Area Forecast Discussion
Issued by NWS Las Vegas, NV

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KVEF 160309
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
810 PM PDT MON SEP 15 2014

.SYNOPSIS...CLOUDS WILL INCREASE TUESDAY WITH A GREATER CHANCE OF
THUNDERSTORMS ACROSS SAN BERNARDINO COUNTY AS MONSOON MOISTURE
SURGES NORTHWARD UNDER THE INFLUENCE OF HURRICANE ODILE.
THUNDERSTORMS WITH THE POTENTIAL FOR HEAVY RAIN ARE EXPECTED TO PUSH
FURTHER NORTH THROUGH THE REGION WEDNESDAY THEN BEGIN TO MIGRATE
EAST THURSDAY.
&&

.UPDATE...ISOLATED SHOWERS AND THUNDERSTORMS ARE FINALLY WANING
ACROSS SOUTHERN MOHAVE COUNTY. A WEAK OUTFLOW BOUNDARY IS PUSHING TO
THE WEST ACROSS MOHAVE COUNTY AND TOWARD LAKE MEAD...BUT SHOULD FALL
APART OVER THE NEXT HOUR. ELSEWHERE...ODILE HAS BEEN DOWNGRADED TO A
TROPICAL STORM AND WILL CONTINUE TO BE THE MAIN INFLUENCE ON THE
AREA WEATHER THIS WEEK. AT THIS POINT NO CHANGES ARE BEING MADE TO
THE FORECAST. WE`LL BE CONTINUING TO MONITOR THE EXACT TRACK OF
ODILE AND ANY ASSOCIATED MOISTURE PUSHES INTO THE MOHAVE DESERT AND
LOWER COLORADO RIVER VALLEY.
&&

.PREV DISCUSSION...
348 PM PDT MON SEP 15 2014

.SHORT TERM...THROUGH TUESDAY NIGHT...A BIT MORE SHOWER/WEAK
THUNDERSTORM ACTIVITY THIS AFTERNOON THAN ANTICIPATED OVER LINCOLN
COUNTY ALONG THE NORTHERN FRINGE OF THE HIGH WHICH IS CENTERED OVER
LAS VEGAS. THESE WILL DISSIPATE RAPIDLY AS SUNSET ARRIVES WITH DRY
CONDITIONS EXPECTED OVERNIGHT. ADDITIONAL MOISTURE IS EXPECTED TO
ADVECT FURTHER INTO SAN BERNARDINO...MOHAVE AND POSSIBLY SOUTHERN
CLARK COUNTY THROUGH TUESDAY. AT THE SAME TIME...THE HIGH PRESSURE
CAPPING MUCH OF THE AREA TODAY IS EXPECTED TO SHIFT NORTHEAST INTO
SOUTHERN UTAH ALLOWING FOR A BIT MORE SHOWER/THUNDERSTORM ACTIVITY.

.LONG TERM...WEDNESDAY THROUGH MONDAY...MODELS HAVE COME INTO TO
SOMEWHAT BETTER AGREEMENT TODAY WITH RESPECT TO THE PATTERN
EVOLUTION THROUGH LATE THURSDAY AND CONFIDENCE HAS RISEN EVER SO
SLIGHTLY. THE CURRENT EVOLUTION TAKES PAGES OUT OF BOTH THE ECMWF
AND GFS PLAYBOOKS FROM THE LAST FEW DAYS. THERE ARE THREE MAIN
FEATURES OF CONCERN THROUGH THE PERIOD...ALL WITH NOTORIOUSLY POOR
PREDICTABILITY MORE THAN A COUPLE DAYS OUT. THE FIRST...HURRICANE
ODILE MADE AN EASTWARD SHIFT IN IT`S PATH OVERNIGHT AND IS NOW
PROGGED TO MOVE ALONG AND OVER THE BAJA PENINSULA THROUGH
TUESDAY...BEFORE WEAKENING AND TURNING NORTHEAST TOWARDS SOUTHEAST
ARIZONA. WITH THIS TYPE OF TRACK WE EXPECT LOW LEVEL MOISTURE TO
PUSH UP THE COLORADO RIVER VALLEY IN THE FORM OF A GULF SURGE...THE
SECOND FEATURE THAT MODELS OFTEN STRUGGLE WITH. THIS IS CURRENTLY
EXPECTED TO ARRIVE SOMETIME LATE TUESDAY INTO WEDNESDAY MORNING. THE
LAST FEATURE IS AN UPPER LEVEL TROUGH OR CUTOFF LOW THAT IS EXPECTED
TO DIG ALONG THE WEST COAST THROUGH AT LEAST FRIDAY. MODELS HAVE
TRENDED TOWARDS DIGGING THE TROUGH SOMEWHERE IN BETWEEN WHERE THE
GFS AND ECMWF HAVE BEEN THE LAST COUPLE DAYS. IN THIS SOLUTION
STRONG MOISTURE ADVECTION IS EXPECTED WEDNESDAY ACROSS THE
SOUTH-CENTRAL PORTIONS OF THE FORECAST AREA. AS A RESULT HEAVY RAIN
AND FLASH FLOODING WILL BE A STRONG POSSIBILITY THROUGH THE DAY AND
A FLASH FLOOD WATCH HAS BEEN ISSUED FOR THESE AREAS FOR WEDNESDAY
AND THURSDAY. FOR THURSDAY DRIER AIR BEGINS TO PUSH IN FROM THE WEST
AND THE CORE OF THE MOISTURE PLUME MOVES NORTHEAST. AT THIS POINT
BOTH THE ECMWF AND GFS HAVE DEVELOPED A RATHER STRONG NORTH-SOUTH
ORIENTED MOISTURE GRADIENT BY THURSDAY AFTERNOON...WHICH MAY ACT AS
A TRIGGERING MECHANISM THROUGH THURSDAY AFTERNOON. HAVE ADDED BOTH
LINCOLN AND NORTHERN MOHAVE COUNTIES TO THE FLASH FLOOD WATCH FOR
THURSDAY ONLY TO ACCOUNT FOR THE NORTHEAST PROGRESSION OF THE
MOISTURE PLUME. IT`S LIKELY THAT WE WILL NEED TO EXPIRE PORTIONS OF
THE WATCH AS THE DRIER ARE PUSHES EAST ACROSS THE AREA THURSDAY.

