Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 011640
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
940 AM PDT SUN MAY 1 2016

.SYNOPSIS...ANOTHER SYSTEM WILL AFFECT THE AREA THROUGH MONDAY
BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS, ESPECIALLY FOR THE
SIERRA AND THE HIGHER TERRAIN OF SOUTHERN NEVADA AND MOHAVE COUNTY,
BUT TEMPERATURES WILL BE ON A WARMING TREND. TEMPERATURES WILL
CONTINUE TO WARM AS THE AREA BRIEFLY DRIES OUT TUESDAY AND WEDNESDAY
BEFORE ANOTHER POTENT, SLOW-MOVING SYSTEM BRINGS MORE INCLEMENT
WEATHER AND COOL TEMPERATURES TO THE REGION BY THE END OF THE
UPCOMING WEEK.
&&

.UPDATE...THE 12Z LAS VEGAS SOUNDING SHOWED ONLY MARGINAL
INSTABILITY AS THE SURFACE HEATS UP THIS AFTERNOON UNDER FULL
SUNSHINE. THE LIFTED INDEX OF -1 AND CAPE AROUND 600 SHOULD STILL BE
SUFFICIENT FOR CONVECTION TO DEVELOP INITIALY OVER THE MOUNTAINS. IN
ADDITION...WATER VAPOR IMAGERY LOOPS SHOWED A WEAK CIRCULATION OVER
SOUTHWEST NEVADA WHICH MAY PROVIDE SOME DYNAMIC SUPPORT AS
CONVECTION GETS GOING. THE LARGER CIRCULATION/VORT MAX CARVING INTO
NORTHERN CALIFORNIA WILL ALSO KEEP COOL TEMPERATURES ALOFT ACROSS
THE  SOUTHERN SIERRA AND WEST CENTRAL NEVADA FOR SLIGHT
DESTABILIZATION. THE STEERING FLOW WILL TAKE ANY SHOWERS OR
THUNDERSTORMS THAT DEVELOP TOWARD THE SOUTH-SOUTHWEST. THE GOING
FORECAST POP/WX GRIDS LOOK OKAY AND NO SIGNFICANT CHANGES ARE
NEEDED.

&&

.PREV DISCUSSION...
259 AM PDT SUN MAY 1 2016

.SHORT TERM...SUNDAY AND MONDAY.

POTENT, SLOW-MOVING UPPER LOW RESPONSIBLE FOR SATURDAY`S
PRECIPITATION AND COOL TEMPERATURES WAS SLOWLY MIGRATING EASTWARD
INTO ARIZONA THIS MORNING. WV IMAGERY IS SHOWING HIGH-AMPLITUDE
RIDGING NOSING INTO THE NORTHERN ROCKIES AND A SUBTLE VORT MAX
PROGRESSING SSW THROUGH OREGON INTO NORTHERN CALIFORNIA. MODEL
GUIDANCE IS IN GOOD AGREEMENT THAT THIS UPSTREAM VORT MAX WILL
CONTINUE ITS PROGRESSION INTO COASTAL CENTRAL CALIFORNIA BEFORE
PIVOTING EASTWARD INTO NORTHERN ARIZONA BY 12Z TUESDAY. MEANWHILE,
THE HIGH-AMPLITUDE RIDGING CONTINUES ITS STRONG HOLD IN THE NORTHERN
ROCKIES, KEEPING THE VORT MAX`S PROGRESSION SLOW. AS SUCH, SHOWERY
WEATHER WILL CONTINUE IN OUR AREA THROUGH MONDAY AS THIS VORT MAX
MEANDERS ITS WAY INTO THE DESERT SOUTHWEST.

A COUPLE OF THINGS TO NOTE ABOUT THIS NEXT SYSTEM. FIRST...ITS TRACK
LOOKS TO BE FARTHER NORTHWARD THAN THIS LAST SYSTEM. AS
SUCH...HIGHEST POPS LOOK TO BE IN THE SIERRA, SOUTHERN GREAT BASIN,
AND MOHAVE COUNTY. SECOND...UPPER-LEVEL DYNAMICS ARE CONSIDERABLY
WEAKER WITH THIS SYSTEM. COMBINE THIS WITH THE VORT MAX`S ORIGINS IN
WESTERN CANADA (IN OTHER WORDS...LESS MOISTURE), AND THE RESULT IS
MORE SCATTERED PRECIP (AIDED BY LOCALIZED PROCESSES SUCH AS TERRAIN
AND DIFFERENTIAL HEATING) AND LOWER QPF OVERALL. IN GENERAL, EXPECT
PRECIP AMOUNTS TO BE UNDER A TENTH OF AN INCH EXCEPT IN THE SIERRA
AND THE HIGHER TERRAIN OF SOUTHERN NEVADA AND NORTHERN MOHAVE
COUNTY. SNOW LEVELS WILL BE ON THE RISE THROUGH THE PERIOD AS
SOUTHWEST FLOW IN ADVANCE OF A DEEP UPPER TROUGH IN THE EASTERN
PACIFIC APPROACHES THE AREA. GENERALLY, THESE LEVELS WILL BE 7000-
8000 FEET THIS MORNING TO AROUND 8500 FEET BY MONDAY MORNING. LIGHT
SNOWFALL TOTALS ARE EXPECTED WITH TRACE AMOUNTS NEAR 8000 FEET TO
PERHAPS 2-4 INCHES ON THE HIGHEST PEAKS OF THE SIERRA.

