Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 011610
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
910 AM PDT WED JUL 1 2015

.SYNOPSIS...
VERY HOT WEATHER CONTINUES ACROSS THE REGION THIS WEEK. SIERRA
THUNDERSTORMS SPREADING TO THE NORTHERN MOUNTAINS THURSDAY AND
FRIDAY AND OVER THE WEEKEND WITH SPRINKLES POSSIBLE IN THE VALLEY
THURSDAY NIGHT. SIERRA SHOWERS DECREASING NEXT WEEK. COOLER
TEMPERATURES OVER THE WEEKEND AND NEXT WEEK BUT REMAINING ABOVE
NORMAL.

&&

.DISCUSSION...

FORECAST ON TRACK THIS MORNING. WARM OVERNIGHT PROVIDED LITTLE
RELIEF FROM THE HEAT WITH MORNING LOWS ONLY DROPPING INTO THE 70S
ACROSS THE VALLEY. AS OF 9 AM, MOST VALLEY LOCATIONS ARE INTO THE
80S WITH 70S IN THE MOUNTAINS AND REDDING AND RED BLUFF ALREADY
INTO THE 90S. TODAY LOOKS TO BE THE HOTTEST OF THE WEEK WITH
CENTRAL AND NORTHERN VALLEY TOPPING OUT IN THE 110-115 DEGREE
RANGE AND THE REST OF THE VALLEY WELL INTO THE 100S. 90S POSSIBLE
ACROSS HIGHER ELEVATIONS. GOING EXCESSIVE HEAT WARNING LOOKS GOOD
AND NOT EXPECTING ANY CHANGES.

LATEST HIRES GUIDANCE STILL SHOWING THE CHANCE FOR SCATTERED
SHOWERS AND THUNDERSTORMS LATER THIS AFTERNOON AND EVENING NEAR
THE SIERRA CREST. AS MENTIONED BY EARLY SHIFTS, MOST ACTIVITY
SHOULD REMAIN SOUTH OF LAKE TAHOE.  CEO

.PREVIOUS DISCUSSION...
HIGH PRESSURE ALOFT EXTENDING FROM THE
FOUR CORNERS AREA TO NORCAL WILL REMAIN IN PLACE THROUGH THE END
OF THE WEEK. VERY WARM CONDITIONS WILL CONTINUE UNDER THIS RIDGE
WITH NEAR RECORD TEMPERATURES EXPECTED THE NEXT COUPLE OF DAYS.
SUBTROPICAL MOISTURE PULLED NORTHWARD INTO NORTHERN CALIFORNIA AND
THE DELTA BREEZE WILL BE THE MAIN CONTROLLERS OF THE WEATHER
THROUGH THE SHORT TERM FORECAST.

FOR TODAY...OVERALL AIRMASS WARMS A BIT FOR SLIGHTLY HIGHER
TEMPERATURES MOST AREAS. EXCEPTION SHOULD BE THE DELTA INFLUENCED
AREAS WHERE A SLIGHT INCREASE IN DELTA BREEZE AND A SLIGHTLY
DEEPER MARINE LAYER SHOULD BRING A SLIGHT COOLING. MODELS ONLY
SHOW MOISTURE AND INSTABILITY OVER THE SIERRA FROM ABOUT TAHOE
SOUTHWARD SO THIS LOOKS LIKE ONLY AFTERNOON MOUNTAIN THUNDERSTORM
THREAT AREA TODAY. MAIN UPPER RIDGE FORECAST BY ALL MODELS TO
RETROGRADE WESTWARD A BIT ON THURSDAY. THIS WILL CAUSE A
SIGNIFICANT INCREASE IN SUBTROPICAL MOISTURE TO BE PULLED
NORTHWARD OVER THE AREA. THIS INCREASE IN MOISTURE WILL ADD AN
AFTERNOON THUNDERSTORM THREAT TO THE COASTAL RANGE AND SHASTA
COUNTY MOUNTAINS WITH AN INCREASE IN CLOUD COVER BRINGING A SLIGHT
COOLING EFFECT ELSEWHERE. THE MOST SIGNIFICANT BATCH OF MOISTURE
IS FORECAST TO MOVE OVER NORCAL ON THURSDAY NIGHT. PRECIPITABLE
WATER VALUES ARE FORECAST TO BE SIGNIFICANTLY HIGH AT OVER AN INCH
AND A HALF TPW UP THE CENTRAL VALLEY. WITH THIS HIGH LEVEL OF
MOISTURE OVER THE REGION AND INSTABILITY OVER THE MOUNTAINS...HAVE
INCLUDED A THREAT OF SPRINKLES OR LIGHT SHOWERS OVER THE VALLEY AS
BLOW OFF FROM THUNDERSTORMS SURROUNDING THE VALLEY COULD BRING A
LITTLE LIGHT RAINFALL TO THE LOWER ELEVATIONS THURSDAY NIGHT. A
SLIGHT COOLING TREND WILL CONTINUE ON FRIDAY AS SKIES REMAIN
MOSTLY CLOUDY WITH AFTERNOON THUNDERSTORMS REMAINING POSSIBLE OVER
THE MOUNTAINS. VERY LITTLE CHANGE IS IN STORE FOR SATURDAY WITH
AFTERNOON MOUNTAIN THUNDERSTORMS CONTINUING AND ONLY A SLIGHT
COOLING AS THE STRONGER ONSHORE FLOW CONTINUES. EVEN WITH COOLING
DAYTIME HIGHS WILL REMAIN WELL ABOVE NORMAL.
&&

.EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)

HIGH PRESSURE WEAKENS OVER NORCAL DURING THE EXTENDED PERIOD AS
THE CENTER OF STRONG HIGH PRESSURE SHIFTS INTO THE GULF OF ALASKA
WITH A WEAK TROUGH FORECAST TO DEVELOP JUST OFFSHORE THE WEST
COAST. THE RESULT WILL BE A COOL DOWN ACROSS THE REGION AS ONSHORE
FLOW BECOMES MORE EXTENSIVE. VALLEY HIGH TEMPERATURES WILL BE
MAINLY IN THE 90S. THE THREAT OF DIURNAL DEEP CONVECTION OVER THE
MOUNTAINS WILL ALSO END AS DEEPER MOISTURE AND INSTABILITY SHIFTS
NORTH AND EAST OF THE AREA.
&&

.AVIATION...

VFR CONDS NEXT 24 HOURS. HIGH AFTERNOON DENSITY ALTITUDES. ISOLD
TSTMS OVER SIERRA NEVADA BETWEEN 22Z-02Z.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
EXCESSIVE HEAT WARNING FROM 2 PM THIS AFTERNOON TO 8 AM PDT
FRIDAY FOR CENTRAL SACRAMENTO VALLEY-CLEAR LAKE/SOUTHERN LAKE
COUNTY-MOUNTAINS SOUTHWESTERN SHASTA COUNTY TO NORTHERN LAKE
COUNTY-NORTHEAST FOOTHILLS/SACRAMENTO VALLEY-NORTHERN SACRAMENTO
VALLEY-SHASTA LAKE AREA / NORTHERN SHASTA COUNTY.

&&

$$


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