Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 021538
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
838 AM PDT THU JUL 2 2015

.SYNOPSIS...
HOT WEATHER CONTINUES OVER THE NORTHERN SACRAMENTO VALLEY TODAY ALTHOUGH
A FEW DEGREES OF COOLING ARE LIKELY. MOUNTAIN THUNDERSTORMS ARE
POSSIBLE EACH AFTERNOON AND EVENING THROUGH THE WEEKEND WITH THE
POSSIBILITY OF A STRAY SHOWER OR TWO IN THE VALLEY LATER THIS
EVENING AND TONIGHT. COOLER TEMPERATURES OVER THE WEEKEND AND
NEXT WEEK BUT REMAINING ABOVE NORMAL. DECREASING CHANCES OF
MOUNTAIN THUNDERSTORMS NEXT WEEK AS UPPER RIDGE SHIFTS EASTWARD.

&&

.DISCUSSION...
NO MAJOR CHANGES TO GOING FORECAST FOR TODAY. ANOTHER MILD START
AS FAIRLY EXTENSIVE CLOUD COVER EXISTED ACROSS THE AREA OVERNIGHT
AND EARLY THIS MORNING. LOWS ONLY DROPPED INTO THE MID TO UPPER
70S ACROSS MOST OF THE VALLEY AND UPPER 50S TO 60S IN THE
MOUNTAINS. AFOREMENTIONED CLOUD COVER SHOULD RESULT IN A FEW
DEGREES OF COOLING TODAY ACROSS THE AREA WHICH SHOULD KEEP THE
CENTRAL AND SOUTHERN VALLEY IN THE 90S. HIGHS OF 100-108 LIKELY
ACROSS NORTHERN VALLEY. ONSHORE FLOW WILL INCREASE DURING THE DAY
INTO THE EVENING HOURS WHICH MAY KEEP DELTA INFLUENCED AREAS IN
THE 80S. MONSOONAL MOISTURE WILL INCREASE IN SOUTHEAST TO EAST
FLOW. LATEST HIRES GUIDANCE IN GENERAL AGREEMENT WITH MAJORITY OF
CONVECTION BREAKING OUT AFTER 20Z ACROSS THE SIERRA...SOUTH OF
LAKE TAHOE...AND SPREADING NORTH DURING THE AFTERNOON AND EVENING
HOURS. A FEW STRONG STORMS POSSIBLE AND HEAVY DOWNPOURS WILL BE
LIKELY IN ANY STORM GIVEN HIGHER PWAT VALUES. STILL CANNOT RULE
OUT A FEW SHOWERS OR THUNDERSTORMS MAKING THEIR WAY INTO THE
VALLEY LATER THIS EVENING AND TONIGHT GIVEN RESIDUAL INSTABILITY
BUT NOT EXPECTING ANYTHING WIDESPREAD.  CEO

.PREVIOUS DISCUSSION...

HIGH PRESSURE ALOFT WILL REMAIN STRETCHED ACROSS THE SOUTHWEST
U.S FROM FOUR CORNERS TO NORCAL THROUGH THE SHORT TERM PERIOD. THE
OVERALL PATTERN WILL NOT CHANGE MUCH DAY TO DAY WITH MOUNTAIN
THUNDERSTORMS POSSIBLE EACH DAY AND POSSIBLY DURING SOME NIGHT
TIME PERIODS AS WELL. A SHORTWAVE TROUGH ROTATING AROUND THE
SOUTHWEST PORTION OF THE HIGH IS BRINGING ONE OF THESE NIGHTTIME
THUNDERSTORM PERIODS THIS MORNING WITH ISOLATED THUNDERSTORMS
BEING GENERATED OVER THE SAN JOAQUIN VALLEY THIS MORNING.
SHORTWAVE MODELS INDICATE THESE THUNDERSTORMS WILL ROTATE WEST OF
THE FORECAST AREA LATER THIS MORNING. SOUTHEAST TO EAST FLOW ALOFT
WILL BRING MOISTURE AND INSTABILITY INTO THE AREA TODAY FOR A
THREAT OF THUNDERSTORMS OVER THE MOUNTAIN AREAS THIS AFTERNOON.
MEANWHILE...CLOUD COVER AND A SLIGHT AIRMASS COOLING WILL BRING A
FEW TO SEVERAL DEGREES OF COOLING TODAY ALTHOUGH HIGHS WILL REMAIN
WELL ABOVE NORMAL. MODELS PUSH A SURGE OF MOISTURE INTO NORCAL
TONIGHT WITH TPW VALUES FORECAST TO TOP 1.5 INCHES. HAVE PUT IN
SLIGHT CHANCE OF LIGHT SHOWERS ACROSS MOST OF THE CWA FOR THE
TONIGHT PERIOD BUT WITH LACK OF HEATING AND DYNAMICS...DO NOT
EXPECT MUCH IN THE WAY OF PRECIPITATION AND MORE LIKELY WILL SEE
ISOLATED SPRINKLES.

