HAMweather.com Area Forecast Discussion for County Warning Area VEF

Thu, 16 Feb 2012 11:10:00 GMT
AREA FORECAST DISCUSSION UPDATE
NATIONAL WEATHER SERVICE LAS VEGAS NV
310 AM PST THU FEB 16 2012

.SYNOPSIS...AN AREA OF LOW PRESSURE LOCATED NEAR THE CALIFORNIA... 
MEXICO BORDER WILL CONTINUE TO DROP SOUTH THIS MORNING. A BAND OF 
LIGHT PRECIPITATION OVER SAN BERNARDINO AND MOHAVE COUNTIES WILL 
DIMINISH BY LATE MORNING. GUSTY NORTH TO NORTHEAST BREEZES WILL BE 
PREVALENT ACROSS THE REGION TODAY. WEAK RIDGING ON FRIDAY AND 
SATURDAY WILL PROVIDE...DRIER CONDITIONS...LIGHTER WINDS...AND 
SEASONABLE TEMPERATURES.

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...AN UPPER LEVEL LOW IS 
EVIDENT ON WATER VAPOR IMAGERY AND RADAR IMAGERY JUST TO THE EAST OF 
SAN DIEGO. A BAND OF LIGHT PRECIP CONTINUES TO ROTATE THROUGH 
SOUTHERN SAN BERNARDINO COUNTY AND MOHAVE COUNTY. SNOW LEVELS ARE 
GENERALLY BETWEEN 3500 AND 4000 FEET. THIS LIGHT PRECIP WILL 
CONTINUE FOR THE NEXT SEVERAL HOURS...BUT SHOULD DIMINISH BY 
NOON...AS THE LOW CONTINUES TO DROP SOUTH AND INTO MEXICO. TRICKY 
TRAVEL CONDITIONS CONTINUE NEAR MOUNTAIN PASS IN SAN BERNARDINO... 
WHERE BLACK ICE AND VERY LOW VISIBILITIES DUE TO FOG AND LOW 
CEILINGS HAVE BEEN REPORTED OVER THE PAST FEW HOURS. EXPECT THESE 
CONDITIONS TO PERSIST THERE THROUGH AT LEAST SUNRISE. LATEST 
GRADIENT FROM ELY TO EED IS 9 MB...WHICH IS ABOUT 1 MB LESS THAN THE 
NAM12 IS INDICATING. THAT GRADIENT IS EXPECTED TO CONTINUE TO 
INCREASE TO 14 TO 15 MB DURING THE MORNING HOURS. WITH THIS...HAVE 
ISSUED A WIND ADVISORY FOR THE 4 ZONES DOWN ALONG THE COLORADO RIVER 
VALLEY. ELSEWHERE...GUSTY NORTH TO NORTHEAST WINDS WILL BE 
COMMON...WITH MANY LOCATIONS SEEING GUSTS OF 30 TO 35 MPH...BUT 
SHOULD REMAIN BELOW WIND ADVISORY LEVELS. BEYOND TODAY...A SHORTWAVE 
RIDGE WILL BE IN PLACE FOR FRIDAY AND MUCH OF SATURDAY...BEFORE THE 
NEXT THROUGH APPROACHES THE AREA LATE IN THE DAY. THE SHORTWAVE 
RIDGE WILL PROVIDE MOSTLY SUNNY SKIES...DRIER CONDITIONS AND HIGH 
TEMPERATURES THAT WILL BE VERY NEAR THE SEASONAL NORMALS ON BOTH 
FRIDAY AND SATURDAY. 

.LONG TERM...A CLOSED LOW IS FORECAST TO APPROACH BRITISH COLUMBIA 
ON FRIDAY IS FORECAST TO BECOME AN OPEN WAVE BY SATURDAY AS IT DROPS 
SOUTHEAST ACROSS THE PAC NW. THE LATEST OPERATIONAL MODELS ARE IN 
GENERAL AGREEMENT WITH MOVING THIS FEATURE SOUTHEAST INTO NEVADA 
SOMETIME ON SUNDAY MORNING BUT SHOW TIMING DIFFERENCES OF ABOUT 6 
HOURS WITH RESPECT TO WHEN THEY SWING THE MID-LEVEL TROUGH AXIS 
THROUGH. WE SPREAD POPS INTO THE NW CWFA EARLY SATURDAY NIGHT AND 
THEN HAVE THEM EXPANDING SOUTH TO AROUND I-15 BY LATE SATURDAY 
NIGHT. MODELS SHOW VERY GOOD FORCING JUST AHEAD OF THE MID-LEVEL 
TROUGH AXIS...SO THERE SHOULD BE A SMALL WINDOW WHERE WE GET 
PRECIPITATION TO WORK ACROSS THE AREA. BY LATE SUNDAY MORNING 
WESTERN PARTS OF THE AREA SHOULD BEGIN TO SEE PRECIP END WITH THE 
EASTERN HALF SEEING PRECIPITATION LAST INTO THE AFTERNOON. SOUTH OF 
I-40...WE HAVE SLIGHT CHANCE POPS OVER MOHAVE COUNTY AND NOTHING 
OVER SAN BERNARDINO COUNTY. THE BEST COMBINATION OF FORCING AND 
MOISTURE (ESPECIALLY IN THE 700-500 MB LAYER) IS SHOWN BY THE ECMWF 
AND GFS TO BE OVER THE NORTHEAST CWFA...SO THE HIGHEST POPS WERE 
PLACED OVER THAT AREA. THIS DOES NOT LOOK LIKE LIKE A SYSTEM THAT 
WILL BRING A LOT OF PRECIPITATION WITH IT...BUT RATHER ONE THAT 
SHOULD PRODUCE MAINLY LIGHT AMOUNTS OF PRECIPITATION. OVERALL WE 
HAVE LESS THAN A TENTH OF AN INCH OF LIQUID PRECIPITATION FORECASTED 
IN MOST VALLEYS. WITH 700 MB TEMPS PROGGED TO DROP TO -8C SNOW 
LEVELS ARE EXPECTED TO DROP TO AROUND 4000 FEET. SNOW ACCUMULATIONS 
OF 2 TO 4 INCHES ARE POSSIBLE IN THE SPRING MOUNTAINS AND SHEEP 
RANGE AS WELL AS IN LINCOLN COUNTY AND NORTHERN MOHAVE COUNTY. AS 
FOR NOW THIS WOULD BE A LOW END ADVISORY LEVEL EVENT AT BEST SHOULD 
IT PAN OUT AS FORECASTED IN THE GRIDS IN THIS MORNING'S PACKAGE. NW 
FLOW SHOULD DRY OUT THE ENTIRE AREA BY SUNDAY NIGHT.

