Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 061640
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
940 AM PDT WED MAY 6 2015

.SYNOPSIS...SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED ONCE AGAIN
TODAY MAINLY ACROSS THE SOUTHERN GREAT BASIN AND INYO COUNTY.
INCREASINGLY BREEZY CONDITIONS WILL DEVELOP TODAY THROUGH THURSDAY
AS A STRONG AND COLD LOW PRESSURE SYSTEM BEGINS TO MOVE TOWARDS THE
AREA. SHOWERS AND THUNDERSTORMS ARE POSSIBLE AREA WIDE FRIDAY AS THE
LOW MOVES THROUGH WITH TEMPERATURES WELL BELOW NORMAL EXPECTED.
DRYING AND WARMING CONDITIONS EXPECTED SUNDAY INTO EARLY NEXT WEEK.
&&

.UPDATE...A MINOR ADJUSTMENT WAS MADE TO THE POP/WX GRIDS TO TRIM
SOUTHERN EXTENT OF COVERAGE OF EXPECTED SHOWERS AND THUNDERSTORMS
THIS AFTERNOON ACROSS INYO CENTRAL NYE AND LINCOLN COUNTIES. A MID
LEVEL CONVERGENCE ZONE OVER THESE AREAS WILL AID CONVECTIVE
DEVELOPMENT THEN THIS ZONE WILL TRANSITION TO A MORE
NORTHEAST/SOUTHWEST ORIENTATION TONIGHT IN RESPONSE TO THE CLOSED
LOW DIVING FROM THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA. THE
12Z NAM/GFS STILL SUPPORT THE REST OF THE FORECAST TRENDS DETAILED
IN THE PREVIOUS DISCUSSION.
&&

.PREV DISCUSSION...
225 AM PDT WED MAY 6 2015

.SHORT TERM...THROUGH FRIDAY NIGHT.

AS ANTICIPATED SHOWERS AND ISOLATED THUNDERSTORMS ARE ONGOING EARLY
THIS MORNING ACROSS THE SOUTHERN GREAT BASIN...ESPECIALLY LINCOLN
COUNTY. THIS ACTIVITY IS BEING SUPPORTED BY A WEAKLY CYCLONIC FLOW
AND AN APPROACHING SHORTWAVE PROVIDING SOME ADDITIONAL ENERGY TO
KICK OFF CONVECTION.  THIS SHORTWAVE WILL LIFT NORTHEAST LATER TODAY
WITH ACTIVITY SPREADING INTO CENTRAL NEVADA BUT SOME SHOWERS AND
STORMS WILL REMAIN POSSIBLE THROUGH THE EVENING ACROSS THE SOUTHERN
GREAT BASIN.

MEANWHILE A STRONG AND COLD TROUGH OF LOW PRESSURE WILL BE TAKING
SHAPE ACROSS CENTRAL OREGON THIS AFTERNOON AND WILL SINK SOUTH INTO
CENTRAL CALIFORNIA BY THURSDAY AFTERNOON. THE RESULT WILL BE
INCREASINGLY BREEZY CONDITIONS AREA WIDE BEGINNING THIS AFTERNOON AND
CONTINUING THROUGH FRIDAY.  WIND HEADLINES WILL BE A POSSIBILITY
ACROSS SOME AREAS THURSDAY AND THURSDAY NIGHT BUT OVERALL WILL BE
PRETTY BORDERLINE....SO RIGHT NOW ITS JUST SOMETHING TO KEEP AN EYE
ON.

THE BIGGER STORY WILL BE INCREASING SHOWERS AND THUNDERSTORMS
THURSDAY ACROSS OUR NORTHWEST ZONES WHICH WILL SPREAD EASTWARD
FRIDAY. WITH 500MB TEMPERATURES OF -25C (OR COLDER) PASSING
OVERHEAD...AND THE STRONG MAY SUNSHINE PEAKING THROUGH ANY CLOUD
COVER...IT WILL NOT TAKE A MUCH TO SPARK OFF SHOWERS AND
THUNDERSTORMS.  SNOW LEVELS WILL FALL QUITE LOW BY EARLY-MAY
STANDARDS AS WELL...POSSIBLY DOWN TO AROUND 6K FEET ON FRIDAY.
ELEVATIONS ESPECIALLY ABOVE 7K MAY SEE A QUICK DUSTING OR MORE OF
SNOW WITH THE HEAVIER SHOWERS.

