Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 220949
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
249 AM PDT MON SEP 22 2014

.DISCUSSION...AN UPPER LOW CENTERED OVER NORTHEAST NEVADA THIS
MORNING IS MOVING SWIFTLY OFF TO THE NORTHEAST. SHOWERS AND ISOLATED
THUNDERSTORMS WE HAD LAST EVENING HAVE DISSIPATED. WE WILL SEE SOME
LEFT OVER CLOUDS THIS MORNING, BUT THOSE ARE ALREADY CLEARING OUT. A
SHORT WAVE IS APPROACHING THE COAST IN THE SOUTHWEST FLOW ALOFT, AND
THIS WILL BRING ADDITIONAL CLOUDS OVER US TODAY. THERE IS SOME
INSTABILITY THIS AFTERNOON FROM THE CASCADES EAST, AND THE MODELS
ARE SHOWING ISOLATED THUNDERSTORMS FROM AROUND CRATER LAKE ACROSS
NORTHERN KLAMATH AND LAKE COUNTIES THIS AFTERNOON. OTHERWISE, WE
SHOULD BE DRY TODAY.

FURTHER OUT IN THE PACIFIC, A MODERATE ZONAL JET EXTENDS ALL THE WAY
FROM ASIA TO A LARGE, NEBULOUS TROUGH OVER THE NORTHEAST PACIFIC. AS
ENERGY FEEDS INTO THIS TROUGH FROM THE WEST, A CUTOFF FORMS INSIDE
OF 140W TUESDAY WHICH PUSHES A FRONT ONSHORE WEDNESDAY. THIS FRONT
WILL TAP INTO SUBTROPICAL MOISTURE AND BECOME A FAIRLY SIGNIFICANT
ATMOSPHERIC RIVER (AKA PINEAPPLE EXPRESS). MODELS ARE IN GENERAL
AGREEMENT THAT THIS FRONT WILL BE QUITE WET WITH PWATS OF 1.75 TO 2
INCHES IMPINGING ON THE COAST TUESDAY NIGHT AND WEDNESDAY. IN THIS
SCENARIO, OROGRAPHIC EFFECTS USUALLY PRODUCE 2-3 TIMES AS MUCH RAIN
OVER THE CURRY COAST AND MOUNTAINS AS WHAT THE MODELS SHOW FOR QPF
OR PWAT. THAT YIELDS 3-5 INCHES OF RAIN IN THESE LOCATIONS, AND I
DID CRANK UP OUR QPF GRIDS AS A RESULT.

INLAND FROM THE COAST, RAINFALL AMOUNTS ARE SUBJECT TO MORE
UNCERTAINTY. TYPICALLY, SYSTEMS LIKE THIS PRODUCE A LOT OF SOUTHERLY
FLOW WHICH DOWNSLOPES IN THE ROGUE VALLEY AND TO A LESSER DEGREE IN
THE UMPQUA BASIN. THE GLOBAL MODELS CERTAINLY PRODUCE A LOT OF RAIN
OVER ALL THE WEST SIDE, BUT THEY USUALLY DON`T PICK UP ON THESE
EFFECTS AS WELL AS, SAY, THE NAM. FOR NOW, I WILL LEAVE THE MODEST
QPF WE HAVE OVER INLAND AREAS. THIS YIELDS AROUND A QUARTER TO A
HALF INCH ALL TOTALED. AT ANY RATE, THIS IS LIKELY TO BE A GOOD
SOAKER FOR OUR AREA AT LEAST FROM THE CASCADES/SISKIYOUS WESTWARD
AND AT LEAST WESTERN SISKIYOU COUNTY. THE EAST SIDE COULD GET IN
ON IT WEDNESDAY NIGHT INTO THURSDAY, DEPENDING ON HOW WELL THE
FRONT HOLDS TOGETHER AS IT MOVES INLAND. THE CONFIDENCE IN THIS IS
LOWER, HOWEVER. THIS SYSTEM WILL PRODUCE BREEZY TO WINDY
CONDITIONS ALONG THE COAST, THE SHASTA VALLEY, AND EAST SIDE
LOCATIONS WEDNESDAY AND POSSIBLY THURSDAY AS WELL.

THE UPPER LOW THEN GRADUALLY MOVES THROUGH THE PACNW FRIDAY INTO THE
WEEKEND. WE SHOULD START TO WARM UP AND DRY OUT SUNDAY INTO EARLY
NEXT WEEK, BUT THERE IS SOME UNCERTAINTY AS TO THE TIMING OF THE
SYSTEM`S EXIT AND THE RIDGE THAT BUILDS IN BEHIND IT. FEW CHANGES
WERE MADE TO THE FORECAST BEYOND THURSDAY DUE TO THESE
UNCERTAINTIES. -WRIGHT

&&

.AVIATION...BASED ON THE 22/06Z TAF CYCLE...IFR/MVFR CIGS/VSBYS
ALONG THE COAST WILL SPREAD BACK INTO THE COASTAL VALLEYS AND THE
LOWER UMPQUA BASIN LATE TONIGHT AND PERSIST INTO MONDAY MORNING.
ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24
HOURS...EXCEPT FOR LOCAL MVFR VSBYS IN SMOKE NEAR WILDFIRES IN
JOSEPHINE COUNTY AND THE WESTERN PORTION OF SISKIYOU COUNTY.
SOME SHOWERS ARE POSSIBLE ALONG THE CASCADES MONDAY AFTERNOON AND
EVENING.

&&

.MARINE...UPDATED 1130 PM PDT SUN 21 SEP 2014...HIGH PRESSURE
WILL REMAIN OVER THE WATERS INTO EARLY MONDAY WITH LIGHT TO
MODERATE SOUTHERLY WINDS AND SEAS. SOUTHERLY WINDS WILL INCREASE
MONDAY AFTERNOON AS A SERIES OF COLD FRONTS APPROACH THE REGION. THE
FIRST FRONT WILL ARRIVE MONDAY NIGHT...WITH OTHERS FOLLOWING THROUGH
THE WEEK. EACH WILL BRING PERIODS OF RAIN WITH INCREASED WINDS AND
STEEP TO VERY STEEP SEAS. EXPECT SMALL CRAFT ADVISORY CONDITIONS FOR
MUCH OF THIS TIME...WITH GALES AND HAZARDOUS SEAS LIKELY TO
ACCOMPANY THE STRONGER COLD FRONT MIDWEEK. CONDITIONS SHOULD IMPROVE
BY FRIDAY WHEN HIGH PRESSURE ONCE AGAIN BUILDS INTO THE AREA.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR ORZ624-625.

CA...FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR CAZ281-282-284-285.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 8 AM TO
     11 PM PDT TUESDAY FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 AM TO 11 PM PDT
     TUESDAY FOR PZZ350-356.
     GALE WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY EVENING FOR
     PZZ370-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 2 AM TO 11 PM PDT TUESDAY
     FOR PZZ370-376.
     HAZARDOUS SEAS WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY
     EVENING FOR PZZ370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 11 PM THIS EVENING
     TO 11 PM PDT TUESDAY FOR PZZ370-376.

$$





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