Flash Flooding and Heavy Snow in California, March 5 to 6, 2019

Area Forecast Discussion
National Weather Service Las Vegas NV
945 PM PST Tue Mar 5 2019

.SYNOPSIS...The incoming Pacific Storm still looks like it will
direct the main plume of moisture across Inyo County and south
central Nevada tonight and Wednesday. This will also bring strong
gusty winds Wednesday over northwest Arizona. Another, colder storm
system will impact the region Friday with less threat of heavy
precipitation but lower snow levels.
&&

.UPDATE...The latest satellite and radar trends indicate the system
is coming in about as expected...with the Southern Sierra currently
in the path of the primary deep moisture plume. A predecessor more
diffuse moisture band was moving across far Southeast California and
Southern Nevada this evening. Much of the precipitation spreading
into Clark County has been intercepted by the Spring Mountains where
up to a half-inch of rain has fallen in Kyle Canyon. The far west
side of the Vegas Valley has received up to 0.04" and trace amounts
have fallen over other parts. More extensive upstream showers over
northern San Bernardino County should move into Clark County between
1 AM and 4 AM for increasing shower coverage. Gusty west winds 25 to
35 mph that developed this evening are forecast to drop off after 10
PM though localized brief gusts 20-30 mph may still be possible near
showers overnight. The WX and Wind grids were updated based on these
latest trends, but only minor changes were needed to the going
forecast.
&&

.PREV DISCUSSION...
232 PM PST Tue Mar 5 2019

.SHORT TERM...through Friday night.

Changes: Expanded the Flash Flood Watch to include northwest San
Bernardino County, specifically Highway 178, Trona and Searles
Valley in the far northwest corner.

Issued a Wind Advisory for Mohave County Wednesday between 10 am
MST - 7 pm MST.

So far, light rain and snow confined to the southern Sierra and Owens
Valley. Rainfall in the Owens Valley between a tenth and two tenths
of an inch. Confidence high that center of AR will eventually
penetrate further into southwest Inyo County/far northwest San
Bernardino County this evening. Moisture axis will continue
northeast across Death Valley NP, southern Nye County/Spring Mtns,
and Lincoln County. QPF in that area will run between 0.50-1.00",
locally 2+ in the mountains. QPF values drop off quite a bit as one
goes southeast through Clark, eastern San Bernardino and Mohave
Counties. Southwest winds increase across Mohave County Tuesday
morning with 40-50 mph gust possible.

Precipitation will turn more showery Wednesday afternoon as upper
trough lifts northeast across the southern Great Basin. Next colder
trough still slated to cross the region Thursday night and Friday.

.LONG TERM...Saturday through Monday.

A brief period of ridging is progged for Saturday before the next
low pressure system approaches the western seaboard. There is pretty
good agreement in the longer range for this low to slide quite a bit
farther south than many other lows we have experienced this season.
All deterministic solutions currently pass the low center south of
the latitude of Las Vegas with the northernmost solution being the
ECMWF, which is also the wettest for early next week. This evolution
will need to be monitored as a more southward migration of the low
should translate to a drier forecast and vice versa. Moving into the
late week next week, there still appears to be pretty good agreement
in ridge amplification across the west coast and a trend towards
shifting the seemingly endless train of lows and AR events farther
north.
&&

.AVIATION...For McCarran...Light showers around the terminal area
and cloud bases around 8-10 kft AGL can be expected overnight then a
more concentrated band of showers with ceilings around 5 kft AGL
will move across the Vegas Valley generally between sunrise and noon
Wednesday. Gusty southwest to west winds around 25 knots will occur
through the afternoon with clouds gradually diminishing. Expect
turbulence hazards through the period with icing potential in the 8-
10 Kft layer through mid-morning Wednesday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Rain will make its way from west to east across the
region through Wednesday morning, with the most significant band
from China Lake, CA to Ely, NV through midday Wednesday. The lowest
ceilings are expected under this band, mainly for KBIH, with CIGs
around 3-5 Kft, 5-10 Kft for the rest of the region. Winds will
generally favor south to southwest across the region with speeds of
10 to 20 knots. Expect turbulence through the TAF period, with icing
hazards around the 8-10 Kft layer associated with the rain showers.
&&

.SPOTTER INFORMATION STATEMENT...Spotter activation is not
anticipated at this time, however, spotters are encouraged to report
any significant weather according to standard operating procedure.
&&

UPDATE/AVIATION...Adair
SHORT TERM...Pierce
LONG TERM...Boucher

&&

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