Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 210239
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
739 PM PDT SAT SEP 20 2014

.UPDATE...
CONVECTION THIS EVENING IS MAINLY CLUSTERED IN TWO AREAS. THE
CONVECTION ALONG THE CREST AND TO THE WEST IS MORE ASSOCIATED
WITH THE LEADING EDGE OF THE UPPER LOW...ITS COOLER AIR ALOFT AND
INCREASING INSTABILITY. MEANWHILE...A LARGER AREA OF CONVECTION
OVER THE CENTRAL PART OF NEVADA HAS BEEN MORE CLOSELY ASSOCIATED
WITH A JET STREAK IN THAT REGION. LATEST NUMERICAL MODELS TAKE
THIS JET STREAK A BIT MORE WNW AS THE UPPER LOW APPROACHES
TONIGHT. THIS SHOULD ALLOW FOR BETTER FORCING ALOFT OVER WRN
NEVADA. ALSO...THE PRESENCE OF THE UPPER LOW AND ITS COOLING ALOFT
SHOULD BOOST THE CHANCES FOR CONVECTION OVER THE FAR WESTERN AND
SRN CWA. SO...HAVE OPTED TO LOWER POPS SLIGHTLY FOR THE EVENING
OVER WESTERN NEVADA AND NORTHEAST CALIFORNIA WHERE FORCING IS
MINIMAL...BUT LEFT THE HIGHER POPS OVERNIGHT AS THE LOW APPROACHES
AND THE INTERACTION OF THE UPPER JET STREAK AND DEFORMATION AXIS
PRODUCES A BETTER CHANCE FOR RAIN AND EMBEDDED THUNDER.

SMOKE FORM THE KING FIRE POURED INTO THE TAHOE BASIN LATE THIS
AFTERNOON AND EARLY THIS EVENING AS WINDS ALOFT DECREASED FROM THE
EAST AND HAVE STARTING TO BECOME WESTERLY OVER THE BASIN. THESE
WINDS SHOULD EVENTUALLY TURN TO THE WEST OVER SOUTHERN PARTS OF
WRN NV AS WELL...BUT IT IS HARD TO SAY AT THIS POINT WHETHER THE
SMOKE WILL MAKE IT INTO AREAS SOUTH OF CARSON CITY AS STRONG AS
IT WAS IN TAHOE EARLIER. BY SUNDAY MOST LOCATIONS WILL SEE WEST TO
SOUTHWEST WINDS ABOVE THE SURFACE AND THERE IS A BETTER CHANCE OF
THE SMOKE MAKING ITS WAY INTO WRN NEVADA FROM CARSON CITY NORTHWARD.
20

&&

.PREVIOUS DISCUSSION... /ISSUED 325 PM PDT SAT SEP 20 2014/

SYNOPSIS...
LOW PRESSURE MOVING NORTHEAST ACROSS CALIFORNIA AND NEVADA THIS
WEEKEND WILL PRODUCE SHOWERS AND THUNDERSTORMS THIS EVENING, WITH
THE BEST CHANCES FOR RAIN TONIGHT THROUGH SUNDAY AFTERNOON. WARMER
AND DRIER CONDITIONS ARE EXPECTED MONDAY AND TUESDAY, THEN A
STRONGER LOW PRESSURE WILL BRING INCREASING WINDS BY MID WEEK.

SHORT TERM...
UPPER LEVEL LOW PRESSURE OVER CENTRAL CALIFORNIA HAS BEGUN TO LIFT
INTO NEVADA THIS AFTERNOON. SCATTERED THUNDERSTORMS HAVE ALREADY
DEVELOPED OVER EASTERN PERSHING AND CHURCHILL COUNTIES AND WILL
CONTINUE TO EXPAND FURTHER NORTH AND WEST THROUGH THE LATE AFTERNOON
AND EVENING HOURS. A FEW STRONGER STORMS MAY BE POSSIBLE LATE TODAY
IN WEST-CENTRAL NEVADA WHERE THERE IS HIGHER EFFECTIVE BULK SHEAR
AND MUCAPE APPROACHING 1000 J/KG. SMALL HAIL AND STRONG WINDS WILL
BE THE MAIN THREATS.

