834
FXUS65 KREV 182109
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
109 PM PST WED DEC 18 2024
SYNOPSIS
* VALLEY INVERSIONS AND AREAS OF FOG RETURN THROUGH FRIDAY
MORNING. ALSO EXPECT LIGHT WINDS, DRY CONDITIONS, AND SEASONAL
TEMPERATURES DURING THIS TIME.
* AN ACTIVE WEATHER PATTERN BEGINS THIS SATURDAY WITH POTENTIAL
FOR PERIODS OF GUSTY WINDS, RAIN, SNOW, AND TRAVEL IMPACTS
THROUGH CHRISTMAS WEEK.
DISCUSSION
HIGH PRESSURE WILL PERSIST OVER THE REGION THROUGH FRIDAY.
VERTICAL TEMPERATURE PROFILES SUPPORT FREEZING FOG FORMATION (I.E
LOW LEVEL MOISTURE CAPPED BY A STRONG INVERSION WITH LIGHT
WINDS). THE BEST CHANCES FOR THIS TO OCCUR WILL BE FOR VALLEY
LOCATIONS IN THE SIERRA FROM TAHOE BASIN NORTHWARD, LASSEN COUNTY
EAST OF US-395, AND EVEN OUT INTO THE VALLEYS IN THE INNER GREAT
BASIN. THESE SURFACE INVERSIONS ARE ALSO CONDUCIVE FOR AN INCREASE
IN POLLUTANTS TO BUILD UP IN URBAN AREAS.
MODEL ENSEMBLES ARE STILL ALL POINTING TO AN ACTIVE PATTERN
RETURNING TO THE WESTERN US BY SATURDAY, WITH ADDITIONAL BOUTS OF
MOISTURE AND STRONG WINDS ALL THE WAY THROUGH NEXT WEEKEND. AT
THE MOMENT, THE MAIN AR AXIS FOR SATURDAY'S SYSTEM IS STILL
DIRECTED TOWARD NORTHERN CA/SOUTHERN CASCADES. THE BEST CHANCES
FOR PRECIPITATION (>60%) IN THE SIERRA ARE FROM ALPINE COUNTY TO
THE CA/OR BORDER, AS WELL AS INTO NORTHEAST CA AND NORTHERN
WASHOE. CHANCES OF PRECIPITATION DROP OFF TOWARD SOUTHERN MONO
COUNTY (20-40%), AND INTO THE REMAINDER OF WESTERN NV, WHICH MAY
NOT SEE MUCH FROM THIS SATURDAY SYSTEM. STRONG WINDS WILL
MATERIALIZE ALONG THE SIERRA RIDGES, WITH GUSTS LIKELY ABOVE 80
MPH (700MB WINDS AT 40-50KTS). WINDS WILL ADDITIONALLY INCREASE
IN WESTERN NV, WHICH MAY BECOME STRONG SATURDAY AFTERNOON THESE
WINDS WILL BE WATCHED WITH FUTURE HIGH-RESOLUTION MODEL OUTPUT TO
SEE IF THERE ARE ENHANCING FACTORS (I.E. INVERSION AT MOUNTAIN TOP
LEVEL, CRITICAL LAYER).
THE STORM DOOR REMAINS OPEN THROUGH THE CHRISTMAS HOLIDAY, WITH AN
EVEN MORE ROBUST STORM MOVING INTO THE AREA ON CHRISTMAS EVE. FOR
THE CHRISTMAS EVE STORM, ENSEMBLES STILL SHOW STRONGER UPPER
LEVEL FORCING, A DEEPER TROUGH, AND MORE MOISTURE MOVING SOUTHWARD
COMPARED TO SATURDAY'S SYSTEM. THE ACTIVE WEATHER PATTERN WILL
CONTINUE ALL THE WAY THROUGH THE END OF THE YEAR.
-MCKELLAR
AVIATION
FREEZING FOG WILL BECOMING LIKELY AGAIN (>70%) FOR THE NORTHERN
SIERRA VALLEYS INCLUDING KTRK. LOW STRATUS AND FOG MAY ALSO FORM
OVER LAKE TAHOE AND MOVE SOUTH INTO KTVL. MEANWHILE, THERE IS A
70% CHANCE FOR FREEZING FOG OR A VERY LOW CLOUD DECK DEVELOPING
NEAR KSVE AND A 30% FOR KNFL/KLOL. OTHERWISE, VFR CONDITIONS,
VALLEY INVERSIONS, AND LIGHT SFC WINDS PERSIST THROUGH FRIDAY.
-MCKELLAR
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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