Flash Flood Warning 2, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
310 PM PDT MON APR 30 2007

.SHORT TERM...
UPPER RIDGE HAS PUSHED EAST OF THE AREA AND THIS WILL ALLOW FOR
AN INCREASING SOUTHWEST FLOW OVER THE REGION THROUGH WEDNESDAY AS
A PACIFIC TROUGH NEARS THE WEST COAST. THIN CIRRUS WILL SPREAD
OVER THE AREA THIS EVENING AND TONIGHT.

BIGGEST IMPACT OF THE INCOMING STORM WILL BE THE WINDS AS THERMAL
AND PRESSURE GRADIENTS INCREASE OVER THE NEXT 48 HOURS. STRONGEST
WINDS TOMORROW AND WEDNESDAY WILL BE DURING THE AFTERNOON AND
EVENING HOURS WITH GUSTS PEAKING OUT AT 40 TO 45 MPH ALONG THE
EASTERN SIERRA SLOPES AND FAR WESTERN NEVADA. THE USUAL WIND
PRONE AREAS COULD SEE GUSTS NEAR 50 MPH. WINDS ON WEDNESDAY COULD
BE A BIT HIGHER THAN CURRENTLY FORECAST AS THERE IS A COLD FRONT
SET TO PUSH THROUGH THE REGION. HAVE ISSUED A LAKE WIND ADVISORY
FOR TAHOE AND PYRAMID FOR TOMORROW AND WILL LIKELY NEED TO BE
EXTENDED THROUGH WEDNESDAY EVENING.

PRECIPITATION CHANCES WILL START TUESDAY NIGHT FOR THE NORTHERN
SIERRA...THEN SPREAD SOUTH AND EAST ON WEDNESDAY AS THE TROUGH AND
COLD FRONT PUSH THROUGH THE AREA. MODELS FORECAST SOME WEAK
INSTABILITY ALONG THE FRONT THAT COULD PRODUCE A THUNDERSTORM OR
TWO. DECIDED TO LEAVE THUNDERSTORMS OUT OF THE FORECAST FOR
NOW...AS I THINK THE CHANCE IS LESS THAN 10 PERCENT. PRECIPITATION
AMOUNTS FOR THE SIERRA SHOULD BE LESS THAN 0.50 INCHES...WHICH
IS STILL ENOUGH FOR A FEW INCHES OF SNOW ABOVE 5500-6000 FEET.
ACCUMULATIONS ON ROADS...EXCEPT BRIDGES AND OVERPASSES...WILL BE
SLUSHY. VALLEY TEMPERATURES WILL DROP INTO THE MID 50S TO LOWER
60S...WITH THE SIERRA IN 40S.

SNOW LEVELS WILL CONTINUE TO DROP WEDNESDAY NIGHT AND MAY EVEN
LOWER DOWN TO 4000-4500 FEET AS COLD AIR MOVES OVER THE REGION.
THURSDAY WILL BE COOL AND SHOWERY WITH THE COLD CYCLONIC FLOW
ALOFT. A SECOND INSIDE SLIDER TYPE SYSTEM WILL REACH THE NORTHERN
SIERRA THURSDAY NIGHT. RIGHT NOW THE GFS SHOWS THIS SYSTEM HAS THE
POTENTIAL TO BE WETTER THAN THE FIRST...WITH SNOW LEVELS BELOW
5500 FEET NORTH AND BELOW 6500 FEET SOUTH. BRONG

.LONG TERM...FRIDAY THROUGH MONDAY...
THE GFS AND MOST OF ITS ENSEMBLES HAVE FINALLY GOTTEN ON BOARD WITH
THE CONSISTENT ECMWF SOLUTION...SO CONFIDENCE HAS RISEN CONSIDERABLY
FROM PREVIOUS DAYS. A COLD SYSTEM WILL AFFECT THE REGION FRIDAY WITH
PRECIPITATION AND MUCH BELOW NORMAL TEMPERATURES. SEE THE NEXT
PARAGRAPH FOR A FEW MORE DETAILS. WARMER BUT STILL BELOW NORMAL
TEMPERATURES ARE EXPECTED SATURDAY WITH COOL NORTHERLY FLOW
DEVELOPING. SUNDAY AND MONDAY...A RIDGE WILL BUILD BACK OVER THE
REGION FOR CONTINUED WARMING TO AROUND NORMAL BY EARLY NEXT WEEK.

FRIDAYS COLD UPPER LOW OF THE INSIDE SLIDER VARIETY IS CURRENTLY
PROGGED BY BOTH THE GFS AND ECMWF TO TRACK RIGHT OVER THE WESTERN
GREAT BASIN...FOR A POSSIBLE DEFORMATION BAND OF MOSTLY SNOW (WITH
MIXED RAIN AND SNOW POSSIBLE FOR THE LOWEST ELEVATIONS) SOMEWHERE
OVER WESTERN NEVADA AND IN THE SIERRA. OF COURSE I SAY SOMEWHERE FOR
A REASON...AS WHERE EXACTLY A PRECIP BAND MIGHT DEVELOP IS WAY TOO
FINE SCALE TO DETERMINE THIS FAR OUT. THEREFORE...I WENT WITH GOOD
CHANCE POPS FOR THE SIERRA AND FAR WESTERN NEVADA FOR NOW UNTIL
DETAILS EMERGE.

AS FAR AS A STAB AT THE IMPACTS OF ANY SNOW FRIDAY...GIVEN THE WARM
ROAD TEMPERATURES THIS FAR INTO SPRING...IT WOULD TAKE PERSISTENT
HEAVY SNOW TO PRODUCE MORE THAN WET CONDITIONS ON LOWER ELEVATION
ROADS FRIDAY MORNING...WITH MOST ACCUMULATION ON ELEVATED AND
NON-ROAD SURFACES. SNYDER
&&

.AVIATION...
NO CONCERNS THROUGH TUESDAY MORNING. BREEZY TO WINDY CONDITIONS OVER
EASTERN CALIFORNIA AND WESTERN NEVADA TUESDAY AFTERNOON AND EARLY
EVENING. SHOWERS POSSIBLE WITH HIGHER MOUNTAIN OBSCURATION (IN SNOW
SHOWERS) TUESDAY NIGHT AND WEDNESDAY. SNYDER
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY FROM 7 AM TO 9 PM PDT TUESDAY FOR NVZ002-004.

CA...LAKE WIND ADVISORY FROM 7 AM TO 9 PM PDT TUESDAY FOR CAZ072.

&&

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