Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 191924

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PST Mon Feb 19 2018



A very cold airmass has descended over the region this morning,
bringing scattered showers and low snow to many foothill and
mountain locations along the coast and the Sierra. Scattered showers
have also moved through portions of Srn CA, to the MX border. With
the main front well to the south of the region, expect precip to
quickly wrap up this afternoon, leaving very cold temperatures in
its wake. Expect overnight lows to be some of the coldest seen so
far this season, in fact.

Expect an upper low to drop down along the west coast on Tuesday,
and how far offshore it remains will determine how much precip the
region experiences as a result. Models are flopping a bit with the
answer to this, and confidence is low for Tuesday evening through
Wednesday. For now, have some light precip along the coast, with
some showers possible over the Sierra crest on Wednesday.

An upper trough should follow quickly on the heels of the coastal
low. Another inside slider, the system has a meager moisture feed,
but good dynamics and seems to make good use of what`s left behind
through the week. Looks like a similar situation to what we`ve seen
over the last 24-hrs, with cold temperatures, and mainly precip over
far Nrn CA and higher terrain elsewhere. This system does have a
better chance of producing valley precip though, and the current QPF
forecast reflects that.

Expect the trough to push eastward by Friday morning, with a quick
break before another potential system marches down the coast on
Saturday. This is looking to be a more traditional cold frontal
system, with precip picking up on the North Coast Saturday morning,
expanding into the rest of NorCal through the day. The GFS is deeper
and more aggressive timing wise than the EC, and currently the QPF
reflects a compromise solution between the two extended models.


Runoff is expected to be minimal with cold temperatures and light
precipitation in the forecast.

All forecast points are expected to remain below monitor levels for
the next five days.

More information on the CNRFC website at www.cnrfc.noaa.gov



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