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 252306
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
406 PM PDT MON MAY 25 2015

.SHORT TERM...AS THE UPPER LEVEL RIDGE CONTINUES TO
NUDGE TOWARDS THE WEST COAST...MORE STABLE NORTHWEST FLOW
CONTINUES TO CONVERGE WITH WARM...MOIST UNSTABLE FLOW FROM THE
SOUTH OVER EXTREME NORTHERN CALIFORNIA FROM THE MOUNT SHASTA AREA
EASTWARD. WESTERLY STEERING FLOW IS MOVING THESE STORMS TO THE
EAST. THIS PATTERN MAKES A RETURN ON TUESDAY WITH VERY SIMILAR
RESULTS.

ON WEDNESDAY NORTHWESTERLY FLOW SPREADS ACROSS THE INLAND AREAS
WITH OFFSHORE FLOW SPREADING FURTHER INLAND. THIS WILL PUSH THE
AREAS OF INSTABILITY AND THETA E CONVERGENCE SOUTH AND EAST OF THE
FORECAST AREA. THE UPPER LEVEL RIDGE THEN BEGINS TO POSITION OVER
THE COASTAL WATERS WITH OFFSHORE FLOW SPREADING ACROSS THE EAST
SIDE BY THURSDAY MORNING. A HIGH PRESSURE RIDGE WILL BUILD IN TO
THE WEST COAST ON THURSDAY WITH MOST LOCATIONS LIKELY TO RECORD
THEIR HIGHEST TEMPERATURES OF THE YEAR SO FAR. /SVEN

.LONG TERM...THE STRONG RIDGE WILL PERSIST OVER CALIFORNIA ON
FRIDAY WHILE A TROUGH MOVES INTO BRITISH COLUMBIA. THIS WILL BRING
A MODEST INCREASE OF 700-500 MB MOISTURE WHILE HIGH TEMPERATURES
WILL AGAIN BE MUCH ABOVE NORMAL...ABOUT THE SAME AS ON THURSDAY.
THIS WARRANTS INCLUDING A SLIGHT CHANCE OF AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS FROM THE SISKIYOU AND CASCADE MOUNTAINS
EASTWARD WITH THE STRONGEST LIFT LIKELY EAST OF THE KLAMATH BASIN.
LITTLE CHANGE IS EXPECTED ON SATURDAY. THE REGION OF FOCUS FOR
THUNDERSTORM ACTIVITY WILL DEPEND LARGELY UPON THE POSITIONING OF
THE TWO MAIN UPPER LEVEL FEATURES. THE 700MB STEERING FLOW WILL
LIKELY BE FROM THE SOUTH OR SOUTHWEST.

MODEL DIFFERENCES INCREASE BY SUNDAY. ANOTHER TROUGH WILL BE
APPROACHING OUR COAST FROM THE WEST OR SOUTHWEST. THE POSITION OF
THIS LOW IS UNCERTAIN. IF IT IS FASTER/MORE PROGRESSIVE, WHICH IS
CLOSER TO THE GFS SOLUTION, THEN SOUTHERLY FLOW ALOFT AND
INSTABILITY ARE LIKELY TO BE ENHANCED ON SUNDAY. BUT, THERE IS ABOUT
AN EQUAL PROBABILITY THAT RIDGING WILL STRENGTHEN ON SUNDAY AND LEAD
TO A LOWER PROBABILITY OF SHOWERS AND THUNDERSTORMS THAN ON
SATURDAY. BY MONDAY, IT IS MORE LIKELY THAT THE LOW WILL BE
SUFFICIENTLY NEAR OUR REGION TO BRING AN INCREASE OF CLOUDS, LOWER
TEMPERATURES AND A MORE WIDESPREAD SLIGHT CHANCE TO CHANCE OF
SHOWERS AND THUNDERSTORMS. THE EARLY OUTLOOK IS FOR HOT AND DRY
WEATHER TO FOLLOW ON DAY 8 THROUGH 10.

&&

.AVIATION...FOR THE 25/18Z TAF CYCLE...LOW CLOUDS HAVE RETREATED
FROM THE COAST WHILE ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
HAVE DEVELOPED OVER SISKIYOU AND MODOC COUNTIES. THIS CONVECTIVE
ACTIVITY WILL DIMINISH LATE THIS EVENING WHILE AREAS OF IFR CIGS
REDEVELOP ALONG THE COAST. A MIX OF IFR AND MVFR STRATUS WILL SURGE
INTO THE COASTAL AND UMPQUA VALLEYS OVERNIGHT THEN PERSIST UNTIL
AROUND 18Z TUESDAY MORNING. /DW

&&

.MARINE...UPDATED 300 PM PDT MONDAY 25 MAY 2015...HIGH PRESSURE
OFFSHORE AND A THERMAL TROUGH NEAR THE COAST WILL PEAK IN STREGTH
MONDAY EVENING...THEN GRADUALLY WEAKEN MONDAY NIGHT THROUGH
THURSDAY. THIS WILL CREATE MODERATE TO STRONG NORTHERLY WINDS OVER
THE WATERS RESULTING STEEP TO VERY STEEP WIND DRIVEN SEAS THROUGH
MONDAY EVENING, ESPECIALLY IN THE VICINITY OF CAPE BLANCO AND SOUTH.
WINDS WILL WEAKEN AS THE PRESSURE PATTERN WEAKENS, HOWEVER NORTH
WINDS WILL CONTINUE TO BE GUSTY IN THE AFTERNOONS AND EVENINGS
KEEPING SMALL CRAFT CONDITIONS GOING THROUGH THE WEEK...MOSTLY IN
THE SOUTHERN OUTER WATERS. /MND

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT
     THIS EVENING FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT THURSDAY
     FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ350-370.
     GALE WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.
     HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ376.

$$

SBN/DW/MND



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