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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 041542
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
842 AM PDT SAT JUL 4 2015

.DISCUSSION...ANOTHER DAY WITH WELL ABOVE NORMAL TEMPERATURES IS
FORECAST FOR THIS INDEPENDENCE DAY...WITH SOME THUNDERSTORM
CHANCES IN THE SOUTHEASTERN HALF OF THE FORECAST AREA.

SOUTHERN OREGON AND NORTHERN CALIFORNIA REMAIN UNDER A RELATIVELY
STAGNANT PATTERN...IN A COL AREA BETWEEN TROUGHING TO THE
SOUTHWEST AND NORTHEAST...AND RIDGING TO THE SOUTHEAST AND
NORTHWEST. MOISTURE AND INSTABILITY IS FOCUSED OVER NORTHERN
CALIFORNIA AND SOUTHERN LAKE AND KLAMATH COUNTIES...AND THAT IS
WHERE WE EXPECT THE BEST CHANCE OF THUNDERSTORMS TODAY. ONE NOTE
IS THE ADDITION OF THUNDERSTORM CHANCES IN KLAMATH FALLS TODAY
WITH THE MORNING UPDATE. THE LATEST RUN OF THE HOURLY HRRR MODEL
SHOWS SHOWERS AND A SOME THUNDERSTORMS IN THE EASTERN
SISKIYOU...SOUTHERN KLAMATH...SOUTHERN LAKE...AND MODOC COUNTIES
FROM ABOUT 4PM-8PM.

WE ARE MAINTAINING A FIRE WEATHER WATCH FOR THE SOUTHEASTERN
PORTION OF THE FORECAST AREA...AND AS IS TYPICAL...ITS NOT A CUT
AND DRY SITUATION FOR THUNDERSTORM FORMATION TODAY INTO TOMORROW.
THE WATCH IS FOUND AT RFWMFR...AND PLEASE SEE THE LATEST FIRE
WEATHER DISCUSSION BELOW.

SOME HIGH CLOUDS WILL TRAVERSE THE FORECAST AREA...AND WITH A
GENERALLY COOLER AIR MASS IN PLACE...TEMPERATURES WILL BE A FEW
DEGREES COOLER THAN YESTERDAY. HOWEVER...WITH ALL THE OUTDOOR
ACTIVITIES EXPECTED TODAY...WE HAVE MAINTAINED AN IMPACT-BASED
HEAT ADVISORY FOR THE ROGUEUTHE LATEST MODELS SUGGEST COOLING FOR
THE FORECAST AREA WILL BE VERY GRADUAL UNTIL THE MIDDLE OF NEXT
WEEK WHEN AN UPPER LOW MOVES THROUGH AND BRINGS TEMPERATURES TO
NEAR OR BELOW NORMAL. NOTE THIS COULD BE THE FIRST ROUND OF
WIDESPREAD BELOW NORMAL TEMPERATURES IN MORE THAN 30 DAYS.

&&

.AVIATION...FOR THE 04/12Z TAF CYCLE...ALONG THE COAST...IFR AND
LIFR CONDITIONS MAINLY FROM CAPE BLANCO NORTHWARD WILL BURN OFF TO
VFR BY MID-MORNING...BUT WILL REMAIN OFFSHORE. THE LOWER
CONDITIONS WILL MOVE BACK ONSHORE THIS EVENING. OVER THE
REMAINDER OF THE AREA...VFR CONDITIONS WILL PREVAIL THROUGH
TONIGHT...BUT ISOLATED TO SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS WILL DEVELOP OVER NORTHERN CALIFORNIA AND THE
SOUTHERN PORTIONS OF LAKE AND KLAMATH COUNTIES.

&&

.MARINE...UPDATED 300 AM PDT SATURDAY 4 JULY 2015...A THERMAL TROUGH
NEAR THE COAST WILL WEAKEN THROUGH THE WEEKEND. SMALL CRAFT ADVISORY
SEAS WILL PREVAIL INTO THIS AFTERNOON...WITH SMALL CRAFT
CONDITIONS FOR SEAS GENERALLY BEYOND 3NM FROM SHORE. SEAS WILL
GRADUALLY SUBSIDE LATER THIS EVENING AND WINDS AND SEAS WILL
REMAIN LIGHT THROUGH AT LEAST MIDWEEK. STRATUS AND FOG WILL
INCREASE IN COVERAGE AND AFFECT MOST OF THE COASTAL WATERS BY
SUNDAY.

