000
FXUS65 KVEF 292132
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
230 PM PDT THU JUL 29 2010

.SYNOPSIS...ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED MAINLY
ACROSS NORTHWEST ARIZONA AND SOUTHEAST NEVADA THROUGH FRIDAY WHILE A
STABLE AIR MASS HOLDS OVER THE WESTERN HALF OF THE REGION. MONSOONAL
MOISTURE MAY SPREAD WEST OF THE ARIZONA BORDER SATURDAY AND SUNDAY
IN RESPONSE TO A LOW PRESSURE SYSTEM MOVING FROM ARIZONA TOWARD
SOUTHERN CALIFORNIA.
&&

.SHORT TERM...MOIST AND UNSTABLE AIR IS IN PLACE OVER MOHAVE COUNTY
THIS AFTERNOON AND EXTENDS UP ACROSS EASTERN LINCOLN COUNTY AS WELL.
THUNDERSTORMS WERE PRODUCING SOME HEAVY RAIN IN THE SOUTHERN PART OF
MOHAVE COUNTY AND THESE STORMS FIRED UP ALONG THE BOUNDARY BETWEEN
THE DRY AND MOIST AIR WHICH IS EVIDENT ON WATER VAPOR IMAGERY. THE
MODELS ARE SHOWING LITTLE CHANGE THROUGH FRIDAY AND I CONTINUED TO
FORECAST ISOLATED TO SCATTERED THUNDERSTORMS ACROSS MOHAVE COUNTY
AND EASTERN LINCOLN COUNTY. THE GFS AND NAM12 DIFFER IN THAT THE GFS
CONTINUES TO SHOW THE DRIER AND MORE STABLE AIR FARTHER EAST. THE
FORECAST THROUGH FRIDAY IS MORE OR LESS A COMPROMISE BETWEEN THE TWO
MODELS.

MEANWHILE...A WAVE OVER SOUTHWEST NEW MEXICO THIS AFTERNOON WILL
CONTINUE TO WEAKEN AND MOVE WESTWARD OVER THE NEXT FEW DAYS. THERE
IS POTENTIAL FOR THIS FEATURE TO CAUSE MOISTURE TO INCREASE
NORTHWESTWARD INTO MORE OF OUR FORECAST AREA SATURDAY THROUGH
SUNDAY. MODELS WERE DIFFERING WITH THIS TREND WITH THE GFS ACTUALLY
PUSHING THE MOISTURE AND INSTABILITY EASTWARD. EVEN THE NAM12 DOES
NOT BRING THE MOISTURE AND INSTABILITY MUCH FARTHER WESTWARD THAN
MOHAVE COUNTY. THIS GOES AGAINST MY INTUITION WITH THAT WAVE
APPROACHING SO I PUT THUNDERSTORM CHANCES WEST INTO MUCH OF LINCOLN
AND CLARK COUNTIES AND EASTERN SAN BERNARDINO COUNTY WITH THE
HIGHEST POPS STILL IN MOHAVE COUNTY. I WAS EVEN CONCERNED THAT IF
THAT WAVE HOLDS TOGETHER IT COULD CAUSE FAIRLY WIDESPREAD ORGANIZED
CONVECTION AND A FLASH FLOOD WATCH MAY BE NEEDED FOR SATURDAY OR
SUNDAY OR BOTH. WILL WAIT FOR LATER MODEL RUNS BEFORE MAKING THAT
CALL HOWEVER. THE REST OF THE FORECAST AREA DEFINITELY LOOKS DRY AND
STABLE.

.LONG TERM...MONDAY THROUGH THURSDAY...THE INCREASED PRECIPITATION
COVERAGE FROM THE WEEKEND UPPER LEVEL CIRCULATION WILL STILL BE
AROUND MONDAY. IT DEPENDS ON THE MODEL AS TO HOW WIDESPREAD IT WILL
BE...BUT MOST AGREE ON THE AREA THAT WILL BE IMPACTED THE GREATEST
WILL BE MOHAVE COUNTY. AFTER MONDAY MODELS SHOW MINOR BITS OF ENERGY
IN THE SOUTHWEST FLOW ON THE BACKSIDE OF THE SOUTHERN U.S. RIDGE.
THIS SHOULD KEEP SOME ACTIVITY IN MOHAVE COUNTY FOR ANOTHER DAY OR
TWO. ESSENTIALLY MADE BUT MINOR CHANGES TO THE PREVIOUS
FORECAST...WHICH CALLS FOR DECREASED POP COVERAGE IN OUR EASTERN CWA
EACH DAY AND FOR TEMPERATURES TO INCREASE A LITTLE TO NEAR NORMAL
LEVELS BY WEDNESDAY.
&&

.AVIATION...FOR MCCARRAN...WINDS WILL BE VARIABLE FROM 150-220
DEGREES AT ABOUT 10-12 KNOTS GUSTING TO NEAR 20 KNOTS THROUGH ABOUT
02-03Z. CLOUDS WILL VARY FROM SCATTER TO BROKEN AT ABOUT 15K FT THIS
AFTERNOON AND EVENING AND SHOULD GO BROKEN THIS EVENING AND STAY THAT
WAY. IT IS POSSIBLE FOR THUNDERSTORMS TO FORM OVER THE SPRING AND
SHEEP MOUNTAINS THIS AFTERNOON AND EVENING AND AGAIN FRIDAY
AFTERNOON. NOT EXPECTING ANY THUNDERSTORMS IN THE VALLEY BUT
OUTFLOWS FROM DISTANT STORMS IN ARIZONA COULD INFLUENCE THE WINDS AT
KLAS TONIGHT. THE PEACH SPRINGS CORRIDOR WILL SEE ISOLATED
THUNDERSTORMS THIS AFTERNOON/EVENING AND FRIDAY AFTERNOON.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS WILL GENERALLY FOLLOW A DIURNAL PATTERN AND
REMAIN AROUND 10-15KTS. FOR THURSDAY AND FRIDAY AFTERNOONS AND
EVENINGS ISOLATED TO SCATTERED THUNDERSTORMS ARE POSSIBLE IN MOHAVE
COUNTY ARIZONA AND IN LINCOLN COUNTY NEVADA. THE ARIZONA STORMS WILL
HAVE HEAVY RAINFALL RATES ACCOMPANY THEM. OUTFLOW BOUNDARIES FROM
THE STORMS WILL MAKE FOR ERRATIC AND GUSTY CONDITIONS NEAR THEM.
&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
AZ...NONE.
CA...NONE.
&&

$$

HARRISON/JACQUES

HTTP://WEATHER.GOV/LASVEGAS

NWS VEF Office Area Forecast Discussion