Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 252211
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
211 PM PST THU DEC 25 2014

.SYNOPSIS...LOW PRESSURE WILL GRADUALLY MOVE AWAY FROM THE AREA BUT
COLD NORTHERLY FLOW WILL CONTINUE OVER THE REGION RESULTING IN NORTH
WINDS CONTINUING THROUGH SATURDAY MORNING. THIS COLDER AIRMASS WILL
REMAIN IN PLACE THROUGH THE WEEKEND AND REINFORCEMENTS ARE ON THE
HORIZON FOR NEXT WEEK AS ANOTHER...POTENTIALLY COLDER SYSTEM
APPROACHES FROM THE NORTH. PEOPLE ARE ENCOURGAED TO PAY CLOSE
ATTENTION TO FORECAST OUTLOOKS OVER THE COMING DAYS.

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT.

WIND ADVISORIES HAVE BEEN ALLOWED TO EXPIRE IN ALL AREAS. HOWEVER,
THERE REMAINS A FEW OBSERVATIONAL SITES AS OF 2 PM REPORTING WIND
GUSTS AROUND 40 MPH. THEY ARE LOCALIZED TO FAVORED AREAS FOR WINDS
BLOWING IN THIS DIRECTION BUT THE OVERALL TREND IS DOWN.

AN AREA OF LOW PRESSURE WILL MOVE EAST OF THE AREA TONIGHT...LEAVING
THE AREA UNDER A COLD NORTHERLY FLOW. SHOWER CHANCES WILL BE LIMITED
BUT STILL POSSIBLE IN LINCOLN/NORTHERN MOHAVE COUNTIES THIS EVENING
BEFORE DRY CONDITIONS RETURN AREA WIDE FRIDAY AND SATURDAY.

TEMPERATURES ALOFT PLUMMETED LAST NIGHT AND THE COLD AIR WILL MAKE
ITS WAY INTO THE LOWER VALLEYS TONIGHT. THE LAS VEGAS LOW FRIDAY
MORNING IS OFFICIALLY FORECAST TO REACH 35 DEGREES BUT MANY AREAS
AWAY FROM THE CENTER OF THE CITY COULD SEE TEMPERATURES 2-4 DEGREES
COLDER. GUSTY NORTH WINDS WILL CONTINUE ON FRIDAY AS A WEAK WEATHER
DISTURBANCE MOVING OUT OF CANADA TONIGHT...DIVES THROUGH NEVADA
FRIDAY. HOWEVER, WINDS WILL NOT BE AS STRONG AS CHRISTMAS DAY WITH
EXPECTED WIND SPEEDS GENERALLY 10-20 MPH. DAYTIME HIGHS FRIDAY ARE
EXPECTED TO BE 7-10 DEGREES BELOW NORMAL.

THE TROUGH BEGINS ITS FINAL DEPARTURE FRIDAY EVENING WITH A BREAK IN
WINDS BY SATURDAY AFTERNOON WHEN THE AREA IS BETWEEN STORM SYSTEMS.
THE ONLY EXCEPTION WILL BE LINGERING NORTH WINDS ALONG THE COLORADO
RIVER VALLEY THROUGH THE DAY SATURDAY. WITH THE AREA FULLY INVOLVED
IN THE COLD AIRMASS SATURDAY MORNING...LOWS ARE EXPECTED TO
OFFICIALLY REACH FREEZING AT THE LAS VEGAS AIRPORT BUT COULD REACH
INTO THE UPPER 20S IN SOME PARTS OF THE VALLEY. THE ONLY SAVING
GRACE COULD BE CONTINUED NORTH WINDS OF 10-15 MPH DURING THE MORNING
HOURS WHICH MAY LIMIT THE IMPACTS SOMEWHAT. LITTLE MOVEMENT EXPECTED
IN SATURDAY DAYTIME TEMPERATURES WITH HIGHS REMAINING 8-10 DEGREES
BELOW NORMAL. SUNDAY MORNING LOWS SHOULD BE A FEW DEGREES WARMER
THAN SATURDAY.

.LONG TERM...SUNDAY THROUGH NEW YEARS DAY. ANOTHER LOW CONFIDENCE
FORECAST AS THE OPERATIONAL MODELS CONTINUE TO WHIPSAW AROUND FROM
RUN TO RUN BUT NEARLY IN LOCK STEP WITH EACH OTHER.