&&

.FIRE WEATHER...UPDATED 830 AM PDT SATURDAY 4 JULY 2015...MOISTURE
FLOW WILL BE ENHANCED TODAY, AND ISOLATED TO SCATTERED THUNDERSTORMS
LOOK TO BE POSSIBLE OVER NORTHERN CALIFORNIA AND OREGON`S EAST SIDE.
MID LEVEL DRY AIR LOOKS LIKE IT WILL ALSO MOVE IN AND INHIBIT
THUNDERSTORM DEVELOPMENT WEST OF MEDICINE LAKE AND NORTH OF SUMMER
LAKE. THIS, TAKEN WITH THE MODEL INSTABILITY AND THE TRACKING OF
ENERGY FROM THE SOUTH, WOULD PLACE THE PRIMARY THREAT FOR SCATTERED
THUNDERSTORMS OVER MODOC COUNTY, EASTERN SISKIYOU COUNTY, AND
SOUTHERN LAKE AND KLAMATH COUNTIES BEGINNING SOMETIME LATE THIS
AFTERNOON AND INTO THE EVENING. MODEL SOLUTIONS DEPICT AREAS OF
INSTABILITY PERSISTING OVERNIGHT TONIGHT, AND DUE TO THIS, HAVE KEPT
A CHANCE FOR NOCTURNAL STORMS IN PLACE THROUGH TONIGHT INTO EARLY
SUNDAY MORNING. SCATTERED THUNDERSTORMS ARE LIKELY TO DEVELOP
SUNDAY AFTERNOON AND EVENING AS DAYTIME HEATING INCREASES, AND
MOISTURE INFLOW REMAINS AIMED AT OUR AREA. WE ARE EXPECTING LOW
LEVELS OF THE ATMOSPHERE TO REMAIN DRY, AND ALTHOUGH MOST OF THE
STORMS TODAY AND SUNDAY SHOULD BE WET, THERE SHOULD BE ABUNDANT
LIGHTNING STRIKES OUTSIDE STORM CORES. THE DRY LOW LEVELS WOULD
ALSO INCREASE THE POTENTIAL FOR GUSTY AND ERRATIC WINDS IN THE
VICINITY OF THUNDERSTORMS. WITH THE POTENTIAL OF NUMEROUS NEW
STARTS, INITIAL ATTACK RESOURCES COULD BE STRETCHED THIN. FOR
THESE REASONS, IT IS POSSIBLE THAT THE CURRENT WATCHES WILL BE
UPGRADED TO WARNINGS DURING THE DAY, AFTER COORDINATING WITH LOCAL
AGENCIES.

INCREASED MOISTURE AND THE PRESENCE OF AN UPPER LEVEL TROUGH WILL
KEEP AFTERNOON AND EVENING THUNDERSTORM CHANCES IN THE AREA THROUGH
THE NEXT WEEK. -BPN/SVEN

