Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 210520
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1020 PM PDT Sun Jul 20 2014

.Synopsis...
An upper level disturbance continues over northern California
today with the greatest probability for thunderstorms over
mountains.  An offshore trough may trigger thunderstorms over
Tehama, Shasta, and Plumas county area Monday and Tuesday. Then
expect a warming trend Wednesday through the weekend.

&&

.Short Term Discussion (Today through Tuesday)...
Looks like the persistent band of showers along the I-80 corridor
will continue until short wave energy...now beginning to rotate W of
the SFO/MTR area...finally stretches out/pulls farther away from our
area. This feature was/is not modeled well at all and was supposed
to lift Nwd...but is actually being shunted Swd by the deformation
zone over the CA/OR border. This feature in turn is being reinforced
by the stronger trof approaching the Pac NW. These latter two
features combined with monsoon moisture and caused a cluster of
showers/storms in our NErn zones late this evening which should lift
NEwd out of our CWA shortly after midnight.    JHM

.Previous Discussion...

A low pressure trof deepening along the coast may enhance activity
over the northern areas both for Monday. Increased cloud cover for
Sunday and Monday will bring cooler temperatures.

The low will deepen along the coast on Tuesday and may continue to
bring afternoon thunderstorms to the northern mountain areas as a
weak disturbance moves through the region from the southwest.
Good onshore flow will continue the next several days and
temperatures will be below normal for this time of year.

The trough will begin to move into the Pacific Northwest on
Wednesday. Skies should be clearing and thunderstorm activity
should be focused more north of the area and into Oregon.
Temperatures should warm a little but still be below seasonal
normals.

.Extended Discussion (Thursday through Sunday)

Upper low forecast by extended models to move through the PacNW
early Thursday with southern portions of the trough extending
into NorCal. Main impact appears to be minor synoptic cooling with
an increased onshore flow. 4 corners high then progged to
gradually build northwestward back into NorCal for a warming trend
beyond midweek. Triple digit heat appears to return to portions of
the Central Valley by Friday with additional warming into the
weekend. Will need to watch for the potential of monsoonal
moisture to make its way into forecast area late in the period but
for now will keep a dry forecast through day 7.

&&

.Aviation...

Subtrpl mstr ovr the fcst area lifts sloly Nwd ovr the nxt 24 hrs
with mnly VFR and sct-ovc clds genly AOA 120 amsl. Sct tstms poss
ovr Siernev with isold poss ovr fthls, Srn Sac and Nrn San Joaquin
Vlys and hyr elevs of Wrn Plumas and Ern Shasta cntys thru abt 05z
Mon. S-E flow alf bcmg SWly Mon. Lcl Wly sfc wnd gsts to arnd 30
kts poss ovr hyr mtn trrn til 05z, stgr nr stms, and thru Delta
ovngt into Mon.

&&

.STO Watches/Warnings/Advisories...
None.

&&

$$





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