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Area Forecast Discussion

000
FXUS65 KVEF 010101
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
600 PM PDT THU JUL 31 2014

.SYNOPSIS...ISOLATED TO SCATTERED THUNDERSTORMS OVER EAST CENTRAL 
NEVADA AND NORTHWEST ARIZONA WILL GRADUALLY DISSIPATE THIS EVENING. 
THUNDERSTORMS WILL BE MORE ISOLATED OVER THE REGION UNDER A SLIGHTLY 
DRIER AND MORE STABLE AIR MASS FRIDAY. ANOTHER PUSH OF MOISTURE AND 
AN UPPER LEVEL DISTURBANCE ARE EXPECTED TO SPREAD UP ACROSS THE 
REGION OVER THE WEEKEND FOR AN UPSWING IN SHOWERS AND THUNDERSTORMS.
&&

.UPDATE...ISOLATED TO SCATTERED THUNDERSTORMS WERE CONTINUING PRETTY 
MUCH WHERE FORECAST FOR THE EVENING...MAINLY ALONG THE SIERRA AND IN 
LINCOLN AND MOHAVE COUNTIES. FAIRLY EXTENSIVE BAND OF HIGH CLOUDS 
ACROSS THE SOUTHEAST PART OF THE FORECAST AREA HAS A BIT MORE 
OPAQUENESS THAN FORECAST. SAME STORY WITH HIGH CLOUDS BLOWING OFF 
THUNDERSTORM TOPS ALONG THE SIERRA CREST TOWARD THE NORTHEAST. I 
UPDATED SKY GRIDS FOR TONIGHT ACCORDINGLY. -HARRISON-
&&

.PREV DISCUSSION...
320 PM PDT THU JUL 31 2014

.SHORT TERM...THROUGH SATURDAY NIGHT...THE MAIN AREA FOR 
THUNDERSTORMS THROUGH THIS EVENING WILL BE LINCOLN AND MOHAVE 
COUNTIES. THUNDERSTORMS WERE IGNITING OVER EAST CENTRAL NEVADA AIDED 
BY A CIRCULATION MOVING INTO WESTERN UTAH AND ALSO A JET STREAK 
ORIENTED OVER UTAH AND EASTERN NEVADA. HIGH RES MODELS CONTINUE TO 
SHOW STORMS EXPANDING IN COVERAGE OVER NORTHERN AND CENTRAL LINCOLN 
COUNTY AND PUSHING TO THE SOUTHEAST DURING THE LATE AFTERNOON AND 
EVENING. THIS COULD LEAD TO THUNDERSTORMS BRUSHING THE SHEEP 
RANGE...NORTHEAST CLARK AND NORTHERN MOHAVE COUNTY THIS EVENING. 
STORM COVERAGE WAS BECOMING FAIRLY EXTENSIVE OVER THE ARIZONA RIM 
COUNTRY AND SOME HIGH RES MODELS INDICATE STORMS WILL BACKBUILD 
TOWARD SOUTHEAST MOHAVE COUNTY. CLOUD DEVELOPMENT WAS SLOW TO BUILD 
OVER THE SOUTHERN SIERRA BUT WE COULD STILL SEE A FEW SHOWERS AND 
THUNDERSTORMS FIRE UP AS THE DAY PROGRESSES. DEWPOINTS HAVE BEEN 
DROPPING INTO THE LOW 40S ACROSS MUCH OF THE AREA. CONVECTION SHOULD 
DIMINISH DURING THE LATE EVENING AND OVERNIGHT. FRIDAY LOOKS TO 
BRING FEWER THUNDERSTORMS BUT STILL THE POSSIBILITY OF STORMS OVER 
THE SOUTHERN SIERRA...CENTRAL NEVADA AND MOHAVE COUNTY ARIZONA.

AS WE GO INTO FRIDAY NIGHT AND SATURDAY...ATTENTION WILL BE TURNED 
TOWARD THE SOUTH AS A CIRCULATION CURRENTLY OVER SOUTHERN BAJA IS 
FORECAST TO LIFT UP TOWARD NORTHERN BAJA AND FAR SOUTHERN CALIFORNIA 
SATURDAY THEN HEAD INTO SOUTHERN NEVADA SATURDAY NIGHT. THIS WILL BE 
ACCOMPANIED BY A SIGNIFICANT INCREASE IN MOISTURE AND I WOULD EXPECT 
THE LEADING EDGE OF THE CIRCULATION TO PROVIDE SOME FORCING FOR 
OVERNIGHT SHOWER AND THUNDERSTORM DEVELOPMENT SATURDAY NIGHT. THE 
LATEST MODELS WERE IN FAIRLY GOOD AGREEMENT WITH THE TRACK AND 
TIMING OF THESE FEATURES AND NO SIGNIFICANT CHANGES WERE MADE TO THE 
GOING POP/WX AND TEMP TRENDS.