&&

.PREV DISCUSSION... /ISSUED 319 AM PDT SAT JUL 4 2015/

DISCUSSION...CURRENT WATER VAPOR IMAGE SHOWS THAT WE ARE SANDWICHED
BETWEEN THE UPPER LOW OFF THE CALIFORNIA COAST AND NORTHWEST FLOW
ALOFT IN WASHINGTON STATE. THIS HAS IN A SENSE LEAVES US IN A COL
WITH A WEAK DEFORMATION ZONE THAT HAS SINCE MOVED NORTH OF OUR AREA.
TODAY WON`T BE MUCH DIFFERENT THAN YESTERDAY WITH WEAK SHORTWAVES
EXPECTED TO MOVE UP FROM THE SOUTH INTO NORTHERN CAL LATER THIS
AFTERNOON WHICH SHOULD PROVIDE SUFFICIENT TRIGGER FOR THUNDERSTORMS
TO FIRE UP. THE NAM SHOWS MORE SHORTWAVE ACTIVITY APPROACHING
NORTHERN CAL LATE THIS AFTERNOON, BUT MID LEVEL MOISTURE IS LACKING.
THEREFORE THE MAJORITY OF STORMS WILL BE ISOLATED. MODELS SHOW
WEAK STEERING WINDS BETWEEN 5-10 KTS, BUT THEY DIFFER WITH THE
DIRECTION. THE GFS IS SOUTHERLY WHILE THE NAM IS FROM THE
SOUTHWEST. EITHER WAY, STORMS THAT DEVELOP WILL BE SLOW MOVERS.

THE NAM SHOWS STRONGER SHORTWAVES MOVING NORTH INTO MODOC...KLAMATH
AND LAKE COUNTIES TONIGHT, BUT WE`LL BE LOSING DAYTIME HEATING
AND EXPECT ANY STORMS TO BE ISOLATED. OF NOTE, THE GFS SHOWS MORE
QPF IN NORTHERN CAL AND SOUTHWEST OREGON, BUT THERE`S NO TRIGGER
AND IT`S FAIRLY DRY AT THE MID LEVELS, SO FIND THIS SOLUTION
SUSPECT.

SUNDAY WILL BE SIMILAR TO TODAY...BUT THERE WILL BE MORE
SHORTWAVE ACTIVITY MOVING INTO THE AREA AROUND THE TIME OF MAX
HEATING, THEREFORE COVERAGE OF THUNDERSTORMS WILL BE GREATER AND
MORE WIDESPREAD. STEERING WINDS REMAIN WEAK BETWEEN 5-10 KTS FROM
THE SOUTHWEST, SO STORMS THAT DEVELOP WILL TEND TO DRIFT
NORTHEAST.

THE ISOLATED TO SCATTERED SHOWER AND THUNDERSTORM PATTERN WILL
PERSIST OVER THE AREA FOR MOST OF NEXT WEEK AS THE UPPER LOW
GRADUALLY MOVES TOWARDS THE NORTHERN CALIFORNIA COAST AND MOISTURE
AND ENERGY MOVES AROUND THE LOW AND INTO THE AREA. GIVEN THE
PATTERN OF SOUTHEAST MOISTURE FLOW AROUND THIS LOW...EXPECT
INCREASED CHANCES FOR SHOWERS AND THUNDERSTORMS WEST OF THE
CASCADES...POSSIBLY EVEN NEAR THE COAST NEXT MONDAY THROUGH THURSDAY
TEMPERATURES WILL CONTINUE TO COOL...BUT IT WILL STILL BE HOT.

THE MODELS ARE IN FAIRLY GOOD AGREEMENT SHOWING THE UPPER LOW
FINALLY MOVING INLAND FRIDAY FOLLOWED BY A WEAK TROUGHINESS THE
FOLLOWING WEEKEND WITH THE RIDGE SHIFTING EAST INTO THE CENTRAL
PLAINS. THIS WILL BRING COOLER TEMPERATURES TO THE AREA, BUT THERE
WILL STILL BE A CHANCE OF SHOWERS AND THUNDERSTORMS, MAINLY ALONG
AND EAST OF THE CASCADES. -PETRUCELLI

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM 6 PM PDT THIS EVENING THROUGH SUNDAY
     EVENING FOR ORZ624-625.
     HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ024-026.
     FIRE WEATHER WATCH FROM THIS EVENING THROUGH SUNDAY EVENING FOR
     ORZ621-623.

CA...FIRE WEATHER WATCH FROM 6 PM PDT THIS EVENING THROUGH SUNDAY
     EVENING FOR CAZ280-281-284-285.
     HEAT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CAZ080-081.
     FIRE WEATHER WATCH FROM THIS EVENING THROUGH SUNDAY EVENING FOR
     CAZ282.

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

$$

NSK/MAP/SBN

NWS MFR Office Area Forecast Discussion