Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 232153
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
253 PM PDT TUE SEP 23 2014

.SYNOPSIS...

DEVELOPING LOW PRESSURE IN THE PACIFIC WILL BRING INCREASING
SOUTHWEST FLOW AND CONTINUED WARM AND DRY CONDITIONS THROUGH
WEDNESDAY. SMOKE FROM THE KING FIRE WILL CONTINUE TO AFFECT THE
TAHOE BASIN AND WESTERN NEVADA UNTIL FIRE ACTIVITY DIMINISHES.
THE LOW PRESSURE SYSTEM WILL MOVE INLAND ON THURSDAY WITH COOLER
TEMPERATURES AND POSSIBLE SHOWERS FOR THE END OF THE WEEK.

&&

.SHORT TERM...

NO MAJOR ADJUSTMENTS WERE NECESSARY TO THE EXISTING FORECAST. ONLY
SLIGHT CHANGES WERE MADE TO REFLECT MOST CURRENT OBSERVATIONS AND
MODEL TRENDS. THE MAIN CONCERNS FOR THIS FORECAST CONTINUE TO BE
SMOKE AND HAZE DUE TO THE KING FIRE AND CRITICAL CONDITIONS FOR
FIRE WEATHER AS SOUTHWESTERLY FLOW INCREASES WHILE A DRY SLOT
PRECEDES THE APPROACHING LOW.

SMOKE WILL CONTINUE TO IMPACT THE REGION WHILE FLOW REMAINS
SOUTHWESTERLY. THIS WILL DRIVE POOR AIR QUALITY THAT HAS PLAGUED
THE SIERRA FROM THE TAHOE BASIN NORTHWARD AND THE RENO METRO AREA.
THE ONLY THING THAT WILL DISRUPT THIS PATTERN WILL BE WHEN THE LOW
MOVES OVER THE SIERRA AND NEVADA LATER THIS WEEK. SOME RELIEF MAY
COME FROM RAIN AS PRECIPITATION KNOCKS FINER PARTICULATES OUT OF
THE AIR. WE HAVE DECIDED TO EXTEND THE DENSE SMOKE ADVISORY BASED
ON AIR QUALITY IMPACTS THROUGH 11 PM WEDNESDAY EVENING. THIS IS
DUE MORE TO CONDITIONS BEING WORST IN THE LATE AFTERNOON AS NEW
SMOKE PUSHES ACROSS AND TERRIBLE AIR QUALITY IN THE MORNING AS
SMOKE SETTLES IN AREA VALLEYS.

MODELS CONTINUE TO BE FAIRLY CONSISTENT FROM ONE RUN TO ANOTHER,
AND SOLUTIONS ARE SIMILAR BETWEEN GRIDDED AND GLOBAL DETERMINISTIC
RUNS. WHILE THEY ALL DIFFER ON SUBTLE TIMING OF MAJOR FEATURES,
THE OVERALL STORY IS THE SAME. LOW PRESSURE DROPS OUT OF THE GULF
OF ALASKA DOWN THE PACIFIC COAST WITH A RELATIVELY STRONG
ASSOCIATED UPPER LEVEL TROUGH TODAY THROUGH THURSDAY. SOUTHWEST
WINDS RESPOND BY INCREASING EACH DAY AS THE PRESSURE GRADIENT
TIGHTENS AHEAD OF THE TROUGH STARTING THIS AFTERNOON. GENERALLY,
GUSTS WILL BE UP TO 25 MPH TODAY, UP TO 35 MPH TOMORROW, AND UP
TO 40 MPH BY THURSDAY. ALSO, A DRY SLOT PRECEDES THE MAIN CORRIDOR
OF PRECIPITATION AND WILL REMAIN IN PLACE THROUGH WEDNESDAY
EVENING. FOR MORE SPECIFICS ON WINDS AND HOW THIS WILL IMPACT FIRE
WEATHER, SEE THE FIRE WEATHER DISCUSSION BELOW.

