National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KSTO 172235
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
335 PM PDT FRI MAY 17 2013

.SHORT TERM DISCUSSION...

UPPER LEVEL TROUGH IS MOVING EAST INTO THE GREAT BASIN THIS
AFTERNOON. CONVECTION HAS NOT MATERIALIZED THUS FAR THIS AFTERNOON
MUCH AS THE HRRR HAS PREDICTED. THE MAIN SUPPRESSOR SEEMS TO BE
WARMING ABOVE 8000 FEET WHICH HAS CAPPED THE ATMOSPHERE. DELTA
BREEZE HAS DEVELOPED WITH WINDS GUSTING TO 30 MPH OVER THE DELTA.
TROUGH WILL CONTINUE EAST TONIGHT WITH DRIER AIR FILTERING INTO
NORCAL PROVIDING CLEAR SKIES.

UPPER RIDGE WILL BUILD INTO NORCAL TOMORROW WITH A DRY NORTHWEST
FLOW DEVELOPING. TEMPERATURES WILL WARM INTO THE LOW TO MID 80`S
FOR VALLEYS. WEAK DISTURBANCE PASSING THROUGH OREGON AND
WASHINGTON WILL BRUSH THE NORTHERN MOUNTAINS LATE IN THE AFTERNOON
WITH SOME INCREASED CLOUD COVER. ALSO ADDED SLIGHT SHOWER CHANCES
OVER THE NRN SIERRA NEAR LASSEN.

UPPER TROUGH WILL DEEPEN OVER THE ROCKIES ON SUNDAY WITH GUSTY
NORTH WINDS DEVELOPING ON THE BACKSIDE OF THIS FEATURE OVER THE
SAC VALLEY. GUSTS UP TO 35 MPH WILL BE POSSIBLE AND WIND ADVISORY
MAY BE NEEDED IF WIND FORECAST CONFIDENCE INCREASES. TEMPERATURES
WILL WARM INTO THE MID-UPPER 80`S FOR VALLEY LOCATIONS. RIDGE WILL
STRENGTHEN ON MONDAY WITH TEMPS WARMING INTO THE LOW 90`S AT MOST
VALLEY LOCATIONS.


.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY)

A CLOSED UPPER-LEVEL LOW WITH REACH THE PACIFIC NW BY THE MIDDLE
OF NEXT WEEK. BASED ON PREDICTABILITY AND ENSEMBLE PLOTS...MODELS
ARE SHOWING A HIGH DEGREE OF CERTAINTY IN THIS FEATURE. THE MAIN
EFFECT FOR OUR AREA WILL BE COOLER TEMPERATURES...WITH PERHAPS
SOME SHOWERS FROM SHASTA COUNTY NORTHWARD. FIRST CHANCE WOULD BE
TUESDAY NIGHT AS THE INITIAL WAVE AT THE BASE OF THE LOW BRUSHES
OUR NORTHERN REACHES. SLIGHT CHANCES LINGER THROUGH
THURSDAY...BEFORE A SECONDARY WAVE TAKES AIM AT NORCAL. THIS IS
WHERE MODELS DIVERGE. THE 12Z ECMWF CHANGED SIGNIFICANTLY FROM THE
00Z SOLUTION...NOW TRENDING TOWARDS A PROGRESSIVE LOW AFFECTING
OUR AREA NORTH OF I80 THURSDAY NIGHT THEN QUICKLY LIFTING EASTWARD
(THE 00Z HAD AN SLOWER CLOSED LOW CENTERED RIGHT OVER SAC BY
FRIDAY). THE GFS MEANWHILE IS LESS PROGRESSIVE...AND DIGS A DEEPER
TROUGH ALONG THE WEST COAST FROM FRIDAY INTO THE WEEKEND. OVERALL
MESSAGE IS COOLER TEMPERATURES WITH A CHANCE OF RAIN SHOWERS OVER
THE MOUNTAINS. -DVC

&&

.AVIATION...

VFR CONDITIONS CONTINUE OVER INTERIOR NORCAL TAF SITES NEXT 24
HOURS. A WEAK LOW PRESSURE SYSTEM WILL BRUSH TO THE NORTH OF THE
AREA TOMORROW AFTERNOON...WITH THE ONLY EFFECT BEING A FEW MID-
LEVEL CLOUDS FROM AROUND KRBL NORTH. GENERALLY LIGHT WINDS EXPECTED
THROUGH THE PERIOD. -DVC


&&

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

$$