Winter Weather Advisory 2, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
233 PM PST MON JAN 4 2016

.SYNOPSIS...

A MORE ACTIVE STORM PATTERN WILL SET UP ACROSS THE REGION THIS WEEK
WITH PERIODS OF IMPACT TO TRAVEL, ESPECIALLY ACROSS THE SIERRA. AT
THIS TIME, THE GREATEST IMPACTS WILL BE TUESDAY AND WEDNESDAY AS
A COUPLE OF STRONGER STORMS BRING MORE WIDESPREAD AND MODERATE
SNOWFALL POTENTIAL.

&&

.SHORT TERM...

THE SHORT TERM FORECAST IS COMPOSED OF TWO SEPARATE WINTER STORMS
DIVIDED BY A PERIOD OF ABOUT 12-18 HOURS. THE FIRST OF THESE
STORMS STARTS LATE TONIGHT AND LASTS INTO TUESDAY EVENING WHILE
THE SECOND MOVES INTO THE REGION LATE WEDNESDAY MORNING AND
SHOULD AFFECT PARTS OF THE SIERRA THROUGH THURSDAY MORNING.

THE LEADING EDGE OF PCPN MOVING NORTH ON THE WEST SIDE OF THE
SIERRA TODAY IS BECOMING SHEARED OUT AND SHOULD NOT PRODUCE
SIGNIFICANT AMOUNTS OF PCPN LATE THIS AFTERNOON AND EARLY THIS
EVENING. BUT...A LONG WAVE TROUGH MOVING INTO THE WEST COAST
TONIGHT WILL PRODUCE SIGNIFICANTLY MORE LIFT STARTING LATE THIS
EVENING AND CONTINUING INTO THE DAYTIME HOURS TUESDAY AS THE
TROUGH MOVES TROUGH THE REGION. THE JET PLACEMENT AHEAD OF THIS
TROUGH IS WELL SOUTH OF THE REGION AND IS STEERING THE GREATEST
ENERGY...AND PCPN...INTO MONO COUNTY. CONSEQUENTLY...THE HIGHEST
LIQUID AND SNOW AMOUNTS SHOULD BE FROM HIGHWAY 50 SOUTH IN THE
SIERRA AND TEMPERATURES ARE LIKELY TO BE BELOW AVERAGE FOR MOST
LOCATIONS. WINDS ALOFT HAVE BACKED OFF A BIT WITH THIS SYSTEM SO
WE HAVE DECREASED RIDGE WINDS THROUGH THE NORTHERN SIERRA...BUT
THE SOUTHERN SIERRA WINDS STILL LOOK AS THOUGH THEY COULD GUST
OVER 80 MPH. IN NORTHEAST CALIFORNIA AND FAR NORTHWEST NEVADA THE
PCPN WILL WORK ITS WAY INTO THE REGION LATE TONIGHT/EARLY
TUESDAY MORNING.

EAST OF THE SIERRA A PERIOD OF LOW TO MID LVL SOUTHERLY WINDS
WILL LIKELY HOLD OFF ANY PCPN TONIGHT. SOME PCPN IS LIKELY BY
TUESDAY MORNING SOUTH OF HIGHWAY 50 AND WEST OF HIGHWAY 95. ANY
DELAY IN PCPN MOVING INTO WESTERN NEVADA WILL ALLOW TEMPS TO RISE
WELL INTO THE 30S. THIS WOULD IMPACT THE AMOUNT OF SNOW
RECEIVED...AND COULD EVEN PRODUCE A BRIEF PERIOD OF RAIN OR A
RAIN/SNOW MIX DURING THE DAY TUESDAY. BUT...PCPN SHOULD BE HEAVY
ENOUGH AT TIMES TO DRIVE THE SNOW LEVELS TO THE VALLEY FLOORS AND
ALLOW FOR SOME ACCUMULATIONS FROM THE SURPRISE VALLEY SOUTH
THROUGH RENO AND CARSON CITY. THUS...WINTER WEATHER ADVISORIES
HAVE BEEN ADDED FOR THOSE AREAS FOR TUESDAY. PRIMARY IMPACTS WILL
BE TO TRAVEL AS ACCUMULATIONS ON THE ROADS WILL CREATE HAZARDOUS
DRIVING CONDITIONS. THE HIGHEST ACCUMULATIONS AROUND THE
RENO/CARSON CITY AREA WILL BE IN THE FOOTHILLS AND THE SOUTHERN
END OF THE CARSON VALLEY.

