Flash Flood in California, October 18, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
250 AM PDT SUN OCT 18 2015

.SYNOPSIS...

LOW PRESSURE OVER NORTHERN CALIFORNIA WILL KEEP SHOWER ACTIVITY
ACROSS THE REGION TODAY WITH ISOLATED THUNDERSTORMS POSSIBLE.
TEMPERATURES WILL COOL OFF TO NEAR SEASONAL NORMALS BEFORE
WARMING AGAIN NEXT WEEK.

&&

.SHORT TERM...

THE CORE OF AN UPPER LEVEL CLOSED LOW IS CURRENTLY MOVING ACROSS
NORTHERN CALIFORNIA. THIS IS SPARKING OFF A LINE OF SHOWERS AND
THUNDERSTORMS ACROSS THE WEST SLOPES OF THE SIERRA THROUGH SONORA
PASS AND PORTIONS OF THE TAHOE BASIN. THIS CONVECTIVE LINE MAY
IMPACT TRAVEL ACROSS SONORA PASS THIS MORNING WITH SMALL HAIL AND
SNOWFALL POSSIBLE AS THE STRONGER CELLS DRAG SNOW LEVELS TO NEAR
PASS LEVEL. ON TOP OF THE DEVELOPING SHOWERS AND STORMS THIS
MORNING, AREAS OF FOG HAVE DEVELOPED AS A RESULT OF RECENT
RAINFALL AND BREAKS IN CLOUD COVER. AREAS NEAR TRUCKEE ARE
REPORTING VISIBILITY NEAR 1/4 MILE WITH AREAS OF FOG ALSO EVIDENT
AROUND MINDEN, CARSON CITY, BOGARD, AND THE NEAR THE INTERSECTION
OF HWY 36/44 WEST OF SUSANVILLE.

FOR TODAY, SIMILAR CONDITIONS TO YESTERDAY ARE EXPECTED AS THE LOW
PROVIDES WIDESPREAD AREAS OF SHOWERS WITH EMBEDDED THUNDERSTORMS.
THE BEST CHANCES FOR PRECIPITATION WILL SHIFT A LITTLE EASTWARD
TODAY WITH HIGHER CHANCES AND AMOUNTS EXPECTED ACROSS EASTERN
PERSHING AND CHURCHILL COUNTIES. ACCUMULATION AMOUNTS OF
0.5-0.75" ARE POSSIBLE IN THIS REGION WITH GENERALLY UNDER 0.25"
ACROSS FAR WESTERN NEVADA AND THE SIERRA. LOCALLY HEAVIER AMOUNTS
ARE ALWAYS POSSIBLE IN THUNDERSTORM ACTIVITY.

THE LOW WILL CONTINUE TO TRACK EASTWARD MONDAY AND TUESDAY WHICH
WILL BEGIN TO END SHOWERS ACROSS THE SIERRA MONDAY AFTERNOON WITH
LINGERING ACTIVITY REMAINING OVER EASTERN CHURCHILL AND PERSHING
COUNTIES THROUGH MONDAY EVENING. TEMPERATURES WILL BE SEASONABLE
TO START THE WEEK WITH WESTERN NEVADA'S HIGHS REMAINING IN THE MID
60S AND SIERRA VALLEYS STAYING IN THE MID TO UPPER 50S. FUENTES

.LONG TERM...WEDNESDAY THROUGH SATURDAY...

MEDIUM RANGE OPERATIONAL MODELS AND MANY OF THE GEFS ENSEMBLE
MEMBERS ARE STILL SUFFERING FROM AN OVERALL LACK OF RUN TO RUN
CONSISTENCY...SO CONFIDENCE IN ANY MODEL SOLUTION REMAINS ON THE LOW
END OF THE SPECTRUM. A FEW CHANGES WERE MADE TO THE EXTENDED
FORECAST THIS CYCLE...MAINLY TO TAKE POPS OUT OF THE FORECAST FOR
FRIDAY AND SATURDAY BASED ON SOME SLIGHT AGREEMENT BETWEEN THE
MODELS FOR THIS CYCLE ONLY. BUT...AS STATED...THE MODELS DO NOT SHOW
MUCH RUN TO RUN AGREEMENT WITH THEMSELVES.

UPPER LOW OVER AZ MAY KEEP A FEW CLOUDS OVER NV EARLY WEDNESDAY. A
RIDGE TRIES TO BUILD INTO THE REGION DURING THE DAY BUT QUICKLY
STARTS TO FLATTEN. ZONAL FLOW DEVELOPS BY THURSDAY WITH THE GFS
TRYING TO PUSH A WEAK SHORT WAVE THROUGH THE AREA. BY FRIDAY THE
ECMWF TRIES TO DEVELOP A SHORT WAVE RIDGE OVER THE AREA. THE GFS
KEEPS THE RIDGE OFF SHORE WITH NORTHWEST FLOW OVER OUR REGION. AT
THE SAME TIME MOST OF THE GEFS ENSEMBLE MEMBERS SHOW SOME DEGREE OF
ZONAL FLOW...BUT A FEW FAVOR THE GFS SOLUTION. WHATEVER THE OUTCOME
FOR FRIDAY...ALL OF THE MODELS HAVE PULLED ANY CHANCE OF POPS...SO
OUR SLIGHT CHANCES WERE REMOVED.

BY SATURDAY THE ENSEMBLE MEMBERS START TO SHOW A TRANSITION TO WEST-
SOUTHWEST FLOW ALOFT ALONG WITH THE ECMWF. MEANWHILE THE GFS IS MORE
ZONAL. AGAIN POPS WERE TAKEN OUT FOR SATURDAY. WILL KEEP SOME
CLOUDINESS OVER THE REGION FOR FRIDAY AND SATURDAY. ANY HINT OF THE
UPPER LOW THAT WAS BEING DROPPED INTO THE BY MODELS 24 HOURS AGO IS
NOW GONE. HIGH TEMPERATURES SHOULD HOVER AROUND AVERAGE IN ZONAL
FLOW THROUGH THE EXTENDED PERIOD. 20

&&

.AVIATION...

THE PRESENCE OF AN UPPER LOW OVER NORTHERN CA THIS MORNING DRIFTING
EAST THROUGH THE DAY SHOULD RESULT IN THE REDEVELOPMENT OF SHOWERS
AND THUNDERSTORMS FOR MUCH OF THE AREA. SHOWERS WILL BE MORE
WIDESPREAD WITH ONLY ISOLATED THUNDERSTORMS. THE BEST COVERAGE
SHOULD BE EAST OF HIGHWAY 95 BY THIS AFTERNOON. THE PRESENCE OF
LOWERED CEILINGS AND VISIBILITIES IN THE HEAVIER SHOWERS AND STORMS
SHOULD OBSCURE MOUNTAINS BY LATE MORNING INTO THE AFTERNOON.

SFC WIND GUSTS SHOULD BE IN THE 15-20 KT RANGE MOST AREAS. STRONGER
WIND GUSTS ARE POSSIBLE NEAR THUNDERSTORMS ALONG WITH A LITTLE SMALL
HAIL AND TURBULENCE.

COVERAGE OF SHOWERS AND THUNDERSTORMS BEGINS TO DECREASE LATE
TONIGHT AND EARLY MONDAY...BUT DEVELOPING LOW LEVEL NORTHEAST TO
EAST FLOW WILL KEEP LOW LEVEL MOISTURE TRAPPED NEAR THE SIERRA AND
COULD PROLONG MOUNTAIN OBSCURATIONS WELL INTO MONDAY. 20

&&

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

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