Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PDT Tue Mar 28 2017

...SYSTEM TO BRING PRECIP TO NORTHERN AREAS MIDWEEK...

.24 HOUR PRECIPITATION TOTALS (ENDING MAR 28 AT 500 AM PDT)...

An upper trough moving across the region brought light showers to
portions of srn OR and mainly nrn/cntrl CA/NV.  Amounts on the
nrn/cntrl CA coast were around 0.1" or less except 0.2-0.3" in the
Smith basin.  The cntrl valley saw a few hundredths of an inch on
the eastern side of the valley, with similar amounts above Shasta
Lake.  The upper Klamath basin saw 0.2" or less in the lower
elevations and up to 0.4" in the srn OR Cascades. NE CA picked up
around 0.1" or less, while the Sierra received around 0.15" or less
on the west slope and 0.1" or less on the east side.  Amounts in NV
were generally 0.2" or less except 0.3-0.7" in favored higher-
terrain areas of NE NV.


.METEOROLOGICAL CONDITIONS (SHORT TERM: TUE AM - FRI AM)...

Satellite this morning shows mainly westerly flow over the region,
with the upper jet moving into the Pacific NW. Dry conditions will
continue today and much of Wednesday. Over the next 36-hrs, expect
an upper trough to drop out of the GOA, bringing a frontal system to
the Pac NW with some light to moderate precip. Models hold the front
together long enough to make it into Northern CA, and showers should
behind over the Smith and Upper Klamath Basins during the morning
hours on Wednesday.

The upper low holds together through the day Weds and into Thursday,
as the cold front brings precip to areas north of I-80 through Thurs
am. Trough axis should shift to near the CA/NV border by Thurs
afternoon, and precip should be focused over the Sierra and east
side, and into much of NV. Expect precip to wrap over overnight into
Friday morning. Overall, light to moderate amounts are expected,
heaviest over the Smith and Upper Klamath. Weak dynamics and a
narrow and lackluster moisture plume don`t allow much more to
develop with this system. Expect freezing levels around 7000-ft near
the OR/CA border when precip begins on Wed, quickly lowering to
around 4500- overnight and into Thursday. Freeing levels over the
Sierra should range from around 6000-7000 ft.


.METEOROLOGICAL CONDITIONS (LONG TERM: FRI AM - MON AM)...

On Fri, expect an upper low to be moving east of the forecast area
near the four-corners region.  Expect lingering showers over ern
portions of NV Fri with a mainly nly flow aloft.  Sat looks dry with
ridging building into the region.  Followed the 06 UTC GFS/00 UTC
GEM models for this weekend with the ECMWF looking like more of an
outlier.  Even the ECMWF ensemble mean showed some differences with
the deterministic solution.  The favored solution takes an upper
trough over the region later Sun.  Expect light showers to track
across mainly the far nrn portion of the region Sun into Sun night.


.HYDROLOGICAL CONDITIONS...

Many locations along the San Joaquin are expected to stay above
their monitor levels throughout the forecast period due to upstream
reservoir releases.

The Humboldt is expected to stay above flood stage at Battle
Mountain and Comus through the forecast period due to routed water
from upstream.

As temperatures warm over the next few days, higher elevation basins
in the Sierra are expected to see flows increase some due to
snowmelt, but are expected to remain below monitor levels.


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

KL/JM/KL/BW

$$



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