PRECIPITATION LAGS UNTIL LATE WEDNESDAY NIGHT SLOWLY MOVING
THROUGH THE SIERRA BEFORE SPREADING INTO WESTERN NEVADA ON
THURSDAY. AS IS TYPICAL OF THIS FORECAST AREA, THERE WILL BE
QUITE A BIT OF PRECIPITATION SHADOWING TO THE LEE OF THE SIERRA.
ALSO, ENERGY EXITS THE TROUGH BEFORE ANY MEANINGFUL PRECIPITATION
CAN FALL LOWERING CHANCES AND LIMITING TOTALS. THEREFORE, SIERRA
LOCATIONS CAN GENERALLY EXPECT TOTALS LESS THAN 0.15" WITH THE
SHADOWED LOCATIONS RECEIVING LESS THAN 0.05". PRECIPITATION SHOULD
FALL AS RAIN SINCE COLDER AIR WILL BE MORE ASSOCIATED WITH THE
CORE OF THE UPPER LOW RATHER THAN THE FRONT EDGE OF THE TROUGH.
STILL, A FEW FLURRIES WILL BE POSSIBLE FOR THE HIGHEST ELEVATIONS
GENERALLY ABOVE 8500 FEET. BOYD

.LONG TERM...FRIDAY THROUGH TUESDAY...
ONLY SMALL ADJUSTMENTS TO THE LONG TERM FORECAST, MAINLY TO KNOCK
TEMPERATURES DOWN TO AROUND FREEZING IN SOME TYPICALLY COLDER LOWER
VALLEYS FOR MONDAY MORNING.

AN UPPER LOW WILL MOVE INTO THE WEST COAST FRIDAY BEFORE SETTLING
OVER EASTERN CALIFORNIA AND WESTERN NEVADA FOR THE BULK OF NEXT
WEEKEND. THE 12Z OPERATIONAL GFS/EC/GEM INDICATE THE MAIN FRONTAL
PRECIPITATION OVER CENTRAL AND EASTERN NEVADA WITH A MORE UNCERTAIN
DEFORMATION BAND TO THE NORTH AND EAST OF THE UPPER LOW CENTER FOR
FRIDAY NIGHT AND/OR SATURDAY. THE DEFORMATION BAND WOULD BE THE MAIN
FOCUS FOR RAIN OVER NORTHEAST CALIFORNIA AND WESTERN NEVADA.
HOWEVER, MODELS VARY CONSIDERABLY ON WHERE TO PUT THE DEFORMATION BY
SATURDAY, WITH THE GFS/GEM OVER NORTHWEST NEVADA AND NORTHEAST
CALIFORNIA AND THE ECMWF MORE OVER OREGON. WITH THIS IN MIND, I WAS
UNABLE TO MAKE ANY MEANINGFUL ADJUSTMENT TO POP WITH THIS PACKAGE.

DAYTIME TEMPERATURES WILL FALL TO AROUND 6 TO 10 DEGREES BELOW
AVERAGE OVER THE WEEKEND AS THE UPPER LOW SETTLES OVERHEAD. THE
COOLER HIGHS WILL SET THE STAGE FOR NEAR FREEZING TEMPERATURES FOR
TYPICALLY COLDER LOWER VALLEYS. THIS IS POSSIBLE BY SUNDAY MORNING
BUT MOST LIKELY BY MONDAY MORNING AS SURFACE HIGH PRESSURE BUILDS
INTO WESTERN NEVADA AND POTENTIAL CLOUD COVER (DEFORMATION BAND) ON
SUNDAY CLEARS OUT.

DRIER CONDITIONS RETURN EARLY NEXT WEEK AS THE UPPER LOW KICKS OFF
TO THE EAST. HOWEVER, TEMPERATURES WILL BECOME MORE UNCERTAIN AS THE
ECMWF AND GEM DROP ADDITIONAL ENERGY INTO THE NORTHWEST CONUS FOR
CONTINUED BELOW AVERAGE TEMPERATURES WHILE THE GFS BUILDS A FLAT
RIDGE OVERHEAD FOR MORE TYPICAL (MID-UPPER 70S LOWER VALLEYS) HIGHS
BY EARLY NEXT WEEK. SNYDER

&&

.AVIATION...
KING FIRE SMOKE WILL CONTINUE TO PLAGUE THE TAHOE BASIN AND WESTERN
NEVADA FOR THE NEXT COUPLE DAYS AS THE FIRE IS EXPECTED TO REMAIN
ACTIVE. WITH THE SOUTHWEST FLOW, THICKER SMOKE WILL AGAIN RETURN BY
EARLY AFTERNOON FOR THE TAHOE BASIN (MAINLY NORTH OF KTVL) AND LATE
AFTERNOON/EARLY EVENING FOR KCXP/KRNO, WITH SFC VIS TO REDUCE TO
1-2SM AT TIMES AFTER 20Z/23Z, RESPECTIVELY. EXPECT A RETURN TO MVFR
VIS FOR KTRK/KTVL/KCXP/KRNO BY LATE EVENING. SLANTWISE VISIBILITIES
SHOULD BE THE WORST AROUND MID MORNING AND LATE AFTERNOON/EARLY
EVENING DUE TO THE STEEPER SUN ANGLE AND, IN THE CASE OF THE
EVENING, THE HEAVIEST SMOKE CONCENTRATIONS.

