Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 181015
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
415 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...A MID LEVEL RIDGE SITUATED ALONG THE UT/AZ BORDER IS
SHIFTING EASTWARD EARLY THIS MORNING...AS AN UPPER LOW CURRENTLY
SPINNING ALONG THE OREGON COASTLINE SLOWLY DROPS SOUTHWARD ALONG
THE CALIFORNIA COASTLINE OVER THE NEXT COUPLE OF DAYS. THIS WILL
ALLOW A DEEP LAYER SOUTHERLY TO SOUTHWESTERLY FLOW TO DEVELOP
ACROSS THE REGION...ALLOWING MOISTURE CURRENTLY BOTTLED UP ACROSS
SOUTHERN AZ/SOUTHEAST CA TO SPREAD NORTHWARD INTO SOUTHERN UT AS
EARLY AS THIS AFTERNOON...THEN QUICKLY NORTHWARD OVER THE
REMAINDER OF THE FORECAST AREA TONIGHT INTO EARLY TUESDAY.

THE MODELS ARE IN FAIRLY GOOD AGREEMENT ROTATING A WAVE NORTHWARD
ACROSS THE FORECAST AREA TONIGHT THROUGH TUESDAY MORNING...AND THE
COMBINATION OF ASCENT AND MOISTURE SHOULD BRING AT LEAST SCATTERED
SHOWERS AND THUNDERSTORMS INTO SOUTHERN UT BY THIS EVENING...THEN
SPREADING NORTHWARD ACROSS THE REMAINDER OF THE FORECAST AREA
OVERNIGHT INTO TUESDAY MORNING. AS SUCH HAVE RAISED POPS 20-30
PERCENT DURING THIS TIMEFRAME. IT REMAINS TO BE SEEN IF SUBSIDENCE
BEHIND THIS WAVE COMBINED WITH A FAIRLY STABLE AIRMASS OWING TO
CLOUD COVER/PRECIPITATION CAN RECOVER IN TIME FOR CONVECTIVE
REDEVELOPMENT TUESDAY AFTERNOON/EVENING. GIVEN THE UNCERTAINTY
HAVE LEFT POPS ALONE DURING THIS TIMEFRAME ALTHOUGH THEY MAY BE A
BIT HIGH. GIVEN THE AIRMASS ADVECTING INTO THE AREA HEAVY RAIN
WILL BE POSSIBLE OVERNIGHT INTO TUESDAY WITH ANY THUNDERSTORMS
WHICH DEVELOP.

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...THE SLC TERMINAL WILL SEE VFR CONDITIONS TODAY WITH SOME
INCREASING CLOUDS. SOUTHEAST WINDS ARE EXPECTED TO SHIFT TO THE
NORTHWEST BETWEEN 18Z AND 20Z.

&&

.FIRE WEATHER...HIGH PRESSURE HAS SHIFTED EAST OF THE AREA THIS
MORNING...AND THIS HAS ALLOWED SOUTHERLY FLOW TO DEVELOP. THIS FLOW
WILL ALLOW MONSOONAL MOISTURE TO RETURN THROUGH THE SOUTH TODAY AND
TOMORROW. THIS WILL GIVE MUCH OF THE DISTRICT A GOOD CHANCE OF
WETTING RAIN. DRIER AIR WILL MOVE INTO THE AREA BY MIDWEEK...WITH
THE POSSIBILITY OF MOISTURE RETURNING LATER IN THE WEEK.

&&

&&

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

$$

SEAMAN/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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