Heavy Snow and Winter Weather in California, February 22 to 23, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
830 AM PST SUN FEB 22 2015

.SYNOPSIS...A WINTER STORM WILL IMPACT THE REGION TODAY AND MONDAY
BRINGING WIDESPREAD RAIN...MOUNTAIN SNOW AND MUCH COOLER CONDITIONS
TO THE AREA. WEATHER CONDITIONS WILL IMPROVE BY TUESDAY AND CONTINUE
THROUGH THURSDAY WITH SEASONAL TEMPERATURES EXPECTED. MORE UNSETTLED
WEATHER CONDITIONS ARE POSSIBLE HEADING INTO NEXT WEEKEND.
&&

.UPDATE...THE MUCH ANTICIPATED STORM SYSTEM IS WELL UNDERWAY THIS
MORNING WITH WIDESPREAD OVERCAST CONDITIONS AND SOME LIGHT
PRECIPITATION ACROSS THE AREA...AS WELL AS MUCH COOLER TEMPERATURES.
CONDITIONS WILL CONTINUE TO DETERIORATE THIS AFTERNOON WITH
PRECIPITATION INCREASING ACROSS EASTERN CALIFORNIA SHORTLY AFTER THE
NOON HOUR AND EXPANDING EASTWARD THROUGH THE AFTERNOON HOURS. SNOW
LEVELS THIS MORNING HAVE BEEN RUNNING A TOUCH LOWER THAN INITIALLY
FORECAST...AROUND 4500 FEET ACROSS LINCOLN COUNTY AND JUST ABOVE
5000 FEET IN NORTHERN MOHAVE COUNTY.  I ADJUSTED SNOW LEVELS DOWN
SLIGHTLY TO ACCOUNT FOR THIS. I ALSO RAISED POPS ACROSS MUCH OF THE
AREA TO BETTER REFLECT RADAR TRENDS AND SHORT TERM GUIDANCE.

PRECIPITATION IN THE LAS VEGAS VALLEY SHOULD BEGIN TO INCREASE
AROUND THE 2PM HOUR AND INCREASE IN COVERAGE AND INTENSITY THROUGH
THE EVENING.

-OUTLER-

&&

.AVIATION...FOR MCCARRAN...WINDS WILL GENERALLY FAVOR A NORTH TO
NORTHEAST DIRECTION STRADDLING THE LINE BETWEEN CONFIG 2 AND 3.
WIND SPEEDS WILL BE AROUND 8 TO 12 KTS THROUGH THIS AFTERNOON. CIGS
WILL GRADUALLY DECREASE TODAY...LOWERING TO NEAR 5K BY MID
AFTERNOON AND THEN LOWER TO UNDER 5K FT TONIGHT THROUGH MONDAY.
FREQUENT MOUNTAIN OBSCURATIONS ARE EXPECTED WITH RAIN AND
PERIODICALLY REDUCED VISIBILITY AT THE TERMINAL.  CIGS MAY FALL
BELOW 2K AFTER 6Z TONIGHT.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...CLOUDS WILL SPREAD OVER THE ENTIRE REGION TODAY WITH
CIGS GENERALLY BETWEEN 5-10K FT. RAIN AND SNOW SHOWERS ARE POSSIBLE
TODAY ESPECIALLY NORTH OF INTERSTATE 15 WITH MORE WIDESPREAD RAIN
AND SNOW TONIGHT INTO MONDAY. FREQUENT MOUNTAIN OBSCURATIONS...LOW
CIGS...AND PERIODIC REDUCTIONS IN VISIBILITY ARE EXPECTED.

&&

.SHORT TERM...TODAY THROUGH MONDAY NIGHT.

LOW PRESSURE CONTINUES TO SINK SOUTHWARD INTO THE SOUTHERN GREAT
BASIN AND AN EXTENSIVE CLOUD SHIELD WAS PRESENT ACROSS THE NORTHERN
ZONES...NORTHERN CLARK AND NORTHERN MOHAVE COUNTIES. CLOUDS ARE
BEGINNING TO RAPIDLY DEVELOPMENT ACROSS THE MOJAVE DESERT AS WELL
AFTER HAVING CLEAR SKIES THROUGH SATURDAY EVENING. SO FAR THROUGH 1
AM...THERE WERE NO REPORTS OF ANY PRECIPITATION REACHING THE GROUND.