LIGHT WESTERLY WINDS ARE PUSHING SMOKE FROM THE KING FIRE UP THE
WESTERN SLOPES AND NEAR THE SIERRA CREST THIS AFTERNOON, WHILE EAST
WINDS GUSTING AROUND 25 MPH REMAIN OVER THE SIERRA CREST. THERE IS A
POSSIBILITY THAT SOME SMOKE WILL MAKE IT OVER THE CREST AND PUSH
INTO THE BASIN LATE THIS AFTERNOON BUT IT WILL BE LIMITED DUE TO
EAST FLOW ALOFT.

TONIGHT, AS THE LOW PRESSURE CONTINUES TO LIFT THROUGH THE REGION,
WE WILL SEE INCREASING PRECIPITABLE WATER TO AROUND ONE INCH IN
WESTERN NEVADA. THIS DEEP MOISTURE IS EXTREMELY ANOMALOUS FOR LATE
SEPTEMBER, NEARING THE 99TH PERCENTILE FOR PRECIPITABLE WATER IN
WESTERN NEVADA...CLOSER TO SOMETHING WE`D SEE IN JULY OR AUGUST.

WIDESPREAD RAIN SHOWERS WILL DEVELOP THIS EVENING AND OVERNIGHT,
CONTINUING INTO SUNDAY MORNING. A DEFORMATION ZONE RAIN BAND WILL
ALSO SET UP FROM RENO-TAHOE TO WINNEMUCCA OVERNIGHT WITH STEADY
LIGHT TO MODERATE RAINFALL INTO SUNDAY MORNING. RAINFALL TOTALS
OVERNIGHT AND INTO SUNDAY AFTERNOON MAY EXCEED 0.50" IN EASTERN
PERSHING AND CHURCHILL COUNTIES, WITH 0.10 TO 0.25" IN THE EASTERN
SIERRA AND ALONG THE WESTERN NEVADA SIERRA FRONT ESPECIALLY AROUND
THE INTERSTATE 80 CORRIDOR. THESE RAINFALL AMOUNTS WILL BE HIGHLY
DEPENDENT ON WHERE THE DEFORMATION BAND SETS UP OVER THE REGION,
WHICH COULD SHIFT UP TO 50 MILES BASED OFF OF PREVIOUS EXPERIENCE.

WIDESPREAD CLOUDS AND SHOWERS ON SUNDAY WILL KEEP TEMPERATURES
COOLER. COLD AIR ALOFT WILL KEEP THE ATMOSPHERE UNSTABLE ENOUGH FOR
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE FORECAST
AREA. CONVECTION WILL WIND DOWN QUICKLY SUNDAY EVENING AS THE LOW
MOVES OUT OF THE AREA AND ALLOWS FOR SHORTWAVE RIDGING TO BUILD OVER
THE REGION THROUGH MONDAY.

WINDS FOR THE TAHOE BASIN ARE EXPECTED TO BECOME LIGHT WESTERLY LATE
SUNDAY, WHICH WOULD HELP TO BRING SMOKE INTO THE RENO-TAHOE AREA
AGAIN SUNDAY EVENING AND MONDAY AS WELL. HOON

LONG TERM...TUESDAY THROUGH SATURDAY...
THE LARGE SCALE PATTERN IN THE EXTENDED WILL FOCUS ON THE
PROGRESSION OF AN UPPER LEVEL TROUGH. ENSEMBLES AND DETERMINISTIC
MODELS ARE IN GOOD AGREEMENT WITH THE DEVELOPMENT OF THIS TROUGH BUT
FAR GREATER UNCERTAINTY EXISTS WITH ITS INLAND PROGRESSION AND
RESULTANT TIMING OF IMPACTS. NONETHELESS WE CAN EXPECT AN INCREASE
IN WIND SPEEDS ALONG WITH INCREASED SOUTHWESTERLY FLOW ALOFT
THOROUGH AT LEAST THURSDAY. THIS WILL ALLOW SMOKE FROM THE KING FIRE
TO BE TRANSPORTED BACK ACROSS THE EASTERN SIERRA AND WESTERN NEVADA
DEPENDENT UPON THE FIRE`S SMOKE PRODUCTION AT THAT TIME.

