510
FOUS11 KWBC 191856
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT MON OCT 19 2026
VALID 00Z TUE OCT 20 2026 - 00Z FRI OCT 23 2026
..SOUTHERN SIERRA NEVADA
DAY 2-3...
AN ANOMALOUSLY DEEP MID AND UPPER-LEVEL LOW OFF THE SOUTHERN CA
COAST (WITH PROGGED HEIGHTS BELOW ALL VALUES IN THE CFSR
CLIMATOLOGY FOR THIS TIME OF YEAR VALID AT 12Z WEDNESDAY) WILL
DIRECT RICH TROPICAL MOISTURE FROM THE EAST PACIFIC INTO THE
SOUTHWEST U.S. MID TO LATE WEEK. AT THE SAME TIME, INCREASING
DIFFLUENCE COUPLED WITH A STRONG 110KT 300MB JET ON THE DOWNSTREAM
FLANK OF THE MID/UPPER LOW WILL OVERSPREAD SOUTHERN CALIFORNIA,
ALLOWING LARGE SCALE FORCING FOR ASCENT TO BECOME MAXIMIZED. THE
FETCH OF TROPICAL MOISTURE COMBINED WITH THE INCREASING LARGE SCALE
FORCING WILL LEAD TO THE DEVELOPMENT OF WIDESPREAD LOW ELEVATION
RAIN AND HIGH ELEVATION SNOW ACROSS THE REGION BEGINNING WEDNESDAY
NIGHT AND CONTINUING THROUGH THE DAY ON THURSDAY. 850-500MB MEAN
FLOW OUT OF THE SOUTH WILL FOSTER A FAVORABLE SETUP FOR MODERATE TO
OCCASIONALLY HEAVY PRECIPITATION RATES ALONG UPSLOPE FAVORED
TERRAIN OF THE SOUTHERN SIERRA NEVADA. HOWEVER, THE AIR MASS IN
PLACE AHEAD OF THE LOW IS NOT OVERLY COLD AND THE COLDER
TEMPERATURES WITHIN THE CLOSED LOW LARGELY STAY WELL OFFSHORE
THROUGH THE FORECAST PERIOD. AS A RESULT, MOST OF THE ACCUMULATING
SNOW WILL FALL ABOVE 8,000-9,000FT THROUGH 00Z FRIDAY, WITH THE
HIGHEST AMOUNTS ABOVE 10,000-11,000FT.
PROBABILITIES FOR SNOWFALL ACCUMULATIONS GREATER THAN 4" HAVE
INCREASED TO ROUGHLY 20-50% ABOVE 9,000FT, AND 50-90% ABOVE
10,000-11,000FT. ADDITIONALLY, THE PROBABILITY FOR GREATER THAN 8"
ABOVE 10,000-11,000FT IS UP TO ROUGHLY 50-80 PERCENT. THE
PROBABILISTIC WINTER STORM SEVERITY INDEX (WSSI-P) SHOWS LOW
CHANCES (10-30%) FOR MODERATE IMPACTS AS LOW AS 9,000FT, AND LOW TO
MEDIUM CHANCES (30-50%) ABOVE 10,000-11,000FT. THIS ALL SUGGESTS
THAT THERE COULD BE SLICK AND SNOW-COVERED ROADS AND PASSES IN THE
HIGHEST TERRAIN OF THE SOUTHERN SIERRA NEVADA MID TO LATE WEEK.
MILLER
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