393
FXUS66 KMFR 220548
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
902 PM PST SAT NOV 21 2009
DISCUSSION...TIGHT
RAPIDLY DEVELOPING DEEP SURFACE LOW MOVING
QUICKLY TOWARD THE NORTHERN OREGON COAST. NAM POSITION SLIGHTLY
TOO FAR NORTH AND EAST. EXPECT THE TRACK TO BE SOUTH OF NAM
FORECAST POSITION. CURRENT FORECASTS TAKE THIS INTO ACCOUNT AND
LOOK GOOD. STORM FORCE WINDS ALREADY IN THE OUTER WATERS NORTH
OF THE CAPE AND WINDS SHOULD COME UP RAPIDLY IN THE NEXT 3 HOURS
ALONG THE COAST. PROGS SHOW THE WEATHER SETTLING DOWN SUNDAY AND
MONDAY...THEN HIGH PRESSURE DOMINATING UNTIL THE END OF NEXT WEEK.
NO UPDATES NEEDED THIS EVENING.
AVIATION
CURRENT VFR CEILINGS WILL BE SHORT-LIVED AS THE
OFFSHORE FRONT DROPS CEILING TO MVFR IN LOW CLOUDS AND SHOWERS IN
THE NEXT FEW HOURS. COASTAL TERMINALS WILL LIKELY BE IMPACTED BY
LOW LEVEL WIND SHEAR WITH GUSTY WINDS TO 35KT BUT EVEN STRONGER
50-60KT WINDS JUST ABOVE THE SURFACE. STRONG WINDS WILL ALSO
IMPACT THE CASCADES AND THE EAST SIDE LATE TONIGHT AND SUNDAY
MORNING. MOUNTAINS AND EAST SIDE WILL HAVE SNOW LATE TONIGHT AND
SUNDAY MORNING...REDUCING VISIBILITIES. MOUNTAIN OBSCURATION WILL
BE WIDESPREAD BY TONIGHT THROUGH SUNDAY AS DEEP MOISTURE PUSHES
INTO THE REGION.
PREV DISCUSSION
/ISSUED 301 PM PST SAT NOV 21 2009/
DISCUSSION...QUICK-MOVING DEVELOPING FRONTAL SYSTEM WILL IMPACT
THE CWA TONIGHT THROUGH SUNDAY MORNING. THE MAIN IMPACTS WILL BE
STRONG WINDS AND SOME SNOW OVER THE CASCADES AND THE EAST SIDE.
THE FAST MOVEMENT OF THIS SYSTEM...ALONG WITH MORE WESTERLY
WINDS...WILL FAVOR THE CASCADES RECEIVING MORE SNOWFALL AND THE
MOUNT SHASTA AREA RECEIVING LESS THAN THE PREVIOUS STORM. MODELS
HAVE SETTLED ON A 990MB LOW CENTERED WEST OF THE WA/OR BORDER LATE
TONIGHT. THE STRONGEST WINDS WILL IMPACT COASTAL WATERS AND
COASTAL ZONES TONIGHT...WITH WINDS AFFECTING THE CASCADES THROUGH
THE EAST SIDE LATE TONIGHT THROUGH SUNDAY MORNING. VERY STRONG H8
FLOW OF 50KT IS NOTED OVER NORTHWESTERN PORTION OF THE CWA LATE
TONIGHT...BUT STABILITY SHOULD KEEP MOST OF THIS AREA FROM GETTING
ADVISORY LEVEL WINDS. THIS SITUATION MAY NEED TO BE LOOKED AT
DURING THE LATE AFTERNOON. SIGNIFICANT SNOW WILL FALL DURING A
SHORT PERIOD BETWEEN TONIGHT AND TOMORROW MORNING. A FOOT IS
POSSIBLE IN THE HIGHER TERRAIN OF THE CASCADES WITH SEVERAL INCHES
EXPECTED EAST OF THE CASCADES IN KLAMATH COUNTY. ON SUNDAY IN THE
POSTFRONTAL ENVIRONMENT EXPECT SNOW SHOWERS ABOVE 3500 FEET AND
RAIN SHOWERS IN THE LOWER ELEVATIONS. RIDGING WILL BUILD OVER THE
REGION SUNDAY NIGHT...ESSENTIALLY ENDING THE PRECIPITATION OVER
THE CWA.
MODELS HAVE BEEN VERY PERSISTENT WITH UPPER RIDGING FROM MONDAY
THROUGH WEDNESDAY OVER NORTHERN CA AND SOUTHWESTERN OR...WITH THE
RESULTANT WEATHER IMPACTS BEING MORNING FOG MONDAY THROUGH
WEDNESDAY IN THE FAVORED LOW ELEVATION AREAS LIKE THE ROGUE AND
ILLINOIS VALLEYS...AND THE UMPQUA BASIN. A WEAK WARM FRONT BRUSHES
THE COAST ON WEDNESDAY BUT WILL NOT LIKELY RESULT IN ANY
SIGNIFICANT PRECIPITATION. GFS AND ECMWF BOTH PUT AN END TO THE
DRY WEATHER ON THANKSGIVING DAY BUT THEIR SOLUTIONS ARE STILL
FAIRLY DIFFERENT. THERE ARE STILL UNKNOWNS REGARDING THE FORECAST
FOR THURSDAY...BUT AT THIS POINT IT SEEMS REASONABLE TO EXPECT
LIGHT SNOW IN THE MOUNTAINS AND LIGHT RAIN IN THE VALLEYS ON LATE
THURSDAY. IT STILL SEEMS THERE WILL NOT BE A LARGE STORM FOR
THANKSGIVING DAY TRAVELERS IN THE REGION.
MFR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL 7 AM PST SUNDAY FOR ORZ027-ORZ028-
ORZ029-ORZ030.
WIND ADVISORY UNTIL 7 AM PST SUNDAY FOR ORZ031.
HIGH WIND WARNING UNTIL 4 AM PST SUNDAY FOR ORZ021-ORZ022.
CA...WIND ADVISORY UNTIL 4 AM PST SUNDAY FOR CAZ081.
PACIFIC COASTAL WATERS...STORM WARNING UNTIL 4 AM PST SUNDAY FOR
PZZ350-PZZ370.
HAZARDOUS SEAS WARNING UNTIL 4 AM PST MONDAY FOR PZZ350-PZZ356-
PZZ370-PZZ376.
GALE WARNING UNTIL 4 AM PST SUNDAY FOR PZZ356-PZZ376.
DDG
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