Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 191104

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
404 AM PDT Mon Mar 19 2018

Dry weather will continue over the region through Tuesday morning.
A storm system will bring generous precipitation to much of the
central California interior from late Tuesday into Thursday. A
break from wet weather is expected Thursday night through


Big change now looming out over the Pacific as an Upper Low sits
between the West Coast and Hawaii. Water vapor satellite imagery
is showing a well defined circulation able to wrap moisture around
it that will find its way toward California. In the meanwhile,
weak ridging over the West Coast will provide quiet conditions for
the next 24 to 36 hours across the region. Skies are expected to
clear this Monday and allow temperatures to reach seasonal values.
Yet, this will be short-lived as moisture from an atmospheric
river (Hawaiian Pineapple Express) surges northeastward and into
the region within the next 48 hours (between Tuesday night and
Wednesday morning). Currently, satellite blended total precip-
water imagery shows the head of the atmospheric river`s surge
still at about 800 miles southwest of Los Angeles and is trending
toward a Southern/Central California trajectory. Therefore, after
one to two more days of dry weather, the region is store for a
heavy precipitation event with models showing high confidence
Central California experiencing a good hydrologic (possible
localized flooding) during the mid-week period.

Again, models are showing higher confidence in having a good
precipitation event start late Tuesday as precipitation returns to
the region in the form of a possible Atmospheric River. While
models still showing some uncertainty in the position of the upper
low off the west coast toward next Tuesday, they still lean toward
developing a closed low circulation some 800 miles West of San
Francisco that will support the eastward surge of subtropical
moisture into the region. Model Integrated Water Vapor Transport
and Standardized Anomaly Analysis still support the arrival of
subtropical moisture into the region later on Tuesday.
Standardized Anomaly Analysis even has up to 4 standard deviations
above climatological normal with precip-water values above 1 inch
a possibility late Tuesday into Wednesday. Furthermore, Ensemble
model precip-water return interval analysis is showing this event
as a 1 day in every 5 to 10 years which makes it a not so common
event. Therefore, confidence is high that significant
precipitation will return to the area around the mid-week period
before models place a stronger ridge pattern over the west around
next weekend. Therefore, before the ridge pattern, the district
will remain unsettled with precipitation potential through at
least the end of the week. One thing to note is a majority of the
event will be ahead of the cold front that will push through later
this week. Before that occurs, warm moist air will invade the
region producing very high snow levels as rain may fall at
elevations below 7000 feet.


VFR/MVFR conditions will prevail for the next 24 hours.





The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit for additional information
an/or to provide feedback.


.HNX Watches/Warnings/Advisories...



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