACROSS THE FAR NORTH EARLY THIS MORNING
BUT HAVE SINCE DISSIPATED. SHOWERS AND ISOLATED STORMS REMAIN OVER
FAR SOUTHERN IDAHO WHERE AN AREA OF MID LEVEL MOISTURE CONVERGENCE
EXISTS HOWEVER.

ISOLATED MOUNTAIN BASED CONVECTION WILL REMAIN POSSIBLE TODAY BUT
BUFR PROFILES INDICATE THESE WILL BE HIGH BASED AND WITH PWAT AT
OR BELOW .6 INCHES MINIMAL THREAT OF HEAVY RAIN EXISTS THROUGH
ABOUT 00Z OR SO.

MONSOONAL MOISTURE REMAINS PINNED ALONG AND SOUTH OF THE
AFOREMENTIONED RIDGE AXIS BUT THIS WILL BE SHORT LIVED AS BOTH
FEATURES CONTINUE TO MOVE EAST AND SOUTH RESPECTIVELY. GUIDANCE
SUGGEST THE NOSE OF MONSOONAL MOISTURE WILL REACH THE UT/AZ BORDER
AROUND 00Z THIS EVENING AS THE SHORT WAVE BEGINS TO APPROACH FROM
THE SOUTH. GFS/NAM/ECMWF AGREE THIS WAVE AND ASSOCIATED MOISTURE WILL
CONTINUE TO LIFT NORTH INTO THE STATE OVERNIGHT AND TOMORROW
MORNING FORMING A WEAK CIRCULATION CENTER OVER NORTHERN UTAH
TOMORROW AFTERNOON.

MANY INGREDIENTS EXIST FOR MORE ROBUST CONVECTION THIS EVENING
ACROSS THE FAR SOUTH AND AREAWIDE TOMORROW. THIS SAID...TIMING OF
WAVE COULD VERY WELL INDUCE ENOUGH SUBSIDENCE ACROSS THE SOUTH AND
FAR WEST DURING PEAK HEATING HOURS TOMORROW TO INHIBIT CONVECTIVE
POTENTIAL THOSE AREAS. CLOUD COVER COULD LIMIT HEATING POTENTIAL
AS WELL. COMBINATION OF LIFT ASSOCIATED WITH THE SHORT
WAVE...ESPECIALLY NORTH AND EAST OF THE WAVE...AND PWAT IN EXCESS
OF AN INCH DOES ALLOW FOR A THREAT OF LOCALLY HEAVY RAIN WITH THE
MORE MATURE CONVECTION LATE MORNING AND AFTERNOON.

NO SIGNIFICANT UPDATES TO NOTE AT THIS TIME. PREVIOUS DISCUSSION
BELOW...

BEYOND TUESDAY THE MODELS HAVE STRUGGLED RECENTLY WITH RESPECT TO
THE EVOLUTION OF THE UPPER LOW ALONG THE CA COAST...AND ALTHOUGH
THE 00Z GFS/EC BOTH BRING THIS LOW INLAND DURING THE MIDWEEK
PERIOD...THEY DIFFER WITH RESPECT TO TRACK/TIMING AND AVAILABLE
MOISTURE ACROSS THE EASTERN GREAT BASIN. GIVEN THE UNCERTAINTY DID
NOT CHANGE THE PRECIPITATION FORECAST FOR THE LATTER HALF OF THE
PERIOD...MAINTAINING ONLY A SMALL THREAT OF SHOWERS AND
THUNDERSTORMS OVER THE HIGHER TERRAIN. WHAT THE MODELS ARE IN
AGREEMENT WITH IS THE DEVELOPMENT OF A LONGWAVE TROUGH ACROSS THE
PACIFIC NORTHWEST/NORTHERN ROCKIES...WHICH WILL KEEP TEMPERATURES
THROUGH THE EXTENDED PERIOD A BIT BELOW CLIMATOLOGICAL NORMS.


&&

.AVIATION...OPERATIONAL WEATHER CONCERNS ARE EXPECTED TO REMAIN
MINIMAL AT THE KSLC TERMINAL TODAY. LIGHT SOUTHEAST WINDS ARE
EXPECTED TO TREND LIGHT AND VARIABLE THROUGH 18Z BEFORE GRADUALLY
SHIFTING TO THE NORTH. NORTHWEST WINDS GREATER THAN 7 KNOTS ARE
NOT EXPECTED UNTIL AFTER 19Z.

&&

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

$$

MERRILL/SEAMAN


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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