MOUNTAIN THUNDERSTORMS REMAIN IN THE FORECAST FRIDAY AND SATURDAY
AFTERNOONS WITH STABILITY PROGS SHOWING MODERATE INSTABILITY OVER
THE MOUNTAIN AREAS WHILE VALLEY LOCATIONS REMAIN UNDER PARTLY
CLOUDY SKIES. DAYTIME TEMPERATURES CONTINUE TO COOL BOTH DAYS AS
THE UPPER RIDGE IS WEAKENED BY A SYSTEM PASSAGE TO THE NORTH. A
MODERATE DELTA BREEZE WILL KEEP THE DELTA INFLUENCED HIGH
TEMPERATURES CLOSE TO NORMAL ON INDEPENDENCE DAY WHILE ELSEWHERE
HIGHS ARE FORECAST TO COME IN AROUND 5 TO 10 DEGREES ABOVE NORMAL.

CONDITIONS STABILIZE A BIT ON SUNDAY AS A LOW OFF THE COAST EDGES
A BIT CLOSER TO THE COAST BRINGING SLIGHTLY MORE ONSHORE FLOW.
AFTERNOON MOUNTAIN THUNDERSTORMS WILL STILL BE POSSIBLE BUT LIKELY
NOT AS WIDESPREAD. MOST LOCATIONS WILL SEE A SLIGHT COOLING AS
WELL.

&&
.EXTENDED DISCUSSION (MONDAY THROUGH THURSDAY)

OUR CWA WILL BE BETWEEN A LOW OVER THE EASTERN PACIFIC OCEAN AND
A RIDGE OVER THE GREAT BASIN THROUGH EARLY NEXT WEEK. 12Z GFS IS
NOW TRENDING TOWARDS THE EC SHOWING THE UPPER LOW MOVING INLAND
MIDWEEK. SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS ALONG SIERRA
CREST FOR MONDAY AND TUESDAY...THEN DRY ACROSS OUR CWA WEDNESDAY
AND THURSDAY.

HIGH TEMPERATURES WILL TREND DOWN SLIGHTLY THROUGH THE EXTENDED
FORECAST PERIOD AS UPPER HIGH WEAKENS AND ONSHORE FLOW INCREASES.
MAX TEMPERATURES MONDAY & TUESDAY EXPECTED MAINLY IN THE 90S FOR
THE CENTRAL VALLEY, 80S FOR THE DELTA AND FOOTHILLS, AND 70S FOR
THE MOUNTAINS...WHICH WILL BE NEAR AVERAGE. SLIGHT COOLING ON
WEDNESDAY AND THURSDAY WILL PUT TEMPERATURES A FEW DEGREES BELOW
AVERAGE. JBB

&&

.AVIATION...

PREDOMINANTLY VFR CONDITIONS TODAY, HOWEVER, PERIODS OF MVFR
POSSIBLE IN MOUNTAIN THUNDERSTORMS. ONSHORE WINDS FOR TAF SITES
WILL STRENGTHEN THIS AFTERNOON/EARLY EVENING AFTER 20Z WITH WINDS
10-20 KTS FOR TAF SITES. DELTA WINDS WILL RANGE 15-25 KTS. JBB

&&

.STO WATCHES/WARNINGS/ADVISORIES...
EXCESSIVE HEAT WARNING UNTIL 7 PM PDT THIS EVENING FOR MOUNTAINS
SOUTHWESTERN SHASTA COUNTY TO NORTHERN LAKE COUNTY-NORTHERN
SACRAMENTO VALLEY-SHASTA LAKE AREA / NORTHERN SHASTA COUNTY.

&&

$$


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