Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 130623 AAA
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
1018 PM PST FRI FEB 12 2016

.SYNOPSIS...WARM AND DRY CONDITIONS WILL CONTINUE ACROSS THE REGION
THROUGH EARLY NEXT WEEK. BREEZY CONDITIONS WILL OCCUR ALONG THE
LOWER COLORADO RIVER VALLEY, ESPECIALLY ON SUNDAY AND MONDAY. THE
NEXT CHANCE FOR PRECIPITATION COMES LATE NEXT WEEK AS A STORM SYSTEM
MOVES THROUGH THE AREA.
&&

.UPDATE...

FORECAST IN GOOD SHAPE AND NO UPDATES PLANNED.
&&

.DISCUSSION...

UPPER-LEVEL RIDGE THAT HAS BEEN ANCHORED ACROSS THE WEST THIS WEEK
IS SLOWLY BEGINNING TO MIGRATE EASTWARD AND FLATTEN AS A SERIES OF
VORTICITY MAXIMA APPROACH COASTAL BRITISH COLUMBIA AND THE PACIFIC
NORTHWEST TODAY. WV IMAGERY SHOWING A SOUTHWEST-NORTHEAST ELONGATED
STREAM OF UPPER-LEVEL MOISTURE DOWNSTREAM OF THESE VORT MAXIMA
BRUSHING THE NORTHWEST PORTIONS OF THE REGION THIS AFTERNOON.
PASSING HIGH CLOUDS HAVE REACHED THE AREA TODAY, THOUGH THEIR IMPACT
ON TEMPERATURES HAS BEEN MINIMAL. SOUTHERN STREAM PORTION OF THE
TROUGH WILL MOVE THROUGH THE REGION TOMORROW NIGHT. 18Z GFS HAS COME
IN A BIT STRONGER WITH THE TROUGH, AND HI-RES GUIDANCE HAS INCREASED
THE NORTHERLY FLOW AND SURFACE PRESSURE GRADIENT AFTER PASSAGE OF
THIS SYSTEM. AS SUCH, BUMPED UP WINDS A BIT ON SUNDAY AND MONDAY,
PARTICULARLY IN THE COLORADO RIVER VALLEY, WHERE SPEEDS MAY APPROACH
LAKE WIND ADVISORY CRITERIA. WILL CONTINUE TO MONITOR AS THE SYSTEM
APPROACHES THIS WEEKEND. OTHERWISE, THE TROUGH PASSAGE IS EXPECTED
TO BE DRY.

MOS GUIDANCE IS IN UNUSUALLY STARK DISAGREEMENT REGARDING
TEMPERATURES AFTER TROUGH PASSAGE, WITH GFS MOS NOTICEABLY WARMER
THAN ECMWF MOS GUIDANCE. UNFORTUNATELY, IT IS NOT ENTIRELY CLEAR
WHICH TO PREFER AS COMPETING PROCESSES ARE AT PLAY. THOUGH SOME
COOLING IS EXPECTED WITH WEAK COLD AIR ADVECTION AFTER TROUGH
PASSAGE ON SUNDAY, THIS MAY BE COUNTERACTED BY INCREASED MIXING AS
THE NORTHERLY WINDS INCREASE. FOR NOW, THINK A COMPROMISE BETWEEN
THE TWO CAMPS IS BEST. AS SUCH CONTINUED TO DECREASE TEMPS BY ABOUT
1-4 DEGREES ON SUNDAY VERSUS SATURDAY.

THREE OTHER NOTES...THOUGH TEMPS WERE BUMPED UPWARD A DEGREE OR TWO
TOMORROW, PRESENCE OF HIGH CLOUDS MAY TEMPER WARMING SOMEWHAT. SO IT
IS POSSIBLE MAX TEMPS MAY BE A DEGREE OR TWO COOLER THAN FORECAST
TOMORROW. SECOND, GUIDANCE IS WAY TOO WARM WITH TEMPS IN SNOW-
COVERED LOCATIONS OF NORTHWEST LINCOLN COUNTY AND ADJACENT CENTRAL
NYE COUNTY. FOR EXAMPLE, MOS/GRIDDED TEMPS FOR RACHEL HAVE
CONSISTENTLY BEEN 10-15 DEGREES TOO HIGH THE PAST SEVERAL DAYS.
BUMPED TEMPS DOWN HERE AT LEAST 5 DEGREES THROUGH MUCH OF THE COMING
WEEK, ESPECIALLY THROUGH THIS WEEKEND, AS SNOW COVER REMAINS FAIRLY
EXTENSIVE IN THIS AREA. THIRD, GUIDANCE HAS GENERALLY BEEN TOO WARM
WITH OVERNIGHT LOWS ACROSS THE AREA, SO HAVE CUT MIN TEMPS A DEGREE
OR TWO THROUGH THE SHORT TERM.

