Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 050941
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
241 AM PDT TUE MAY 5 2015

.SYNOPSIS...

WEAK DISTURBANCE MOVING THROUGH SOUTHERN CALIFORNIA WILL KEEP THE
BEST CHANCES FOR THUNDERSTORMS TODAY SOUTH OF HIGHWAY 50. FROM
WEDNESDAY THROUGH FRIDAY, A STRONGER LOW PRESSURE DROPPING SOUTH
FROM WESTERN CANADA WILL BRING MUCH COOLER TEMPERATURES AND
INCREASED SHOWER COVERAGE, WITH SNOW POSSIBLE IN THE SIERRA. WARMER
CONDITIONS AND DECREASING SHOWER CHANCES RETURN FOR THE WEEKEND.

&&

.SHORT TERM...

OVERALL FORECAST REMAINS ON TRACK FOR THE NEXT FEW DAYS, WITH
COOLER AND WETTER CONDITIONS STILL LIKELY FOR WEDNESDAY AND
THURSDAY.

THE TROUGH WHICH PRODUCED YESTERDAY`S CONVECTION HAS PUSHED EAST
INTO THE FOUR CORNERS REGION. FOR TODAY, A WEAK UPPER LEVEL
DISTURBANCE MOVING INTO SOUTHERN CA WILL KEEP A POCKET OF
INSTABILITY IN PLACE FOR THIS AFTERNOON AND EARLY EVENING FOR
AREAS SOUTH OF HIGHWAY 50. INCREASING WEST TO NORTHWEST FLOW
SHOULD LIMIT MOST CONVECTION NORTH OF HIGHWAY 50. THE ONLY
POSSIBLE EXCEPTION IS FOR A SMALL PORTION OF NORTHEAST CA-
NORTHWEST NV ROUGHLY FROM SUSANVILLE TO GERLACH, WHERE ISOLATED
THUNDERSTORMS MAY OCCUR BETWEEN 2 AND 6 PM. THE LATEST GUIDANCE
CAME IN WITH MORE INSTABILITY FOR THESE AREAS, WITH A LOW LEVEL
CONVERGENCE ZONE ALSO SETTING UP. THIS IS A BIT FARTHER SOUTH THAN
THE TYPICAL LASSEN CONVERGENCE ZONE, AS DRIER AND MORE STABLE AIR
SHOULD INHIBIT CONVECTIVE DEVELOPMENT ACROSS NORTHERN LASSEN
COUNTY, SURPRISE VALLEY AND FAR NORTHWEST NV.

THE MORE SIGNIFICANT WEATHER IMPACTS ASSOCIATED WITH A STRONGER
LOW PRESSURE DROPPING SOUTH FROM CANADA WILL ARRIVE WEDNESDAY AND
CONTINUE THROUGH THURSDAY. DAYTIME HIGHS WILL DROP INTO THE 60S
FOR MOST AREAS WEDNESDAY, WITH FURTHER COOLING INTO THE 50S ON
THURSDAY, ABOUT 10-15 DEGREES BELOW SEASONAL NORMALS. BRISK NORTH
TO NORTHEAST WINDS AT TIMES WITH POSSIBLE GUSTS AROUND 30 MPH
WILL ALSO ENHANCE THE CHILLY CONDITIONS ESPECIALLY ON THURSDAY.

DESPITE THE COOLER SURFACE TEMPERATURES WITH MORE WIDESPREAD CLOUD
COVER, COOLING ALOFT AND INCREASED UPPER LEVEL FORCING BASED ON
THE FORECAST TRACK OF THE LOW WILL KEEP THE POSSIBILITY OF
THUNDERSTORMS FOR BOTH WEDNESDAY AND THURSDAY. ALTHOUGH WE KEPT
THE MENTION OF THUNDER LIMITED TO THE AFTERNOON AND EVENING TIME
PERIODS, SOME ELEVATED INSTABILITY MAY GENERATE A FEW LIGHTNING
STRIKES OVERNIGHT.