MOST HI-RES GUIDANCE IS KEEPING PRECIP OUT OF THE DESERT
VALLEYS...BUT GIVEN THE COLD MIDLEVEL AIR ASSOCIATED WITH THIS
SYSTEM AND RESULTANT INSTABILITY SUNDAY AND MONDAY...THINK PRECIP
MAY BE A LITTLE UNDERDONE IN THE VALLEYS. IN ADDITION...GIVEN THE
ANTICIPATED INSTABILITY...THUNDER CHANCES WERE RETAINED DURING THE
AFTERNOON AND EVENING HOURS SUNDAY AND MONDAY.

TEMPERATURES WILL TREND WARMER WITH HIGHS TODAY ABOUT 7-12 DEGREES
WARMER THAN SATURDAY. ANOTHER 3-8 DEGREES OF WARMING IS EXPECTED ON
MONDAY AS THE WARMER SOUTHWEST UPPER-LEVEL FLOW COMMENCES.

.LONG TERM...TUESDAY THROUGH SUNDAY.

RIDGING ALOFT WILL MOVE OVER THE REGION TUESDAY, PROVIDING DRY AND
WARM CONDITIONS. THE RIDGE AXIS WILL SLOWLY MOVE EAST WEDNESDAY AS A
LARGE EASTERN PACIFIC TROUGH APPROACHES THE WEST COAST. BREEZY TO
LOCALLY WINDY SOUTH WINDS WILL USHER IN EVEN WARMER TEMPERATURES ON
WEDNESDAY. THE TROUGH WILL THEN SPIN INTO A CLOSED, CUTOFF LOW ON
THURSDAY AND GRADUALLY SLIDE EAST INTO OUR AREA LATE THURSDAY
THROUGH AT LEAST SATURDAY NIGHT, EVEN LONGER IF THE 00Z GFS SOLUTION
PANS OUT. WE COULD SEE SOME LIGHT PRECIP WEDNESDAY AFTERNOON ACROSS
NORTHERN INYO COUNTY, BUT BETTER CHANCES EXIST THURSDAY. MOISTURE
AND PRECIP CHANCES WILL SPREAD EAST THURSDAY NIGHT AND FRIDAY AS THE
UPPER LOW SPINS OVER SOUTHEAST CALIFORNIA AND SOUTHERN NEVADA. TOUGH
TO TELL WHEN THIS UPPER LOW WILL EXIT TO THE EAST. THE ECMWF IS THE
FASTER SOLUTION THIS MORNING, WHILE THE GFS WANTS TO KEEP THE LOW
OVERHEAD THROUGH EARLY MONDAY. 24 HOURS AGO, THE GFS WAS THE FASTER
SOLUTION. THE MEAN FROM BOTH THE GEFS AND NAEFS ARE SLIGHTLY LEANING
TOWARD THE ECMWF, YET WITH PLENTY OF SPREAD IN SOLUTIONS, WILL KEEP
PRECIP CHANCES GOING THROUGH SUNDAY NIGHT. AS THE LOW APPROACHES,
TEMPERATURES WILL TREND COOLER. TEMPERATURES 5-10 DEGREES BELOW
NORMAL ARE EXPECTED FRIDAY THROUGH THE WEEKEND.
&&

.AVIATION...FOR MCCARRAN...FEW-SCT CLOUDS AROUND 10K FEET WITH CIGS
ABOVE 12K FEET THIS MORNING. SCT SHRA/TSRA EXPECTED TO DEVELOP OVER
THE HIGHER TERRAIN AFTER 18Z WITH A SLIGHT CHANCE OF STORMS
DEVELOPING IN THE VALLEYS. CIGS PSBL DOWN TO 8K FEET BY THIS
AFTERNOON ALONG WITH LOCAL MOUNTAIN OBSCURATIONS. NORTHEAST WINDS
AFTER 18Z AROUND 7KTS...BUT COULD GET GUSTY AND VARIABLE WITH NEARBY
STORMS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...FEW-SCT CLOUDS AROUND 8-10K FEET THIS MORNING WITH SCT
SHRA/TSRA DEVELOPING OVER THE HIGHER TERRAIN AFTER 18Z. CIGS DOWN TO
7-8K FEET POSSIBLE NEAR STORMS ALONG WITH LOCAL MOUNTAIN
OBSCURATIONS. NORTH TO NORTHEAST WINDS UP TO 10KTS...BUT VARIABLE
AND GUSTY NEAR STORMS.
&&

.SPOTTER INFORMATION STATEMENT...ACTIVE WEATHER IS EXPECTED
THROUGH MONDAY. SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT
WEATHER ACCORDING TO STANDARD OPERATING PROCEDURES.
&&

$$

UPDATE...ADAIR
SHORT TERM...SHAFER
LONG TERM...PADDOCK
AVIATION...GORELOW

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