Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 050240
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
840 PM MDT SAT JUL 4 2015

.SYNOPSIS...HIGH PRESSURE WILL REMAIN CENTERED OVER THE SOUTHERN
ROCKIES INTO EARLY NEXT WEEK. ABUNDANT MOISTURE ALONG WITH WEAK
WEATHER DISTURBANCES MOVING THROUGH THE REGION WILL GENERATE
SHOWERS AND THUNDERSTORMS INTO EARLY NEXT WEEK.


&&

.DISCUSSION...DEEP LAYER SOUTHERLY FLOW AROUND THE PERIPHERY OF A
MID LEVEL RIDGE CENTERED OVER NM PREVAILS ACROSS THE EASTERN GREAT
BASIN THIS EVENING. THIS FLOW HAS ADVECTED MOISTURE FROM SOUTH TO
NORTH ACROSS THE FORECAST AREA...WHERE PW VALUES ARE GENERALLY
NEAR 1 INCH...AND SURFACE DEW POINTS HAVE CLIMBED INTO THE 50S
ACROSS MOST VALLEYS. A WAVE EMBEDDED WITHIN THIS SOUTHERLY FLOW IS
CURRENTLY LIFTING NORTHWARD ACROSS CENTRAL UT...AND HAS AIDED IN
THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS NORTHWEST UT
EARLY THIS EVENING. DESPITE THE MOISTURE...SPC MESOANALYSIS SHOWS
CAPE VALUES REMAIN MARGINAL...WITH THE AXIS OF HIGHEST INSTABILITY
CONFINED OVER THE GSL DESERT. THIS AREA SHOULD SEE THE GREATEST
AREAL COVERAGE OF CONVECTION THROUGH THE REMAINDER OF THE
EVENING...HOWEVER AS THE AFOREMENTIONED WAVE SLOWLY LIFTS NORTH
OVER NIGHT NUMEROUS RUNS OF THE HRRR INSIST THIS AREA WILL EXPAND
EASTWARD INTO THE WASATCH FRONT. MEANWHILE IN THE WAKE OF THIS
WAVE SUBSIDENCE HAS SPREAD INTO SOUTHERN UT WHERE CONVECTION HAS
BECOME MUCH MORE ISOLATED. UPDATED THE FORECAST EARLIER TO ADJUST
POPS UPWARDS ACROSS THE NORTH THROUGH THE LATE EVENING AND
OVERNIGHT WHILE CUTTING BACK ACROSS THE SOUTH.

PREVIOUS DISCUSSION FROM SUNDAY ONWARD FOLLOWS...

&&

.PREV DISCUSSION...AFOREMENTIONED WAVE PROGGED TO STRETCH/SHEAR
NEAR THE UT/ID BORDER TOMORROW AS IT BEGINS TO INTERACT WITH THE
NORTHERN BRANCH STREAM. EASTWARD TRANSLATION TOMORROW AFTERNOON
WILL ALLOW FOR A FAIRLY SHARP H5/H7 TROUGH AXIS PASSAGE LATE DAY
WITH MODEST MID LEVEL MOISTURE CONVERGENCE ALONG AND AHEAD ACROSS
NORTHERN UTAH. SPC SREF DOES SHOW CORE OF THE INSTABILITY AXIS
COINCIDENT AND AHEAD OF THIS. OPTED TO RAISE POPS ACROSS THE NORTH
SOME 10 TO 20 PERCENT AS CONVECTION POTENTIAL APPEARS QUITE GOOD
AT THIS TIME...INHIBITING FACTORS COULD BE A SLOW INITIATION DUE
TO INITIAL WAVE PASSAGE SUPPRESSION/CLOUD COVER THAT WILL OCCUR
LATE TONIGHT/TOMORROW MORNING.

SOME MIDLEVEL DRYING IS EXPECTED MONDAY IN A NEAR WESTERLY
FLOW ALOFT...BUT LIMITED LOWER LEVEL DRYING OF RESIDUAL MOISTURE
IN PLACE OCCURS AS STREAMLINES INDICATE A CONVERGENT MID LEVEL
AND MODESTLY MOIST FLOW OVER NORTHERN UTAH BETWEEN THE UPPER LOW
OFF THE CALI COAST AND CYCLONIC FLOW OVER THE NORTHERN ROCKIES.
CONVECTION AT THAT TIME WILL LIKELY BE OF THE DIURNAL VARIETY WITH
FOCUS OVER THE MTNS...BUT SLIGHT CHANCES WILL EXIST FOR MOST ALL
VALLEYS AS WELL.

