Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 271049
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
249 AM PST Mon Feb 27 2017
.SYNOPSIS...A trough of low pressure will move southward across
the region today and tonight bringing a chance of precipitation.
A warming and drying trend will then take place between Tuesday
and next weekend as high pressure builds over the region.
.DISCUSSION...Radar shows increasing coverage of shower and snow
shower activity from mainly Fresno County northward early this
morning. Webcam images from the Shaver Lake area indicate some
light snow has fallen under the 20-30 dbz echoes. Meanwhile, water
vapor satellite imagery shows a weak frontal boundary stretching
from near Reno to north of San Francisco and farther upstream the
center of low pressure and cold pool now moving into far Northern
California. Of note is the large area of moisture to the west and
Southwest of the SoCal coast showing a trajectory into California.
Given the trajectory of these features a continued increase in
shower activity will occur through the day as the colder air
arrives this afternoon. As to just how cold the air and
associated snow levels will be is well noted on the latest
sounding from Medford where the freezing level was about 1500 feet
agl or 2700 feet mean sea level. Although some moderation of the
airmass will occur before it reaches the Central California
interior, snow levels to 3000 feet seem likely and some snow could
fall briefly to 2500 feet in heavier cells.
In the shortest of terms, the HRRR model increases shower coverage
through mid morning and then attempts to bring a consolidated
band of precipitation through the San Joaquin Valley around 9 am,
finally showing diminishing showers during the afternoon. This
scenario seems plausible however other models keep at least some
chance of showers going through sunset and this seem logical.
Additionally, the HRRR keeps the southwest moisture feed limited
to areas from near Orange County to east of Barstow and as of now
it doesn`t look to threaten even the Kern County Desert.
By this evening the only location that should see precipitation is
the Kern County mountains with the north and northwest facing
slopes realizing the best chances in the cold, unstable northwest
flow. Again, snow levels should be below 3500 feet a potentially
down to 3000 feet and this may cause some issues over I-5 over the
Grapevine as will as Highway 58 over Tehachapi Pass. Accumulation
up to an inch or so is possible however just where the snow
showers target is difficult to nearly impossible to pin point at
this juncture. Pops are maximized near the Grapevine this evening
and this area will need to be watched during the day to see if the
threat of any heavier snow is realized.
By later tonight all of the moisture moves east and the trough of
low pressure is progged to move east leaving the area in a
relatively dry northwest flow. From Wednesday through Friday
models build high pressure out along 20N/130W and this keeps the
storm track will to the north for the next several days with
warming and dry conditions.
Areas of MVFR conditions in precipitation with local IFR conditions
possible in heavier showers over the Sierra Nevada. Precipitation
expected to spread southward into Kern County between 12Z and 15Z
this Monday morning. Otherwise, VFR conditions will prevail across
the central CA interior during the next 24 hours.
.AIR QUALITY ISSUES...
On Monday February 27 2017... Fireplace/Wood Stove Burning Status
is: No Burning Unless Registered in Fresno... Kern... Kings and
Further information is available at Valleyair.org
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
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.