Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 070857
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
157 AM PDT TUE JUL 7 2015

.SYNOPSIS...

LOW PRESSURE NEAR THE CALIFORNIA COAST WILL SLOWLY MOVE ONSHORE
AND KEEP THE THREAT OF THUNDERSTORMS OVER THE REGION THROUGH
FRIDAY. LOCALLY HEAVY RAINFALL AND WET GROUND CONDITIONS MAY
PRODUCE FLASH FLOODING THIS AFTERNOON AND EVENING. A COOLING TREND
IS EXPECTED THROUGH THURSDAY AS CLOUD COVER INCREASES. BY THE
WEEKEND, THUNDERSTORM POTENTIAL WILL GRADUALLY DECREASE.

&&

.SHORT TERM...

MULTIPLE REPORTS OF FLOODING OCCURRED YESTERDAY WITH EFFICIENT
RAIN-PRODUCING THUNDERSTORMS. STORM TOTALS ASSOCIATED WITH THE
FLOODS WERE GENERALLY BETWEEN 0.5 AND 1.0 INCH WHICH FELL IN LESS
THAN AN HOUR. RADAR PRECIP MAP SHOWS SOME POCKETS OF RAIN ABOVE 1
INCH, ALTHOUGH ACCUMULATING HAIL WAS ALSO PRESENT WITH STRONGER
STORMS YESTERDAY.

FOR TODAY, WE HAVE ALREADY ISSUED A FLASH FLOOD WATCH AS A
VIRTUAL REPEAT OF THUNDERSTORM ACTIVITY IS EXPECTED TO FIRE UP
AROUND MIDDAY NEAR THE SIERRA, THEN SPREAD ACROSS MUCH OF EASTERN
CA AND WESTERN NV THRU THE AFTERNOON. THERE ARE SOME MID-HIGH
LEVEL CLOUDS THAT HAVE BEEN SLOW TO DISSIPATE SO FAR TONIGHT, BUT
THERE SHOULD BE ENOUGH BREAKS BY LATE MORNING TO ALLOW FOR HEATING
SUFFICIENT TO PRODUCE DECENT CONVECTION. CELL MOTION MAY BE A
LITTLE FASTER TODAY, BUT WITH UPPER LEVEL FORCING ALSO INCREASING
AS A SHORTWAVE ROTATES INTO THE REGION LATER TODAY, MORE ORGANIZED
CONVECTION WITH CELL REDEVELOPMENT OVER SAME LOCATIONS WILL BE
POSSIBLE. THEREFORE THE POTENTIAL FOR MORE FLASH FLOODING
CONTINUES, ESPECIALLY IN AREAS THAT HAVE BEEN SATURATED FROM
HEAVY RAINFALL SINCE THE START OF THIS MONTH, AND RECENT WILDFIRE
BURN SCARS. WE MAY SEE MORE WIDESPREAD CONVECTION SPREAD INTO
NORTHEAST CA AS UPPER DIVERGENCE INCREASES OVER THIS AREA.
NORTHWEST AND WEST CENTRAL NV MAY HAVE A LOWER OVERALL FLASH FLOOD
POTENTIAL, BUT THEY COULD RECEIVE A PERIOD OF LIGHT OR MODERATE
RAINFALL THIS EVENING AS DEFORMATION ZONE SETS UP OVER THESE
AREAS. LINGERING SHOWERS WITH EMBEDDED THUNDER COULD CONTINUE
OVERNIGHT MAINLY IN AREAS NORTH OF I-80.

BY WEDNESDAY AND THURSDAY, THE UPPER LOW IS PROJECTED TO MOVE
SLOWLY INLAND ACROSS CENTRAL CA. WIDESPREAD MOISTURE AND
INSTABILITY WILL CONTINUE TO KEEP THE THUNDERSTORM THREAT GOING,
ALTHOUGH INDIVIDUAL CELLS ARE LESS LIKELY TO BE AS STRONG WITH
REDUCED DAYTIME HEATING. BY THURSDAY, CLOUD COVER IS MORE LIKELY
TO BECOME THICK ENOUGH TO FURTHER LIMIT THUNDERSTORM INTENSITY,
BUT A LARGE BAND OF WRAP AROUND MOISTURE COULD STILL GENERATE
WIDESPREAD LIGHT TO MODERATE RAINFALL AMOUNTS FOR MUCH OF THE
REGION.