THE SYSTEM WILL CONTINUE TO EVOLVE AS IT SINKS INTO THE SOUTHWEST
WITH MODEL MOISTURE/DYNAMIC PROFILE FAVORABLE FOR A SIGNIFICANT
PRECIPITATION EVENT FOR MUCH OF THE AREA. THERE REMAINS DIFFERENCES
BETWEEN THE MODELS IN PRECIP PLACEMENT AND AMOUNTS BUT ALL MODELS
HIT THE SIERRA FAIRLY HARD WITH UP TO INCH OF LIQUID AND SLAM
NORTHERN MOHAVE COUNTY ONE TO TWO INCHES. HOWEVER, SNOW LEVELS ARE
EXPECTED TO BE LOWER IN THE SIERRA (BETWEEN 4000 AND 5000 FEET) AND
5000 TO 6000 FEET IN NORTHERN MOHAVE COUNTY. AMOUNTS IN THE SPRING
MOUNTAINS ARE LESS CERTAIN WITH THE GFS/NAM SUGGESTING 6-10 INCHES
OF SNOW ABOVE 5000 FEET WHILE THE LATEST ECMWF HAS ABOUT 3-5 INCHES.
A BIG QUESTION MARK REMAINS FOR THE SOUTH CENTRAL NEVADA MOUNTAINS
WITH THE NAM STILL HITTING THEM WITH FAIRLY IMPRESSIVE AMOUNTS WHILE
THE GFS/EC ARE MORE INLINE WITH THE CURRENT WINTER WEATHER ADVISORY.
THE LOWER ELEVATIONS OF THE MOJAVE DESERT AND SOUTHERN GREAT BASIN
INCLUDING THE LAS VEGAS VALLEY COULD SEE BETWEEN A .25 INCH AND .75
INCH OF RAIN BETWEEN 4 PM TODAY TO 4 PM MONDAY. AREAS SOUTH OF
INTERSTATE 40 AND IN ESMERALDA COUNTY WILL LIKELY SEE LESS THAN .25
INCH.

ALL CURRENT WINTER WEATHER HAZARDS LOOK GOOD AND NO CHANGES WERE
MADE ALTHOUGH IF MODELS CONTINUE TO HIT THE EASTERN SIERRA SLOPES
HARD...AN UPGRADE MAY BECOME NECESSARY. ONE OTHER ITEM OF NOTE: EVEN
THOUGH THE WINTER WEATHER HAZARDS OFFICIALLY START AT 4 AM THIS
MORNING...THE ACTUAL START TIMES FOR ACCUMULATING SNOW WILL VARY
DEPENDING ON LOCATION WITH THE HEAVIEST PRECIPITATION HOLDING OFF IN
MANY LOCATIONS UNTIL LATER TODAY THROUGH EARLY MONDAY.

TEMPERATURES WILL STRUGGLE TO WARM MUCH TODAY WITH LOW PRESSURE
MOVING OVER THE AREA AND ABUNDANT CLOUD COVER EXPECTED THROUGH THE
DAY. THE CLOUD COVER MAY HELP KEEP TEMPERATURES A BIT WARMER MONDAY
MORNING THAN THEY WOULD BE OTHERWISE. MONDAY IS EXPECTED TO BE EVEN
COOLER THAN TODAY WITH HIGH TEMPERATURES POTENTIALLY 10 OR MORE
DEGREES BELOW NORMAL.

.LONG TERM...TUESDAY THROUGH SATURDAY.

THE UPPER LEVEL LOW WILL BE EXITING TO THE EAST ON TUESDAY...BUT A
LINGERING SHOWER IS STILL POSSIBLE IN THE MORNING OVER THE
NORTHWEST PLATEAU OF MOHAVE COUNTY. NORTHERLY FLOW ALOFT AND AT THE
SURFACE WILL DEVELOP BEHIND THE LOW...PRODUCING FAIRLY STRONG WINDS
DOWN THE COLORADO RIVER VALLEY...AND THE POTENTIAL FOR A LAKE WIND
ADVISORY. A WEAK IMPULSE WILL SKIRT ACROSS THE SOUTHERN GREAT BASIN
ON WEDNESDAY...PROVIDING SOME INCREASE IN CLOUD COVER AND ANOTHER
REINFORCING SHOT OF NORTHERLY FLOW BEHIND IT. THE NEXT SYSTEM WILL
BEGIN TO APPROACH THE AREA ON FRIDAY...PROVIDING THE POTENTIAL FOR
ANOTHER ROUND OF PRECIPITATION ACROSS THE AREA FRIDAY NIGHT AND
SATURDAY. AT THIS POINT HAVE INCREASED POPS MODESTLY AS ENSEMBLE
SPREAD IS STILL FAIRLY HIGH WITH STRENGTH AND TIMING OF THE SYSTEM.
THE SYSTEM LOOKS TO BE FAIRLY COLD WITH SNOW LEVELS OF 4000 TO
5000 FEET ON AVERAGE...POTENTIALLY LOWER.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
HOWEVER...SNOW AND RAINFALL REPORTS WOULD BE APPRECIATED TODAY AND
MONDAY.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
HOWEVER...SNOWFALL REPORTS TODAY AND MONDAY WOULD BE APPRECIATED.
&&

SHORT TERM/AVIATION...SALMEN
LONG TERM....CZYZYK

FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE:

HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER