Winter Storm Watch 1, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
300 PM PST FRI DEC 31 2010

.SYNOPSIS...WELL BELOW NORMAL TEMPERATURES ARE EXPECTED THROUGH THE
WEEKEND AS A BROAD AREA OF LOW PRESSURE LIES OVER THE FOUR CORNER
STATES. LIGHT WINDS TONIGHT WILL ALLOW TEMPERATURES TO DROP TO THE
COLDEST READINGS SO FAR THIS WINTER. A STORM DROPPING DOWN THE
CALIFORNIA COAST WILL BRING A CHANCE OF RAIN AND SNOW TO WESTERN
INYO COUNTY AND THE WESTERN MOJAVE DESERT THIS WEEKEND. ONCE THE LOW
MOVES INLAND EARLY NEXT WEEK IT WILL BRING A CHANCE OF RAIN AND SNOW
TO MUCH OF THE REGION.
&&

.SHORT TERM...VERY COLD DAY ACROSS THE CWA TODAY WITH SEVERAL
RECORD LOW MAX TEMPERATURES BROKEN AND EXPECTING A VERY COLD NIGHT
TONIGHT. SATELLITE IMAGERY SHOWING HIGH CLOUDS STARTING TO APPROACH
THE WESTERN PORTIONS OF THE FORECAST AREA AND IT IS POSSIBLE THAT
LOW TEMPERATURES MAY BE HELD UP JUST A BIT DUE TO THE CLOUDS.
HOWEVER...WITH A COVERAGE OF HIGH CLOUDS TOMORROW TEMPERATURES MAY
BE HELD DOWN A FEW DEGREES AND CURRENT GUIDANCE MAY BE A BIT TOO
WARM. OVERNIGHT TEMPERATURES WILL WARM A COUPLE OF DEGREES
THROUGH MONDAY...BUT MANY LOCATIONS WILL CONTINUE TO EXPERIENCE
BELOW FREEZING TEMPERATURES.

ALTHOUGH THERE IS BETTER AGREEMENT IN THE MODELS REGARDING THE NEXT
SYSTEM DROPPING DOWN THE CALIFORNIA COAST IT IS STILL DIFFICULT TO
PINPOINT WHERE THE LOW WILL FINALLY END UP. THE GFS/ECMWF HAVE NOT
SHOWN MUCH CHANGE OVER THE PAST COUPLE OF RUNS WHILE THE NAM HAS
STARTED TO TREND SLOWER...WHICH IS MORE IN LINE WITH THE OTHER
MODELS. HAVE KEPT THE PREVIOUS FORECASTERS THINKING AND KEPT THE
GRIDS BASED ON THE 12/18Z GFS. A WEAK DISTURBANCE AHEAD OF THE MAIN
LOW WILL BRING PRECIPITATION INTO WESTERN INYO COUNTY SATURDAY
AFTERNOON...BUT PRECIPITATION AMOUNTS DO NOT LOOK TOO SIGNIFICANT
WITH THIS INITIAL SYSTEM. THE MAIN AREA OF PRECIPITATION IS EXPECTED
TO PUSH INTO THE SIERRA LATE SATURDAY NIGHT AND EVENTUALLY INTO
WESTERN SAN BERNARDINO COUNTY SUNDAY MORNING. WITH COLD TEMPERATURES
ALREADY IN PLACE ITS LIKELY THAT THE PRECIPITATION WILL START AS
SNOW BEFORE CHANGING TO RAIN IN THE LOWER VALLEYS. THE PRECIPITATION
WILL MOVE EAST DURING THE DAY SUNDAY AND SPREAD OVER MUCH OF THE CWA
SUNDAY NIGHT. AGAIN...WITH COLD AIR IN PLACE MANY LOWER VALLEYS WILL
LIKELY SEE PRECIPITATION BEGIN AS SNOW. THE LOW IS FORECAST TO TRACK
EAST SUNDAY NIGHT AND MONDAY WITH SHOWERS CONTINUING THROUGH MONDAY
BEFORE WEAK RIDGING TAKES PLACE MONDAY NIGHT AND TUESDAY.
TEMPERATURES WILL REMAIN SEVERAL DEGREES BELOW NORMAL THROUGH THE
SHORT TERM.

