Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 180429 AAA
AFDREV

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RENO NV
929 PM PDT THU APR 17 2014

.UPDATE...
NO UPDATES PLANNED THE REMAINDER OF THIS EVENING. AN EARLIER
UPDATE WAS DONE TO START THUNDERSTORMS A BIT EARLIER AS HEATING
ACROSS THE BASIN AND RANGE AHEAD OF INCREASING HIGH CLOUDS WAS
SUFFICIENT TO INTERACT WITH DYNAMICS ALOFT TO KICK OFF ISOLATED
THUNDERSTORMS NORTH OF LOVELOCK. THESE STORMS HAVE SINCE MOVED
NORTHEAST AND ENDED, BUT SHOWERS CONTINUE TO POP OVER THE EASTERN
BASIN AND RANGE AS BACK EDGE OF FORCING SLOWLY PULLS OFF TO THE
NORTHEAST. FURTHER WEST, FRONT WAS APPROACHING WITH A BAND OF
SHOWERS ACROSS NORTH CENTRAL CA. THUNDERSTORMS DEVELOPED EARLIER
AHEAD OF THIS BAND WEST OF WESTWOOD WITH A FEW ANVIL STRIKES
IN WESTERN LASSEN COUNTY. 00Z NAM KEEPS A BAND OF SHOWERS GOING
ACROSS FAR NORTHERN AREAS OVERNIGHT WHILE THE GFS/HRRR INDICATE A
QUICKER DEMISE OF PRECIPITATION. SO WILL LEAVE THE SCATTERED
SHOWERS FOR THOSE AREAS OVERNIGHT AS FRONT PUSHES SOUTHEASTWARD
ALTHOUGH OVERALL FORCING WILL BE DIMINISHING. HOHMANN

&&

.PREVIOUS DISCUSSION... /ISSUED 214 PM PDT THU APR 17 2014/

SYNOPSIS...

A FAST MOVING DISTURBANCE DROPS ACROSS THE REGION TONIGHT BRINGING
SHOWERS TO MUCH OF THE AREA, AND POSSIBLY EVEN A FEW THUNDERSTORMS
EAST OF HIGHWAY 95. ISOLATED SHOWERS AND THUNDERSTORMS WILL LINGER
INTO FRIDAY, THEN DECREASE SATURDAY AS A WEAK RIDGE REBUILDS OVER
THE AREA. A STRONGER SYSTEM IS POSSIBLE THE EARLY PART OF NEXT
WEEK BRINGING BELOW NORMAL TEMPERATURES ALONG WITH RAIN AND SNOW
SHOWERS TO THE REGION.

SHORT TERM...
MAIN CHANGES TO THE SHORT TERM FORECAST TODAY WERE JUST TWEAKS TO
POPS TONIGHT AND FRIDAY AND TO ADD A SLIGHT CHANCE OF THUNDERSTORMS
ACROSS ERN PORTIONS OF THE CWA TONIGHT.

SHORT RANGE MODELS ARE STILL TRYING TO PUSH A MID/UPPER LVL
DISTURBANCE AND ITS SFC BOUNDARY THROUGH THE REGION LATE TONIGHT.
AHEAD OF THIS SYSTEM A FEW SHOWERS MAY DEVELOP IN WEAKLY UNSTABLE
AIR OVER THE SRN CWA LATE THIS AFTERNOON AND THIS EVENING.
SOUNDINGS FROM THE ERN PART OF THE CWA SHOW ELEVATED INSTABILITY
TONIGHT AND EARLY FRIDAY SO HAVE ADDED A SLIGHT CHANCE OF THUNDER
TO AREAS EAST OF HIGHWAY 95 AND ALONG I-80 FOR LATER THIS EVENING
AND OVERNIGHT. GFS IS STILL A BIT MORE AGGRESSIVE WITH QPF WITH
THIS SYSTEM THAN THE NAM...BUT ECMWF IS A BIT MORE AGGRESSIVE NOW
AS WELL. SO INCREASED POPS ACROSS THE NRN AND ERN PORTIONS OF THE
CWA TONIGHT. WILL STILL LIMIT COVERAGE TO SCATTERED...BUT COULD
BE A BIT MORE CONCENTRATED JUST ALONG AND BEHIND THE SFC BOUNDARY.

WEAK UPPER LOW OFF THE SRN CA COAST THAT MOVED ON SHORE TODAY IS
DISCONNECTED FROM THE TROUGH SWINGING THROUGH TONIGHT AND WILL
REMAIN JUST SOUTH OF THE REGION THROUGH SATURDAY. THIS...AND A
WEAK SECONDARY MID LVL TROUGH MOVING DOWN FROM THE WEST NORTHWEST...
MAY PROVIDE ENOUGH INSTABILITY TO PRODUCE SHOWERS AND ISOLATED
THUNDERSTORMS OVER SRN PORTIONS OF THE CWA FRIDAY. ONLY PROBLEM
COULD BE CLOUD COVER KEEPING A LID ON LOW LVL HEATING. THAT WOULD
LIMIT THE LIKELIHOOD OF DEEPER CONVECTION.

BY SATURDAY FLOW BECOMES MORE ZONAL AND INCREASES OVER THE NRN
CWA. FLOW OVER THE SOUTH REMAINS LIGHTER...BUT SHEAR INCREASES
THROUGH THE DAY. THIS MAY LIMIT ANY RESIDUAL CONVECTION OVER THE
FAR SOUTH SATURDAY. HAVE KEPT JUST SLIGHT CHANCE OF TSTMS IN FOR
THAT TIME BUT THIS OCCURRENCE IS OF LOW CONFIDENCE.

