Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 231213
Area Forecast Discussion
National Weather Service Sacramento CA
413 AM PST MON NOV 23 2015
DRY AND MILD WEATHER WILL CONTINUE THIS AFTERNOON. PATTERN CHANGES
TONIGHT AS A COLDER PACIFIC STORM BRINGS PRECIPITATION LATE
TONIGHT THROUGH WEDNESDAY. DRIER WEATHER EXPECTED THANKSGIVING.
Today through this afternoon will be the last chance to enjoy the
mild, dry weather before the pattern changes tonight. From Tuesday
onward, daytime highs will be below normal.
Have not made any major changes to the forecast package in regards
to the upcoming storm system that will impact NorCal late tonight
through Wednesday with some lingering Sierra showers possible into
Did adjust snow amounts slightly after using the lastest CNRFC
guidance. The most notable difference is that it slightly lowered
snow amounts for the mountains in Shasta County (Ex - Interstate 5
corridor in Shasta only shows a max of 2 inches) and it raised
snow amounts a bit across parts of the Sierra. Overall, the
general amounts expected with this storm have not varied that much
with the latest guidance and the Winter Storm Watch is still in
effect. Main message is that any holiday travelers, especially
Tuesday & Wednesday should take caution as winter driving
conditions will impact mountain travel.
Snow accumulations expected with this storm: 12 to 18 inches along
the crest...6 to 12 inches above 4000 feet....2 to 6 inches above
2000 feet for the Motherlode with...1 to 4 inches expected for the
Northeast Foothills. Locally snow may fall as low as 1500 feet.
The tricky part of the forecast was whether or not to mention
thunderstorms on Tuesday and Wednesday. Now that the track of the
storm stays over or near NorCal, this could mean that cloud cover
will prevent any afternoon thunderstorm development. The NAM model
Modified Total Totals index for instability shows possibility for
thunderstorms Tuesday & Wednesday, but the MU CAPE index isn`t as
supportive. Have not officially added them into the forecast since
cloud cover may be the big inhibitor.
The center of the storm will be east of our area by Wednesday
afternoon, but we expect snow showers over the Sierra to linger
into Thursday. Otherwise, the rest of interior NorCal will be dry
for Thanksgiving with valley highs in the 50s, mountains in the
20s (near Sierra crest) to 40s (foothills).
.EXTENDED DISCUSSION (Friday THROUGH Monday)
The cold airmass and light wraparound flurries over the Sierra
will linger into the weekend as the system slowly shifts east.
Temperatures will remain quite cool with the potential for
widespread near freezing temperatures in the Valley during the
late night and morning hours. Temperatures in the mountains and
mountain valleys could be quite cold dropping to teens and single
digits. A limiting factor for cold morning temperatures will be
northerly winds, which could keep the atmosphere more mixed and
warmer, along with some cloud cover.
Uncertainty remains for early next week as there is very little
consistency in model solutions at this time.
SWly flow alf as upr low movs thru tda. Genly VFR conds ovr Intr
NorCal nxt 24 hrs exc lcl MVFR/IFR in BR/FG in Cntrl Vly fm vcnty
KMYV Swd into SJ Vly til arnd 18Z-20Z. Sfc wnds genly lgt.
Winter Storm Watch from Tuesday morning through Wednesday
morning for Motherlode-West Slope Northern Sierra Nevada-Western
Plumas County/Lassen Park.