FIRST THE MID LEVELS OF THE ATMOSPHERE. PICKING UP SUNDAY
MORNING...THERE IS VERY GOOD AGREEMENT AMONG THE OP RUNS AND
ENSEMBLE MEMBERS SHOWING A HIGH AMPLITUDE SHORT WAVELENGTH RIDGE
OVER THE EASTERN PACIFIC WITH A LONGWAVE TROUGH OVER MOST OF THE
UNITED STATES. THE MAIN FEATURE OF INTEREST IS A SHORTWAVE TROUGH
DIGGING DOWN THE FRONT SIDE OF THE RIDGE INTO THE PACIFIC NORTHWEST.
UNLIKE MOST SYSTEMS WHICH HAVE AFFECTED OUR AREA THIS SEASON...THIS
ONE IS TAKING A PATH ALMOST COMPLETELY OVER LAND INSTEAD OF
WATER...MEANING IT IS MUCH COLDER. BY MONDAY MORNING ABOUT TWO
THIRDS OF THE ENSEMBLE MEMBERS AGREE ON A CLOSED LOW DEVELOPING OVER
THE PACIFIC NORTHWEST...BUT WITH SOME SPREAD IN ITS LOCATION AND
DEPTH. TUESDAY MORNING IS WHEN THINGS REALLY START TO GET
INTERESTING AS THE LOW DIGS FARTHER SOUTH. FORECAST POSITIONS RANGE
FROM IDAHO TO WESTERN ARIZONA...WITH A DECENT CLUSTER OF SOLUTIONS
OVER NORTHERN NEVADA. BY WEDNESDAY MORNING THE SPREAD INCREASES
GREATLY...WITH FORECAST POSITIONS ANYWHERE FROM OFFSHORE OF NORTHERN
CALIFORNIA TO NEAR THE FOUR CORNERS. THERE IS A REASONABLE CLUSTER
NEAR THE CENTRAL CALIFORNIA COAST. BY THURSDAY MORNING THE SPREAD IS
ALL THE WAY FROM STILL OFFSHORE OF CALIFORNIA TO THE PLAINS...BUT
WITH A DECENT CLUSTER OVER SOUTHERN NEVADA.

IN THE LOW LEVELS IS WHERE THINGS GET EVEN MORE INTERESTING. THERE
IS REASONABLE CONSENSUS ON A SIGNIFICANT COLD FRONT DIVING THROUGH
THE CWA MONDAY NIGHT INTO TUESDAY...WITH NORTH TO NORTHEAST WINDS
CONTINUING TO ADVECT IN COLD AND DRY AIR ALL THE WAY INTO NEW YEARS
DAY.

WHAT ALL THIS MEANS FOR THE WEATHER GOES SOMETHING LIKE THIS. IF WE
FOLLOW THE CLUSTER OF MODEL SOLUTIONS THROUGH THE PERIOD...THE COLD
FRONT BRINGS IN COLD AND DRY AIR MONDAY NIGHT AND TUESDAY...AND THEN
THE UPPER LEVEL LOW ADVECTS IN MOISTURE AND ALSO PROVIDES LIFT
BEGINNING IN THE NORTHERN CWA TUESDAY AND SPREADING AREAWIDE TUESDAY
NIGHT AND WEDNESDAY...POSSIBLY LINGERING INTO THURSDAY. THIS COULD
LEAD TO A LOW ELEVATION SNOW EVENT FOR MUCH OF THE MOJAVE DESERT. IT
IS IMPORTANT TO EMPHASIZE THAT THIS IS ONLY ONE POSSIBLE OUTCOME. IF
THE LOW MOVES FASTER LIKE ONE ENSEMBLE MEMBER SHOWS...IT WILL BE
LONG GONE BY NEW YEARS EVE. IF IT MOVES SLOWER AS A FEW ENSEMBLE
MEMBERS SHOW...IT MAY NOT EVEN GET HERE BY THEN. DUE TO THE GREAT
UNCERTAINTY...RAISED POPS ONLY A LITTLE...MAINLY SLIGHT CHANCES WITH
A FEW LOW END CHANCES...AND SPREAD POPS OVER SEVERAL 12 HOUR TIME
PERIODS. AS NOTED ABOVE...CONFIDENCE IN THE DETAILS IS VERY LOW. BUT
THE POSSIBILITY...NOTE THAT WORD POSSIBILITY...OF SUCH AN EVENT IN
LAS VEGAS ON OR AROUND NEW YEARS EVE NEEDS TO BE NOTED.
&&

.AVIATION...FOR MCCARRAN...WINDS WILL CONTINUE TO BE GUSTY OUT OF
NORTHWEST THROUGH FRIDAY BUT THERE WILL BE A NOTICEABLE DECREASE IN
WIND SPEEDS. SCT CLOUDS AROUND 7K FEET THROUGH THE REST OF AFTERNOON
THEN CLEARING OVERNIGHT. WIND SPEEDS OF 10-20 KTS EXPECTED FRIDAY
THROUGH SATURDAY MORNING BECOMING LIGHT SATURDAY AFTERNOON.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...GUSTY NORTHWEST WINDS WILL CONTINUE ACROSS THE REGION
THROUGH FRIDAY BUT WIND SPEEDS WILL GRADUALLY DECREASE. SCT-BKN
CLOUDS 5-7K FT OVER MUCH OF THE NORTHERN FORECAST AREA WITH FEW-SCT
6-8K FEET ELSEWHERE. A FEW SHOWERS ARE POSSIBLE IN LINCOLN AND
NORTHERN MOHAVE COUNTIES THROUGH THIS EVENING WITH MOUNTAIN
OBSCURATIONS AT TIMES. WINDS GENERALLY 10-20 KTS EXPECTED FRIDAY
WITH SCT CLOUDS NORTH AND EAST.
&&

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

$$

SALMEN/MORGAN

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