HAMweather.com Area Forecast Discussion for County Warning Area REV

Thu, 16 Feb 2012 05:29:55 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
904 PM PST WED FEB 15 2012

.UPDATE...
PERSISTENT UPSLOPE FLOW OVER SRN MONO COUNTY IS RESULTING IN SOME
LIGHT ACCUMULATIONS. HAVE OPTED TO INCREASE POPS ALONG AND WEST OF
HIGHWAY 395 SOUTH OF BRIDGEPORT AND INTRODUCE SOME LIGHT
ACCUMULATIONS OVERNIGHT. ACCUMULATIONS WILL BE STILL BE LOCALIZED
AND SHOULD NOT EXCEED 2 INCHES. MLF

.PREVIOUS DISCUSSION... /ISSUED 759 PM PST WED FEB 15 2012/ 

UPDATE...
STUBBORN LOW/MID LVL CLOUDS HOLDING ON OVER THE SRN 1/3 OF THE CWA
THIS EVENING WITH OCCASIONAL SNOW SHOWERS NOTED IN OBSERVATIONS
AND WEB CAMS. THIS IS DUE TO PROXIMITY OF THE UPPER LOW SOUTHEAST OF
THE AREA AND UPSLOPE LOW LVL NE FLOW. AS LOW BEGINS TO DRIFT SOUTHEAST
LATER TONIGHT THE UPSLOPE FLOW WILL EASE WITH DECREASING SNOW
SHOWERS. CLOUDS WILL THIN LATE TONIGHT AS WELL AS SLIGHTLY DRIER
AIR PUSHES IN FROM THE NORTH. FOR NOW WILL LEAVE MENTION OF SCATTERED
SNOW SHOWERS IN FOR MONO COUNTY WITH ISOLATED SNOW SHOWERS FOR
MINERAL/SRN LYON COUNTIES. MLF

PREVIOUS DISCUSSION... /ISSUED 505 PM PST WED FEB 15 2012/ 

UPDATE...
WINDS ON PYRAMID LAKE HAVE DECREASED QUITE A BIT AND SHOULD
REMAIN FAIRLY LIGHT OVERNIGHT IN NORTH TO NORTHEAST FLOW.
NORTHEAST FLOW GENERALLY PRODUCES STRONGER WINDS ON LAKE TAHOE SO
WILL ALLOW THAT LAKE ADVISORY TO CONTINUE. OTHERWISE NO CHANGES AS
CLOUD PERSIST OVER THE SRN HALF OF THE CWA WITH A FEW SNOW SHOWERS
POSSIBLE THROUGH THE EVENING WELL SOUTH OF HIGHWAY 50. MLF

PREVIOUS DISCUSSION... /ISSUED 245 PM PST WED FEB 15 2012/ 

SHORT TERM...

NORTHEAST FLOW OVER THE REGION HAS MADE FOR A BRISK AFTERNOON SO 
FAR. A DEPARTING SHORTWAVE HAS MOVED INTO SOUTHERN NV, WITH A FEW 
LINGERING LOW CLOUDS AND ISOLATED SHOWERS IN WESTERN NEVADA AND THE 
EASTERN SIERRA SOUTH OF TAHOE. THIS INSIDE SLIDER SYSTEM BROUGHT 
MODERATE AMOUNTS OF SNOW TO THE TRUCKEE MEADOWS AND SURROUNDING 
VALLEYS EARLY THIS MORNING, WITH REPORTS OF 2-5 INCHES IN WESTERN 
NV. FOR THE EASTERN SIERRA, WE SAW GENERALLY 3-6 INCHES BELOW 7000 
FEET AND OVER 8 INCHES ABOVE 7000 FEET INCLUDING TAHOE AND MONO 
COUNTY. 

ISOLATED SNOW SHOWERS ARE EXPECTED TO CONTINUE OVERNIGHT IN MONO 
COUNTY, DUE TO UPSLOPE NORTHEAST FLOW INTO THE SIERRA. BREEZY 
NORTHEAST WINDS OVERNIGHT WILL KEEP CHOPPY CONDITIONS ON LAKE TAHOE 
THROUGH EARLY THURSDAY MORNING. LAKE WIND ADVISORY REMAINS IN EFFECT 
THROUGH 7 AM THURSDAY.

DID ADD IN PATCHY FOG FOR THE TRUCKEE AREA TONIGHT AND THURSDAY 
MORNING, DUE TO THE RECENT SNOWFALL. THE ONLY THING GOING AGAINST 
IT, WE HAVE COLD AIR ADVECTION AND NORTHEAST FLOW STILL OVER THE 
AREA TONIGHT WHICH COULD POSSIBLY INHIBIT ANY FOG FORMATION.

AS WE GO INTO THURSDAY-FRIDAY, RIDGING WILL BUILD OVER THE WEST 
COAST WITH DRY CONDITIONS. TEMPERATURES WILL WARM ALOFT, CAUSING 
VALLEY INVERSIONS AND OVERALL LIGHTER WINDS. FOG FORMATION WILL 
LIKELY BECOME EASIER AS THE RIDGE BUILDS IN.