.LONG TERM (AFTER 0600 UTC TUE)...FLAT UPPER LEVEL RIDGE AXIS
REMAINS OVER THE FOUR CORNERS REGION WITH AN UPPER LEVEL LOW
SITUATED OFF THE CENTRAL CALIFORNIA COAST.  BETWEEN THESE FEATURES A
MID LEVEL DEFORMATION AXIS STRETCHES FROM SW OREGON THROUGH NRN
UTAH. SOUTH OF THE DEFORMATION AXIS RESIDUAL MOISTURE REMAINS IN
PLACE WITH PRECIPITABLE WATER VALUES GREATER THAN .75" EXPECTED
ACROSS UTAH. THUS WILL CONTINUE WITH IDEA OF SLIGHT CHANCE VALLEY
POPS AND GENERALLY CHANCE POPS OVER THE HIGHER TERRAIN FOR TUESDAY
AFTERNOON AND EVENING.

THE UPPER LEVEL LOW MOVES SLIGHTLY EAST ON WEDNESDAY AND A DRY
SOUTHWEST FLOW SETS UP OVER MUCH OF THE DESERT SOUTHWEST.
HOWEVER...IT WILL PROBABLY TAKE A BIT OF TIME TO SCOUR THE MOISTURE
AND WILL KEEP SLIGHT CHANCE POPS FOR VALLEY LOCATIONS ACROSS THE NRN
HALF OF UTAH AS WELL AS SLIGHT CHANCE TO CHANCE POPS ACROSS THE
HIGHER TERRAIN STATEWIDE.

UNDER THE PERSISTENT SOUTHWEST FLOW ALOFT THE AIRMASS REALLY DRIES
OUT LATE IN THE WEEK WITH PRECIPITABLE WATER VALUES LESS THAN
.75" THU DECREASING TO LESS THAN .50" ACROSS UTAH ON FRIDAY. AS THE
UPPER LEVEL LOW OFF OF THE CALIFORNIA COAST MOVES INTO THE WESTERN
GREAT BASIN LATE IN THE WEEK THE FLOW ALOFT INCREASES AND EXPECT AN
INCREASE IN SOUTH-SOUTHWEST SURFACE WINDS...ESPECIALLY FOR FRI WHICH
HAS THE POTENTIAL TO BE A BREEZY DAY ACROSS THE WESTERN HALF OF THE
STATE. THIS INCREASE IN FLOW ALONG WITH THE DRYING AIRMASS WILL BE
SOMETHING TO MONITOR FOR POTENTIAL FIRE WEATHER CONCERNS.

THE UPPER LEVEL LOW BECOMES AN OPEN WAVE AND LIFTS ACROSS NV INTO
THE NRN INTERMOUNTAIN REGION FRIDAY INTO SATURDAY. THE ECMWF IS A
LITTLE SLOWER THAN THE GFS WITH THE EJECTION OF THE UPPER
WAVE...ALTHOUGH THE IDEA IS SIMILAR. WHILE THE SYSTEM WILL BE PRETTY
MOISTURE STARVED THE FAR NORTHWEST CORNER OF UTAH MOISTENS UP JUST A
BIT ON SAT AS WAVE SLIPS BY TO THE NORTHWEST AND WILL HAVE SLIGHT
CHANCE OF THUNDERSTORMS FOR FAR NORTHWEST UTAH AND THE NORTHERN
WASATCH MOUNTAINS NEAR THE ID BORDER.

TEMPERATURES THROUGH THE PERIOD WILL BE NEAR NORMAL WITH LITTLE IN
THE WAY OF SIGNIFICANT THERMAL ADVECTION EXPECTED. HOWEVER...AS THE
WAVE SLIDES NORTHWEST OF UTAH...700 HPA TEMPERATURES DIP TO +10-12C
ACROSS NRN UT.  THIS WILL ALLOW FOR SOME MINOR COOLING AND IT IS
POSSIBLE THAT NEXT WEEKEND WILL START WITH HIGH TEMPERATURES IN THE
MID TO UPPER 80S ACROSS NRN UTAH.

&&

.AVIATION...PREDOMINANT WIND DIRECTION AT KSLC THROUGH THE LATE
EVENING AND OVERNIGHT SHOULD REMAIN SOUTHERLY...HOWEVER THERE IS A
40 PERCENT CHANCE WINDS BECOME GUSTY AND ERRATIC AT TIMES WITH
PASSING SHOWERS. VFR CONDITIONS WILL PREVAIL...HOWEVER THERE IS A
10 PERCENT CHANCE A THUNDERSTORM DIRECTLY IMPACTS THE TERMINAL
THROUGH THE OVERNIGHT HOURS.

&&

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

$$

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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