Wildfire in California, May 7, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
1009 AM PDT THU MAY 7 2015

.SYNOPSIS...A COLD STORM SYSTEM WILL APPROACH THE AREA TODAY
RESULTING IN GUSTY SOUTH TO SOUTHWEST WINDS THAT LAST THROUGH THIS
EVENING. SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON
THROUGH SATURDAY AS THIS STORM SYSTEM MOVES ACROSS THE AREA. SNOW
LEVELS MAY DROP AS LOW AS 5000 FEET WITH ACCUMULATIONS LIKELY IN THE
HIGHER ELEVATIONS. AFTER A SHARP DROP IN TEMPERATURES ON
FRIDAY...READINGS WILL REBOUND OVER THE WEEKEND.
&&

.UPDATE...THE APPROACHING LOW PRESSURE SYSTEM WAS CIRCULATING OVER
CENTRAL CALIFORNIA THIS MORNING WITH MOST OF THE MOISTURE ASSOCIATED
WITH THE COLD POOL STILL WELL TO THE WEST OF THE SIERRA CREST. IT
STILL APPEARS SHOWERS AND THUNDERSTORMS WILL LIKELY DEVELOP OVER THE
SOUTHERN SIERRA THIS AFTERNOON BUT SNOW LEVELS WILL REMAIN FAIRLY
HIGH OVER THE EASTERN SLOPES UNTIL THE CLOSED LOW BEGINS TO MOVE
OVER THE SIERRA THIS EVENING. THIS WILL BE ADJUSTED WITH THE WINTER
WEATHER MESSAGE UPDATE. ASIDE FROM THE SLIGHTLY SLOWER EASTWARD
PROGRESSION OF THE SYSTEM...THE LATEST MODEL SOLUTIONS SUPPORT THE
FORECAST TRENDS ELSEWHERE ACROSS THE REGION THAT ARE  DETAILED IN
THE PREVIOUS DISCUSSION. &&

.PREV DISCUSSION...
347 AM PDT THU MAY 7 2015

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT.

AFTER A WINTER THAT WAS MORE LIKE SPRING ACROSS THE AREA, IT LOOKS
LIKE WE ARE RETROGRADING BACK A SEASON OVER THE NEXT FEW DAYS AS A
COLD STORM SYSTEM IMPACTS THE AREA. THE MAIN IMPACTS WILL BE WIND,
PRECIPITATION AND MUCH COLDER TEMPERATURES.

THE STORM SYSTEM RESPONSIBLE FOR THIS ACTIVE WEATHER CAN BE SEEN
THIS MORNING ON WATER VAPOR SWIRLING ACROSS NORCAL. FOR TODAY, THIS
SYSTEM WILL BE FAR ENOUGH TO OUR NORTH THAT ONLY NORTHERN SECTIONS
OF THE AREA WILL BE AT RISK TO SEE A FEW SHOWERS AND THUNDERSTORMS,
MAINLY THIS AFTERNOON. I REMOVED THE SOUTHERN EDGE OF OUR POPS BASED
ON HOW DRY WE ARE GOING TO START OUT AND ALSO GIVEN THE LACK OF
MOISTURE SLATED TO ARRIVE BY THIS AFTERNOON. AHEAD OF THIS NICELY
DEFINED MID/UPPER LEVEL LOW, A BROAD 60 KT+ JET HEADS NORTHEAST
ACROSS THE MOJAVE DESERT AND THIS COMBINED WITH TIGHTENING NORTH-
SOUTH SURFACE PRESSURE GRADIENTS WILL INCREASE WINDS AT THE SURFACE
THIS AFTERNOON AND EVENING AS STRONGER WINDS ALOFT GET MIXED DOWN TO
THE SURFACE. THE HIGHEST WINDS LOOK TO BE IN THE WESTERN PART OF THE
MORONGO BASIN, WHERE THE ARW AND NMM MODELS SUGGEST WE COULD SEE
SOME LOCALIZED DOWNSLOPE COMPONENT OFF THE SAN BERNARDINO RANGE.
FAVORED WINDY SPOTS SUCH AS BARSTOW AND FORT IRWIN WILL ALSO SEE
GUSTY WINDS THIS AFTERNOON AND EVENING AS WELL. WIND ADVISORIES WERE
THUS POSTED FOR ALL OF NORTHERN SAN BERNARDINO COUNTY AS WELL AS THE
MORONGO BASIN FOR THIS AFTERNOON AND EVENING FOR GUSTS OF 40-50 MPH.
ELSEWHERE WE COULD SEE NEAR ADVISORY LEVEL WINDS OR POCKETS OF 40-45
MPH GUSTS FOR AN HOUR OR TWO IN SOUTHERN PARTS OF NYE COUNTY, DEATH
VALLEY NATIONAL PARK, KINGMAN AND THE FAR SOUTH END OF THE LAS VEGAS
VALLEY NEAR THE I-15 GAP WHICH WILL IMPACT AREAS SUCH AS SOUTHERN
HIGHLANDS, SILVERADO RANCH AND SEVEN HILLS. WINDS WILL SLOWLY DROP
OFF THIS EVENING AS THE UPPER SUPPORT WEAKENS AND SURFACE PRESSURE
GRADIENTS DECREASE. OTHERWISE ENJOY TODAY AS TOMORROW WILL BE A REAL
SHOCK TO THE SYSTEM.

