Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 312233
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
333 PM PDT FRI JUL 31 2015

.SYNOPSIS...
A SLOW COOLING TREND CONTINUES INTO NEXT WEEK. DAYTIME HIGHS NEAR
NORMAL BY SUNDAY AND AT OR BELOW NORMAL MUCH OF NEXT WEEK.
SCATTERED MOUNTAIN THUNDERSTORMS THROUGH MONDAY AS MONSOON
MOISTURE IS PULLED NORTHWARD...ELSEWHERE CONTINUED DRY.

&&

.DISCUSSION...THE UPPER LEVEL RIDGING WHICH BROUGHT A HEAT WAVE
ACROSS THE AREA THIS WEEK IS GIVING WAY. MONSOONAL MOISTURE WITH
A DISTURBANCE MOVING THROUGH NORCAL IS SPREADING SHOWERS AND A
FEW ISOLATED THUNDERSTORMS IN THE MOUNTAINS. THE MAIN CHANGE FOR THE
REST OF THE AREA IS A BIG DROP IN TEMPERATURES TODAY, WITH
TEMPERATURES AT 3 PM 6 TO 11 DEGREES LOWER THAN THIS TIME
YESTERDAY. THIS IS DUE TO A COOLER AIRMASS...ONSHORE FLOW WITH THE
DELTA BREEZE...AND INCREASED CLOUD COVER. MOISTURE WITH THE
MONSOONAL FLOW IS MAKING IT FEEL MORE HUMID THAN
NORMAL...THOUGH...WHICH IS COUNTERING SOME OF THE COOLING AFFECTS.

THE DISTURBANCE IS A NICELY DEFINED VORTMAX, CLEARLY VISIBLE
ROTATING ON THE SATELLITE LOOP. THIS IS MOVING NORTHWARD THROUGH
THE AREA, CURRENT CENTERED AROUND GLENN COUNTY.

PRECIPITATION HAS MAINLY BEEN FOCUSED OVER THE MOUNTAINS TODAY
EXCEPT FOR SOME LIGHT SHOWERS/SPRINKLES IN THE MORNING. THE MOST
NOTABLE STORM SO FAR IS A THUNDERSTORMS THAT DEVELOPED NEAR THE
SIERRA CREST AND TRACKED TO THE NORTHWEST OVER BLUE CANYON. THIS
SYSTEM PASSED CLOSE TO THE LOWELL FIRE...BRINGING WINDS GUSTING TO
AROUND 31 MPH. THERE WERE QUITE A FEW LIGHTNING STRIKES WITH THIS
STORM...AT LEAST ONE OF WHICH STARTED A NEW WILDFIRE NEAR ALTA. AS
EXPECTED...THERE HAS BEEN LIMITED RAIN WITH THESE INITIAL
STORMS...WHICH INCREASES THE FIRE DANGER. SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO GET PROGRESSIVELY MORE WET AS MORE
MOISTURE PUSHES NORTHWARD INTO THE AREA TONIGHT AND THROUGH THE
WEEKEND.

THE OVERALL AIRMASS COOLS A BIT MORE ON SATURDAY AS THE UPPER
RIDGE SHIFTS EASTWARD A BIT IN RESPONSE TO AN UPPER LOW OFF THE
CENTRAL CA COAST SHIFTING COASTWARD. A CONTINUED STRONG DELTA
BREEZE WILL KEEP DAYTIME TEMPERATURES IN DELTA INFLUENCED AREAS AT
OR BELOW NORMAL. MOISTURE...INSTABILITY AND OROGRAPHIC LIFT WILL
BRING ANOTHER DAY OF ISOLATED THUNDERSTORMS OVER THE MOUNTAINS
SATURDAY. UPPER RIDGE AXIS SHIFTS FARTHER INLAND ON SUNDAY WITH AN
INCREASE IN ONSHORE FLOW BRINGING STILL COOLER TEMPERATURES.
DAYTIME HIGHS ON SUNDAY SHOULD COME IN CLOSE TO OR EVEN BELOW
NORMAL MOST AREAS. MOUNTAIN THUNDERSTORMS WILL CONTINUE TO
REDEVELOP IN THE AFTERNOON BUT AREA OF EMPHASIS WILL LIKELY SHIFT
TO THE NORTHERN MOUNTAINS UNDER A MORE SOUTHERLY FLOW ALOFT. UPPER
TROUGH DEVELOPMENT IN THE EASTERN PACIFIC WITH SOUTHWEST FLOW
ALOFT OVER THE NORTH STATE SHOULD SHIFT ANY AFTERNOON THUNDERSTORM
DEVELOPMENT TO THE SIERRA CASCADE CREST ON MONDAY. INCREASED
ONSHORE FLOW AND COOLER AIRMASS WILL BRING DOWN HIGH TEMPERATURES
TO BELOW NORMAL FOR THIS TIME OF YEAR WITH THESE BELOW NORMAL
TEMPERATURES LASTING THROUGH MUCH OF THE COMING WEEK.

&&
.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY)

MODELS ADVERTISING OFFSHORE UPPER LOW WITH UPPER RIDGING OVER THE
PLAINS EARLY NEXT WEEK. SOUTHWESTERLY FLOW ALOFT OVER NORCAL
WITH MODEL DIFFERENCES IN STRENGTH OF EMBEDDED VORT MAXES. DIFFERENCES
GROW THROUGH MIDWEEK AS EC PROGS MAIN UPPER LOW INLAND WHILE THE
GFS IS ABOUT 48 HOURS SLOWER. WILL MAINTAIN DRY FORECAST BUT
POTENTIAL MAY EXIST FOR SOME DEEP MOIST CONVECTION OVER THE
MOUNTAINS TUESDAY AND BEYOND. HIGH TEMPERATURES FORECAST TO BE
NEAR TO SLIGHTLY BELOW NORMAL THROUGH THE EXTENDED FORECAST
PERIOD.


&&

.AVIATION...

MNLY VFR CONDS NXT 24 HRS EXC ISOLD MVFR POSS IN TSTMS...MNLY
OMTNS. GSTY SWLY SFC WNDS THRU DELTA AND VCNTY OF TSTMS.
&&

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

$$


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