Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 252150
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
250 PM PDT TUE OCT 25 2016
.SYNOPSIS...Weak high pressure will build over the region today
and Wednesday before another Pacific weather system moves in
Thursday afternoon and Friday bringing another chance of rain and
.DISCUSSION...Upper ridge over the Great Basin is the main
weather feature over the southwestern CONUS today. GOES high
density wind indicating Southwest flow prevailing over Central CA
while WV is showing a moisture fetch with embedded shortwave
impulses streaming cross Norcal. Radar composites have been
indicating some echos as far south as Merced and Mariposa
Counties, but there have not been any reports of measurable
precipitation in our CWFA as of 1300 PDT. While Visible imagery is
indicating some mid level clouds north of Fresno County. After a
relatively cool morning thanks to clear skies overnight from
Fresno County southward, temperatures have rebounded nicely is
providing for another afternoon with above normal readings.
12Z WRF is indicating the Great Basin ridge will amplify tonight
and Wednesday shifting the moisture fetch further north and
provide our area with a mostly sunny day on Wednesday. Rises in
heights and thicknesses will result in another day with much
warmer than normal temperatures across our area on Wednesday. The
more significant impact though is that an incoming Pacific trough
will pull up some deep tropcial moisture from Hurricane Seymour
currently centered near 16N/116W and progged to track northward on
Wednesday and Thursday over open water. The trough is expected to
push into Norcal on Thursday then push inland Thursday Night
spreading widespread precipitation across our area. While there
is fairly high confidence in the timing of this system,
confidence in how much rainfall we receive is low due to the
uncertainty on how much moisture from Seymour will be picked up
by this system. At this time the Central San Joaquin Valley might
pick up a half inch of rain from late Thursday afternoon through
Friday morning while portions of the Southern Sierra Nevada
receive over an inch of liquid precipitation. With most of the
moisture with this system being tropical in nature and the
prevailing airmass being warm snow levels will be close to 10000
feet for most of this event. Showers will be possible throughout
our CWFA on Friday with the upslope favored Sierra Crest being the
most favored area. Temperatures will remain mild for late October
with a modified tropical airmass remaining in place.
The medium range models agree with a warm southwest flow
continuing across our area on Saturday which will provide for one
more mild day although a slight chance of showers cannot be ruled
out as some WAA takes place ahead of another system progged to
push through CA on Sunday. This colder system will bring a chance
of precipitation to our area on Sunday and Sunday night with snow
levels expected to be significantly lower than with the Thursday
Night storm and possible bring possibly impact the Tioga and
Kennedy Passes. This will be followed by a secondary upper low
pushing across norcal on Monday. The operational GFS is further
south than the ECMWF and many ensemble members, and is indicating
much better chances of precipitation for our area with these
systems. While the bulk of the moisture from this system is still
progged to remain north of our area, a slight chance of showers
cannot be ruled out. The ECMWF is showing another system pushing
across central CA Tuesday Night and Wednesday while the GFS has
been indicating this midweek system will remain north of our area.
Confidence remains low in any one model solution for this system
as well, but the potential exists for more rainfall toward the
middle of next week mainly from Fresno County northward.
.AVIATION...VFR conditions can be expected for the central
California interior during the next 24 hours.
.AIR QUALITY ISSUES...None.
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is low.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.