THE AFOREMENTIONED CLOSED COLD MID/UPPER LEVEL LOW IS SLATED TO MOVE
EAST ACROSS THE MOJAVE DESERT TOMORROW AND THEN TO THE EAST BY
SATURDAY. WITH THE COLD LOW OVERHEAD AND STRONG FORCING FROM THE
LOW, THIS WILL CREATE A VERY FAVORABLE SET-UP TO GENERATE
PRECIPITATION ACROSS MUCH OF THE AREA THOUGH SOME SPOTS WILL MISS
OUT. HOWEVER, MODEL QPF PLACEMENT IN THIS TYPE OF SET-UP IS NOT THE
BEST SO EVERYONE WILL KEEP A CHANCE FOR SHOWERS AS THEY MAY BE SEEN
AT SOME POINT IN THEIR PART OF THE DISTRICT. THE MAIN ISSUES WILL BE
THE VERY COLD AIR ALOFT ASSOCIATED WITH THE LOW. THE 00Z OPERATIONAL
ECMWF DROPS 700 MB TEMPS DOWN TO -8C UNDER THE CENTER OF THE LOW
WHICH BASED ON LOCAL RULES OF THUMB WOULD PUT SNOW LEVELS AS LOW AS
4500 FEET. STRONG BURSTS OF PRECIPITATION WILL HAVE THE POTENTIAL TO
DO THIS ALTHOUGH WHERE AND WHEN IS TOUGH TOO CALL. THE LOW FREEZING
LEVELS WILL ALSO MAKE SMALL HAIL AND GRAUPEL A POSSIBILITY AS WELL
EVEN IN LOWER VALLEYS. GIVEN THE UNUSUAL NATURE OF THIS STORM, WE
HAVE ISSUED WINTER WEATHER HEADLINES FOR SEVERAL AREAS. DESPITE THE
GROUND BEING SO WARM,IF IT PRECIPITATES HEAVY ENOUGH IT WILL HAVE NO
TROUBLE GETTING FROZEN PRECIP TO STICK. HIKERS SHOULD BEWARE THROUGH
SATURDAY AS THIS COULD BE A LIFE-THREATENING SITUATION IF CAUGHT
OFFGUARD, ESPECIALLY IN THE SOUTHERN SIERRA. WE ALSO COULD SEE A
LITTLE SNOW EVEN IN SPOTS WHERE IT IS RARE FOR THIS TIME OF YEAR
SUCH AS TOWNES PASS AND MOUNTAIN SPRINGS SUMMIT.

WITH THE COLD LOW OVERHEAD AND CLOUDS, TEMPS WILL STRUGGLE TO WARM
UP MUCH ON FRIDAY. I SLASHED READINGS DOWN A FEW DEGREES AND WE MAY
NOT BE COLD ENOUGH. THE RECORD LOW MAXIMUM FOR FRIDAY IN LAS VEGAS
IS THE COLDEST EVER IN MAY...60 SET IN 1979. WORTH NOTING IS OUR
COLDEST HIGH IN ALL OF APRIL WAS ONLY 67 ON THE 15TH. SO PLACE YOUR
BETS ON THIS ONE IF YOU LIKE TO PLAY AGAINST LOW ODDS.

