Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 301655
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 AM PDT TUE JUN 30 2015

.SYNOPSIS...
VERY HOT WEATHER CONTINUES ACROSS THE REGION THIS WEEK. SIERRA
THUNDERSTORMS THROUGHOUT THE WEEK. SOME SHOWERS OR SPRINKLES MAY
MOVE INTO PORTIONS OF THE VALLEY THURSDAY AND FRIDAY.

&&

.DISCUSSION...
HAVE TAKEN A LOOK AT TEMPERATURES FOR THE NEXT SEVERAL DAYS AND
FORECAST LOOKS ON TRACK. MAY MAKE SOME MINOR ADJUSTMENTS BUT THE
MAIN MESSAGE OF VERY HOT WEATHER WITH WARM OVERNIGHT LOWS
CONTINUES. THE MONTEREY OFFICE HAS ISSUED A HEAT ADVISORY FOR
THEIR EAST BAY COUNTIES INCLUDING NAPA COUNTY. WILL LOOK AT AREAS
WEST OF OUR WATCH AREA, LIKE SOUTHERN LAKE COUNTY, TO SEE IF WE
NEED TO ADJUST THE HEAT WATCH AND PLAN TO HAVE AN UPDATE OUT BY
NOON.

AS FOR TODAY`S HEAT, REDDING IS FORECAST TO REACH 111 DEGREES
TODAY WHICH IS THE RECORD FROM 2014. MODESTO WILL BE NEAR THE
RECORD OF 108 (1950) AS IT IS FORECAST TO HIT 107 TODAY. OTHER
COMMON SITES LIKE STOCKTON, SACRAMENTO, AND RED BLUFF WILL BE A
FEW TO SEVERAL DEGREES SHY OF THEIR RECORDS TODAY.

THE HRRR MODEL IS INDICATING THAT THUNDERSTORMS SHOULD START
DEVELOPING ALONG THE SIERRA CREST AROUND 1-2 PM. HOWEVER, MOST OF
THE ACTIVITY WILL BE SOUTH OF THE LAKE TAHOE REGION AND NEAR OR
EAST OF THE CREST. JBB
.PREVIOUS DISCUSSION...MAIN FORECAST CONCERN CONTINUES TO CENTER
AROUND HOT WEATHER THIS WEEK. HEAT CRANKS UP ACROSS THE INTERIOR
OF NORCAL THE NEXT SEVERAL DAYS AS STRONG HIGH PRESSURE EXTENDS
WESTWARD BRINGING A HOT AIRMASS AND SUPPRESSING ANY REMAINING
COASTAL INFLUENCE INLAND. HIGHS THE NEXT 3 DAYS ACROSS THE
NORTHERN HALF OF THE SACRAMENTO VALLEY WILL LIKELY BE IN THE 110
TO 115 DEGREE RANGE WITH OVERNIGHT LOWS IN THE UPPER 70S TO LOWER
80S, SO THE EXCESSIVE HEAT WATCH WILL CONTINUE FOR THAT AREA.
TEMPERATURES WON/T BE QUITE AS HOT ACROSS THE REMAINDER OF THE
REGION, BUT THE WARMEST READINGS SO FAR THIS SUMMER CAN BE
EXPECTED IN MANY AREAS.

AS THE RIDGE AXIS SHIFTS NORTHWARD LATER IN THE WEEK, THERE WILL
BE AN OPPORTUNITY FOR THE MARINE LAYER TO ONCE AGAIN DEEPEN
THURSDAY BEGINNING THE PROCESS OF SPREADING SOME COOLING INLAND
LATE IN THE WEEK.

ANOTHER ITEM TO KEEP AN EYE ON WILL BE MOISTURE MOVING UP FROM THE
SOUTHEAST AROUND THE PERIPHERY OF THE RIDGE. DESPITE A FAIR AMOUNT
OF MID AND UPPER LEVEL MOISTURE, DIURNAL THUNDERSTORMS WILL
LIKELY BE FAIRLY LIMITED OVER THE MOUNTAINS THE NEXT COUPLE OF
DAYS AS MID-LEVEL TEMPS WARM. BY THURSDAY AND FRIDAY, MOISTURE IS
FORECAST TO INCREASE WITH TPW OF AROUND 1.5 INCHES FORECAST BY THE
GFS, HOWEVER, SIMILAR TO LAST WEEKEND, THE MOISTURE IS MOSTLY
CONCENTRATED ABOVE 500 MBS SO THE MAIN THUNDERSTORM THREAT WILL
REMAIN OVER THE MOUNTAINS WITH THE POSSIBILITY OF LIGHT SHOWERS OR
SPRINKLES AT THE LOWER ELEVATIONS. IF ANY STRONGER LIFTING
MECHANISM APPEARS IN THE SOUTHEAST FLOW, THEN MORE WIDESPREAD
THUNDERSTORM CHANCES WILL BE POSSIBLE.

&&
.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)

OVER THE WEEKEND, INTERIOR NORTHERN CALIFORNIA SANDWICHED BETWEEN
FOUR CORNERS UPPER HIGH AND OFFSHORE UPPER LOW. SOUTHERLY FLOW
ALOFT WILL CONTINUE TO DRAW SOME MONSOONAL MOISTURE INTO THE
AREA. MAIN INSTABILITY, AND THUS THREAT OF SHOWERS AND
THUNDERSTORMS, DEPICTED OVER THE MOUNTAINS IN THE AFTERNOONS INTO
EARLY EVENINGS. DRIER AND MORE STABLE SOUTHWEST FLOW ALOFT
DEVELOPS MONDAY INTO TUESDAY AS DOWNSTREAM UPPER HIGH PROGRESSES.
THREAT OF AFTERNOON DEEP MOIST CONVECTION SHIFTS EAST OF THE
SIERRA NEVADA CREST.

HIGH TEMPERATURES THROUGH THE EXTENDED FORECAST PERIOD WILL BE
COOLER. MAX READINGS WILL RANGE FROM THE MID 80S IN THE DELTA TO
AROUND 100 IN THE NORTHERN SACRAMENTO VALLEY, WITH UPPER 70S TO
AROUND 90 FOR THE MOUNTAINS AND FOOTHILLS.

&&

.AVIATION...
UPPER HIGH OVER THE ROCKIES EXTENDS WESTWARD INTO NORCAL WITH
SOUTHERLY FLOW ALOFT. MAINLY VFR CONDITIONS FOR THE NEXT 24 HOURS.
ISOLATED THUNDERSTORMS POSSIBLE ALONG THE SIERRA CREST BETWEEN
21Z-02Z THEN DRIFT EASTWARD.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
EXCESSIVE HEAT WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
MORNING FOR CENTRAL SACRAMENTO VALLEY-NORTHEAST
FOOTHILLS/SACRAMENTO VALLEY-NORTHERN SACRAMENTO VALLEY.

&&

$$


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