ADVANCING TO THE LONG TERM PORTION OF THE FORECAST, LONG-ADVERTISED
CUTOFF LOW SHOULD DEVELOP IN THE SUBTROPICAL EAST PACIFIC LATE THIS
WEEKEND THROUGH EARLY NEXT WEEK AS A RIDGE REBUILDS TO ITS NORTH.
OUR REGION`S PROXIMITY TO THE RIDGE AND THE DOWNSTREAM NORTHWESTERLY
FLOW WILL KEEP THE AREA WARM AND DRY EARLY NEXT WEEK. MOS GUIDANCE
HAS COME IN A BIT WARMER TODAY FOR THIS PERIOD, AND GIVEN THE
STRONGER GENERAL APPEARANCE TO THE RIDGING...FOLLOWED SUIT WITH MAX
TEMPS IN THE GRIDS MONDAY THROUGH WEDNESDAY. WEDNESDAY COULD BE VERY
WARM IF STRONGER SOUTHWEST WINDS MIX TO THE SURFACE. CONTINUED TO
TREND SLIGHTLY BELOW GUIDANCE FOR LOWS, HOWEVER, GIVEN THE POSITIVE
BIAS IT HAS EXHIBITED RECENTLY.

FINALLY, A RESPECTABLE SYSTEM MOVES INTO THE WEST LATE NEXT WEEK.
UNFORTUNATELY, THE CUTOFF LOW MAY BE TOO FAR SOUTH TO DEEPEN THE
TROUGH SUFFICIENTLY AND THE RIDGING TO ITS NORTH MAY PROVE TOO MUCH
FOR THE TROUGH TO PROVIDE WIDESPREAD PRECIPITATION TO OUR REGION
LATE NEXT WEEK. MODELS HAVE CERTAINLY BEEN HINTING AT THIS FOR THE
PAST SEVERAL RUNS. MODELS CONTINUE TO DISAGREE ON TIMING AND
STRENGTH OF THE SYSTEM AND THE GENERAL STORM TRACK, HOWEVER, AS
12Z/18Z GFS REMAIN(S) FASTER, WEAKER, DRIER, AND FARTHER NORTH WITH
THE SYSTEM THAN THE 00Z/12Z ECMWF (WHICH LOOKS TO PRODUCE A FAIRLY
DECENT WINTER STORM FOR THE SIERRA). 12Z CMC IS FASTER THAN THE EURO
BUT LOOKS MORE REMINISCENT IN TERMS OF STRUCTURE TO IT VERSUS THE
GFS. 06Z/18Z DGEX LOOK(S) VERY SIMILAR TO THE GFS SIMULATIONS.
ENSEMBLES SUGGEST A LOT OF DISAGREEMENT IN TERMS OF TIMING/STRENGTH,
WITH MEANS ESSENTIALLY WASHING OUT THE AMPLITUDE OF THE TROUGH AND
UPSTREAM/SUBSEQUENT RIDGING. DID NOT CHANGE INHERITED POPS MUCH,
THOUGH DID SLOW THE TIMING OF THEM IN THE GRIDS GIVEN THE SUBTLE
SLOWING TREND OF THE GFS IN RECENT SOLUTIONS. HAVE A HUNCH THE GFS
IS EXHIBITING ITS FAST/WEAK BIAS WHEN SYSTEMS APPROACH BROAD
RIDGING, BUT THE EURO HAS ALSO BEEN A BIT TOO BULLISH MOST OF THIS
WINTER. THINKING A COMPROMISE SOLUTION IS BEST AT THIS POINT. AS THE
GRIDS REFLECTED THIS WELL ALREADY, WAS NOT INCLINED TO CHANGE MUCH
BEYOND WEDNESDAY.

ONE FINAL NOTE...GFS/ECMWF DIVERGE EVEN MORE SUBSEQUENT TO THE
TROUGH PASSAGE. INTERESTINGLY, MEX MOS KEEPS MCCARRAN ABOVE 70
THROUGH NEXT FRIDAY WHEREAS EURO MOS ENDS THE 70+ STREAK ON
THURSDAY. MY INCLINATION IS THAT THE STREAK WILL END BY THURSDAY
OR FRIDAY, AND THE GRIDS REFLECT THIS. NOT A SURE THING, THOUGH.
&&

.AVIATION...FOR MCCARRAN...LIGHT WINDS DRIVEN BY DIURNAL PROCESSES
WILL BE IN CONTROL THROUGH SATURDAY. WINDS WILL REMAIN AOB 6 KTS
THROUGH SATURDAY NIGHT. BREEZIER NORTH OR NORTHEAST WINDS ARE
FORECAST TO OCCUR ON SUNDAY.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...KIFP WILL CONTINUE TO SEE SOMEWHAT STRONGER NORTHERLY
WINDS DURING THE DAY TOMORROW BUT SHOULD BE AOB 10 KTS DURING THE
OVERNIGHT HOURS. DIURNALLY DRIVEN WINDS WILL CONTINUE AT THE
REMAINING TERMINALS THROUGH SATURDAY. BREEZIER NORTH OR NORTHEAST
WINDS WILL LIKELY OCCUR ACROSS THE AREA ON SUNDAY AFTER PASSAGE OF A
WEAK SYSTEM SATURDAY NIGHT.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED.
PLEASE REPORT ANY SIGNIFICANT WEATHER ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

$$

GORELOW/SHAFER

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