Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 181119
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
319 AM PST THU DEC 18 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE REGION TODAY BEFORE ANOTHER
WEAK STORM SYSTEM BRINGS CHANCES FOR RAIN AND SNOW FRIDAY THROUGH
SATURDAY. HIGH PRESSURE WILL THEN BUILD SUNDAY THROUGH THE FIRST
PART OF NEXT WEEK.

&&

.SHORT TERM...
WEAK STORM SYSTEM ACROSS NORTHERN CALIFORNIA TONIGHT HAS FALLEN
APART AS IT APPROACHES THE SIERRA. FORECAST MODELS AS WELL AS
OBSERVATIONS INDICATE THAT LITTLE TO NO PRECIPITATION IS LIKELY TO
OCCUR ALONG OR EAST OF THE CREST. SNOWFALL AMOUNTS MAY REACH UP
TO 2 INCHES ALONG THE SIERRA CREST, IF WE ARE LUCKY, BUT OTHERWISE
ONLY WEAK SNOW SHOWERS ARE EXPECTED. WHILE AMOUNTS ARE EXPECTED
TO BE LIGHT, TRAVEL MAY BECOME SLICK OVERNIGHT INTO THIS MORNING
FOR THE SIERRA PASSES, ESPECIALLY DONNER AND ECHO SUMMITS AND
ALONG HIGHWAY 89. THIS WAVE MOVES EAST THIS AFTERNOON WITH A FEW
LINGERING SHOWERS DURING THE DAY. A BRIEF PERIOD OF RIDGING
DEVELOPS LATE THIS EVENING.

THE NEXT SYSTEM DROPS INTO THE REGION ON FRIDAY AND SATURDAY WITH A
WEAK COLD FRONT PUSHING ACROSS THE SIERRA AND WESTERN NEVADA LATE
FRIDAY MORNING. THE BEST DYNAMICS AND FORCING WITH THIS SYSTEM WILL
REMAIN NORTH OF NEVADA, ACROSS OREGON, BUT THE SOUTHERN PORTION OF A
WEAK COLD FRONT WILL BRUSH THROUGH NORTHERN NEVADA. PRECIPITATION
WILL BEGIN ACROSS NORTHEAST CALIFORNIA INTO NORTHERN WASHOE COUNTY
MID MORNING FRIDAY AND THEN SAG FURTHER SOUTH WITH THE WEAKENING
FRONT INTO THE CENTRAL BASIN AND RANGE AND TO THE INTERSTATE 80
CORRIDOR. FORECAST MODELS CONTINUE TO SHADOW MUCH OF THE SIERRA
FRONT INCLUDING RENO/CARSON CITY, BUT LEFT IN LOW CHANCES FOR
SHOWERS DURING FRIDAY AFTERNOON. ALTHOUGH THE SYSTEM QUICKLY EXITS
EAST ON FRIDAY EVENING, THERE IS QUITE A BIT OF MOISTURE AND UPSLOPE
FLOW BEHIND IT THAT MAY ALLOW SHOWERS TO CONTINUE ALONG THE SIERRA
FROM TAHOE NORTHWARD INTO NORTHERN LASSEN AND NORTHERN WASHOE
COUNTIES. SNOW LEVELS WILL BE AROUND 4500-5500 FEET NORTH OF HIGHWAY
50 WITH 5500-6500 FEET SOUTH OF THERE. TRAVEL IMPACTS ALONG WITH
SLICK ROADS WILL REMAIN A POSSIBILITY AS SHOWERS MOVE ACROSS THE
REGION.

BY SATURDAY AND SUNDAY A DIRTY RIDGE BUILDS INTO THE WEST WITH WARM
AIR ADVECTION PRECIPITATION POSSIBLE ACROSS NORTHERN CA/NV. THE JET
RIDING OVER THE TOP OF THE RIDGE MAY PRODUCE ENOUGH LIFT ALONG WITH
THE MOISTURE TO PRODUCE SOME SHOWERS ACROSS THE SIERRA, BUT
DIFFERENCES IN JET PLACEMENT BETWEEN THE MODELS MAKE IT DIFFICULT TO
NAIL DOWN WHERE BEST PRECIPITATION CHANCES WILL BE AT THIS TIME.
KEPT THE SLIGHT CHANCES FOR PRECIPITATION AREA WIDE TO COVER THE
POSSIBILITY OF SHOWERS AS FAR SOUTH AS MONO AND MINERAL COUNTIES.
WEISHAHN

.LONG TERM...SUNDAY THROUGH THURSDAY (CHRISTMAS DAY)...

THE UPPER LEVEL RIDGE STRENGTHENS OVER CALIFORNIA SUNDAY THROUGH
TUESDAY. THIS RIDGE LOOKS "DIRTY" WITH ABUNDANT CLOUDS/MOISTURE
NORTH OF RENO. WARM AIR ADVECTION WILL WARM UP TEMPERATURES IN THE
SIERRA, ALTHOUGH LIGHT WINDS AND LOW SUN ANGLES WILL LIMIT MIXING IN
THE LOWER VALLEYS OF WESTERN NEVADA EARLY NEXT WEEK WITH INVERSIONS
LIKELY. THIS MAY LEAD TO DEGRADED AIR QUALITY THROUGH SUNDAY THROUGH
WEDNESDAY.

THE 00Z GFS/ECMWF/GEM AND ENSEMBLES CONTINUE SHOW AN INSIDE SLIDER
DROPPING THROUGH THE PAC NW AND INTO THE GREAT BASIN LATE ON
CHRISTMAS EVE AND POSSIBLY INTO CHRISTMAS MORNING. THIS IS THE THIRD
DAY IN A ROW THAT WE`VE SEEN THE ECMWF SHOW THIS FEATURE ON
CHRISTMAS EVE NIGHT, VERY GOOD RUN-TO-RUN CONSISTENCY FOR 7 DAYS
OUT. THE GFS ENSEMBLES STILL SHOW QUITE A BIT OF SPREAD IN THE
FRONTAL TIMING AND EAST-TO-WEST TRACK OF PRECIP. NONETHELESS, THE
DECENT MODEL AGREEMENT THIS FAR OUT IS LEADING TO A MODERATE
FORECAST CONFIDENCE OF A STRONG FRONTAL PASSAGE LATE TUESDAY
(CHRISTMAS EVE) WITH MUCH COLDER TEMPERATURES ON CHRISTMAS DAY.
WE`LL HAVE TO WATCH THIS COLD FRONT VERY CLOSELY FOR POTENTIAL OF
SEEING SNOW ON THE VALLEY FLOORS ON CHRISTMAS EVE NIGHT. HOON

&&

.AVIATION...

RIDGE OF HIGH PRESSURE BUILDS OVER THE REGION WITH DRY CONDITIONS
THROUGH TONIGHT. ANOTHER COLD FRONT MOVES THROUGH THE REGION FRIDAY
WITH POTENTIAL FOR MOUNTAIN SNOW AND REDUCTIONS TO CIG/VIS. HOON

&&


.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&

$$

FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/RENO (ALL LOWER CASE)





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