Area Forecast Discussion
Issued by NWS Medford, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMFR 221606
AFDMFR

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

.DISCUSSION...MADE A FEW ADJUSTMENTS TO THE FORECAST TODAY. THE
12Z NAM SUGGEST THERE MAY BE ENOUGH INSTABILITY FOR ISOLATED
THUNDERSTORMS TO DEVELOP LATE THIS AFTERNOON AND EVENING MAINLY
FROM AROUND CRATER LAKE NORTH AND IN PARTS OF LAKE AND KLAMATH
COUNTIES. ANY ISOLATED STORMS WILL END THIS EVENING.

THE MAIN FOCUS AHEAD WILL BE TUESDAY NIGHT THROUGH WEDNESDAY.
PRELIMINARY LOOK AT THE 12Z NAM AND GFS ARE SIMILAR WITH THE
TIMING OF THE FRONT TUESDAY NIGHT INTO WEDNESDAY, THEN THE GFS
PUSHES THE FRONT SLIGHTLY FASTER THAN THE NAM WEDNESDAY NIGHT INTO
THURSDAY. GIVEN THAT THE FRONT WILL BE NEARLY PARALLEL TO THE
UPPER FLOW THAT THE GFS MAY BE TOO FAST. BOTH CONTINUE TO SHOW
HEFTY QPF AMOUNTS, ESPECIALLY FOR COAST, COASTAL MOUNTAINS AND
CASCADES. THE PREVIOUS DISCUSSION OUTLINES THE DETAILS THIS WELL.
-PETRUCELLI



&&

.AVIATION...BASED ON THE 22/12Z TAF CYCLE...MVFR CIGS ALONG THE
COAST EXTEND INTO THE COASTAL VALLEYS AND THE UMPQUA BASIN BUT WILL
GRADUALLY IMPROVE TO VFR THIS MORNING. THESE MVFR CIGS WILL LINGER
LONGEST AT THE COAST. A WEAKENING FRONT WILL REACH THE COAST
AFTER 03Z THIS EVENING WITH A RETURN OF MVFR CIGS AND LIGHT RAIN
DEVELOPING. THOSE CONDITIONS WILL THEN PERSIST INTO TUESDAY MORNING.

ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24
HOURS WITH AN INCREASE IN MID LEVEL AND UPPER LEVEL CLOUDS...EXCEPT
FOR LOCAL MVFR VSBYS IN SMOKE NEAR WILDFIRES IN JOSEPHINE COUNTY AND
THE WESTERN PORTION OF SISKIYOU COUNTY. ISOLATED SHOWERS ARE
POSSIBLE ALONG THE CASCADES THIS AFTERNOON AND EVENING.


&&

.MARINE...UPDATED 630 AM PDT MON 22 SEP 2014...HIGH PRESSURE
WILL PERSIST THIS MORNING WITH LIGHT TO MODERATE WINDS AND SEAS.
SOUTHERLY WINDS WILL INCREASE LATER TODAY AHEAD OF A COLD FRONT.
THE FRONT WILL ARRIVE TONIGHT AND BE THE FIRST IN A SERIES OF
FRONTS. THE STRONGEST WINDS ARE LIKELY TUESDAY AFTERNOON AND
EVENING BUT WINDS WILL THEN REMAIN MODERATE WHILE WEST SWELL BUILDS
TO A PEAK OF AROUND 14 FT AT 14 SECONDS ON WEDNESDAY EVENING.
PERIODS OF RAIN WITH STRONG WINDS AND STEEP TO VERY STEEP SEAS ARE
EXPECTED THROUGH THE WEEK.


&&

.PREV DISCUSSION... /ISSUED 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


&&

.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.

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.