Issued by NWS Reno, NV
000 FXUS65 KREV 211135 AFDREV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RENO NV 335 AM PST SAT NOV 21 2009 .SHORT TERM... KRGX RADAR LOOP IS INDICATING A NARROW BAND OF PROBABLE SNOW SHOWERS NORTH OF PYRAMID LAKE...WHILE FARTHER NORTH LIGHT SNOW IS LIKELY OCCURRING IN FAR NWRN NV AND SURPRISE VALLEY. NEARBY OBSERVATIONS FROM ALTURAS REPORTED LIGHT SNOW WHILE MESOWEST DATA FROM CEDARVILLE AND FT BIDWELL HAVE ACCUMULATED 0.01 TO 0.02 INCH OF PRECIP PER HOUR SINCE LATE FRI EVENING. WEAK SECONDARY VORT CENTER MOVING ACROSS NRN CA ON WATER VAPOR SATELLITE LOOP APPEARS TO BE THE FORCE BEHIND THIS LIGHT SNOW. THIS FEATURE WILL EXIT THE REGION BY DAYBREAK SO ANY LEFTOVER SNOW SHOWERS SHOULD WIND DOWN DURING THE NEXT COUPLE OF HOURS. THE FORECAST WILL INCLUDE MENTION OF ISOLD SNOW SHOWERS THRU 15Z FOR A SMALL PART OF NWRN NV. OTHERWISE TODAY WILL BE DRY AND COOL WITH TEMPS ONLY REACHING THE 40S ACROSS MOST VALLEYS TODAY. HIGH CLOUDS WILL BE ON THE INCREASE AS ANOTHER WEAKER SHORTWAVE APPROACHES THE NWRN US TONIGHT. THIS SYSTEM WILL HAVE LITTLE MOISTURE TO WORK WITH AND ONLY ISOLD SNOW AND RAIN SHOWERS ARE EXPECTED FOR PARTS OF NERN CA-NWRN NV AND PORTIONS OF THE TAHOE BASIN LATE TONIGHT THRU SUN MORNING. LITTLE OR NO SNOW ACCUMULATION IS EXPECTED WITH THIS SYSTEM...WITH THE MOST SIGNIFICANT EFFECT BEING INCREASED WINDS. 700 MB FLOW BRIEFLY REACHES 50 KT BTWN 12Z-18Z SUNDAY WHICH WOULD PRODUCE A NOTABLE INCREASE IN RIDGE WINDS. WHILE THE PEAK SPEEDS ARE UNLIKELY TO COME CLOSE TO THE 100+ MPH VALUES THAT OCCURRED YESTERDAY...THE POTENTIAL EXISTS FOR 70-80 MPH GUSTS IN HIGHER ELEVATIONS FOR A FEW HOURS SUNDAY. WITH SOME MIXING LIKELY SUNDAY AFTERNOON...WINDS HAVE ALSO BEEN INCREASED FOR LOWER ELEVATIONS MAINLY NORTH OF HIGHWAY 50 WITH GUSTS 35-40 MPH. LAKE WIND ADVY WILL LIKELY BE NECESSARY FOR BOTH TAHOE AND PYRAMID UNLESS NEXT RUN OF GUIDANCE BACKS OFF ON THE 700 MB FLOW. MAX TEMPS WILL BE A FEW DEGREES WARMER THAN TODAY DUE TO THIS MIXING...WHICH WILL PARTIALLY OFFSET THE COLD AIR ADVECTION BEHIND THE SHORTWAVE. FOR SUN NGT-MONDAY...RIDGE WILL BUILD OVER CA-NV AND PRODUCE GENERALLY LIGHT WINDS AND DRY CONDITIONS OVER THE REGION. WEAK NE SFC FLOW AND WARMING MID LEVEL TEMPS WILL PRODUCE INVERSION CONDITIONS RESULTING IN LIMITED HEATING FOR VALLEYS BUT PUSH TEMPS IN HIGHER ELEVATIONS UP SEVERAL DEGREES FROM SUNDAY. MJD .LONG TERM...TUESDAY THROUGH FRIDAY... MODELS REMAIN IN GOOD AGREEMENT WITH RIDGE BUILDING OVER THE WEST AS THE PATTERN OVER NORTH AMERICA AMPLIFIES. RIDGE AXIS SHOULD PROGRESS INTO THE EASTERN GREAT BASIN AND THE ROCKIES BY THURSDAY OR FRIDAY. THIS WILL ALLOW PACIFIC ENERGY TO ENTER THE WEST COAST...FOR A LOW CHANCE OF RAIN AND INCREASED WINDS LATE NEXT WEEK. TEMPERATURES TO REMAIN NEAR NORMAL IN THE NEVADA VALLEYS...WITH SLIGHTLY ABOVE NORMAL READINGS IN THE SIERRA WITH THE HIGH PRESSURE ALOFT. RIDGE WILL MAINTAIN INVERSIONS IN THE NEVADA VALLEYS WITH LIGHT NORTH TO NORTHEAST FLOW TO PREVENT A MORE SIGNIFICANT WARMING TREND. ECMWF REMAINS MORE CONSISTENT AND AGGRESSIVE WITH ENERGY ENTERING THE WEST COAST LATE IN THE WEEK. THUS HAVE LEFT THE LOW CHANCE OR RAIN/SNOW ACROSS THE NORTHERN AREAS THURSDAY NIGHT INTO FRIDAY. GFS AND IT ENSEMBLES ARE FARTHER NORTH WITH THE ENERGY...WITH A WARMER AND DRIER SOLUTION FOR THE SIERRA AND WESTERN NEVADA. BOTH ECMWF AND GFS WOULD SUPPORT SOME POTENTIAL FOR BREEZY TO WINDY CONDITIONS THURSDAY NIGHT AND FRIDAY. BRONG && .AVIATION... NORTHWEST FLOW WILL AFFECT THE AREA SATURDAY AND SUNDAY AS A SYSTEM PASSES NORTH OF THE AREA. RAIN/SNOW SHOWERS ARE POSSIBLE IN THE SIERRA AND FOR AREAS NORTH OF I-80. INCREASE IN MOISTURE SHOULD BRING MVFR CEILINGS TO THE SIERRA WITH MOUNTAIN OBSCUREMENTS. WINDS MAY INCREASE AFTER 08Z TONIGHT AS SYSTEM PASSES THROUGH OREGON. GUSTS IN THE VALLEYS COULD REACH 30KTS EARLY SUNDAY MORNING...WITH THE NORTHERN SIERRA RIDGE WINDS NEAR 40-50 KTS. BRONG && .REV WATCHES/WARNINGS/ADVISORIES... NV...NONE. CA...NONE. && $$ HTTP://WEATHER.GOV/RENO