.LONG TERM...SUNDAY THROUGH WEDNESDAY...MODELS ARE IN DECENT 
AGREEMENT THAT A DISTURBANCE WILL MOVE NORTH FROM ARIZONA/NORTHERN 
MEXICO SATURDAY AND SATURDAY NIGHT. AS THIS FEATURE PUSHES NORTH 
SUNDAY THROUGH MONDAY NIGHT IT SHOULD PROVIDE AMPLE FORCING IN A 
MOISTURE-RICH ENVIRONMENT [850-500MB MIXING RATIOS OF 6-9 G/KG 
ACROSS ALL BUT THE FAR WESTERN AREAS] TO PRODUCE AT LEAST AT LEAST 
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE REGION. WITH THE 
ADDED DYNAMICS STORMS MAY CONTINUE THROUGH THE OVERNIGHT HOURS. THE 
QUESTION WILL BE JUST HOW MUCH INSTABILITY WILL DEVELOP EACH DAY AND 
THEREFORE HOW MUCH THUNDER THERE WILL ACTUALLY BE...THIS IS OFTEN 
THE BIG QUESTION WITH THESE SYSTEMS. BOTH THE LATEST GFS AND ECMWF 
INDICATE A PUNCH OF DRIER AIR OVER THE EASTERN CWA ABOVE 500MB BY 
SUNDAY AFTERNOON WHICH MAY PRODUCE ENOUGH CLEARING TO ALLOW FOR SOME 
SIGNIFICANT INSTABILITY TO DEVELOP. THE GFS IS NOT AT ALL 
ENTHUSIASTIC ABOUT DEVELOPING INSTABILITY IN THIS AREA WHILE THE 
ECMWF IS MORE AGREEABLE AND WAS LEANED ON MORE HEAVILY. LESS CLOUD 
COVER IS FORECAST FOR MONDAY...BUT MOISTURE WILL ALSO BE DECREASING. 
FOR THE MOMENT HAVE INDICATED HIGHER POPS FOR SUNDAY. ISOLATED 
POCKETS OF ENHANCED SHEAR [MAINLY SUNDAY] COULD SET THE STAGE FOR A 
FEW ORGANIZED STORMS...BUT WITH THE HIGH MOISTURE CONTENT THE MOST 
SIGNIFICANT THREAT WILL BE FLASH FLOODING BOTH DAYS...ESPECIALLY IN 
AREAS WITH VERY SLOW STORM MOTION. UNFORTUNATELY IT'S TOO EARLY TO 
HAVE MUCH CONFIDENCE IN EXACTLY WHERE THESE AREAS WILL BE. 

FOR TUESDAY AND BEYOND EXPECT SHOWER/THUNDERSTORM CHANCES TO BECOME 
INCREASINGLY LIMITED TO THE FAR NORTHERN AREAS AS MOISTURE SLOWLY 
PUSHES NORTH INTO CENTRAL NEVADA. TEMPERATURES SHOULD RISE FROM 5-10 
DEGREES BELOW NORMAL SUNDAY BACK TOWARDS NORMAL BY MID-WEEK.
&&

.AVIATION...FOR MCCARRAN...SOUTHWEST WINDS THROUGH MUCH OF THE 
EVENING MAY GIVE WAY TO NORTHEAST WINDS PUSHING DOWN FROM LINCOLN 
COUNTY TOWARD MIDNIGHT. ISOLATED THUNDERSTORMS IN THE PEACH SPRINGS 
AND MORMON MESA CORRIDORS SHOULD DISSIPATE BY LATE EVENING. A MORE 
SOUTHEASTERLY WIND COMPONENT IS FORECAST TO DEVELOP LATE FRIDAY 
MORNING AND AFTERNOON WHICH MAY FAVOR RUNWAY CONFIG 4.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...ISOLATED TO SCATTERED THUNDERSTORMS OVER EAST CENTRAL 
NEVADA...NORTHWEST ARIZONA AND THE SOUTHERN SIERRA WILL GRADUALLY 
DISSIPATE THIS EVENING. FEWER THUNDERSTORMS ARE EXPECTED ACROSS THE 
REGION FRIDAY. SCT-BKN BASES AROUND 12-15 KFT MSL. DIURNAL WINDS 
GENERALLY LESS THAN 15 KTS CAN BE EXPECTED AWAY FROM THUNDERSTORM 
INFLUENCES.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED 
AT THIS TIME. HOWEVER...SPOTTERS ARE ENCOURAGED TO REPORT ANY 
SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING 
PROCEDURES.
&&

SHORT TERM/AVIATION...ADAIR
LONG TERM...WOLCOTT

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