NEEDLESS TO SAY...WITH SUCH COLD TEMPERATURES ALOFT...TEMPS IN THE
LOWER ELEVATIONS WILL ALSO BE CHILLY.  HIGH TEMP DEPARTURES OF 15 TO
20 DEGREES BELOW NORMAL ARE LOOKING MORE AND MORE LIKELY FOR FRIDAY.
THE LAS VEGAS FORECAST HIGH TEMP OF 67F WOULD BE SOME 18 DEGREES
BELOW AVERAGE WITH TEMPERATURES NEAR MT CHARLESTON IN THE 30S.  DO
BE PREPARED IF PLANNING OUTDOOR RECREATION FRIDAY FOR CHANGEABLE
WEATHER CONDITIONS AS WELL AS UNSEASONABLY COOL TEMPERATURES. ENJOY
THESE COOL TEMPERATURES WHILE THEY LAST AS THIS MAY BE THE LAST TIME
WE SEE THINGS THIS COOL FOR SEVERAL MONTHS.

.LONG TERM...SATURDAY THROUGH TUESDAY.

EVEN AS MAIN LOW SHIFTS EAST INTO THE FOUR CORNERS REGION SATURDAY,
MODELS INSIST ADDITIONAL ENERGY MOVING SOUTH WITHIN BACKSIDE OF
TROUGH WILL KEEP A CHANCE OF SHOWERS AND A FEW THUNDERSTORMS ACROSS
MAINLY SOUTHERN NEVADA AND INYO COUNTY SATURDAY. FOR SUNDAY, ANY
REMAINING INSTABILITY WILL CONFINE ISOLATED SHOWERS TO EASTERN
LINCOLN AND NORTHERN MOHAVE COUNTIES. DRY/STABLE AIR MASS ASSOCIATED
WITH RIDGING WILL START BUILDING IN FROM THE WEST. RIDGE QUICKLY
SHIFTS EAST MONDAY AS WINDS ALOFT BACK SOUTHWESTERLY ON TUESDAY
AHEAD OF NEXT TROUGH DEVELOPING NEAR THE PAC NW COAST. THERE IS SOME
SPREAD IN THE POSITIONING OF THIS NEXT TROUGH. AFTER THE DRAMATIC
COOL DOWN FRIDAY, TEMPERATURES WILL STEADILY WARM DURING THE PERIOD
RETURNING TO NORMAL OR SLIGHTLY ABOVE NORMAL MONDAY AND TUESDAY.
&&

.AVIATION...FOR MCCARRAN...WINDS GENERALLY FROM THE SOUTHEAST 6-10KT
EXPECTED THROUGH 19Z. BREEZY CONDITIONS DEVELOP IN THE AFTERNOON
WITH SUSTAINED WINDS 15 TO 20 KTS WITH GUSTS AS HIGH AS 30KTS. WINDS
WILL EASE SOMEWHAT AFTER SUNSET BUT WILL REMAIN GUSTY AT TIMES
THROUGH THE NIGHT.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...SCT SHOWERS AND TSTORMS POSSIBLE ACROSS THE SOUTHERN
GREAT BASIN AND INYO COUNTY TODAY. GUSTY SURFACE WINDS AND LOCALLY
STRONG UPDRAFTS POSSIBLE NEAR CONVECTION. ELSEWHERE DRY CONDITIONS
ARE EXPECTED. INCREASINGLY BREEZY SOUTH OR SOUTHWEST WINDS OF 15-
20KTS WITH GUSTS TO 30KTS AFTER 18Z EXPECTED ACROSS THE AREA.

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

$$

UPDATE...ADAIR
PREV DISCUSSION...OUTLER/PIERCE

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