Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 061608
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
908 AM PDT MON JUL 6 2015

.DISCUSSION...OVERALL, COMPARED TO YESTERDAY, TODAY SHOULD BE
LESS ACTIVE THUNDERSTORM-WISE ACROSS THE CWA. THE REASON FOR THIS
IS WE`RE LACKING THE FAVORABLE SHORT WAVE ENERGY THAT WAS PRESENT
OVER THE AREA YESTERDAY AND JET DYNAMICS ARE PRETTY WEAK. EVEN
SO, WITH SOME GOOD INSTABILITY AND HEATING, WE SHOULD AT LEAST SEE
ISOLATED TO SCATTERED THUNDERSTORMS THIS AFTERNOON AND EVENING.
EXPECT INITIATION OVER THE HIGHER TERRAIN FROM THE CASCADES AND
SISKIYOUS SOUTH AND EASTWARD ABOUT 1-2 PM. IT IS DIFFICULT TO
PINPOINT AN AREA FAVORED FOR ABUNDANT LIGHTNING THIS AFTERNOON,
BUT IT APPEARS AS IF THE BEST CHANCE WILL BE OVER THE CASCADES
FROM ABOUT LAKE OF THE WOODS NORTHWARD ACROSS NORTHERN KLAMATH AND
PORTIONS OF NORTHWEST LAKE COUNTIES. ANOTHER AREA OF
THUNDERSTORMS MAY DEVELOP IN LASSEN COUNTY AND MOVE NORTHEASTWARD
INTO SOUTHERN MODOC COUNTY. THESE AREAS HAD SUBSTANTIAL RAINFALL
THIS WEEKEND. CONSULTATION WITH LOCAL FUELS FOLKS WILL BE DONE
THIS MORNING TO SEE IF WE NEED TO AMEND THE RED FLAG WARNING THAT
IS OUT CURRENTLY.

AN UPPER LEVEL LOW OFF THE CALIFORNIA COAST WILL MOVE TOWARD THE
BAY AREA TUESDAY AND THEN ONSHORE WEDNESDAY. THIS WILL BRING MORE
WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN OREGON AND
NORTHERN CALIFORNIA. PRECIPITABLE WATER VALUES ARE SIGNIFICANTLY
ABOVE NORMAL, SO STORMS THAT DO DEVELOP WILL LIKELY PRODUCE
RAINFALL, SOME OF IT HEAVY. SPILDE

&&

.AVIATION...FOR THE 06/12Z TAF CYCLE...ALONG THE COAST...IFR CIGS
AND LOWER TO LIFR IN AREAS ALONG THE COAST WILL LIFT BY LATE MORNING
BUT REMAIN IN PLACES IN THE COASTAL WATERS. ALSO EXPECT PATCHY FOG
TO LOWER VISIBILITIES TO MVFR ALONG THE COAST...WITH AREAS OF IFR
VIS...ALSO LIFTING BY LATE MORNING. ELSEWHERE...SCATTERED
THUNDERSTORMS WILL DEVELOP AGAIN THIS AFTERNOON FROM THE CASCADES
EAST AND SISKIYOUS SOUTH...WITH THE HIGHEST CHANCE OVER THE CASCADES
NEAR CRATER LAKE. /SVEN

&&

.MARINE...UPDATED 300 AM PDT MONDAY 6 JULY 2015...WINDS WILL BE
LIGHT AND SLOWLY SHIFT NORTH TO NORTHWEST MIDWEEK...AS PRESSURE
BUILDS OFFSHORE AND DROPS INLAND. LOW NORTHWESTERLY SWELL WILL
CONTINUE THROUGH THE WEEK. BOTH GFS AND EC SHOW AN UPPER LOW OVER
THE CENTRAL CA COAST MID WEEK...THAT SLOWLY MOVES OVER N-CAL/S-OR BY
FRIDAY MORNING. THIS WILL ENHANCE NORTHERLY WINDS THIS
WEEKEND...ESPECIALLY IN THE SOUTHERN WATERS...BUT THERE IS STILL
MODEL DISCREPANCY REGARDING THE STRENGTH OF THE LOW...BUT CURRENTLY
WINDS LOOK TO STAY BELOW ADVISORY LEVELS THROUGH THE WEEKEND. SVEN

