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  Forecast Discussion for Southern Oregon and Northern California  

Forecast: Forecast Discussion | 7 Day Forecast

Forecast Discussion for MFR NWS Office

000
FXUS66 KMFR 042145
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
245 PM PDT TUE AUG 4 2015

.SHORT TERM...TODAY AND TONIGHT, A SHORTWAVE MOVING UP FROM THE
SOUTHWEST WILL ALLOW ISOLATED TO SCATTERED THUNDERSTORMS TO
DEVELOP OVER EASTERN AND SOUTHERN PORTIONS OF THE AREA. THIS WILL
MAINLY AFFECT NORTHERN CALIFORNIA AND AREAS EAST OF THE CASCADES.
MODELS CONTINUE TO INDICATE THE BEST CHANCE FOR THUNDERSTORMS IS
OVER WESTERN SISKIYOU COUNTY AND EAST OF THE CASCADES, ESPECIALLY
NEAR SUMMER RIM.

THIS DISTURBANCE WILL SHIFT EAST ON WEDNESDAY AND EXPECT MAINLY
DRY AND WARM CONDITIONS OVER THE AREA. A SURFACE THERMAL TROUGH
WILL DEVELOP ALONG THE COAST WEDNESDAY NIGHT INTO THURSDAY. THIS
WILL BRING BREEZY OFFSHORE FLOW TO THE COASTAL RIDGES WITH A
CHETCO EFFECT BRINGING WARM TEMPERATURES TO THE BROOKINGS AREA.
LATE THURSDAY, EXPECT AN UPPER LOW TO SHIFT INTO THE COAST OF
CENTRAL CALFIORNIA THEN MOVE INLAND THURSDAY NIGHT. AS THIS
FEATURE MOVES INLAND EXPECT SOUTHERLY MOISTURE TO MOVE INTO
SOUTHEAST PORTIONS OF THE AREA WITH A SLIGHT CHANCE OF
THUNDERSTORMS BY FRIDAY MORNING OVER NORTHERN CALIFORNIA ZONES. AS
THE UPPER LEVEL TROUGH SHIRTS NORTHEASTWARD INTO NORTHEAST
CALIFORNIA AND NORTHWEST NEVADA, THE CHANCE FOR THUNDERSTORMS WILL
INCREASE FRIDAY AFTERNOON AND EVENING, MAINLY OVER NORTHERN
CALIFORNIA AND FROM THE CASCADES EAST IN SOUTHERN OREGON.

AREAS OF SMOKE WILL CONTINUE TO AFFECT AREAS FROM THE CASCADES
WEST AT LEAST THROUGH THUS WEEKEND AS DAYTIME NORTH TO NORTHWEST
FLOW PREVAILS. OFFSHORE FLOW ON THURSDAY MAY BRING LESS SMOKE TO
THE CASCADES BUT INCREASED SMOKE TO THE CURRY COAST.

.LONG TERM...SATURDAY THROUGH EARLY NEXT WEEK...MODELS ARE SHOWING
AN UPPER LOW WILL GRADUALLY MOVES DOWN THE COAST OF BRITISH
COLUMBIA AND BECOMES CENTERED OFF THE COAST OF WASHINGTON SUNDAY
NIGHT INTO MONDAY. AHEAD OF THIS FEATURE, LINGERING MOISTURE AND
INSTABILITY WILL BRING A SLIGHT CHANCE OF THUNDERSTORMS FROM THE
CASCADES EAST AND OVER NORTHERN CALIFORNIA ON SATURDAY. THEN ON
SUNDAY WITH THE LOW SHIFTING FURTHER SOUTH AND A RIDGE
STRENGTHENING INLAND, EXPECT A SLIGHT CHANCE OF THUNDERSTORMS OVER
CENTRAL AND EASTERN PORTIONS OF THE AREA, WITH BEST CHANCES FROM
THE WESTERN CASCADE FOOTHILLS IN OREGON EAST INTO THE CASCADES AND
NORTHERN KLAMATH COUNTY. SOUTH TO SOUTHWEST 700 MB WINDS INCREASE
ON SUNDAY AND MAY SEE SOME GUSTY WINDS DEVELOP OVER THE HIGHER
TERRAIN ESPECIALLY IN THE CASCADES. MODELS ARE SHOWING BETTER
AGREEMENT WITH THE UPPER TROUGH SHIFTING INLAND ON MONDAY INTO
TUESDAY WITH A SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS POSSIBLE
IN CENTRAL AND EASTERN PORTIONS OF THE AREA.

THE SOUTHERN PORTION OF THE TROUGH MAY CUTOFF AND BRING A CUTOFF
LOW TO NORTHERN CALIFORNIA AROUND WEDNESDAY. HOWEVER, CONFIDENCE
IS LOW IN THE DETAILS FOR WEDNESDAY GIVEN THE VARIABILITY IN MODEL
ENSEMBLE FORECASTS ON WHETHER A CUTOFF LOW WILL DEVELOP AND WHERE
IT MAY BE POSITIONED.


