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 111209 CCA
AFDMFR

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE MEDFORD OR
507 AM PDT FRI JUL 11 2014

.DISCUSSION...VERY WARM TEMPERATURES WILL CONTINUE INTO THE
WEEKEND AS THE UPPER LEVEL RIDGE WILL ONLY WEAKEN TEMPORARILY. A
LOW PRESSURE TROUGH APPROACHING NORTHERN CALIFORNIA COAST THIS
MORNING WILL SEND A BAND OF MOISTURE INTO OUR FORECAST AREA ALONG
WITH AREAS OF INSTABILITY. SO FAR THERE HAVE BEEN CLOUD TO CLOUD
LIGHTNING STRIKES JUST SOUTH OF SISKIYOU COUNTY OVERNIGHT.
MOISTURE IS EXPECTED TO SPREAD INTO EASTERN SISKIYOU COUNTY MAINLY
FROM THE CASCADES EASTWARD AROUND DAY BREAK. THE NAM12 TAKES MOST
OF THIS MOISTURE NORTH ALONG AND JUST EAST OF THE CASCADES WITH
ANOTHER BAND OF MOISTURE ROTATING BACK ACROSS SW OREGON. THE SHORT
TERM HRRR MODEL SHOWS A SIMILAR TRACK ON FORECAST RADAR RETURN BUT
SHOWS A MODERATE RETURN (30-40DBZ) EXPANDING BACK INTO NW JACKSON
COUNTY AND EASTERN DOUGLAS COUNTY INTO FIRE ZONE 617 BY THIS
AFTERNOON. THE NAM12 SHOWS MORE INSTABILITY FURTHER WEST INTO
JOSEPHINE AND JACKSON COUNTY WHERES THE GFS KEEPS NEGATIVE LIFTED
INDEX MAINLY NEAR THE CASCADES WHILE ERODING ANY CAPPING BY MID
MORNING. MY FEELING ON THIS IS THAT WE MAY SEE TWO DISTINCT BAND
OF CONVECTION, ONE TRAVELLING NORTH INTO THE KLAMATH BASIN AND THE
OTHER COMING UP THROUGH THE HAPPY CAMP DISTRICT INTO THE ILLINOIS
VALLEY AND THEN NORTHWARD INTO THE UMPQUA BASIN. CURRENT RED FLAG
WARNING COVERS THIS TREND AND WILL KEEP AREAL COVERAGE AS IS. BOTH
MODELS SHOW CLEARING ACROSS THE WEST SIDE THIS AFTERNOON AND THIS
MAY BE CONDUCIVE TO THE SECOND ROUND OF CONVECTION FROM SURFACE
HEATING.

FOR SATURDAY..THERE WILL BE MORE H7-H5 MOISTURE EAST OF THE
CASCADES AND THIS IS WHERE MOST CONVECTION WILL BE LOCATED. THE
AIR MASS WILL BE MUCH DRIER WEST OF THE CASCADES. HAVE KEPT ALL OF
THUNDERSTORMS FORECAST TO THE EAST OF THE CASCADES.

ON SUNDAY..ANOTHER ROUND OF TROUGH WILL APPROACH THE COAST AGAIN.
ONE THING THAT MAKES THIS TROUGH DIFFERENT IS THE PRESENCE OF 75KT
JETMAX MOVING INTO NW CALIFORNIA AND SW OREGON. IN ADDITION BOTH
MODELS INDICATE ENOUGH MOISTURE TO GENERATE THUNDERSTORMS. /FB

&&

.AVIATION...BASED ON THE 11/06Z TAFS...IFR CONDITIONS
ARE PRESENT ALONG THE COAST AND ARE EXPECTED TO PERSIST THROUGH
EARLY THIS MORNING...WITH CLEARING IN THE LATE FRIDAY MORNING.
ELSEWHERE...EXPECT MAINLY VFR CONDITIONS EARLY THIS MORNING THEN AS
THUNDERSTORMS DEVELOP MAY SEE LOCAL MVFR CIGS DEVELOP DURING THE DAY
WITH A RETURN TO VFR DURING THE EVENING.  THUNDERSTORMS WILL HAVE
THE LARGEST IMPACT ON INLAND AREAS TODAY.  THUNDERSTORMS WILL AFFECT
NORTHERN CALIFORNIA FIRST EARLY THIS MORNING...AND THEN SPREAD INTO
SOUTHERN OREGON DURING THE MORNING AND CONTINUING INTO THE
AFTERNOON. GREATEST COVERAGE OF THUNDERSTORMS EXPECTED
LATE IN THE MORNING INTO THE AFTERNOON. VERY GUSTY  WINDS AND HAIL
ARE EXPECTED WITH SOME OF THESE STORMS. /CC