&&

.FIRE WEATHER...UPDATE 900 AM PDT...WE ARE ASSESSING THE STATE OF
THE FUELS ACROSS PORTIONS OF OUR AREA TODAY SINCE MANY AREAS HAD
WETTING RAINFALL OVER THE WEEKEND. THIS MAY RESULT IN THE REMOVAL
OF SOME OF OUR FIRE WEATHER ZONES FROM THE RED FLAG WARNING.
SPILDE

&&

.PREV DISCUSSION... /ISSUED 310 AM PDT MON JUL 6 2015/

DISCUSSION...CURRENT WATER VAPOR SHOWS A DEFORMATION ZONE OVER OUR
AREA AS WE REMAIN SANDWICHED BETWEEN THE UPPER LOW OFF THE
CALIFORNIA COAST AND NORTHWEST FLOW OVER WASHINGTON STATE. THIS WAS
IN PART RESPONSIBLE FOR THE THUNDERSTORMS THAT DEVELOPED YESTERDAY
AFTERNOON AND EVENING. THE DEFORMATION ZONE WAS STRETCHING WITH WEST
WINDS ALOFT ALONG AND EAST OF THE CASCADES AND EAST WINDS WEST OF
THE CASCADES. THIS CREATED A "STRETCH" WHICH ALLOWED STORMS TO FIRE
UP WITH SOME MOVING EAST AND OTHERS MOVING WEST. OF NOTE MEDFORD HAS
REACHED 100 DEGREES OR HIGHER FOR 6 CONSECUTIVE DAYS AND IF WE GET
TO A 100 TODAY WILL MAKE IT 7 WHICH WILL TIE FOR THE 6 LONGEST ON
RECORD.

THE DEFORMATION ZONE IS EXPECTED TO REMAIN OVER THE AREA WITH SOME
STRETCHING IN NORTHERN CAL AND CASCADES. IT`S IN THESE AREAS WHERE
STORMS ARE EXPECTED TO DEVELOP AND THEY COULD BECOME MORE FREQUENT.
THE MID LEVEL MOISTURE DEPICTED BY THE MODELS TODAY ARE A BIT
MISLEADING BECAUSE IT`S FAIRLY DRY AT 500 MB AND VERY MOIST AT
700MB. ADDITIONALLY, LI`S WILL BE IN THE NEGATIVE THIS AFTERNOON IN A
GOOD CHUNK OF THE AREA. SO DESPITE THE LACK OF A TRIGGER, THE ABOVE
MENTIONED SCENARIOS SHOULD BE SUFFICIENT ENOUGH TO GENERATE
SCATTERED STORMS ALONG AND EAST OF THE CASCADES...WESTERN SISKIYOU
AND MOST OF MODOC COUNTY LATE THIS AFTERNOON INTO EARLY EVENING.
ALSO...700 MB WINDS WILL BE FROM THE SOUTH, SO THERE`S A CHANCE
STORMS THAT DEVELOP OVER THE SISKIYOUS COULD MIGRATE NORTH INTO THE
WESTSIDE UP TOWARDS THE UMPQUA DIVIDE AND EASTERN JOSEPHINE COUNTY.

THE PATTERN WILL BECOME MORE ACTIVE STARTING MONDAY NIGHT THROUGH
TUESDAY. THE UPPER LOW WILL SLOWLY MOVE NORTH AND TAP INTO A MOIST
SOUTH TO SOUTHEAST FLOW WITH HIGH PWATS OF 1+ INCHES ALONG AND WEST
OF THE CASCADES. THESE ARE ANOMALOUSLY HIGH VALUES...AND WITH MODELS
NOW ON THE SECOND DAY OF SHOWING THIS SCENARIO...WE HAVE INCREASED
POPS AND QPF FOR MUCH OF THE SOUTHERN TWO-THIRDS OF THE FORECAST
AREA. IN ADDITION STRONGER SHORTWAVES WILL ROTATE THROUGH THE AREA,
PROVIDING THE TRIGGER NECESSARY FOR SCATTERED THUNDERSTORMS. THERE
IS ALSO CONCERN FOR NOCTURNAL STORMS AT NIGHT...INCLUDING THE
WESTSIDE OUT TOWARDS THE MARINE WATERS.

