Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 020431

930 PM PDT Fri Aug 1 2014

Hot temperatures with a cooling trend beginning Sunday. A return
to Sierra showers and thunderstorms possible again early/mid week
next week.



The eastward shift of the continental high has allowed SW flow aloft
over interior Norcal. This has shifted the instability to our
E...but has not resulted in any cooling as max temps were rather
persistent over the Nrn portion of the CWA today...and were several
deg warmer over the Srn portion. General trend of the guidance is to
suggest some cooling on Sat with a deepening marine layer and
stronger onshore flow. Not certain this will happen as high pressure
remains locked in place and 5H heights remain above 588 dam as a nrn
Baja low forms and seems to reinforce the ridge during the day. A
short wave passed through the area today...touching off some storms
to our NE...with another wave spreading a patch of cirrus from the
Bay area NEwd which should move over the area tonight. This sets up
drier/sinking air now W of 130W to spread over our area on Sat.

Based on the recovering marine layer and forecast strengthening of
onshore gradients...we could expect some cooling in the Delta
influenced areas...but not any significant cooling in areas farther
from the Delta. So we will ponder these factors in the forecasts we lean toward near persistence in max temps away
from the Delta. We will wait for all of the 00z data before we make
the changes however.     JHM

.Previous Discussion...

Monsoon season upper high has shifted east with trough developing
over the eastern Pacific. This has allowed a dry southwest flow to
develop with Precipitable water values dropping to below 0.75
inches. Very hot afternoon in progress across NorCal with
temperatures several degrees above 100 degrees at valley
locations. Afternoon high temperatures should remain a few degrees
under record values. The southwest flow is keeping thunderstorms
near the crest with motion east and northeast toward Nevada. Not
much relief overnight with weak delta breeze push.

Slightly cooler Saturday then a few more degrees of cooling Sunday
as delta breeze/onshore flow develops...but still slightly above
normal. Moisture will remain east of the area keeping
thunderstorms over Nevada Saturday. Moisture will increase over
the southern Sierra Sunday as disturbance moves north from Baja
California to SoCal with thunderstorms possible mainly over
Tuolumne county.

Disturbance will move north into Nevada Monday spreading moisture
north over all of the Sierra. Isolated thunderstorms will be
possible mainly near the crest with the best chances east over
Nevada. Onshore flow will continue with temperatures cooling to
near normal levels.


.Extended Discussion (Tuesday through Friday)

Extended models are suggesting a return of some moist southerly
flow over the area by next week as a weak low edges closer to the
coast and some ridging lingers somewhere over the western US.
NAEFS mean precipitable water ensembles continue to show an
increase in moisture Tuesday through Friday. In addition, GFS
MUCAPE and Total Totals during the extended show an increase over
the higher terrain for a threat of thunderstorms. Signatures are
not as abundant for Thursday and Friday afternoons, though
thunderstorms over the higher terrain cannot be ruled out.
Temperatures will be near to slightly above normal through the



VFR conditions across interior Northern California the next 24
hours. Winds will remain generally below 15 kts except SW 10-20
kts near the Delta.



.STO Watches/Warnings/Advisories...

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