Severe Thunderstorm Warning 26, NWS Reno, NV

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
855 AM PDT FRI AUG 2 2002

A MOIST AND UNSTABLE AIRMASS REMAINS OVER NW NV THIS MORNING...
ESPECIALLY OVER THE SOUTHERN PART OF OUR FORECAST AREA.  FLOW ALOFT
IS RELATIVELY LIGHT AND THE BIGGEST THREAT FROM THUNDERSTORMS TODAY
WILL PROBABLY BE FLASH FLOODING.  ABOUT THE ONLY NEGATIVE FACTOR IS
THE SMALL SUBSIDENCE CAP SHOWN ON THE OAKLAND SOUNDING. THIS COULD
BE FROM THE PASSAGE OF THE WEAK AND POORLY ORGANIZED UPPER LEVEL
VORT LOBE NOW OVER WESTERN NV.  ADDING THIS CAP TO THE RENO SOUNDING
DOES NOT QUITE CUT OFF DEEP CONVECTION THOUGH. SOUTHWEST FLOW
STRENGTHENS ON SATURDAY AS THE WEAK UPPER LOW NOW NEAR 34/132W NEARS
AND A TROUGH STARTS TO DEVELOP OFF THE COAST.  AIRMASS HERE BECOMES
MORE STABLE ALTHOUGH THE 12Z ETA KEEPS SOME INSTABILITY OVER THE
EASTERN PART OF OUR FORECAST AREA.  THE FLOW CONTINUES TO STRENGTHEN
ON SUNDAY AS THE TROUGH DEEPENS.  WINDS WILL BE STRONG ENOUGH TO
CAUSE PROBLEMS FOR BOATERS.  COREY

.REV...NONE.

FFP INDEX - PROTOTYPE FLASH FLOOD POTENTIAL OUTLOOK

                                FOR

  NORTHEAST CALIFORNIA, THE EAST CENTRAL SIERRA, AND WESTERN NEVADA

THIS EXPERIMENTAL PRODUCT IS ISSUED DAILY BY 6 AM AS A TEXT VERSION
AND ALSO SENT TO THE WEB AS A GRAPHIC.  NEITHER PRODUCT IS UPDATED.
SEE THE WEB ADDRESS AT THE BOTTOM OF THIS PAGE TO ACCESS THE FFP
GRAPHIC.

THIS TEXT PRODUCT WILL BE ISSUED IN THIS FORMAT UNTIL OCTOBER 1,
2002.  AT THAT TIME, EQUIVALENT INFORMATION WILL BE INCORPORATED
INTO A MULTI-HAZARD HAZARDOUS WEATHER OUTLOOK (HWO) THAT WILL BE
ISSUED EACH MORNING BY ALL NATIONAL WEATHER SERVICE OFFICES.

FFP NUMBERS BELOW IN THIS TEXT PRODUCT ARE THE MOST REPRESENTATIVE
VALUE FOR EACH FORECAST ZONE AS DISPLAYED IN THE GRAPHICAL FFP.

ZONE     FFP TODAY-SATURDAY   FORECAST AREA

NVZ001           3-1          MINERAL AND SOUTHERN LYON COUNTIES
NVZ002-CAZ072    1-1          GREATER LAKE TAHOE AREA
NVZ003           2-1          GREATER RENO-CARSON CITY-MINDEN AREA
NVZ004           3-1          WESTERN NEVADA BASIN AND PYRAMID LAKE
NVZ005-CAZ070    2-1          NORTHERN WASHOE COUNTY-SURPRISE VALLEY
CAZ071           2-1          LASSEN-EASTERN PLUMAS/SIERRA COUNTIES
CAZ073           2-1          MONO COUNTY

FFP 1-NIL  2-LOW  3-MODERATE  4-HIGH  5-VERY HIGH  6-EXTREME

THE FLASH FLOOD POTENTIAL (FFP) IS AN INDEX OF THE AIRMASS POTENTIAL
FOR HEAVY RAINFALL TO PRODUCE FLASH FLOODING.  IT IS NOT STRICTLY A
FORECAST OF PRECIPITATION, BUT INCORPORATES THE RISK OF
THUNDERSTORMS, AVAILABLE MOISTURE, LARGE SCALE TERRAIN DIFFERENCES,
AND SIGNIFICANT PAST RAINFALL.  LOCAL IMPACTS MAY VARY DUE TO STEEP
TERRAIN, FLOOD PRONE AREAS, VEGETATION, AND ANY MAN-MADE STRUCTURES
OR DRAINAGES.

WHILE AN INCREASING INDEX DOES NOT NECESSARILY INDICATE AN EXPANDING
AREAL RISK OF PRECIPITATION, THE TREND FROM DAY TO DAY IS IMPORTANT
IN ASSESSING THE POTENTIAL FOR HEAVY RAINFALL WITH ANY
THUNDERSTORMS.  THE FFP SHOULD BE USED IN CONCERT WITH THE CURRENT
ZONE OR AREA WEATHER FORECAST.  USERS OF THE FFP SHOULD MONITOR
DEVELOPING WEATHER AND REMAIN ALERT FOR ANY WATCHES, WARNINGS, OR
ADVISORIES ISSUED BY THE NATIONAL WEATHER SERVICE.

A DETAILED GRAPHICAL VERSION OF THE FFP PRODUCT CAN BE FOUND AT:
HTTP://WWW.WRH.NOAA.GOV/RENO/DIGITAL/FFP.SHTML  (USE ALL LOWER CASE)