MODELS IN GENERAL AGREEMENT TUESDAY AND WEDNESDAY WITH A DRY
SOUTHWEST FLOW IN PLACE ACROSS THE SIERRA AND WESTERN NEVADA. LATEST
GUIDANCE HAS TRENDED A TAD SLOWER WITH THE INLAND PROGRESSION OF THE
TROUGH AND WITH A DRY SLOT ACROSS THE AREA HAVE REDUCED SKY COVER
AND POPS THROUGH THIS PERIOD. LIGHT SOUTHWEST WINDS WILL DEVELOP
LATE TUESDAY WITH BREEZIER CONDITIONS EXPECTED BY WEDNESDAY
AFTERNOON ESPECIALLY TOWARDS THE OREGON BORDER AS AN UPPER LEVEL
JET MOVES IN FROM THE NORTH. TEMPERATURES WILL STAY WARM WITH HIGH
TEMPERATURES IN THE UPPER 80S ACROSS WESTERN NEVADA AND UPPER 70S
ACROSS THE SIERRA.

BEYOND THURSDAY CONSIDERABLE UNCERTAINTY ENTERS THE FORECAST AS THE
GFS BECOMES MORE PROGRESSIVE WITH THE LOW WHILE THE EC LINGERS A
CLOSED LOW OVER THE WEST INTO NEXT WEEKEND. THIS WILL HAVE TIMING
IMPACTS ON THE PASSAGE OF A COLD FRONT ANYWHERE FROM THURSDAY
AFTERNOON INTO THE LATE FRIDAY TIMEFRAME. AHEAD OF THE FRONT WE WILL
SEE LIKELY OUR STRONGEST PRESSURE GRADIENT AND STRONGEST WINDS AS A
RESULT. SUSTAINED WINDS IN THE 15-25 MPH ARE POSSIBLE WITH THIS
GRADIENT BUT THIS THIS WILL LIKELY BE ADJUSTED IN THE COMING DAYS
WITH MORE REFINEMENTS ON TIMING. NONETHELESS, THE LOW WILL HELP COOL
TEMPERATURES ALOFT CREATING INSTABILITY AND CHANCES FOR SHOWERS
BEGINNING THURSDAY INTO NEXT WEEKEND. COOLER TEMPERATURES ARE
ALSO EXPECTED WITH HIGHS AROUND 10 DEGREES BELOW AVERAGE POSSIBLE
BY FRIDAY. FUENTES

AVIATION...
AREAS OF HAZE WILL CONTINUE THIS EVENING WITH EAST FLOW KEEPING THE
BULK OF THE SMOKE FROM THE KING FIRE ACROSS THE WESTERN SIERRA SLOPES
WITH SOME MOUNTAIN TOP OBSCURATION POSSIBLE ALONG THE CREST.

INCREASING COVERAGE OF SHOWERS AND THUNDERSTORMS IS EXPECTED TONIGHT
AS AN UPPER LOW APPROACHES THE REGION. POTENTIAL FOR BANDED
PRECIPITATION TO DEVELOP FROM THE TAHOE BASIN TO BETWEEN I-80 AND
HWY 50 ACROSS WESTERN NEVADA THROUGH 18Z SUNDAY. POTENTIAL FOR MVFR
CIGS/VIS AT MAIN TERMINALS ABOUT 20 PCT FOR KRNO/KCXP/KTVL/KTRK AND
25-30 PCT AT KMMH. FUENTES

&&

.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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