Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 161004
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
304 AM PDT TUE SEP 16 2014

.SYNOPSIS...CLOUDS WILL INCREASE TODAY WITH A GREATER CHANCE OF
THUNDERSTORMS ACROSS MAINLY SAN BERNARDINO AND MOHAVE COUNTIES 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 AND FRIDAY.
&&

.SHORT TERM...THROUGH THURSDAY NIGHT...A LOW LEVEL MOISTURE SURGE
BEGAN LATE LAST EVENING WITH SURFACE DEWPOINTS REACHING THE LOWER
70S AT BLYTHE. HOWEVER...RECENT SURFACE OBS AND YUMA VAD WIND
PROFILE INDICATE A PAUSE IN THAT MOISTURE SURGE. THE NAM12 IS PRETTY
BULLISH WITH LOW LEVEL MOISTURE AND INSTABILITY OVER MOHAVE...CLARK
AND SAN BERNARDINO COUNTIES TODAY. THE GFS/ECMWF ARE LESS
IMPRESSIVE. NONE OF THE MODELS GENERATE MUCH QPF. THE UPPER HIGH IS
STILL OVER FAR SOUTHERN NEVADA THIS MORNING AND THAT MAY HELP CAP
CONVECTION SOMEWHAT. HOWEVER...THAT HIGH IS FORECAST TO SHIFT NORTH
SOMEWHAT WHICH SHOULD ALLOW AT LEAST ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS OVER MOHAVE...MUCH OF SAN BERNARDINO AND SOUTHERN
CLARK COUNTIES. HOWEVER...WE WILL HAVE TO MONITOR THE POTENTIAL
ADDITIONAL LOW LEVEL MOISTURE SURGE THROUGH THE MORNING AND CONSIDER
INCREASING POPS AND SPREADING THUNDERSTORM CHANCES FARTHER NORTH.

MODELS DIFFER IN HOW MUCH MOISTURE SPREADS UP WEDNESDAY-THURSDAY AND
HOW FAR EAST DRY AIR GETS PUSHED IN DUE TO THE PACIFIC TROUGH
APPROACHING THE COAST WEDNESDAY AND MOVING INTO CALIFORNIA THURSDAY.
DUE TO LACK OF CONFIDENCE I MADE VERY FEW CHANGES...KEEPING LIKELY
POPS SOUTHEAST WEDNESDAY AND ACROSS THE EAST THURSDAY AS LIFT FROM
THE INCOMING PACIFIC TROUGH INCREASES. AT THIS TIME THE FLASH FLOOD
WATCH FOR THE SOUTHEAST ZONES WEDNESDAY AND THE EAST HALF OF THE CWA
THURSDAY STILL LOOKS REASONABLE. INYO COUNTY WILL HAVE THE LOWEST
CHANCE OF THUNDERSTORMS BUT STILL KEPT A SLIGHT CHANCE MENTIONED.
HOWEVER...WE MAY HAVE TO TRIM POPS BACK EVEN MORE IN THE WESTERN CWA
IF THE DRYING TREND OF THE GFS AND ECMWF CONTINUES WITH LATER RUNS.

.LONG TERM...FRIDAY THROUGH MONDAY...HIGH PRESSURE IS FORECAST TO
STRENGTHEN OFF THE WEST COAST FRIDAY WITH TROUGHING OVER THE
SOUTHWEST. THE GFS/GEM FORECAST A CLOSED LOW CENTERED ALONG THE
CENTRAL/SOUTHERN CALIFORNIA COAST WHILE THE ECMWF FORECASTS AN OPEN
WAVE. WITH A LOW IN THIS GENERAL LOCATION, LINGERING MOISTURE OVER
THE AREA COULD BE AN ISSUE. THE GFS AND ECMWF FORECAST THE
TROUGH/LOW WILL SWEEP MOISTURE OFF TO THE EAST...LEAVING DRY AND
STABLE CONDITIONS AREAWIDE FOR MUCH OF THE DAY FRIDAY WITH NO
PRECIPITATION FORECAST. THE 06Z NAM12, WHICH RUNS THROUGH MID DAY
FRIDAY, STILL GENERATES PRECIP OVER THE EASTERN CWA IN THE MORNING
SO LEFT CHANCE POPS IN LINCOLN/MOHAVE COUNTY IN THE MORNING TO
ACCOUNT FOR THIS BUT THEN LOWERED CHANCES AGAIN IN THE AFTERNOON AS
THE DRY/STABLE AIR PUSHES IN.

LOW FORECAST CONFIDENCE IN THE SAT-MON TIME PERIOD AS MODEL
SOLUTIONS DIVERGE REGARDING HOW THE LOW EVOLVES. THE ECMWF FORMS A
CLOSED LOW OFF THE COAST EARLY SATURDAY AND THEN RETROGRADES IT
WESTWARD OUT TO SEA THROUGH SUNDAY BEFORE BRINGING IT BACK INLAND ON
MONDAY. THIS LEAVES THE ENTIRE FORECAST AREA DRY ALL WEEKEND WITH
CHANCES FOR PRECIPITATION INCREASING AGAIN ON MONDAY. THE GFS DROPS
THE LOW TO NEAR SAN DIEGO SATURDAY AND THEN SLOWLY MOVES IT ACROSS
THE FORECAST AREA SUNDAY AND MONDAY. MOISTURE AND INSTABILITY
INCREASES, ESPECIALLY ACROSS THE SOUTHERN CWA AND THE GFS GENERATES
QPF ACROSS MUCH OF THE AREA BOTH SUNDAY AND MONDAY AS THE LOW
INTERACTS WITH THE MOISTURE. MAINTAINED A MENTION OF THUNDER ACROSS
PORTIONS OF THE AREA SAT-MON TO ACCOUNT FOR THE VARIOUS SOLUTIONS.

TEMPERATURES SHOULD GENERALLY RUN A FEW DEGREES BELOW NORMAL WITH
TROUGHING OVER THE AREA FRI-MON PER THE GFS/GEM HOWEVER, IF THE
ECMWF SOLUTION DOES PAN OUT, THE WEEKEND WOULD BE WARMER/SUNNIER
WITH TEMPERATURES NEAR OR SLIGHTLY ABOVE NORMAL.
&&

.AVIATION...FOR MCCARRAN...SOUTH/SOUTHWEST WINDS UP TO 10 KTS EARLY
THIS MORNING THEN FAVORING EASTERLY UNDER 10 KTS. SOUTH-SOUTHEAST
WINDS ARE LIKELY TO INCREASE EARLY THIS EVENING TO AROUND 10-12
KTS...THEN SETTLING TO SOUTH UNDER 10 KTS AFTER 06Z THIS EVENING.
SCT CUMULUS DEVELOPING THIS AFTERNOON WITH ISOLATED TO SCATTERED
THUNDERSTORMS MAINLY LIMITED TO THE PEACH SPRINGS CORRIDOR AND THE
SURROUNDING MOUNTAINS. ERRATIC WINDS DUE TO THUNDERSTORM OUTFLOW
BOUNDARIES CANNOT BE RULED OUT THIS AFTERNOON AND EVENING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...LIGHT WINDS EARLY WILL GENERALLY BECOME SOUTHERLY 10-15
KTS MUCH OF TODAY THROUGH THIS EVENING. ISOLATED THUNDERSTORMS ARE
EXPECTED OVER MUCH OF MOHAVE AND SAN BERNARDINO COUNTIES AND PERHAPS
SOUTHERN CLARK COUNTY THIS 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.
&&

$$

SHORT TERM/AVIATION...HARRISON
LONG TERM...SALMEN

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