TEMPS WILL START TO REBOUND ON SATURDAY AS THE LOW DEPARTS AND DRIER
AIR STARTS TO WORK IN. WE MAY DRY OUT QUICKER IN SOME AREAS THEN THE
FORECAST SUGGEST BUT ADDITIONAL ENERGY ON THE BACK SIDE OF THE LOW
WARRANTS A CHANCE OF SHOWERS INTO THE AFTERNOON AND EVENING
ESPECIALLY IN THE EASTERN HALF OF THE AREA.

.LONG TERM...SUNDAY THROUGH WEDNESDAY.

KEPT MENTION OF A SLIGHT CHANCE OF SHOWERS NEAR THE UTAH BORDER WITH
LINCOLN AND MOHAVE COUNTIES SUNDAY AS FINAL PIECE OF SHORTWAVE
ENERGY ASSOCIATED WITH EXITING TROUGH MOVES THROUGH SOUTHWEST UTAH.
OTHERWISE, THE WESTERN HALF OF THE AREA WILL BE DRY WITH WARMING
TEMPERATURES AS RIDGE BUILDS IN OVER CALIFORNIA. THE RIDGE QUICKLY
TRANSITIONS EAST ON MONDAY WITH SOUTHWEST FLOW ALOFT DEVELOPING
AHEAD OF A LOW NEAR THE PACIFIC NORTHWEST COAST.

BEYOND MONDAY, THERE IS QUITE A BIT OF MODEL UNCERTAINTY BETWEEN THE
OPERATIONAL MODELS WITH THE HANDLING OF THE NEXT LOW. OPERATIONAL
GFS SEEMS TO BE THE OUTLIER MOVING THE UPPER LOW SOUTH THEN EAST
INLAND INTO SOUTHERN CALIFORNIA NEXT WEDNESDAY. ECMWF/GEM HAVE THE
LOW FURTHER NORTH AND WEST KEEPING THE REGION UNDER A DRY SOUTHWEST
FLOW. GFS ENSEMBLE MEAN HAS THE REGION UNDER A SOUTHWEST FLOW ALOFT
WITH SLIGHTLY LOWER HEIGHTS OVER THE GREAT BASIN NEXT WEDNESDAY THAN
THE ECMWF. THERE WERE TWO ENSEMBLE MEMBERS THAT WERE MORE LIKE THE
OPERATIONAL GFS. DUE TO UNCERTAINTY, KEPT TUESDAY AND WEDNESDAY DRY
WITH NEAR NORMAL TEMPERATURES.
&&

.AVIATION...FOR MCCARRAN...SOUTH-SOUTHWEST WINDS AT 8-14 KTS THIS
MORNING WILL INCREASE TO 15-20 KTS WITH GUSTS OF 25-30 KTS IN THE
AFTERNOON AND EVENING. CLEAR OVERNIGHT WITH SCT-BKN CLOUDS AOA 10-
15K FEET ON THURSDAY ESPECIALLY IN THE AFTERNOON AND EVENING. THERE
IS A CHANCE FOR CIGS AS LOW AS 5K-7K FEET AND SHRA/TSRA AT THE
AIRPORT COMPLEX ON FRIDAY. MOUNTAIN OBSCURATIONS ARE LIKELY THEN.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS WILL INCREASE FROM THE SOUTH TO SOUTHWEST ACROSS
THE AREA BY THIS AFTERNOON AND REMAIN GUSTY INTO THE EVENING WITH
SPEEDS SUSTAINED AT 15-25 KTS WITH GUSTS OF 20-30 KTS EXCEPT IN AND
AROUND KDAG WHERE SUSTAINED WINDS OF 25-35 KTS WITH GUSTS OF 35-45
KTS POSSIBLE. LOCAL AREAS OF BLDU MAY OCCUR REDUCING VSBY. OTHERWISE
EXCEPT SCT-BKN CLOUDS AOA 6K-12K FEET WITH SHRA/TSRA POSSIBLE ALONG
AND NORTH OF KEDW-KDRA-KIGM LINE. GUSTY AND ERRATIC WINDS POSSIBLE
NEAR ANY SHRA/TSRA OR OUTFLOW BOUNDARIES. SHRA/TSRA WILL BE POSSIBLE
AGAIN ACROSS MUCH OF THE AREA ON FRIDAY ALONG WITH MOUNTAIN
OBSCURATIONS. CIGS MAY DROP AS LOW AS 4K-7K FEET.
&&

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

UPDATE...ADAIR
SHORT TERM/AVIATION...STACHELSKI
LONG TERM...PIERCE

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