THIS FIRST TROUGH PUSHES EAST TUESDAY NIGHT WITH A BRIEF BREAK
EARLY WEDNESDAY. ANOTHER TROUGH IS NOW FORECAST TO TAKE A SIMILAR
TRACK WEDNESDAY AND WEDNESDAY NIGHT. THE MODELS ARE STARTING TO
PRODUCE MORE FORECAST PCPN WITH THIS STORM...BUT THERE ARE A FEW
MINOR DISCREPANCIES WITH THE FORECAST MODELS. THE JET REMAINS
SOUTH OF THE REGION SO WE ARE STILL IN THE COLD AIR AND SHOULD SEE
MAINLY SNOW...EVEN TO THE LOWEST VALLEY FLOORS. THE LOCATIONS OF
THE BEST LIFT NORTH OF THE JET WILL DETERMINE THE LOCATION OF THE
HEAVIEST PCPN. THE GFS KEEPS A BROAD AREA OF MODERATE TO HEAVY
PCPN FROM WESTERN LASSEN COUNTY SOUTH INTO MONO COUNTY ALONG THE
SIERRA CREST. THE NAM IS CONCENTRATED MORE FROM INTERSTATE 80
SOUTH THROUGH MONO COUNTY. GIVEN THE LOCATION OF THE JET AND BEING
ON THE NORTH SIDE OF A CYCLONIC CURVED JET...WE WOULD ASSUME THE
BEST LIFT WILL BE SITUATED SOUTH OF HIGHWAY 50. WITH MODEL PCPN
FORECAST TO INCREASE WE HAVE RAISED QPF FOR WEDNESDAY AND
WEDNESDAY NIGHT AND WILL ISSUE A WATCH FOR THE TAHOE BASIN AND
MONO COUNTY. NORTHEAST CALIFORNIA SHOULD RECEIVE LESS WITH THIS
SYSTEM. FOR WESTERN NEVADA SOME SNOW IS LIKELY...BUT AMOUNTS ARE
FAIRLY UNSURE AT THIS POINT. OVERALL THE FORECASTER CONFIDENCE IN
THIS SYSTEM SITS AT MEDIUM FOR THE SIERRA WHERE ISSUES REMAIN
WITH REGARD TO EXACT LOCATIONS OF THE HEAVIEST PRECIPITATION.
CONFIDENCE IS LOW ELSEWHERE AS SNOW AMOUNTS ARE VERY UNSURE. 20

.LONG TERM...THURSDAY THROUGH MONDAY...

WE HAVE MADE SOME CHANGES IN THE EXTENDED FORECAST TO REDUCE PRECIP
CHANCES FROM FRIDAY THRU MONDAY, WITH DRY CONDITIONS IN MORE AREAS
FROM SUNDAY THROUGH MONDAY. MEDIUM RANGE GUIDANCE APPEARS TO BE
TRENDING TOWARD ESTABLISHING A BLOCKING RIDGE ALONG THE WEST COAST
BY THIS WEEKEND. THERE MAY BE A WEAKER STORM SYSTEM UNDERCUTTING THE
RIDGE AND MOVING THROUGH THE REGION ON SATURDAY-SAT NIGHT, BUT
OVERALL THE TREND FAVORS A REDUCED POTENTIAL FOR WIDESPREAD OR
SIGNIFICANT SNOWFALL FROM THIS WEEKEND INTO EARLY NEXT WEEK. WHILE
FORECAST CONFIDENCE IS RATHER LOW FOR PRECIPITATION CHANCES AND
COVERAGE, THERE IS A HIGHER LEVEL OF CONFIDENCE FOR BELOW NORMAL
DAYTIME TEMPS CONTINUING INTO EARLY NEXT WEEK, WITH HIGHS
GENERALLY IN THE 30S TO NEAR 40 DEGREES EACH DAY.

FOR THURSDAY, ONGOING WINTER EVENT IS EXPECTED TO TRANSITION TO MORE
SHOWERY CONDITIONS AS UPPER LOW CENTER MOVES ACROSS CENTRAL CA.
WHILE SOME ADDITIONAL SNOW MAY ACCUMULATE NEAR THE SIERRA ON
THURSDAY, MOST OF THE HEAVIER SHOW SHOULD BE WINDING DOWN BY EARLY
MORNING. MOISTURE WRAPPING AROUND THE LOW COULD GENERATE SOME AREAS
OF LIGHTER SNOW SHOWERS ACROSS WESTERN NV, WITH UPSLOPE FLOW KEEPING
THIS POTENTIAL INTO THURSDAY NIGHT MAINLY SOUTH OF I-80 AS THE LOW
DIPS INTO SOUTHERN CA. EVEN THOUGH SNOW AMOUNTS IN WESTERN NV SHOULD
BE RATHER LIGHT (GENERALLY LESS THAN 1 INCH), THERE COULD BE SOME
TRAVEL IMPACTS ESPECIALLY IN AREAS WHERE SNOW FALLS LATE IN THE DAY.