BY SUNDAY WEAK RIDGE PUSHES EAST AS NEXT LONG WAVE TROUGH BEGINS
TO APPROACH THE REGION. SUNDAY SHOULD BE DRY AND WELL ABOVE
AVERAGE AGAIN WITH SOUTHWEST FLOW INCREASING IN THE AFTERNOON. 20

LONG TERM...MONDAY-THURSDAY...

PRIMARY FOCUS IS ON SPRING STORM FORECAST TO IMPACT THE REGION
MONDAY NIGHT INTO TUESDAY. OVERALL FORECAST CONFIDENCE IS MEDIUM BUT
INCREASING. NORMALIZED SPREADS OFF THE GEFS/EC ENSEMBLES ARE NEAR TO
BELOW AVERAGE - HELPING RAISE CONFIDENCE IN THE PATTERN.

FLOW ALOFT INCREASES MON AFTERNOON WHICH SHOULD YIELD GUSTY S/SW
WINDS ACROSS THE REGION (35-40 MPH TYPE STUFF). TEMPS WILL ALSO BE
FAIRLY MILD WITH LOW AFTERNOON HUMIDITIES. FOLLOWING EC/GFS
GUIDANCE, PRECIP SHOULD MOVE INTO THE CWA MONDAY NIGHT, LASTING INTO
TUESDAY. PRECIP AMOUNTS ARE NOT OVERLY IMPRESSIVE GIVEN LIMITED
MOISTURE TAP AND SPEED OF THE SYSTEM. MAYBE 0.25 TO 0.5 INCH LIQ
EQUIV ALONG THE SIERRA CREST. SPILLOVER INTO WRN NEVADA IS
UNCERTAIN. NO SURPRISE THERE. BUT STRONG FORCING ALONG THE COLD
FRONT MON NIGHT COULD BRING A PERIOD OF SHOWERS TO THE SIERRA FRONT.
SNOW LEVELS LOWER RAPIDLY FROM 7000 FT MON NIGHT TO NEAR 5000 FT BY
TUESDAY AFTERNOON, BUT BEST DYNAMICS HAVE PASSED BY THEN. THIS WOULD
LIMIT ACCUMULATING SNOWS TO MAINLY ABOVE 7000 FT, AND THIS TIME OF
YEAR SNOW CAN BE HARD PRESSED TO ACCUMULATE ON ROADS DURING THE
DAYTIME. WITH THAT SAID THERE`S STILL A CHANCE OF TRAVEL IMPACTS MON
NIGHT INTO TUESDAY FOR THE SIERRA PASSES.

GUSTY GRADIENT-DRIVEN WINDS WILL CONTINUE IN THE COLD ADVECTION
TUESDAY/WEDNESDAY MAKING THE ALREADY RADICAL TEMPERATURE CHANGE
(-20F FROM MON TO TUES) EVEN MORE CHILLING. A NUMBER OF PEOPLE
ALREADY HAVE GARDENS GOING AND BULBS SPROUTING, SO THERE IS WORRY
OUT THERE ABOUT FREEZE POTENTIAL WITH THIS COLD AIRMASS. SO FAR,
FORECAST TEMPS IN THE MAIN AGRICULTURE AND URBAN AREAS SHOULD BE
NEAR OR ABOVE FREEZING. THE HIGHEST RISK OF BELOW 30F IS IN LASSEN
COUNTY UP INTO NORTHERN WASHOE COUNTY ON TUESDAY NIGHT.

LOOKING FURTHER OUT INTO THE D8-14 PERIOD - GUIDANCE SUGGESTS THAT
WE MAY SEE YET ANOTHER STORM PERHAPS FRIDAY/SATURDAY OF NEXT WEEK.
LOW FORECAST CONFIDENCE BUT WORTH KEEPING AN EYE ON. ESRL ANALOGS
SHOW 50-70% CHANCE OF ABOVE NORMAL PRECIP FROM APR 23-30, BUT THIS
TIME OF YEAR IT DOESN`T TAKE MUCH RAIN/SNOW TO BE ABOVE NORMAL. CS

AVIATION...
COLD FRONT BRUSHING BY THE REGION WILL GENERATE SCATTERED SHRA AND
ISOLATED TS, MAINLY NORTH OF A SVE-WMC LINE FROM 0Z/FRI-12Z/FRI.
THIS FRONT WILL ALSO BRING GUSTY SW WINDS TO THE TAF SITES THIS
AFTERNOON/EVENING WITH GUSTS ON THE ORDER OF 25-30 KTS. PERIOD OF
STRONGEST WINDS EXPECTED ROUGHLY 21Z/TODAY-02Z/FRI. CONFIDENCE IN
THE TAFS TODAY IS MEDIUM TO HIGH.

LOOKING OUT TO FRIDAY AFTERNOON, RESIDUAL MOISTURE FROM THE COLD
FRONT AND INSTABILITY MAY GENERATE SCATTERED SHRA AND ISOLATED TS
ALONG THE SIERRA FROM TRK/TVL SOUTHWARD TO MMH. RISK OF A CELL
IMPACTING THESE TAF SITES AFTER 19Z/FRI IS ABOUT 25%, AND IF IT DID
THE IMPACTS WOULD BE MVFR CIGS/VSBY ALONG WITH ERRATIC STRONG WINDS.
FOR RNO/CXP, CONFIDENCE IS LOWER THAT TSTMS WOULD IMPACT THE
TERMINALS FRIDAY AFTERNOON BUT IT CANNOT BE COMPLETELY RULED OUT. CS

&&

.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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