Dust Storm in Arizona, August 25, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
232 PM PDT TUE AUG 25 2015

.SYNOPSIS...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL
CONTINUE TONIGHT INTO WEDNESDAY MORNING AS A SERIES OF DISTURBANCES
MOVE OVER THE REGION. SCATTERED SHOWERS AND THUNDERSTORMS WILL
AFFECT PRIMARILY THE HIGHER TERRAIN WEDNESDAY AND THURSDAY BEFORE
GRADUAL DRYING COMMENCES FRIDAY. DRIER CONDITIONS ARE EXPECTED
THROUGH THE WEEKEND.
&&

.SHORT TERM...THROUGH THURSDAY NIGHT.

WELL DEFINED VORT MAX WHICH WAS INITIALIZED NEAR PHOENIX THIS
MORNING HAS MOVED NORTH TO NEAR PRESCOTT AT MID-AFTERNOON. A LINE OF
HEAVIER RAIN SHOWERS AND EMBEDDED THUNDERSTORMS EXTENDS FROM NEAR
WIKIEUP NORTH TO PEACH SPRINGS...THEN NORTHEAST TOWARD MT TRUMBULL.
LOCALLY HEAVY RAIN HAS OCCURRED WITH THIS LINE IN THE MOUNTAINS
NORTHEAST OF WIKIEUP WITH ONE MOHAVE COUNTY FLOOD CONTROL DISTRICT
STATION REPORTING ABOUT TWO-THIRDS OF AN INCH. HRRR HAS THE SOUTHERN
PORTION OF THE LINE WEAKENING AS IT CONTINUE EAST ACROSS SOUTHERN
MOHAVE COUNTY THE REST OF THIS AFTERNOON.

THE VORT MAX IS PROGGED TO CONTINUE NORTH INTO SOUTHWEST UTAH BY
EARLY WEDNESDAY MORNING. EXPECT A PORTION OF THE NORTHERN LINE TO
SEE ADDITIONAL DEVELOPMENT AS IT CONTINUES NORTHWEST THROUGH
NORTHERN MOHAVE COUNTY POTENTIALLY AFFECTING PARTS OF NORTHEAST
CLARK AND LINCOLN COUNTY THIS EVENING AND OVERNIGHT. ELSEWHERE,
PRECIPITATION HAS BEEN LIGHT AND DO NOT FORESEE THIS CHANGING MUCH
SO DECIDED TO LOWER POPS TONIGHT FOR SAN BERNARDINO COUNTY AND THE
REST OF CLARK COUNTY.

MONSOON MOISTURE THAT MOVED INTO THE REGION TUESDAY WILL STILL BE
AVAILABLE WEDNESDAY. FORECAST SOUNDINGS STILL SHOWING MORE
INSTABILITY TOMORROW. CONVECTION SHOULD BE STRONGLY TERRAIN DRIVEN
WITH ISOLATED POCKETS OF HEAVY RAIN POSSIBLE. FLOW ALOFT WILL TURN
MORE SOUTHWESTERLY THURSDAY AND FRIDAY ALLOWING FOR GRADUAL DRYING
TREND. DID INTRODUCE A SLIGHT CHANCE OF STORMS INTO THE HIGHER
TERRAIN OF MOHAVE COUNTY FRIDAY.

CLOUDINESS HAS KEPT TEMPERATURES BELOW NORMAL TODAY. MORE SUNSHINE
AND DRYING TREND FOR THE REST OF THE WEEK WE WILL SEE TEMPERATURES
RETURN TO ABOUT 5 DEGREES ABOVE NORMAL FRIDAY. OUTSIDE OF GUSTY
WINDS ASSOCIATED WITH CONVECTION NO SIGNIFICANT WINDS
EXPECTED.

.LONG TERM...SATURDAY THROUGH TUESDAY.

DRIER SOUTHWESTERLY FLOW IS EXPECTED TO SWEEP ACROSS THE REGION
FRIDAY...FINALLY SCOURING OUT MOISTURE FROM WEST TO EAST AND
EFFECTIVELY ENDING CHANCES FOR SHOWER AND THUNDERSTORM ACTIVITY.
ALONG WITH BENIGN WEATHER CONDITIONS...THIS WILL YIELD A QUICK
WARMUP IN TEMPERATURES WITH AFTERNOON HIGHS RUNNING SEVERAL DEGREES
ABOVE AVERAGE ACROSS THE AREA FRIDAY.