A NOTE ON THE FLASH FLOOD WATCH...THERE IS STILL HIGH UNCERTAINTY
IN THE EVOLUTION OF THE FORECAST DURING THIS PERIOD AND STORMS MAY
BE ISOLATED TO SCATTERED IN NATURE. HOWEVER...WITH MANY AREAS STILL
RECOVERING FROM FLOOD IMPACTS THE RISK FOR ADDITIONAL IMPACTS IS
HIGH. BURN SCARS...URBAN CENTERS...AND AREAS THAT HAVE RECENTLY
EXPERIENCES RECENT FLOODING SHOULD PAY CLOSE ATTENTION TO FORECASTS
AND WARNINGS.

AS WE MOVE INTO THURSDAY NIGHT AND FRIDAY THE UPPER LEVEL LOW IS
CURRENTLY PROGGED TO BECOME CUT OFF FROM THE MAIN JET. HOWEVER
EXACTLY WHEN AND WHERE IT ENDS UP IS STILL NOT WELL AGREED UPON. IN
ANY CASE MUCH OF THE MOISTURE DOES APPEAR THAT IT WILL HAVE MOVED
EAST OF THE AREA AND HAVE LEFT IN ONLY SLIGHT CHANCE POPS FROM
FRIDAY NIGHT ONWARD. WILL HAVE TO WAIT FOR BETTER MODEL AGREEMENT
BEFORE BEING ABLE TO NAIL THE FORECAST BEYOND FRIDAY DOWN.
&&

.AVIATION...FOR MCCARRAN...WINDS ARE EXPECTED TO FOLLOW TYPICAL
DIURNAL TRENDS THROUGH MID-DAY TOMORROW. SOUTH-SOUTHEAST WINDS ARE
LIKELY TO INCREASE TUESDAY AFTERNOON TO AROUND 10-12 KTS WITH
OCCASIONAL HIGHER GUSTS. FEW-SCT CUMULUS DURING THE DAYTIME.
ISOLATED TO SCATTERED THUNDERSTORMS TUESDAY AFTERNOON...MAINLY
LIMITED TO THE PEACH SPRINGS CORRIDOR.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS WILL FAVOR TYPICAL DIURNAL TRENDS THROUGH
TONIGHT. SOUTH TO SOUTHEAST WINDS ARE EXPECTED IN INCREASE SLIGHTLY
BY TOMORROW AFTERNOON. ISOLATED THUNDERSTORMS ARE POSSIBLE OVER
PORTIONS OF MOHAVE...SAN BERNARDINO AND PERHAPS SOUTHERN CLARK
COUNTY TOMORROW AFTERNOON AND EARLY EVENING. THUNDERSTORM CHANCES
WILL INCREASE FROM SOUTH TO NORTH WEDNESDAY.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
THROUGH TUESDAY. HOWEVER SPOTTERS ARE ENCOURAGED TO REPORT ANY
SIGNIFICANT WEATHER ACCORDING TO STANDARD OPERATING PROCEDURES.
SPOTTER ACTIVATION MAY BE NECESSARY FOR WEDNESDAY AND THURSDAY
DEPENDING ON WHAT HAPPENS WITH THE MOISTURE FROM HURRICANE ODILE.
&&

$$

CZYZYK/WOLCOTT

FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE:

HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER










USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.