.LONG TERM...MODELS STILL SHOWING DIFFERENCES WITH HANDLING THE
EVOLUTION OF THE TWO UPPER LEVEL LOWS DURING THE EXTENDED PERIOD.
GFS AND GEM MODELS SHOW TWO DISTINCT LOWS DROPPING INTO THE BASE OF
THE MEAN TROUGH WHILE THE ECMWF KEEPS THE SECOND SYSTEM CONFINED TO
THE NORTHERN JET STREAM. IN EITHER SCENARIO...MODELS DO SHOW A
DECREASING PRECIPITATION TREND WITH THIS SITUATION WITH THE LOW
EITHER MOVING OFF THE COAST OR EJECTING EASTWARD. MODEL SOUNDINGS
INDICATE AIRMASS CONTINUES TO REMAIN COLD AND UNSATURATED NEAR THE
SURFACE WHICH WILL LEAD TO CONTINUED LOW SNOW LEVELS DUE TO WET BULB
EFFECTS FOR ANY REMAINING PRECIPITATION TUESDAY. AFTER THIS HAVE
SHOWN A DECREASING CHANCE OF PRECIPITATION AND A WARMING
TREND...ALBEIT A SLOW ONE ESPECIALLY IN VALLEY LOCATIONS WHICH WILL
HAVE TO STRUGGLE TO MIX OUT RESIDUAL COLD AIR. HAVE CONTINUED TO
UNDERCUT MOS TEMPS DUE TO ITS TREND TOWARD CLIMATOLOGY AND ALSO DUE
TO COLD AIR BEING SLOW TO MODIFY IN VALLEYS WITHOUT MECHANICAL
MIXING FROM THE WIND. MODELS INDICATE A POTENTIAL INCREASE TO CLOUDS
AND PERHAPS AN INCREASED THREAT FOR PRECIPITATION BY NEXT
WEEKEND...BUT LOW CONFIDENCE REMAINS THROUGH THIS ENTIRE PERIOD DUE
TO MODELS VARIED SOLUTIONS ON HANDLING THIS COMPLEX SITUATION.  &&

.AVIATION...FOR MCCARRAN...WINDS HAVE BEEN THE MAIN PROBLEM FOR THE
PAST TWO DAYS...BUT GRADIENTS HAVE FINALLY RELAXED AND GENERALLY
LIGHT NORTHEAST TO EAST WINDS HAS SET UP FOR THIS EVENING. WINDS
WILL DECOUPLE FURTHER THIS EVENING BECOMING LIGHT AND VARIABLE UNDER
A STRENGTHENING INVERSION. WINDS WILL REMAIN LIGHT SATURDAY BUT
PREFER AN EASTERLY COMPONENT BY LATE MORNING INTO THE AFTERNOON.
SOME HIGH CLOUDS WILL SPREAD OVER THE VALLEY LATER TONIGHT AND
THROUGH THE DAY SATURDAY LOWERING THROUGH THE DAY TO AROUND 15K
FEET.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS BECOMING LIGHT AND VARIABLE TONIGHT IN MOST
AREAS. INCREASING HIGH CLOUDS CAN BE EXPECTED MOVING FROM NORTHWEST
TO SOUTHEAST WHICH WILL LOWER THROUGH THE DAY SATURDAY TO AROUND 15K
FEET AND LOCALLY LOWER NEAR THE SIERRA.
&&

.CLIMATE...VERY COLD AIRMASS REMAINS OVER THE AREA. SO FAR THE HIGH
AT MCCARRAN AIRPORT HAS BEEN 38 DEGREES WHICH WILL BREAK THE RECORD
LOW MAX FOR THE DAY OF 45. IT IS LIKELY OTHER LOCATIONS WILL ALSO
BREAK THEIR RECORDS FOR THE LOWEST HIGH TEMPERATURE. A FEW SITES MAY
ALSO SEE RECORD LOW MINIMUM TEMPERATURES AND RECORD LOW MAXIMUM
TEMPERATURES ON NEW YEAR'S DAY. BELOW IS A LIST OF RECORDS FOR
SEVERAL STATIONS IN OUR AREA...