A SLIGHT CHANGE IN OUR WEATHER COULD BE IN STORE FOR THE WEEKEND AS
THE LATEST OPERATIONAL MODELS SHOW GOOD AGREEMENT IN A SHORTWAVE
ASSOCIATED WITH AN UPPER LEVEL LOW OFF OF THE PACIFIC NORTHWEST
COAST TO EJECT ACROSS THE PACIFIC NORTHWEST AND NORTHERN GREAT
BASIN. THIS WILL YIELD A COOLING TREND IN TEMPERATURES AND BREEZY
CONDITIONS ACROSS THE SOUTHERN GREAT BASIN AND MOJAVE DESERT THROUGH
THE END OF THE WEEKEND. THOUGH GUIDANCE IS MORE IN LINE WITH THE
OVERALL EVOLUTION OF THE UPPER LOW TONIGHT...LARGE DISCREPANCIES IN
THE OVERALL TIMING AND STRENGTH OF THIS FEATURE CONTINUE TO EXIST
TONIGHT. THE 00Z ECMWF OUTPUT IS MUCH MORE PROGRESSIVE AND LESS
AMPLIFIED THAN THE 00Z GFS...WHICH IS 24-36 HOURS SLOWER IN
TRAVERSING THE UPPER LOW ACROSS THE PACIFIC NORTHWEST/NORTHERN GREAT
BASIN. THESE DIFFERENCES YIELD A 3-4 DEGREE TEMPERATURE SPREAD IN
NUMERICAL GUIDANCE AFTER SUNDAY...THEREFORE A BLEND OF BOTH
SOLUTIONS WAS USED FOR MAX AND MIN FORECASTS FOR MONDAY AND TUESDAY.
DESPITE THESE DIFFERENCES...THE BOTTOM LINE IS THAT WE CAN EXPECT
DRY...BREEZY...AND COOLER CONDITIONS THROUGH THE END OF THE PERIOD.
&&

.AVIATION...FOR MCCARRAN...DECREASING CHANCES FOR RAIN SHOWERS
THROUGH THE REST OF THE AFTERNOON WITH WINDS GENERALLY FROM A SOUTH
DIRECTION. HOWEVER THEY MAY SHIFT BACK AND FORTH BETWEEN SOUTHEAST
AND SOUTHWEST AT TIMES. SOME OF THE HI-RES MODELS SHOW THE POTENTIAL
OF STRONGER SOUTHEAST WINDS POSSIBLY AFFECTING THE LAS VEGAS VALLEY
THIS EVENING. CONFIDENCE IS TOO LOW TO INCLUDE IN THE TAF AT THIS
TIME. CHANCES FOR SHOWERS WILL INCREASE AGAIN LATE THIS EVENING AND
PERSIST THROUGH WEDNESDAY. CIGS WILL DROP FROM 15-20K FEET THIS
AFTERNOON TO AROUND 8-10K FEET OVERNIGHT.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WIDESPREAD CLOUDS WITH CIGS IN THE 10-20K FEET RANGE
WILL BE COMMON TODAY ALONG AND EAST OF A KDAG-KTPH LINE. SCATTERED
LIGHT SHOWERS AND SPRINKLES WILL BE POSSIBLE EAST OF THIS LINE AS
WELL...WITH ISOLATED THUNDERSTORMS POSSIBLE PRIMARILY ACROSS MOHAVE
COUNTY. SURFACE WINDS WILL BE GUSTY AND VARIABLE NEAR STORMS BUT
OTHERWISE GENERALLY LIGHT AND SOUTHERLY. MODELS INDICATED THE
POSSIBILITY IF ENHANCED EAST TO SOUTHEAST WINDS THIS EVENING AND
OVERNIGHT MOVING ACROSS THE COLORADO RIVER VALLEY...HOWEVER
CONFIDENCE IN STRENGTH AND TIMING IS LOW AT THIS TIME. CIGS ARE
EXPECTED TO DECREASE TO 6-10K FEET OVERNIGHT WITH CHANCES FOR STORMS
CONTINUING OVERNIGHT AND THROUGH WEDNESDAY.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT
ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

SHORT TERM...PIERCE
AVIATION...WOLCOTT
LONG TERM...PULLIN

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