|
Massive storm to hit west coast for 5 days.
Thursday, December 11, 2008 5:14:13 PM
"VERY WINDY CONDITIONS DEVELOPING FRIDAY NIGHT AND CONTINUING THROUGH SATURDAY MORNING...SOME LIGHT SNOWFALL POSSIBLE THIS WEEKEND BECOMING HEAVY SUNDAY NIGHT INTO MONDAY" BLIZZARD CONDITIONS POSSIBLE AT TIMES.
FORECAST UPDATE THURSDAY EVENING:
UPDATED SNOWFALL FORECAST FOR MAMMOTH LAKES AT 9,000 FEET:
4 TO 6 INCHES FRIDAY NIGHT THROUGH SATURDAY NIGHT.
15 TO 30 INCHES BETWEEN SUNDAY NIGHT THROUGH TUESDAY NIGHT.
SNOW TO WATER RATIONS 20 TO 30:1 LIKELY OVER HIGHER ELEVS
THE MAIN CHANGES IN BOTH 00Z AND 06Z GFS AND 12Z ECMWF WERE IN THE CIRCULATION OF THE DEVELOPING UPPER CYCLONE OVER THE FAR WEST. THE MAIN MESSAGE IS THAT THEY ARE A BIT LESS FAVORABLE FOR THE HEAVIER SNOWFALL ACCUMULATIONS DUE TO THE FACT THAT 500MB WIND TRAJECTORIES ARE NO LONGER EXPECTED FROM THE SOUTHWEST AND....THE SYSTEM IS DEVELOPING A BIT MORE OVER LAND........HOWEVER THERE WILL STILL BE PLENTY OF WESTERLY FLOW MONDAY INTO TUESDAY, AND SO WE WILL STILL GET A GOOD SHOT OF SNOWFALL...BUT NOT AS MUCH AS WAS SHOWN FOR THE EXTENDED PERIOD YESTERDAY. SUNDAY NIGHT THROUGH TUESDAY APPEAR TO THE THE BEST DAYS FOR SNOW ACCUMULATION IN A COLD WESTERLY FLOW ALOFT. ONE TO TWO FEET SEEMS REASONABLE AT THE MOMENT FOR THE UPPER ELEVATIONS DURING THAT TIME FRAME.
THE TWIST IN THE PATTERN SEEMS TO HAVE A GREATER EFFECT ON HOW THE JET WILL BE BEHAVING. EARLY SATURDAY MORNING A 150KNOTT JET WILL BE EFFECTING MAMMOTH...WHICH WILL BE UNDER THE FRONT RIGHT EXIT REGION. ANTECEDENT WARMTH FROM OUR CURRENT WEATHER AND THE DYNAMICS FROM A STRONG ARCTIC FRONT EARLY SATURDAY MORNING HAS PROMPTED THE NWS TO HOIST HIGH WIND WATCHES FOR THE EASTERN SIERRA FRIDAY NIGHT AND MAINLY AFTER MIDNIGHT FOR SOUTHERN MONO COUNTY. THE STRONGEST WINDS MAY OCCUR ABOUT SUNRISE HERE LOCALLY. THIS IS ONE OF THOSE RARE SITUATIONS WHERE THE UPPER JET CAN BE PULLED DOWN TO THE SURFACE SATURDAY MORNING.
THE MODELS ARE SHOWING A "TROPO-FOLD" WITH THE JET INTO OUR AREA ABOUT SUNRISE SATURDAY.
HERE IS AN EXCERPT FROM THE WSFORNO DISCUSSION WITH A TECHNICAL EXPLANATION.
"30AGL NAM12 WINDS WERE 50+KT ALONG THE EASTERN SIERRA FROM I-80 SOUTHWARD THROUGH MONO COUNTY WITH 80+KT AT THE RIDGES. CROSS SECTIONS FROM THE WRF SHOWED WELL DEVELOPED STANDING WAVE ACROSS NORTHERN MONO COUNTY BETWEEN 06Z-12Z SATURDAY. THIS IS ABOUT THE TIME 150KT JET AND TROPOPAUSE FOLD NOSE INTO THE REGION ALONG AND JUST AHEAD OF FRONT."
THE SCREAMING MESSAGE....IS TO SECURE ALL ITEMS OUTSIDE FOR FRIDAY NIGHT THROUGH SATURDAY MORNING AS WINDS COULD GUST TO HURRICANE FORCE LOCALLY OVER THE LOWER ELEVATIONS OF MONO COUNTY.
"THE DWEEBS CRITERIA" FOR 24 HOUR SNOWFALL AMOUNTS HERE IN THE MAMMOTH AREA AT 8000 FEET.
A. LIGHT 1 TO 6 INCHES
B. MODERATE 6+ TO 18 INCHES
C. HEAVY 18+ INCHES TO 36 INCHES
D. VERY HEAVY 36+ INCHES TO 48 INCHES
E. *EXCESSIVE 4 FEET+ IN 24 HOURS
* THIS IS KNOWN TO HAPPEN ONLY A FEW TIMES WITHIN A 10 YEAR PERIOD
|
