Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Sacramento California
322 PM PDT Mon Sep 16 2019
lingering showers and thunderstorms into this evening, then drier
and warmer on Tuesday. Another weather system is forecast to bring a
little rain Tuesday night and Wednesday. Dry weather and warm
temperatures return late this week.
frontal precip exiting our cwa's southeast corner at press time, after
some decent quantitative precipitation forecast numbers over the nrn mtns and west S lope Sierra. A
general swath of half inch to one inch amounts were recorded with
local amounts over an inch (up to 1.44" Bucks Lake and 1.60" at
hillcrest). The convective nature of the showers caused the snow
level to drop to the pass on Donner Summit where some snow did
begin to accumulate around midday. This rain/snow should drop the
ercs below average alleviating fire concerns for about a week, in
spite of the modest nly winds forecast on Thu.
With the upper trof axis moving through the area this afternoon,
energy on the backside of it is forecast to move over norcal this
afternoon. Satellite shows the cluster of lightning strikes off the
north coast/or coast associated with this feature moving inland and
isolated strong cells (>40 dbz) are possible over our Shasta co this
afternoon. In the Post-frontal environment, steep lapse rates could
result in the potential for hail.
Norcal will be in between wx systems on Tue with dry wx and modest
warming. Max temps will still be some 7 to 15 degrees below normal.
A second trof, currently over the goa (gulf of ak), is forecast to
move into the region late Tue nite and Wed. This system is forecast
to be not quite as cold and not as wet, but given a similar
trajectory to the current system the quantitative precipitation forecast may be underdone. The sref
and emc gefs quantitative precipitation forecast plumes are very unimpressive with amounts of only a
few hundredths and even the highest members less than one-quarter
Given the trajectory and forecast instability progs for this second
trof we have expanded the areal coverage of T-storms for the Wed
afternoon and evening forecast, and also in deference to the Storm Prediction Center
outlook as well.
Drier wx is forecast on Thu over most of the area, except over the
Sierra where cyclonic flow will keep a chance of showers in the
forecast for that area. A moderation in temps is expected with the
transition to nly winds. Jhm
Extended discussion (friday through monday)...
A warming trend is expected by the end of the week in response to
building ridge along the West Coast. Look for valley highs in the
mid 80s to low 90s, and mostly mid 50s to mid 70s over the
mountains. An upper level trough moving into the pacnw on Sunday
could bring slightly cooler temperatures. Locally breezy northerly
winds possible Friday, as well as early next week. No precipitation
is expected through the period.
areas of MVFR conditions vicinity showers and thunderstorms
through 03z Tuesday. Local surface wind gusts 15-20 kts Central
Valley thru 01z. Areas southwesterly surface wind gusts 25-35 kts
higher elevations northern Sierra Nevada, mainly south of I-80
through 00z Tuesday. Light and variable winds overnight.