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Area forecast discussion...corrected 
National Weather Service Medford or
339 am PST sun Feb 1 2015

Updated aviation and marine discussions and added some wind
highlights for next few systems.

Discussion...today represents a transition day towards an active
weather pattern after weeks of generally stagnant weather. A weak
frontal system will move through the area today...bringing
generally light rain to the area...focused along and north of the
Umpqua Divide and west of the Cascades. This front will mix up the
atmosphere just enough to end the air stagnation advisories by
this afternoon. A second...more potent cold frontal boundary will
bring an inch of rain to the Curry County coast...a quarter inch
to most west side valleys...and a tenth of an inch of rain to the
east side. These precipitation amounts from Sunday night through
Monday night will be virtually all rain...with snow levels at 7500
feet and higher. Additionally...winds will become
gusty...especially east of the Cascades Monday afternoon with
700mb flow reaching 50kt from the west on both the NAM and GFS
models.

This boundary will stall Monday night over northern California...and
then get re-energized as another shot of significant moisture
arrives Tuesday morning...waving north and bringing moderate to
heavy rain to the coast and higher terrain west of the Cascades.
We have favored the heavier rain solutions of the NAM and GFS for
this period...though have tempered them a little by blending some
of the drier European model (ecmwf) solution. Winds will also be significant with
this system...with 700mb winds peaking at 55kt per the GFS...so
east side winds will become very gusty and would not be surprised
if advisory criteria are met...or more. Ridging builds overhead
Wednesday...and this should be the driest day of the week.
Temperatures could get unseasonably warm in valleys if fog does
not develop...and dense fog looks unlikely given that strong
inversions really won't have time to set up behind the front.

Thursday into Friday has the potential of being a heavy rain and
strong wind event. Gefs-based tools that help gauge how significant
a rain event will be are showing good potential for a once-in-ten-
year type event for the coast in terms of rainfall. Rivers are
currently well below normal in terms of streamflow...so antecedent
conditions do not favor flooding...but do believe there is still
some potential for coastal river or stream flooding if the very wet
GFS solution verifies. Certainly there will be marine impacts with
gales and possibly storm force winds over the waters Thursday
into Friday...and gusty winds will impact the coast...high
terrain...Shasta Valley...and east side during the same timeframe.



&&

Aviation...based on the 01/12z taf cycle...mainly VFR conditions
are expected this morning with isolated MVFR visibilities in
patchy fog for inland west side valleys through 16z. Then an
incoming weak frontal system will bring showers and some west side
MVFR ceilings through the day, mainly coast and Umpqua basin. Also
expect partial terrain obscurations Cascades west today. Then this
evening and tonight, MVFR ceilings are expected to become more
widespread as areas of rain continue over the area. Also expect
widespread mountain obscurations to develop this evening into
tonight.



&&

Marine...updated 355 am PST Sunday, February 1, 2015...light winds
will become southerly this morning as a weak frontal system pushes
in from the west with periods of rain. Tonight through Monday
moderate west swell will build into the waters. A somewhat stronger
front will move across the waters on Monday and is expected to
bring gusty southerly winds, reaching Small Craft Advisory levels,
and steep seas. Unsettled conditions continue till midweek. Then a
strong storm system may bring an extended period of south gales into
the waters on Thursday and Friday. The enp model continues to show
the potential for seas of 15 to 20 feet developing late Thursday into
Friday due to wind seas and fresh south to southwest swell. /Cc



&&

Mfr watches/warnings/advisories...
or...air stagnation advisory until 1 PM PST this afternoon for
orz023-024-026-616-620-622.
Air stagnation advisory until 1 PM PST this afternoon for
orz029>031-623>625.

California...none.

Pacific coastal waters...none.

$$

Nsk/nsk/sbn

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