ON FRIDAY, MOST OF THE REGION WILL BE IN BETWEEN WEATHER SYSTEMS,
WITH ONLY LEFTOVER SNOW SHOWERS POSSIBLE NEAR THE SIERRA AND ACROSS
PORTIONS OF WEST CENTRAL NV. LITTLE OR NO ADDITIONAL ACCUMULATIONS
ARE EXPECTED, AND OVERALL TRAVEL CONDITIONS SHOULD IMPROVE.

FOR THIS WEEKEND, THERE ARE GREATER INDICATIONS FOR A BREAK IN STORM
ACTIVITY AS A RIDGE DEVELOPS ALONG THE WEST COAST. THE CENTER OF
THIS RIDGE MAY DEVELOP FAR ENOUGH NORTH TO ALLOW FOR A RELATIVELY
WEAK UPPER LOW TO UNDERCUT THE RIDGE ON SATURDAY-SAT NIGHT. COMPARED
TO PREVIOUS GUIDANCE RUNS THE POTENTIAL FOR SIGNIFICANT SNOWFALL
APPEARS TO BE GREATLY REDUCED, ESPECIALLY FOR AREAS NORTH OF HIGHWAY
50. WE DID NOT COMPLETELY REMOVE SNOW CHANCES FOR SATURDAY-SAT NIGHT
EVEN IN THE NORTH ZONES AS A FEW ENSEMBLE MEMBERS STILL SHOWED A LOW
MOVING ACROSS THE SIERRA OR NORTHERN CA, BUT IF THE CURRENT DRIER
TREND CONTINUES THEN WE WOULD BE REDUCING PRECIP CHANCES EVEN
FURTHER.

FOR SUNDAY AND MONDAY, WE WENT MUCH LOWER ON SHOWER POTENTIAL DUE TO
CONTINUED PRESENCE OF THE RIDGE NEAR THE WEST COAST. WE MAY SEE
ANOTHER TROUGH SWING THROUGH OUR REGION AFTER MONDAY, BUT WE ARE
LIKELY TO BE DEALING WITH ANOTHER SPLIT SYSTEM SO WHATEVER ENERGY
GETS THROUGH TO THE SIERRA WILL PROBABLY BE WEAK. MJD

&&

.AVIATION...

FOR TONIGHT, LIGHT SNOW WILL AFFECT THE TERMINALS NEAR LAKE TAHOE
WITH CIGS/VSBY DROPPING TO MVFR AT TIMES BEFORE 10Z, THEN BECOMING
IFR AFT 10Z WITH SNOW STARTING TO ACCUMULATE ON RUNWAYS. IN LOWER
ELEVATIONS AND FARTHER SOUTH TOWARD KMMH, VFR CONDS ARE LIKELY TO
PREVAIL, BUT CIGS WILL BECOME LOWER WITH HIGHER TERRAIN BECOMING
OBSCURED LATER TONIGHT.

MORE SIGNIFICANT AVIATION IMPACTS ARE EXPECTED TUESDAY THROUGH
TUESDAY EVENING, WITH WIDESPREAD IFR OR WORSE CIGS NEAR THE SIERRA,
AND SEVERAL INCHES OF SNOW ACCUMULATING AT KTRK/KTVL/KMMH. FOR
WESTERN NV, SNOW WILL PRODUCE CIGS/VSBY DOWN TO MVFR/IFR WITH
WIDESPREAD OBSCURATION OF HIGHER TERRAIN. PAVEMENT AT WESTERN NV
TERMINALS INCLUDING KRNO/KCXP IS LIKELY TO REMAIN WET DURING MOST OF
THE DAY, THEN POSSIBLY BECOMING SLUSHY BY EARLY EVENING.

ANOTHER ROUND OF SNOW IS IN TAP FOR WEDNESDAY THROUGH THURSDAY,
PRODUCING SIGNIFICANT AVIATION IMPACTS MAINLY NEAR THE SIERRA DUE TO
ACCUMULATING SNOW AND POOR VISIBILITY. MJD

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM PST TUESDAY NVZ005.

     WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
     NIGHT NVZ002.

     WINTER WEATHER ADVISORY FROM 2 AM TO 4 PM PST TUESDAY NVZ002.

     WINTER WEATHER ADVISORY FROM 7 AM TO 7 PM PST TUESDAY NVZ003.

CA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 PM PST
     TUESDAY CAZ071.

     WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM PST TUESDAY CAZ070.

     WINTER STORM WARNING FROM 7 AM TO 10 PM PST TUESDAY CAZ073.

     WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
     NIGHT CAZ072-073.

     WINTER WEATHER ADVISORY FROM 2 AM TO 4 PM PST TUESDAY CAZ072.

&&

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