Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 211056
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
356 AM PDT Mon Jul 21 2014
An upper level disturbance combines with an eastern Pacific
trough over northern California today with morning showers and
the greatest probability for thunderstorms over the northern
mountains. Lingering thunderstorms over mountains Tuesday, then
expect a warming trend Wednesday through the weekend.
.Short Term Discussion (Today through Wednesday)...
An upper wave with the monsoonal moisture continues to spread
northward over the region today while an eastern Pacific trough
pushes southeast into Oregon. The deformation zone stretching from
SE Oregon to NW California acts as the battle ground between the
two systems. A swath of light showers has existed virtually all
night from the Delta to Plumas county and Lake Tahoe with only a
slight drift northward.
The swath of light showers will likely continue to drift
northward this morning and become more unstable with sunshine in
the mix. By this afternoon, isolated to scattered showers and/or
thunderstorms should form over the northern portion of the
forecast area from Sierra/Plumas to Tehama/Shasta counties.
Redding and Red Bluff areas have the potential to see some
isolated shower/thunderstorm activity. The increased cloud cover
for at least part of the day will likely keep temperatures cool.
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
.Extended Discussion (Thursday through Monday)
Upper trough forecast 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. The SW US high is then forecast to gradually build
northwestward back into NorCal for a warming trend. 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, we will keep the forecast
dry. JClapp - part deux
General VFR conditions with a narrow band of mid level clouds and
light rain showers currently located between KSUU...KSAC...KBLU to
KTRK. This will gradually drift northward to the central
Sacramento Valley by around 16z...the northern Sacramento Valley
by around 19z with ISOLD TSRA developing there and the adjacent
mountains, SCT TSRA eastern Shasta County. ISOLD TSRA also possible
along and east of the Sierra crest 18-24z. Lcl SW gusts to around
20 kts possible over ridges... 30 kt through the Delta. EK