Weather Alerts
Hydrologic Outlook issued February 10 at 4:31PM PST by NWS San Francisco CA
ESFMTR
* WHAT...Unsettled weather is forecast to return to the region
this week. The first round of rain is progged to impact areas
mainly south of the Golden Gate Tuesday night into Wednesday.
Rainfall amounts will range from 0.10"-0.25" over inland and
valley locations to 0.25"-0.75" along the coastal mountain
ranges. Highest precipitation is forecast over the Santa Cruz
Mountains and Santa Lucia range. A stronger and significantly
wetter system will move into the area Wednesday night into
Thursday. Models agree that this system will pack a bigger punch
with strong upper level jet support and ample moisture
associated with an atmospheric river that is taking aim at the
Central Coast. This storm will not only bring heavy rainfall but
also potentially damaging winds. Given the current location of
the moisture axis and dynamic features, this system will
generally favor areas from about San Francisco southward across
the Central Coast. Overall good news in terms of annual rainfall
since southern areas are a bit behind the curve so far this
water year (since Oct 1). An interesting tidbit to include; the
Central Coast watershed which runs along the coast roughly from
Monterey to Arroyo Grande is about 4.37" below normal for the
water year to date. The current forecast for that watershed by
the end of the week is about 3"-6". There is a slight chance
(at least 15%) of rainfall rates resulting in flash flooding
conditions area-wide on Thursday. It is likely that there will
be more of a focus as the event nears and more information about
convective rainfall rates becomes clear from high res guidance.
The system does appear to be rather progressive and should move
through the region relatively quickly, thus hindering any
increase in the probability of flash flooding for now. Guidance
keeps this vigorous wave open and embedded in the flow, so there
is relatively low stall potential. As far as rainfall totals
go, the North Bay will still see respectable totals in the 2"-4"
range, the greater Bay Area will see a range of 1.5"-3" (less
in the rainshadowed South Bay, more along the peninsula), 4"-6"
and locally up to 8" in the Santa Cruz Mtns, 2"-3" across the
Central Coast counties, and 3"-6" along the Big Sur Coast,
locally up to 8".
* WHERE...Bay Area and Central Coast. Latest model guidance
suggests the Bay Area and Central Coast will receive the
greatest accumulation of precipitation with the heaviest
rainfall expected over the Santa Cruz Mountains and Santa Lucia
range.
* WHEN...Tuesday night through Thursday. Light to locally
moderate rainfall expected Tuesday night into Wednesday.
Moderate to locally heavy rain expected Wednesday night into
Thursday.
* ADDITIONAL DETAILS...In addition to the moderate rainfall and
localized ponding of water in low-lying or poorly drained areas,
such as freeway offramps. Locally strong and gusty winds may
result in downed trees, and potential power outages.
Confidence is high that we will receive rainfall from these
systems however, confidence is moderate with respect to the exact
location and timing of the most intense rainfall. Details
regarding this storm will likely change as the system nears.
Therefore, stay tuned to the latest forecast for the most up to
date weather information.