Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 062236
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
336 PM PDT MON JUL 6 2015

.SYNOPSIS...
COOLER THIS WEEK WITH DAILY AFTERNOON AND EVENING THUNDERSTORMS
MAINLY OVER THE MOUNTAINS. THUNDERSTORM COVERAGE MAY INCREASE OVER
THE MOUNTAINS...SAC VALLEY AND SURROUNDING FOOTHILLS LATER TUESDAY
THROUGH THURSDAY AS AN UPPER LOW OVER THE EASTERN PACIFIC MOVES
ACROSS THE REGION.

&&

.DISCUSSION...
THE UPPER LEVEL PATTERN CONTINUES WITH AN UPPER LOW PRESSURE
SYSTEM OFF THE COAST AND RIDGING TO THE EAST. MONSOONAL MOISTURE
IS FLOWING NORTHWARD OVER THE REGION. SOME MOUNTAIN SHOWERS AND
THUNDERSTORMS ARE ONCE AGAIN DEVELOPING THIS AFTERNOON ALONG AND
EAST OF THE SIERRA CREST...WITH SOME CURRENTLY FORMING IN THE
BURNEY BASIN AREA AND IN THE LASSEN NATIONAL PARK AREA. THE
STRONGEST STORMS ARE EAST OF THE CREST AND THIS PATTERN SHOULD
CONTINUE INTO THE EVENING. MOUNTAIN SHOWERS MAY CONTINUE OVERNIGHT INTO
TUESDAY...WITH THUNDERSTORMS EXTENDING INTO THE FOOTHILLS AND
POTENTIALLY THE NORTHERN SACRAMENTO VALLEY FOR THE AFTERNOON AND
EVENING.

A MORE ACTIVE PATTERN BEGINS TUESDAY AS THE UPPER LOW SHIFTS
EASTWARD, EVENTUALLY MOVING INLAND ON WEDNESDAY AND THURSDAY.
THIS WILL BRING INCREASING CHANCES OF MOUNTAIN
THUNDERSTORMS...PERHAPS SPREADING INTO THE NORTHERN SACRAMENTO
VALLEY BY TUESDAY AFTERNOON. MORE WIDESPREAD VALLEY CONVECTION IS
POSSIBLE WEDNESDAY AS THE CORE OF THE LOW PASSES THROUGH.
THERE WILL BE IMPRESSIVE AMOUNTS OF MOISTURE WITH THIS
SYSTEM...WITH NAEFS ENSEMBLES SHOWING STRONG ANAMOLIES FOR
PRECIPITABLE WATER OVER NORTHERN CALIFORNIA WEDNESDAY AND
THURSDAY.

ELEVATED INSTABILITY WILL BE SUFFICIENT TO KEEP SOME CONVECTION
GOING OVERNIGHT TUESDAY NIGHT AND AGAIN WEDNESDAY NIGHT. A SLIGHT
CHANCE OF SHOWERS AND THUNDERSTORMS BECOMES WIDESPREAD WEDNESDAY
AFTERNOON THROUGH THURSDAY AS THE LOW MOVES OVERHEAD, PROVIDING
DECENT LIFT WITH INSTABILITY COMBINING WITH MONSOONAL MOISTURE.
THE BEST CHANCES FOR THUNDERSTORMS OVER ELEVATED TERRAIN, WHERE
LOCALLY HEAVY RAIN IS POSSIBLE. THERE MAY BE QUITE A BIT OF
LIGHTNING THERE, BUT MOISTURE WITH THE STORMS MAY ACT TO REDUCE
THE SPREAD OF ANY FIRES STARTED BY LIGHTNING STRIKES.

THE LOW PRESSURE SYSTEM WILL BRING CLOUDS AND A COOLER AIR MASS.
THIS WILL BRING A COOLING TREND, WITH TEMPERATURES DROPPING TO
BELOW NORMAL LEVELS BY MID WEEK.

EK

&&
.EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)

GFS AND EC MODELS HAVE THE CLOSED LOW WEAKENING ON FRIDAY INTO AN
OPEN TROUGH BEFORE MOVING OUT OF THE REGION BY THE END OF THE DAY.
HOWEVER, A BROADER SYNOPTIC TROUGH PATTERN QUICKLY FOLLOWS IN ITS
WAKE. THIS SECONDARY TROUGH WILL LINGER OVER THE WEST COAST OVER
THE WEEKEND. THE AXIS OF THIS TROUGH WILL RESIDE JUST OFFSHORE
THROUGH THE EXTENDED KEEPING OUR REGION SANDWICHED BETWEEN THAT
TROUGH AND HIGH PRESSURE OVER THE DESERT SOUTHWEST.

FOR FRIDAY AND SATURDAY, THE CHANCE OF MOUNTAIN THUNDERSTORMS
WILL PERSIST AND MAY ALSO IMPACT THE NORTHERN SACRAMENTO VALLEY ON
FRIDAY. BY SUNDAY, THE DESERT SW HIGH PRESSURE CELL WILL
STRENGTHEN AND BUILD INTO OUR REGION CAUSING A WARMING TREND WITH
DRY WEATHER. THROUGHOUT THE EXTENDED, DAYTIME HIGHS WILL START OFF
5-8 DEGREES BELOW NORMAL AND THEN GRADUALLY WARM UP TO NORMAL BY
MONDAY.

JBB/TGD

&&

.AVIATION...

VFR CONDITIONS CONTINUE, EXCEPT LOCAL MVFR/IFR NEAR THE DELTA
AS MARINE STRATUS RETURNS. SOUTH WINDS 8-15 KT IN THE SACRAMENTO
VALLEY (NW IN THE SAN JOAQUIN VALLEY) WILL CONTINUE, WITH SW WIND
GUSTS 25-35 KT NEAR THE DELTA.

JBB/TGD

&&

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

$$


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