LOCATION        RECORD LOW MAX    RECORD LOW MIN   RECORD LOW MAX
                    12/31              1/1              1/1
---------------------------------------------------------------------
LAS VEGAS          45/1975           21/1954          39/1979
MT CHARLESTON      31/1981            0/1995          26/1982
BISHOP             33/1951            8/1976          29/1952
BARSTOW-DAGGETT    47/1988           22/1979          45/1952
DEATH VALLEY       55/1993           21/1919          48/1991
NEEDLES            51/1974           27/1976          48/1952
KINGMAN            36/1918           13/1919          34/1906

FYI...HERE ARE SOME PRELIMINARY STATS FOR LAS VEGAS FOR 2010. ALL
INFORMATION IS FOR THE OFFICIAL CLIMATE STATION AT MCCARRAN AIRPORT.

THE AVERAGE TEMPERATURE THROUGH YESTERDAY 12/30 WAS 69.7 DEGREES.
BEST ESTIMATE BASED ON THE FORECASTED LOW AND HIGH TEMPERATURES FOR
TODAY WOULD PUT THE ANNUAL AVERAGE TEMPERATURE AT 69.6 DEGREES WHICH
WOULD TIE THIS YEAR AS THE 8TH WARMEST ON RECORD WITH 2001.

PRECIPITATION THIS YEAR HAS TOTALED AN IMPRESSIVE 5.90 INCHES WHICH
IS 1.41 INCHES ABOVE NORMAL. THIS RANKS AS THE 14TH WETTEST YEAR
EVER IN LAS VEGAS SINCE 1937 AND THE FIRST TIME WE HAVE HAD AN ABOVE
NORMAL FINISH TO THE YEAR FOR PRECIPITATION SINCE 2005.
&&

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

GORELOW/STAUDENMAIER

HTTP://WEATHER.GOV/LASVEGAS

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE LAS VEGAS NV
342 AM PST FRI DEC 31 2010

AZZ001>003-036-CAZ519>527-NVZ014>022-011000-
NORTHWEST PLATEAU-LOWER COLORADO RIVER VALLEY-NORTHWEST DESERTS-
LAKE MEAD NATIONAL RECREATION AREA-EASTERN SIERRA SLOPES-
OWENS VALLEY-WHITE MOUNTAINS OF INYO COUNTY-
DEATH VALLEY NATIONAL PARK-WESTERN MOJAVE DESERT-
EASTERN MOJAVE DESERT-MORONGO BASIN-CADIZ BASIN-
SAN BERNARDINO COUNTY-UPPER COLORADO RIVER VALLEY-
ESMERALDA AND CENTRAL NYE COUNTY-LINCOLN COUNTY-
NORTHEAST CLARK COUNTY-WESTERN CLARK AND SOUTHERN NYE COUNTY-
SHEEP RANGE-SPRING MOUNTAINS-LAS VEGAS VALLEY-
SOUTHERN CLARK COUNTY-
342 AM PST FRI DEC 31 2010 /442 AM MST FRI DEC 31 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST
ARIZONA...CALIFORNIA AND SOUTHERN NEVADA.

.DAY ONE...TODAY AND TONIGHT

WELL BELOW NORMAL TEMPERATURES WILL OCCUR TODAY AND TONIGHT. TAKE THE
NECESSARY PRECAUTIONS TO PROTECT PIPES...PLANTS AND PETS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

TEMPERATURES WILL STAY WELL BELOW NORMAL THROUGH THE HOLIDAY
WEEKEND. A STORM SYSTEM MOVING DOWN THE CALIFORNIA WILL LEAD TO A
CHANCE OF RAIN AND SNOW OVER WESTERN INYO COUNTY AND THE WESTERN
MOJAVE DESERT THIS WEEKEND. THE CHANCE OF RAIN AND SNOW SPREADS
EAST ACROSS THE REMAINDER OF THE MOJAVE DESERT AND SOUTHERN GREAT
BASIN SUNDAY NIGHT THROUGH TUESDAY.

.SPOTTER INFORMATION STATEMENT...

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