WINDS SHOULD INCREASE AHEAD OF THIS SYSTEM MAINLY OVER NW SAN 
BERNARDINO COUNTY ON SUNDAY BUT ACTUALLY APPEAR TO BE A BIGGER ISSUE 
MONDAY NIGHT INTO WEDNESDAY ON THE BACK SIDE OF THIS SYSTEM AS A 
80-100 KT JET AT 250 MB MOVES ACROSS THE AREA. THIS WOULD RESULT IN 
GUSTY NORTH WINDS ACROSS THE AREA ESPECIALLY IN THE COLORADO RIVER 
VALLEY. BASED ON 700 MB WINDS OF 25-35 KTS...TUESDAY INTO TUESDAY 
NIGHT APPEARS TO BE THE STRONGEST PERIOD FOR WINDS AND HEADLINES MAY 
BE A POSSIBILITY FOR THEN. DESPITE THE NORTHERLY FLOW TEMPS WILL 
ACTUALLY MODERATE ACROSS THE AREA AS A RIDGE ALOFT SETS UP OFF OF 
CALIFORNIA. TEMPS ALOFT WARM...AND HIGHS SHOULD RISE A FEW DEGREES 
FROM MONDAY INTO TUESDAY...THEN JUMP EVEN FURTHER WEDNESDAY WITH 
READINGS LIKELY A FEW DEGREES ABOVE NORMAL. 

ALTHOUGH THE RIDGE STAYS ANCHORED OFFSHORE...NORTHERLY FLOW ALOFT 
LESSENS BY THURSDAY INTO FRIDAY. TEMPS ALOFT CONTINUE TO WARM WITH 
850 MB TEMPS FORECAST TO RISE TO +8 TO +12C. BASED ON LOCAL RULES OF 
THUMB THIS SHOULD SUPPORT HIGHS IN THE LOW-MID 70S FOR LAS VEGAS. 
GIVEN ABUNDANT SUNSHINE PROGGED...I RAISED TEMPS CONSIDERABLY 
PUSHING THEM TOWARDS THE GFS ENSEMBLE MEAN. OVERALL THIS WOULD PUT 
HIGHS ABOUT 8 DEGREES ABOVE NORMAL AND BE A BIG CHANGE FROM THE 
WINTRY CHILL WE CURRENTLY HAVE.

.AVIATION...MCCARRAN...WINDS ARE EXPECTED TO INCREASE BETWEEN 17Z 
AND 19Z THURSDAY WITH SUSTAINED SPEEDS OF 12-18 KTS AND GUSTS OF 
18-26 KTS. WINDS ARE EXPECTED TO GO FROM THE NORTHWEST TO 
NORTH-NORTHEAST BETWEEN 19Z AND 21Z. AROUND 02Z FRIDAY WINDS SHOULD 
DROP TO 6-10 KTS SUSTAINED. CLOUDS SHOULD BEGIN TO SCATTER OUT 
BETWEEN 15Z AND 18Z WITH BASES AOA 4K-7K FEET. MOST IF NOT ALL OF 
THE CLOUDS BELOW 10K FEET SHOULD CLEAR OUT BY EARLY THIS EVENING. 
CLOUDS WILL INCREASE AOA 25K FEET LATE THIS AFTERNOON INTO TONIGHT.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...SCATTERED SHOWERS ARE EXPECTED MAINLY OVER 
MOHAVE...SOUTHEAST SAN BERNARDINO AND FAR SOUTHERN CLARK COUNTIES. 
SNOW LEVELS WILL BE AROUND 4500-5500 FEET. CIGS AS LOW AS 4K-8K FEET 
ARE EXPECTED IN AND NEAR ANY SHOWERS. ELSEWHERE BKN-OVC CIGS OF 
4K-8K FEET WILL SCATTERED OUT BY LATER THIS MORNING WITH CLOUDS AOA 
25K FEET INCREASING LATE THIS AFTERNOON INTO TONIGHT. MAINLY NORTH 
WINDS ACROSS THE AREA SUSTAINED AT 10-20 KTS WITH THE STRONGEST 
WINDS IN THE COLORADO RIVER VALLEY AND ACROSS THE SAN BERNARDINO 
COUNTY DESERTS WHERE SUSTAINED WINDS OF 15-25 KTS AND GUSTS UP TO 35 
KTS. WINDS SHOULD DECREASE ACROSS THE AREA AFTER 02Z FRIDAY WITH 
SPEEDS DROPPING TO 6-12 KTS IN MOST AREAS.

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY FROM 9 AM THIS MORNING TO 6 PM PST THIS EVENING
     FOR NVZ021.
AZ...WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM PST THIS 
     EVENING FOR AZZ002-036.
CA...WIND ADVISORY FROM 9 AM THIS MORNING TO 6 PM PST THIS EVENING
     FOR CAZ527.