THE INHERENT VARIABILITY OF THE TRACK FOR THIS UPPER LOW LIMITS
THE ABILITY TO PROJECT WHERE THE MOST RAIN WILL OCCUR. IN GENERAL,
THE BEST CHANCES FOR PRECIP WILL MIGRATE FROM AREAS NORTH OF I-80
ON WEDNESDAY TO AREAS SOUTH OF HIGHWAY 50 ON THURSDAY. BANDS OF
SHOWERS WILL LIKELY WRAP AROUND THE LOW, SO POTENTIAL FOR AT LEAST
0.10 INCH OF PRECIP COULD AFFECT ANY PORTION OF WESTERN NV AND
EASTERN CA FROM WEDNESDAY THROUGH THURSDAY.

SOME TRAVEL IMPACTS ARE POSSIBLE OVER THE SIERRA PASSES BY EARLY
THURSDAY MORNING AS SNOW LEVELS ARE LIKELY TO DROP TO AROUND 6000
FEET, AND COULD EVEN POSSIBLY DROP TO 5000-5500 FEET IN THE
COLDER SCENARIOS ON THE LATEST GUIDANCE DATA. EVEN IN MAY, ANYONE
PLANNING TRAVEL OVER THE MAIN SIERRA PASSES NEEDS TO REMAIN AWARE
OF THE POSSIBILITY FOR SLICK AND SNOW COVERED ROADS. MJD


.LONG TERM...FRIDAY THROUGH TUESDAY...

MAIN CHANGES TO THE EXTENDED WERE TO WARM TEMPERATURES AND RAISE
SNOW LEVELS FOR FRIDAY THROUGH THE WEEKEND, AS WELL AS LOWER CHANCES
FOR PRECIPITATION FOR THE END OF THE WEEK INTO THE WEEKEND.

LONG RANGE MODELS IN RELATIVELY GOOD AGREEMENT WITH SYNOPTIC PATTERN
THROUGH THE END OF THE WEEK AND INTO THE WEEKEND. THE AREA OF LOW
PRESSURE BRINGING THE COOLER/WETTER TREND CONTINUES TO MIGRATE
SLOWLY SOUTH ON FRIDAY. RESIDUAL SHOWERS FROM THE LOW ARE EXPECTED
TO IMPACT AREAS SOUTH OF HIGHWAY 50 THROUGH EARLY SATURDAY MORNING.

BY THE WEEKEND A WARMING TREND IS EXPECTED AS A RIDGE BUILDS QUICKLY
ACROSS THE WEST. HIGH TEMPERATURES APPEAR TO CLIMB BACK INTO THE
MID 60S AND LOW 70S FOR THE WEEKEND. BEYOND SUNDAY THE FORECAST
LOOKS MORE UNCERTAIN. THE GFS/ECMWF DIFFER DRAMATICALLY ON THE
LARGE SCALE PATTERN, WHICH IS FAIRLY TYPICAL FOR FORECAST MODELS
IN THE SPRING TIME. KEPT IN SLIGHT CHANCES FOR PRECIPITATION IN THE
NORTHERN PORTIONS OF THE REGION AS A NOD TO THE ECMWF DROPPING A
WEAK SHORTWAVE ACROSS NV/OR BORDER ON MONDAY. FORECASTER
CONFIDENCE FOR EARLY NEXT WEEK IS LOW AS THE GFS/ECMWF ARE IN
DISAGREEMENT. WEISHAHN
&&

.AVIATION...

THUNDERSTORM DEVELOPMENT WILL BE LIMITED TO AREAS SOUTH OF HIGHWAY
50 AND ACROSS LASSEN/NORTHERN WASHOE COUNTIES. THUNDERSTORMS MAY
AFFECT KMMH, BUT UNLIKELY TO AFFECT TAHOE AREA TERMINALS AND
KCXP-KRNO. STORMS THAT DEVELOP MAY PERSIST AND PUSH EAST TOWARDS
KNFL LATER THIS EVENING.

A PACIFIC NORTHWEST TROUGH WILL MOVE SOUTH ACROSS THE SIERRA AND
WESTERN NEVADA STARTING WEDNESDAY BRINGING WIDESPREAD SHOWERS WITH
THE POSSIBILITY OF LOWER CIGS AND VSBY WITH STRONGER SHOWERS. WETTER
AND COOLER CONDITIONS WILL PERSIST THROUGH FRIDAY BEFORE THE TROUGH
EXITS THE REGION FOR THE WEEKEND. WEISHAHN
&&


.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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