ANOTHER SLIDER-TYPE SYSTEM IS EXPECTED TO DROP INTO NORTHERN CA/NV 
ON SATURDAY, WITH A STRONG COLD FRONT PUSHING IN. MODELS ARE STILL 
UNCERTAIN WITH THE AMOUNT OF MOISTURE THAT WE WILL SEE, ALTHOUGH IT 
DOES SEEM LIKE THE TREND IS TOWARD A COLDER STORM WITH SNOW LEVELS 
DOWN TO VALLEY FLOORS. MODEL SOUNDINGS LOOK PRETTY IMPRESSIVE WITH 
THE INSTABILITY AROUND 100 J/KG ON SATURDAY NIGHT WITH THE COLD AIR 
ALOFT. DID BUMP UP THE CHANCE OF SNOW OVERNIGHT SATURDAY NIGHT AS 
WELL. NOT TOTALLY SOLD ON THIS STORM JUST YET, BUT IT COULD END UP 
BEING A REPEAT OF WHAT WE SAW EARLY THIS MORNING.  HOON

LONG TERM...SUNDAY THROUGH WEDNESDAY...

MODELS ARE IN DECENT AGREEMENT IN SYNOPTIC SCALE FEATURES FOR THE 
LONG TERM PERIOD, BUT THE DETAILS ARE WHERE QUESTIONS REMAIN. THE 
UPPER LEVEL LOW THAT DROPS INTO THE AREA ON SATURDAY WILL CONTINUE 
TO AFFECT THE REGION ON SUNDAY. PRECIPITATION IS ENHANCED SUNDAY 
ALONG THE EAST SIDE OF THE LOW ALONG AN AREA OF STRONG MID-LEVEL 
FRONTOGENESIS. THIS WILL LIKELY KEEP THE BEST SHOWERS EAST OF THE 
CWA, BUT THE INSTABILITY GENERATED BY THE COLD CORE OF THE LOW 
SHOULD KEEP CHANCES FOR SHOWERS IN THE SIERRA AND WESTERN NEVADA 
SUNDAY. 

THE GEM, EC, AND GFS ALL SHOW A SECONDARY WAVE DROPPING DOWN 
THE BACK SIDE LOW, BUT DIFFER IN BOTH STRENGTH AND POSITION. THE EC 
IS THE STRONGEST AND FURTHEST EAST WITH THIS NEXT WAVE, WHICH WOULD 
BRING ADDITIONAL CHANCES FOR PRECIP IN THE SIERRA SUNDAY NIGHT INTO 
MONDAY MORNING. THE GEM AND THE GFS KEEP THIS PIECE OF ENERGY 
FURTHER WEST, RIDING DOWN THE CA COAST, WHICH WOULD KEEP THE SIERRA 
AND WESTERN NEVADA DRY. 

HIGH PRESSURE CENTERED AROUND 135W REBUILDS A RIDGE ACROSS THE WEST, 
WHICH WILL DEFLECT MOISTURE NORTHWARD INTO THE PACIFIC NORTHWEST. 
SOME WARM AIR ADVECTION MAY LEAD TO LIGHT RAIN ACROSS EXTREME 
NORTHERN CA/NV, BUT FOR NOW WILL LEAVE IT AS JUST AN INCREASE IN 
CLOUDS IN THE FORECAST. TEMPERATURES WILL BE BELOW NORMAL SUNDAY AND 
MONDAY BEFORE REBOUNDING ABOVE NORMAL TUESDAY AND WEDNESDAY UNDER 
THE RIDGE. DF

AVIATION...

NORTH TO NORTHEAST WIND GUSTS OF 25 TO 30 MPH WILL BEGIN TO SUBSIDE 
OVERNIGHT WITH LIGHTER EASTERLY WINDS EXPECTED ON THURSDAY. EASTERLY 
WINDS ACROSS THE RIDGES WILL REMAIN GUSTY (GUSTS UP TO 55 MPH) WITH 
TURBULENCE EXPECTED THROUGH THURSDAY ALONG THE WEST SIDE OF THE 
SIERRA.

SKIES WILL BEGIN TO CLEAR THIS EVENING WITH WIDESPREAD VFR 
CONDITIONS EXPECTED. FRESH SNOW, CLEARING SKIES, AND LIGHTER WINDS 
WOULD ALL SUGGEST THAT KTRK SHOULD FOG OVERNIGHT, BUT THE FACT THAT 
THERE IS STILL DECENT EASTERLY FLOW ALOFT IS THE ONE HINDRANCE. 
THEREFORE WILL SAY THERE IS A 75 PERCENT CHANCE FOR FREEZING FOG AT 
KTRK AND THROUGH THE MARTIS VALLEY. THERE ARE LESSER CHANCES FOR 
PATCHY FREEZING FOG THROUGH OTHER SHELTERED SIERRA VALLEYS. ALL 
OTHER TERMINALS WILL REMAIN FREE OF FOG. DF

.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY UNTIL 7 AM PST THURSDAY FOR LAKE TAHOE IN 
     NVZ002.

CA...LAKE WIND ADVISORY UNTIL 7 AM PST THURSDAY FOR LAKE TAHOE IN 
     CAZ072.