Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 051038
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
338 AM PDT SUN JUL 5 2015

.SYNOPSIS...
GRADUAL COOLING NEXT FEW DAYS ALONG WITH DAILY AFTERNOON AND
EVENING THUNDERSTORMS MAINLY OVER THE MOUNTAINS. THUNDERSTORM
COVERAGE MAY INCREASE OVER THE MOUNTAINS...NORTHERN SAC VALLEY AND
SURROUNDING FOOTHILLS ON TUESDAY AND WEDNESDAY AS AN UPPER LOW
OVER THE EASTERN PACIFIC MOVES TOWARDS THE CA COAST.

&&

.DISCUSSION...
TEMPS AT PRESS TIME TRENDING ABOUT 3 TO 6 DEGREES COOLER THAN 24 HRS
AGO IN THE DELTA INFLUENCED AREAS DUE TO A STRONG DELTA BREEZE AND
DEEPENING MARINE LAYER OVER 2 KFT PER THE FT ORD PROFILER. ONSHORE
GRADIENTS HAVE INCREASED UP TO 4 MBS WITH MORE THAN 2 MBS UP THE SAC
VLY MOST LIKELY FROM THE STRONG THERMAL CONTRAST RESULTING FROM
TRIPLE DIGIT TEMPS IN THE VALLEY ON SAT. EXPECT THIS COOLING TREND
TO CONTINUE IN THE VALLEY TODAY AS THE DELTA BREEZE FINALLY HAS SOME
"FREON" TO PROMOTE SIGNIFICANT COOLING.

SYNOPTIC SCALE PATTERN DOMINATED BY THE 4-CORNERS HIGH AND A LARGE
LOW PRESSURE CELL OFF THE CA COAST ALONG 130W. SHORT WAVE MOVING NWD
OVER WRN NV IS IS PUSHING CONVECTION NNW...WITH OUR SHASTA CO AREA
ON THE SRN FRINGE. HIGHER RESOLUTION QPF/RADAR REF PROGS SUGGEST
SOME SHOWERS/ISOLD TRW MAY BRUSH THE NERN PART OF SHASTA CO THIS
MORNING BEFORE ENDING. OTHERWISE...INSTABILITY PROGS FOCUS THE
CONVECTIVE POTENTIAL OVER THE SIERNEV/SRN CASCADE ZONES SUN/MON
AFTERNOONS AND EVENINGS. REAMPLIFICATION OF THE RIDGE OVER THE
SIERNEV IN THE WAKE OF THE SHORT WAVE WILL LIMIT THE COOLING OVER
THE HIGHER SIERRA ELEVATIONS TODAY HOWEVER...AND IN SOME INSTANCES
PERSISTENCE MAY BE FOLLOWED.

EXPECT AN INCREASE IN AREAL COVERAGE OF CONVECTION TUE/WED AS THE
AFOREMENTIONED LARGE LOW PRESSURE CELL SLOWLY APPROACHES THE COAST.
UPPER LEVEL DIFLUENCE...DYNAMICS AND MOISTURE EXPECTED TO BECOME
MORE FOCUSED OVER NORCAL RESULTING IN MORE WIDESPREAD STORMS. BEGAN
THE UPWARD TREND OF POPS DURING THIS TIME IN THIS MORNING`S
FORECASTS WITH SUFFICIENT MOISTURE AVAILABLE FOR "WETTING RAINS."

SYNOPTIC COOLING MON-WED THIS WEEK WILL LOWER MAX TEMPS BELOW NORMAL
WITH ONSHORE FLOW INCREASING CHANCES OF A STRATUS INTRUSION INTO THE
VALLEY TUE/WED...ALTHOUGH INCREASING CYCLONIC FLOW WILL ALSO RESULT
IN AN INCREASE IN CLOUD COVER AS WELL ESPECIALLY OVER THE MTNS.  JHM


.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)

MEDIUM-RANGE MODELS CONTINUE TO STRUGGLE WITH THE TIMING OF THE
UPPER LOW AS IT APPROACHES CALIFORNIA WITH THE GFS SLIGHTLY FASTER
MOVING IT ONSHORE THURSDAY WHILE THE EC IS ABOUT 24 HOURS SLOWER
WITH THE TIMING. REGARDLESS OF TIMING, MOUNTAIN THUNDERSTORMS ARE
EXPECTED DAILY. TEMPERATURES WILL MODERATE TO SLIGHTLY BELOW
AVERAGE BEFORE WARMING OVER THE WEEKEND AS THE TROUGH SHIFTS EAST.

&&

.AVIATION...

MAINLY VFR CONDS THE NEXT 24 HOURS, EXCEPT LOCAL MVFR/IFR VCNTY
MTN THUNDERSTORMS 22Z-04Z. SLY WINDS 10-15 KT IN THE SAC VLY
(NWLY IN THE SJ VLY) AFT 18Z, WITH SW WIND GUSTS 25-35 KT CONTG
NEAR THE DELTA.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$


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