&&

.AVIATION...FOR THE 04/18Z TAF CYCLE...ALONG THE COAST...AREAS OF
IFR REMAIN OFF SHORE EXCEPT FOR AREAS OF IFR/MVFR CIGS NEAR
BROOKINGS...THEN LOW LEVEL STRATUS RETURNS TO THE COAST EARLY THIS
EVENING. FOR THE WEST SIDE VALLEYS, AREAS OF MVFR AND IFR VSBYS IN
SMOKE WILL PERSIST THROUGH THIS EVENING. NORTH WEST FLOW WILL HELP
KEEP RBG IN VFR CONDITIONS THIS AFTERNOON. FOR THE CASCADES EAST
AND SISKIYOUS SOUTH, VFR CONDITIONS WILL PREVAIL THROUGH THIS
EVENING EXCEPT FOR LOCAL MVFR VSBYS IN SMOKE. ISOLATED TO
SCATTERED THUNDERSTORMS WILL OCCUR AGAIN THIS AFTERNOON AND
EVENING FROM SISKIYOU COUNTY NE INTO THE CASCADES AND KLAMATH/LAKE
COUNTIES. /SMITH

&&

.MARINE...UPDATED 230 PM PDT TUESDAY 4 AUGUST 2015...HIGH PRESSURE
WILL BUILD OFFSHORE AND A THERMAL TROUGH WILL DEVELOP ALONG THE
COAST THEN STRENGTHEN INTO THURSDAY. NORTH WINDS AND SEAS WILL BUILD
TONIGHT/WEDNESDAY AND REMAIN MODERATE THROUGH THURSDAY MORNING. THEN
WINDS WILL STRENGTHEN FURTHER THURSDAY AFTERNOON AND
EVENING...POSSIBLY REACHING GALE FORCE OVER THE SOUTHERN OUTER
WATERS THURSDAY AFTERNOON AND EVENING. THE THERMAL TROUGH WILL
WEAKEN FRIDAY INTO SATURDAY. NORTH WINDS AND SEAS WILL EASE AT THAT
TIME. SPILDE

&&

.FIRE WEATHER...UPDATED 200 PM PDT TUESDAY 4 AUGUST 2015...MODELS
HAVE TRENDED TOWARDS INCREASED CHANCES FOR CONVECTIVE ACTIVITY FOR
THE AFTERNOON AND EVENING TODAY. WHILE THE BULK OF MODEL SOLUTIONS
SHOW A SWATH OF INSTABILITY ACROSS NORTHERN CALIFORNIA AND FROM
THE CASCADES EAST IN OREGON, THERE IS QUITE A DIFFERENCE IN THE
PRECIPITATION OUTLOOK. HOWEVER, THE HIGHER RESOLUTION NAM AND HRRR
PRECIPITATION FIELDS ARE DEPICTING AN AREA OF SCATTERED
THUNDERSTORMS DEVELOPING OVER WESTERN SISKIYOU COUNTY LATE THIS
AFTERNOON, AND ANOTHER AREA OVER LAKE AND KLAMATH COUNTIES LATE
THIS AFTERNOON AND EVENING. THIS APPEARS TO BE THE RESULT OF A
CONVERGENCE OF SEVERAL FACTORS, INCLUDING A WEAK SURFACE BOUNDARY,
THE PASSAGE OF THE UPPER LEVEL TROUGH AND ASSOCIATED VORTICITY,
AND SOME JET SUPPORT ALOFT. THESE FACTORS, WHILE EXISTING ONLY A
SHORT TIME OVER SISKIYOU COUNTY, MAY LAST WELL INTO THE NIGHT
FARTHER EAST, AND THEREFORE NOCTURNAL STORMS ARE NOT OUT OF THE
QUESTION EAST OF THE CASCADES.

DESPITE HIGH LEVELS OF UNCERTAINTY, HAVE OPTED TO ERR ON THE SIDE OF
CAUTION, ESPECIALLY GIVEN THE CURRENT STATUS OF FIREFIGHTING
RESOURCES, AND ISSUED A RED FLAG WARNING FOR THE ABOVE AREAS. SOME
STORMS MAY BEGIN DRY, BUT SHOULD TREND WETTER AS THE EVENING
PROGRESSES. UNTIL THEN, GUSTY WINDS ARE OF PRIMARY CONCERN. OVERALL,
LIGHTING HAS THE POTENTIAL TO PRODUCE NUMEROUS STARTS, ESPECIALLY
GIVEN THE IGNITION RATE OVER THE PAST SEVERAL DAYS.

THUNDERSTORMS SHOULD COME TO AN END BY WEDNESDAY MORNING, AND NO
OTHER CONVECTION IS EXPECTED UNTIL THE WEEKEND. UNTIL THEN,
TEMPERATURES AND HUMIDITIES SHOULD REMAIN STEADY, ALTHOUGH THERE MAY
BE PERIODS OF MODERATE OVERNIGHT RECOVERIES ACROSS RIDGE LINES AT
VARYING TIMES THROUGH THE WEEK AND THIS WEEKEND. GUSTY WINDS MAY
ALSO BE AN ISSUE THIS WEEKEND WITH THE PASSAGE OF A POTENTIALLY
STRONG UPPER LEVEL TROUGH. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING FROM 5 PM THIS AFTERNOON TO 5 AM PDT WEDNESDAY
     FOR ORZ624-625.

CA...RED FLAG WARNING FROM 5 PM THIS AFTERNOON TO 11 PM PDT THIS
     EVENING FOR CAZ280.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT WEDNESDAY FOR
     PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT
     WEDNESDAY FOR PZZ356.
     GALE WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY NIGHT FOR
     PZZ376.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT THURSDAY FOR
     PZZ376.
     HAZARDOUS SEAS WATCH FROM THURSDAY MORNING THROUGH LATE THURSDAY
     NIGHT FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THURSDAY
     FOR PZZ376.

$$

CC

NWS MFR Office Area Forecast Discussion