DAYTIME TEMPS WILL CONTINUE THEIR COOLING TREND FOR THE NEXT FEW
DAYS AS THE UPPER LOW AND ITS ASSOCIATED COOLER TEMPS ALOFT MOVES
CLOSER TO THE SIERRA. BY THURSDAY, HIGHS IN SOME LOWER ELEVATIONS
MAY END UP BELOW 80 DEGREES WHERE THICKER CLOUDS AND RAIN IS MOST
PERSISTENT. MJD

.LONG TERM...FRIDAY THROUGH MONDAY...

VERY LITTLE HAS CHANGED AS FAR AS REASONING GOES IN THE EXTENDED
FORECAST. MEDIUM RANGE MODELS ARE STILL IN GENERAL AGREEMENT THAT
UPPER LOW WILL OPEN INTO A WAVE AND LIFT OUT OF THE AREA LATE FRIDAY
INTO EARLY SATURDAY. LIMITED CHANGES WERE MADE EARLY ON AND THE
FORECAST STILL REFLECTS CHANCE POPS OVER THE NRN AND FAR WRN
SECTIONS FOR FRIDAY WITH BELOW AVERAGE HIGH TEMPS.

MODELS ARE A LITTLE LESS AGGRESSIVE THIS RUN WITH DEVELOPING
SOUTHWEST FLOW ALOFT FOR SATURDAY AS A BROAD LONG WAVE TROUGH STARTS
TO REDEVELOP OFFSHORE. THE FLOW IS BACKED SLIGHTLY ALLOWING FOR THE
PRESENCE OF MORE MOISTURE. HIGH TEMPS SHOULD START TO RISE AND
INTERACT WITH RESIDUAL MOISTURE TO CREATE SHOWERS AND THUNDERSTORMS.
SO WE BUMPED UP POPS SLIGHTLY FOR SATURDAY.

SOUTHWEST FLOW ALOFT BECOMES A BIT STRONGER BY LATE SUNDAY AS THE
TROUGH OFFSHORE STARTS TO STRENGTHEN. THIS IS NORMALLY A DRYING FLOW
FOR MUCH OF THE CWA. WILL CONFINE POPS FOR SUNDAY TO THE NW 1/3 OF
THE CWA. BY MONDAY THE FLOW IS BIT STRONGER OUT OF THE SOUTHWEST
WITH MORE DRYING ACROSS THE CWA...SO WE HAVE NO WEATHER FOR MONDAY.
HIGH TEMPS SUNDAY AND MONDAY ARE LIKELY TO BE AT OR SLIGHTLY ABOVE
AVERAGE AS THIS DRIER FLOW DEVELOPS. 20

&&

.AVIATION...

PRESENCE OF A HIGH TO THE EAST AND LOW TO THE SOUTHWEST WILL KEEP
SOUTH-SOUTHEAST FLOW OVER THE FORECAST AREA WITH THUNDERSTORMS
DEVELOPING AGAIN TODAY. WHILE THE BIGGEST THREAT REMAINS LOCALLY
HEAVY RAIN WITH THESE STORMS...TURBULENCE...HAIL AND GUSTY OUTFLOW
WINDS TO 45-50 KTS ARE ALSO PROBABLE AND WILL POSE A THREAT TO
AVIATION INTERESTS. STORMS SHOULD DEVELOP AFTER 11 AM AND PERSIST
THROUGH ROUGHLY 8-9 PM. LOCATIONS IN THE SIERRA AND FAR WESTERN
NEVADA HAVE THE BEST CHANCE OF SEEING A STORM...AT 35-45%.

STORMS PERSIST THROUGH THE WEEK AS LOW PRESSURE SLOWLY MOVES OVER
THE AREA. BY WEDNESDAY AND THURSDAY THERE COULD BE A LARGER AREA OF
STRATIFORM RAIN WITH A FEW EMBEDDED THUNDERSTORMS LEADING TO LOWERED
CEILINGS. STILL...VFR CONDITIONS SHOULD PREDOMINATE WITH ONLY BRIEF
PERIODS OF MVFR IN THE STRONGEST STORMS. 20

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...FLASH FLOOD WATCH FROM NOON PDT TODAY THROUGH THIS EVENING
     NVZ001>003.

CA...FLASH FLOOD WATCH FROM NOON PDT TODAY THROUGH THIS EVENING
     CAZ071>073.

&&

$$

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



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