&&

.MARINE...UPDATED THURSDAY 11 JULY 300 AM PDT...WINDS HAVE
WEAKENED CONSIDERABLY...AND SEAS WILL GRADUALLY DIMINISH THROUGH
TODAY. SEAS ARE COMING DOWN A BIT SLOWER THAN PREVIOUSLY
FORECAST...SO HAVE EXTENDED THE SMALL CRAFT ADVISORY OUT A FEW MORE
HOURS. A WEAK LOW PRESSURE WILL MOVE THROUGH THE WATERS TODAY INTO
TOMORROW...BUT WINDS WILL REMAIN GENERALLY LIGHT UNTIL SUNDAY
AFTERNOON. THE THERMAL TROUGH PATTERN WILL REDEVELOP SUNDAY AND
STRENGTHEN MONDAY...RESULTING IN ANOTHER ROUND OF MODERATE TO
STRONG NORTH WINDS AND BUILDING SHORT PERIOD SEAS. -BPN

&&

.FIRE WEATHER...SATELLITE AND RADAR IMAGERY TO THE SOUTH SHOW SOME
CONVECTION HAS BEGUN IN ASSOCIATION WITH A SHORT WAVE AND MONSOONAL
MOISTURE THAT WILL BE MOVING INTO OUR AREA LATER THIS MORNING
THROUGH THIS AFTERNOON. SOME CLOUD-TO-CLOUD LIGHTNING HAS ALSO BEEN
DEPICTED WITH THESE BUILDUPS...SUGGESTING THAT A GOOD DEAL OF
INSTABILITY EXISTS OVER THE AREA THIS MORNING EVEN BEFORE SOLAR
HEATING BEGINS. MUCH DEPENDS ON THE TIMING OF THE SHORTWAVE AND THE
ARRIVAL OF  MOISTURE...AS WELL AS WHAT AREAS RECEIVE THE MOST
HEATING...AND THE EXACT LOCATION OF JET ENERGY OVERHEAD WHICH COULD
LEND TO MORE NUMEROUS CELLS. STEERING WINDS ARE EXPECTED TO BE FROM
THE SOUTH AND SOUTHEAST WHICH IS A FAVORABLE FLOW TO GET STORMS TO
SPREAD OUT OVER THE VALLEYS WEST OF THE CASCADES. GIVEN THE DRY
FUELS AND EXPECTED NUMEROUS LIGHTNING STRIKES EXPECTED...HAVE
CONTINUED RED FLAG WARNINGS FOR NORTHERN CAL AND MOST OF OREGON
ZONES. THE EXCEPTION WILL BE THE COASTAL ZONES...WHERE THE
ATMOSPHERE SHOULD REMAIN MUCH MORE STABLE. EVEN THEN...CAN NOT RULE
OUT ISOLATED THUNDERSTORMS FOR FIRE ZONES 615 AND 618. MODELS
SUGGEST THE BULK OF THE ACTION WILL SHIFT NORTH DURING THE DAY TODAY
AND COULD BE OUT OF THE AREA BY THIS AFTERNOON...BUT AGAIN MUCH
DEPENDS ON THE TIMING. ANOTHER UPPER LOW WILL MOVE TOWARDS THE AREA
SUNDAY, BUT THE MODELS SUGGEST MOST OF THE INSTABILITY AND
THUNDERSTORM POTENTIAL WILL BE FROM AROUND CRATER LAKE NORTH. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 6 PM PDT THIS EVENING FOR ORZ624-625.
     RED FLAG WARNING UNTIL 6 PM PDT THIS EVENING FOR
     ORZ616-617-619>623.

CA...RED FLAG WARNING UNTIL 6 PM PDT THIS EVENING FOR
     CAZ280>282-284-285.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THIS
     MORNING FOR PZZ350-356-370-376.

$$

FJB/FJB/CC








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