Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000 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 FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE: HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER

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