Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 151030
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
430 AM MDT FRI AUG 15 2014

.SYNOPSIS...THE AIRMASS ACROSS THE REGION WILL DRY FROM THE WEST
TODAY. HIGH PRESSURE WILL BUILD LATE IN THE WEEKEND THROUGH EARLY
NEXT WEEK.

&&

.SHORT TERM (THROUGH 12Z MONDAY)...
WATER VAPOR LOOP SHOWS A CLOSED LOW OVER THE PACIFIC NORTHWEST.
AMDAR 400-250MB WIND OBSERVATIONS REVEAL A 50-80KT CYCLONIC JET
OVER THE PACIFIC NORTHWEST...AND A 50-70KT SOUTHWESTERLY JET FROM
SOUTHWEST ARIZONA THROUGH THE FOUR CORNERS. GOES/GPS/RAP/00Z RAOB
INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN 0.3" WEST
CENTRAL UTAH TO TO AROUND 1.5" ACROSS THE EASTERN VALLEYS.

AS THE DRIER AIR INFILTRATES UTAH...24HR DEWPOINT CHANGE IS -30F
ACROSS SOME WESTERN VALLEYS. MEANWHILE...DEWPOINTS REMAIN IN THE 55-
60F RANGE ACROSS THE EASTERN AND FAR SOUTHERN VALLEYS. RAP INDICATES
THE PRECIPITABLE WATER VALUE WILL STILL BE AROUND AN INCH ACROSS THE
EASTERN VALLEYS THIS EVENING. GIVEN ALL THIS AND INPUT FROM LOCAL
WRF HIGH RESOLUTION MODELS...HAVE EXPANDED ISOLATED POPS THIS
AFTERNOON ACROSS ALL EASTERN ZONES. LCL IS FORECAST TO RISE AND WARM
CLOUD DEPTH IS FORECAST TO BECOME MORE SHALLOW...SO DONT THINK
RAINFALL RATES WILL BE QUITE AS HIGH AS YESTERDAY.

WITH RIDGING BUILDING IN FROM THE SOUTH THIS WEEKEND...A DRY
WESTERLY FLOW DEVELOPS. HOWEVER...21Z SREF INDICATES ENOUGH
INSTABILITY REMAINS IN PLACE THAT ITS PRUDENT TO KEEP ISOLATED
CONVECTION IN THE EASTERN TERRAIN.

A WARMING TREND IS FORECAST TO GO ALONG WITH DRYING THE NEXT SEVERAL
DAYS.

&&

.LONG TERM (AFTER 12Z MONDAY)...
UPPER LEVEL RIDGE WILL BE IN PLACE OVER THE EASTERN GREAT BASIN
FOR THE EARLY TO MIDDLE PORTION OF NEXT WEEK WITH A CUTOFF LOW OFF
THE COAST OF CALIFORNIA. 0000 UTC GFS AND EC HAVE BOTH MOVED
TOWARD A SOLUTION WHICH DRIVES THE CUTOFF LOW DOWN THE CALIFORNIA
COAST THROUGH MID WEEK AS UPPER LEVEL TROUGHING MOVES INTO THE PAC
NW AND NORTHERN INTERMOUNTAIN REGION. THIS UPPER LEVEL TROUGH
SHUNTS THE RIDGE TO THE EAST AND... WITH THE CUTOFF MOVING DOWN
THE SOUTHERN CALIFORNIA COAST...ALLOWS FOR THE POTENTIAL FOR
MOISTURE TO MOVE BACK NORTH INTO THE EASTERN GREAT BASIN. BOTH THE
GFS AND EC SHOW INCREASING MOISTURE BY MID WEEK. IT IS CLEAR THAT
THERE IS MUCH UNCERTAINTY IN THE EVOLUTION OF THE UPPER LEVEL
FEATURES...PARTICULARLY WITH RESPECT TO THE CUTOFF LOW...DURING
THE MIDDLE TO LATER PORTIONS OF NEXT WEEK. IT IS STILL QUITE
POSSIBLE THAT THIS FEATURE WILL RETROGRADE OFF THE COAST KEEPING
UTAH UNDER THE INFLUENCE OF DRY WEST-SOUTHWEST FLOW ALOFT.
HOWEVER...GIVEN THE POTENTIAL FOR SOUTHERLY MID LEVEL FLOW TO
DEVELOP...ENABLING MOISTURE TO RETURN NORTH...HAVE INTRODUCED
SLIGHT CHANCE POPS OVER THE HIGHER TERRAIN FOR MUCH OF UTAH
BEGINNING MID WEEK.

THE EC CONTINUES TO HAVE 7H TEMPERATURES THAT ARE 1-2C WARMER THAN
THE GFS. WILL CONTINUE TO LEVERAGE BIAS CORRECTED ENSEMBLE-BASED
GUIDANCE FOR TEMPERATURES WHICH ARE EXPECTED TO BE NEAR NORMAL
THROUGH THE MEDIUM RANGE PERIOD.

&&

.AVIATION...VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD AT THE
KSLC TERMINAL. SOUTH WINDS ARE EXPECTED TO BECOME NORTHWEST
BETWEEN 1900-2100 UTC. HOWEVER...THERE IS A 20 PERCENT CHANCE THAT
THE WIND SHIFT HOLDS OFF UNTIL AFTER 2100 UTC.

&&

.FIRE WEATHER...A DRYING WESTERLY FLOW LOOKS TO DEVELOP THROUGH THE
WEEKEND. CONVECTION WILL BE DIURNAL AND MORE ISOLATED...RELEGATED TO
EASTERN UTAH TODAY...AND ONLY THE MOST PRONE TERRAIN OF EASTERN UTAH
THIS WEEKEND.

RH VALUES WILL DRY FURTHER ACROSS ALL VALLEYS TODAY INTO THE
WEEKEND. A WARMING TREND IS FORECAST TO BRING TEMPERATURES CLOSER TO
CLIMATOLOGICAL NORMS FOR THIS TIME OF YEAR.

&&

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

$$

SHORT TERM/FIRE WEATHER...ROGOWSKI
LONG TERM/AVIATION...GRAHAM

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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