Flash Flood in California, July 25, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
300 AM PDT WED JUL 25 2007

.SHORT TERM...
PLENTY OF MID LEVEL MOISTURE STILL AROUND THE AREA THIS
MORNING...WITH ISOLATED SHOWERS OVER ERN CHURCHILL/SERN PERSHING
COUNTIES. THESE SHOWERS WILL MOVE SLOWLY NORTH AND WEAKEN LATER THIS
MORNING. A VERY ISOLATED TSTM CANNOT BE RULED OUT IN THIS AREA
DURING THE MORNING...HOWEVER MOST ACTIVITY WILL HOLD OFF UNTIL THIS
AFTERNOON. SOME CLEARING DURING THE MORNING OVER MONO/MINERAL
COUNTIES WILL ALLOW THE ATMOSPHERE TO DESTABILIZE IN THOSE AREAS
EARLY THIS AFTERNOON. THE GREATEST TSTM COVERAGE IS EXPECTED OVER
SRN ZONES NORTHWARD INTO PERSHING/CHURCHILL COUNTIES NEAR SHORT WAVE
ENERGY...WHERE WIDELY SCATTERED TO SCATTERED TSTM COVERAGE IS
EXPECTED. ELSEWHERE A MID LEVEL CAP IS STILL PRESENT IN THE
RENO/CARSON AREAS AND WE WILL NEED SOME HEATING TO BREAK THAT BEFORE
THE WESTERLIES DEVELOP LATER THIS AFTERNOON AND STABILIZE THE AREA.
THEREFORE ISOLATED CONVECTION IS POSSIBLE FROM RENO/CARSON
NWD...HOWEVER MOST ACTIVITY IS EXPECTED FURTHER EAST WHERE DEEPER
MOISTURE IS PRESENT. PW VALUES OVER ERN/SRN ZONES REMAIN OVER AN
INCH WITH SLOW STORM MOTION. THIS WILL BRING THE THREAT OF LOCALIZED
FLASH FLOODING. HOWEVER SHORT WAVE ENERGY WILL MOVE NORTHEAST AND
PUSH GREATEST THREAT FOR ORGANIZED CONVECTION AND WIDESPREAD FLASH
FLOODING FURTHER NORTH AND EAST OF THE AREA. WILL WORD ZONES TO
ACCOUNT FOR LOCAL AREAS OF HEAVY RAIN IN ERN ZONES.

TONIGHT SHOULD BE THE LAST NIGHT OF NOCTURNAL SHOWERS CONTINUING
INTO THE EARLY MORNING HOURS OVER ERN ZONES AS SHORT WAVE PUSHES
AWAY FROM THE AREA AND MID LEVEL MOISTURE DECREASES OVER WRN NV.
HIGH PRESSURE AND LIGHT FLOW WILL CONTINUE THROUGH THE WEEK MAINLY
OVER SRN ZONES. THIS WILL ALLOW TEMPERATURES TO CLIMB BACK INTO THE
UPPER 90S TO LOW 100S. THE ATMOSPHERE WILL DESTABILIZE OVER NATURAL
CONVERGENCE AREAS IN MONO/MINERAL COUNTIES SOUTH OF HIGHWAY 50
ENOUGH FOR ISOLATED THUNDERSTORMS TO DEVELOP DURING THE
AFTERNOON/EVENING THURSDAY AND FRIDAY. NAM AND ESPECIALLY THE GFS
INDICATES A DECENT 500 MB RH RESPONSE TO ACCOMPANY INSTABILITY IN
THESE AREAS WHICH WOULD INDICATE SOME CONVECTION DEVELOPING.
MODIFIED TOTAL TOTALS ARE ALSO ABOVE THE CRITICAL 30 C NEEDED FOR
CONVECTIVE DEVELOPMENT. ELSEWHERE DRIER SOUTHWEST FLOW SHOULD KEEP
THINGS STABLE ENOUGH TO INHIBIT TSTM DEVELOPMENT. HOWEVER CUMULUS
BUILDUPS ARE POSSIBLE OVER NRN LASSEN/NRN WASHOE COUNTY CONVERGENCE
ZONE...JUST DO NOT THINK THERE WILL BE ENOUGH INSTABILITY TO ALLOW
TSTM DEVELOPMENT.

HIGH TEMPERATURES WILL INCREASE A FEW DEGREES THIS WEEK AS CLOUD
COVER AND SHOWERS DECREASE BY THURSDAY AND FRIDAY. MORNING LOWS WILL
DROP SEVERAL DEGREES BY THURSDAY AND FRIDAY MORNING CONSIDERING
PERSISTENT OVERNIGHT CLOUD SHIELD WILL NO LONGER BE PRESENT. BENINATO

.LONG TERM...SATURDAY THROUGH TUESDAY...
UPPER RIDGE OVER THE FOUR-CORNERS/SOUTHWESTERN US WILL CONTINUE TO
DOMINATE THE WEATHER OVER THE LONG TERM. GFS/ECMWF AND ENSEMBLES ARE
ALL IN GOOD AGREEMENT WITH A TROUGH ANCHORED OVER B.C. EXTENDING
INTO THE PAC NW THROUGH THE WEEKEND. THIS IS EXPECTED TO PROVIDE
ENOUGH WEST TO SOUTHWESTERLY FLOW ALOFT TO KEEP MOISTURE AND
THUNDERSTORM ACTIVITY OUT OF MOST OF THE FORECAST AREA. THE
EXCEPTION WOULD BE OVER THE MONO/MINERAL CONVERGENCE ZONE WHERE WEAK
INSTABILITY LOOKS TO REMAIN. INSTABILITY OVER THIS REGION IS QUITE
MARGINAL...SO CONVECTIVE ACTIVITY SHOULD BE VERY ISOLATED...IF AT
ALL. WITH THE RIDGE HAVING THE GREATEST INFLUENCE ON THE FORECAST
AREA...TEMPS WILL REMAIN AROUND 5-8 DEGREES ABOVE NORMAL WITH
TYPICAL AFTERNOON/EVENING WESTERLY ZEPHYR WINDS AND MOSTLY CLEAR
SKIES. MILNE

&&

.AVIATION...
ISOLATED TO SCATTERED SHOWERS AND STORMS EXPECTED OVER WESTERN NV
AND THE SOUTHERN SIERRA. TVL...TRK AND RNO SHOULD BE JUST WEST OF
ANY THUNDERSTORM ACTIVITY. ROUTES OVER THE SOUTHERN SIERRA AND JUST
EAST OF THE CENTRAL SIERRA WILL SEE LOCALLY HEAVY DOWNPOURS WITH
LIMITED VISIBILITIES AND GUSTY OUTFLOW WINDS. MILNE

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.

HTTP://WEATHER.GOV/RENO