FXUS65 KREV 142109
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
209 PM PDT SUN MAR 14 2010
.SHORT TERM...
RIDGE CONTINUES TO BUILD OVER THE RGN WITH CORRESPONDING DECREASE
IN WINDS AT ALL LVLS OF THE ATMOS. VERY DRY AIR IS IN PLACE
ALOFT...EVIDENCE THE DEW POINT OF -35 AT SLIDE MTN THIS AFTN. THIS
DRY AIR ALOFT SHOULD LIMIT ANY CLOUD COVER TONIGHT. TEMPS WILL
DROP BACK TO NEAR THE READINGS FROM THIS MRNG IN THE VALLEYS. MID
SLOPES AND RIDGES LIKELY TO BE A FEW DEGREES WARMER AS WAA ALOFT
BEGINS WITH THE BUILDING RIDGE. RH VALUES REMAIN LOW AT THE RIDGES
TONIGHT AS WELL.
WARMING TEMPS CONTINUE FOR BOTH MONDAY AND TUESDAY WITH HIGHS
REACHING THE LOWER 60S WRN NV VALLEYS AND LOWER TO MID 50S SIERRA
VALLEYS MONDAY...THEN THE UPPER 60S TO NEAR 70 WRN NV...WITH UPPER
50S TO LOWER 60S SIERRA VALLEYS BY TUESDAY. CORRESPONDING RISE IN
OVERNIGHT LOWS IS ALSO EXPECTED EACH DAY.
RIDGE AXIS SLIDES EAST AND BEGINS TO FLATTEN A BIT BY LATE
TUESDAY. THIS SHOULD ALLOW INCREASED MID/UPPER LVL MSTR INTO THE
CWA BY LATE TUESDAY SO WILL SHOW INCREASING CLOUDS...MAINLY NORTH.
WILL ALSO SEE AN INCREASE IN WINDS FOR THE NRN CWA AND SIERRA
RIDGES BY LATE TUESDAY. MODEL FORECASTS CONTINUE TO TAKE AN UPPER
LOW AND SHORT WAVE INTO THE BC/WA RGN BY LATE TUESDAY NIGHT. A
WEAK SFC BOUNDARY BEGINS TO DROP SOUTH WEDNESDAY ASCD WITH THE
SHORT WAVE BUT CANNOT PROGRESS VERY QUICKLY SOUTH OR VERY FAR INTO
THE CWA BY LATE WED. THE PRESENCE OF THE BOUNDARY SHOULD AID
MIXING BY WED AFTN...SO WED IS LIKELY TO BE AS WARM AS TUESDAY.
BOTH NAM AND GFS SHOW LIFTED INDEX DROPPING TO BELOW ZERO BY
WED...BUT MSTR SEEMS A BIT LACKING IN THE LOW LVL. THERE IS ENOUGH
MSTR FOR INCREASED CLOUDS...MAINLY HIGH BASED CU...BY LATE WED.
BUT INSTABILITY AND MSTR DO NOT APPEAR TO BE SUFFICIENT ENOUGH FOR
ANYTHING MORE THAN SHALLOW CONVECTION...SO MAINLY JUST AN INCREASE
IN CLOUDS. WILL LEAVE ANY MENTION OF SHOWERS OUT OF THE FORECAST
FOR WED/WED EVNG. MLF
.LONG TERM...THURSDAY THROUGH SUNDAY...
GENERALLY QUIET...ALTHOUGH POSSIBLY NOT COMPLETELY DRY...WEATHER
PATTERN IS EXPECTED TO CONTINUE THRU NEXT WEEKEND. A WEAK SHORTWAVE
WITH INLAND TRAJECTORY IS EXPECTED TO PUSH A WEAK COLD FRONT SEWD
OVER THE GREAT BASIN ON THURSDAY. A FEW LIGHT SHOWERS MAY DEVELOP
ALONG THIS FRONT MAINLY FROM W-CNTRL NV IN THE MORNING THEN INTO THE
MINERAL-MONO ZONES BY THURS AFTN. THIS TRACK IS FAVORED BY THE GFS
WHICH IS SUPPORTED BY A FEW ENSEMBLE MEMBERS...WHILE THE ECMWF KEEPS
THIS SYSTEM TOO FAR EAST. WILL KEEP POPS IN SLGT CHC SINCE ANY
ACTIVITY ALONG THIS FRONT WOULD BE SHORT LIVED WITH LACK OF DEEP
MOISTURE AVAILABILITY. THE OTHER MAIN EFFECT OF THIS TROF PASSAGE
WILL BE INCREASING RIDGE WINDS FROM THE N-NE WHICH MAY CONTINUE INTO
FRIDAY.
OTHERWISE...FRIDAY AND SATURDAY WILL BE DRY AND MILD AS RIDGE OFF
THE WEST COAST MOVES INLAND BY FRIDAY THEN EAST ACROSS THE GREAT
BASIN SATURDAY. WEAK DRY SHORTWAVE WILL FLATTEN THE RIDGE A BIT ON
SATURDAY AND SHIFT PREVAILING FLOW TO WEST...POSSIBLY ALLOWING A
LITTLE MORE MIXING AND A SLIGHT INCREASE IN TEMPS OVER FRIDAY.
OVERALL EXPECTING MAX TEMPS BOTH DAYS TO RANGE FROM 4-8 DEGREES
ABOVE NORMAL WITH MID 60S IN MOST LOWER ELEVATIONS.
BY NEXT SUNDAY...SOME DIFFERENCES BEGIN TO SHOW UP WITH TIMING OF
NEXT SHORTWAVE TO REACH THE WEST COAST. THE ECMWF BRINGS IN SOME
LIGHT PRECIP AS SOON AS SUN AFTN OVER THE SIERRA FROM TAHOE NWD AND
NERN CA...WHILE 12Z GFS KEEPS THE REGION DRY. ONLY ONE GFS ENSEMBLE
MEMBER SUPPORTS THE ECMWF WHILE THE REST FAVOR THE DRY GFS SCENARIO.
BY SUN NGT...A FEW ENSEMBLE MEMBERS INDICATE SOME LGT PRECIP MAINLY
NORTH OF I-80. BASED ON THIS DATA...WILL KEEP POPS JUST BELOW THE
15% THRESHOLD FOR MENTION IN THE FORECAST TEXT IN THE NORTH ZONES.
SOME INCREASE IN CLOUD COVERAGE AND WINDS IS LIKELY WITH THE
APPROACH OF THIS SYSTEM. MJD
&&
.AVIATION...
VFR CONDS ALL SITES THRU MONDAY. OTHER THAN EAST WINDS 10-15 KT AT
TIMES THRU 03Z THIS EVENING...WINDS WILL BE LIGHT. MJD
&&
.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&
$$
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