OUTSIDE OF AREAS AFFECTED BY THE KING FIRE SMOKE, VFR CONDITIONS
CONTINUE WITH SOUTHWEST WIND GUSTS PEAKING AROUND 20-25 KTS TODAY
AND TO 25-30 KTS WEDNESDAY AFTERNOON. SNYDER/WALLMANN

&&


.FIRE WEATHER...

TYPICAL AFTERNOON WINDS DEVELOP TODAY WITH PEAK GUSTS 25-30
MPH FROM THE SOUTHWEST. HUMIDITY WILL CONTINUE TO LOWER, BUT
MINIMUMS ARE STILL EXPECTED TO REMAIN 15-25% THIS AFTERNOON.

A DRY SLOT PUSHES INTO THE SIERRA AND FAR WESTERN NEVADA TONIGHT
WITH POOR HUMIDITY RECOVERY EXPECTED ON MID AND UPPER SLOPES.
HUMIDITY RECOVERY TONIGHT WILL BE IN THE 25-35% RANGE FOR MANY MID
AND UPPER SLOPES. WINDS APPEAR TO REMAIN GUSTY ON WEDNESDAY WITH THE
STRONGEST CORE OF WINDS ALONG AND NORTH OF INTERSTATE 80. PEAK GUSTS
AROUND 35 MPH ARE LIKELY NORTH OF INTERSTATE 80 FOR SEVERAL HOURS.
ALTHOUGH MOISTURE ASSOCIATED WITH THE LOW PRESSURE SYSTEM WILL
APPROACH THE NORTHWESTERN PORTIONS OF THE FORECAST AREA, THE
HUMIDITY APPEARS TO REMAIN LOW ENOUGH TO WARRANT CRITICAL FIRE WEATHER
CONCERNS. WENT AHEAD AND UPGRADED THE FIRE WEATHER WATCHES FOR ZONES
270-271-278-458 AND ALSO FOR ZONE 272.

ON THURSDAY, THE DRY SLOT PUSHES EAST OF THE REGION WITH INCREASING
HUMIDITY EXPECTED AREA WIDE. AS THE THERMAL GRADIENT TIGHTENS UP ON
THURSDAY AFTERNOON, WINDS WILL REMAIN STRONG ACROSS THE SIERRA AND
WESTERN NEVADA. SOUTHWEST WIND GUSTS TO 40 MPH FOR THE LOWER VALLEYS
ARE EXPECTED, AS WELL AS RIDGE WIND GUSTS UP TO 80 MPH. HOWEVER, AS
MOISTURE PUSHES INTO THE SIERRA AND WESTERN NEVADA, HUMIDITY VALUES
WILL LIKELY NOT DROP BELOW 20% FOR MOST OF THE REGION. THERE IS
STILL THE POSSIBILITY THAT ZONES 273/453/459 MAY DROP TO NEAR 10%,
BUT IT DEPENDS ON THE TIMING. WILL KEEP AN EYE ON THE POTENTIAL FOR
CRITICAL FIRE WEATHER IMPACTS ON THURSDAY FOR ZONES EAST OF HIGHWAY
95 AND SOUTH OF INTERSTATE 80. WEISHAHN

&&



.REV WATCHES/WARNINGS/ADVISORIES...
NV...RED FLAG WARNING FROM 8 AM TO 11 PM PDT WEDNESDAY NVZ458.

     LAKE WIND ADVISORY FROM 5 AM TO 11 PM PDT WEDNESDAY FOR LAKE
     TAHOE IN NVZ002.

     DENSE SMOKE ADVISORY UNTIL 11 PM PDT WEDNESDAY NVZ002.

     DENSE SMOKE ADVISORY UNTIL 11 PM PDT WEDNESDAY NVZ003.

     LAKE WIND ADVISORY FROM 8 AM TO 8 PM PDT WEDNESDAY FOR PYRAMID
     LAKE IN NVZ004.

CA...RED FLAG WARNING FROM 8 AM TO 11 PM PDT WEDNESDAY CAZ270-271-278.

     RED FLAG WARNING FROM 5 AM TO 11 PM PDT WEDNESDAY CAZ272.

     LAKE WIND ADVISORY FROM 5 AM TO 11 PM PDT WEDNESDAY FOR LAKE
     TAHOE IN CAZ072.

     DENSE SMOKE ADVISORY UNTIL 11 PM PDT WEDNESDAY CAZ072.

&&

$$

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










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