THE UPPER LOW WILL MOVE INLAND SOUTH OF THE BAY AREA WEDNESDAY AND
THE FOCUS FOR THUNDERSTORMS WILL SHIFT SLIGHTLY SOUTH. WE EXPECT
THUNDERSTORMS TO BE MOST FREQUENT SOUTH OF THE UMPQUA DIVIDE. MODELS
ARE ALSO SHOWING HEFTY QPF AMOUNTS IN NORTHERN CAL AND SOUTHERN
OREGON. THEREFORE THUNDERSTORMS WILL BE RAIN PRODUCERS, BUT WE COULD
STILL GET FREQUENT LIGHTING WHICH WILL BE A CONCERN FOR NEW STARTS.

THE ISOLATED TO SCATTERED SHOWER AND THUNDERSTORM PATTERN WILL
PERSIST OVER THE AREA THURSDAY AS THE UPPER LOW NEARLY STALLS IN
CALIFORNIA AND WEAKENS. DYNAMICS AND INSTABILITY REMAIN FAVORABLE
OVER THE AREA.

THE UPPER LOW WILL CONTINUE WEAKEN AND OPEN TO A WEAK UPPER TROUGH
ON FRIDAY WITH THE BEST CHANCE FOR THUNDERSTORMS ALONG AND EAST OF
THE CASCADES. BEFORE WEST WINDS ALOFT BEGIN TO STABILIZE AND DRY
THINGS OUT ON SATURDAY FROM WEST TO EAST. THE WEEKEND MAY SIGNAL A
BREAK FROM THE STEADY CHANCES OF THUNDERSTORMS...BUT SOUTHERLY FLOW
SETS UP AGAIN ON SUNDAY AS AN UPPER TROUGH APPROACHES FROM THE WEST.
THIS TROUGH WILL BRING COOLER TEMPERATURES TO THE AREA.
-PETRUCELLI

AVIATION...FOR THE 06/12Z TAF CYCLE...ALONG THE COAST...IFR CIGS
AND LOWER TO LIFR IN AREAS ALONG THE COAST WILL LIFT BY LATE MORNING
BUT REMAIN IN PLACES IN THE COASTAL WATERS. ALSO EXPECT PATCHY FOG
TO LOWER VISIBILITIES TO MVFR ALONG THE COAST...WITH AREAS OF IFR
VIS...ALSO LIFTING BY LATE MORNING. ELSEWHERE...SCATTERED
THUNDERSTORMS WILL DEVELOP AGAIN THIS AFTERNOON FROM THE CASCADES
EAST AND SISKIYOUS SOUTH...WITH THE HIGHEST CHANCE OVER THE CASCADES
NEAR CRATER LAKE. /SVEN

MARINE...UPDATED 300 AM PDT MONDAY 6 JULY 2015...WINDS WILL BE
LIGHT AND SLOWLY SHIFT NORTH TO NORTHWEST MIDWEEK...AS PRESSURE
BUILDS OFFSHORE AND DROPS INLAND. LOW NORTHWESTERLY SWELL WILL
CONTINUE THROUGH THE WEEK. BOTH GFS AND EC SHOW AN UPPER LOW OVER
THE CENTRAL CA COAST MID WEEK...THAT SLOWLY MOVES OVER N-CAL/S-OR BY
FRIDAY MORNING. THIS WILL ENHANCE NORTHERLY WINDS THIS
WEEKEND...ESPECIALLY IN THE SOUTHERN WATERS...BUT THERE IS STILL
MODEL DISCREPANCY REGARDING THE STRENGTH OF THE LOW...BUT CURRENTLY
WINDS LOOK TO STAY BELOW ADVISORY LEVELS THROUGH THE WEEKEND. SVEN

FIRE WEATHER...UPDATED 300 AM PDT MONDAY 6 JULY 2015...THUNDERSTORM
ACTIVITY WILL BE SLIGHTLY LESS WIDESPREAD MONDAY...BUT WILL INCREASE
TUESDAY AND WEDNESDAY. THE FAVORED AREA ON MONDAY ACTIVITY WILL BE
FROM THE CASCADES EAST AND SISKIYOUS SOUTH. TUESDAY AND WEDNESDAY
WILL SEE GREATER COVERAGE WITH SOME OF THE THUNDERSTORMS POSSIBLY
VERY WET. EVEN THE COASTAL AREA MAY SEE SOME THUNDERSTORMS IN THAT
TIME FRAME. THE ACTIVITY WILL GRADUALLY SHIFT TO THE EAST SIDE
TOWARD THE END OF THE WEEK.

TEMPERATURES WILL REMAIN HOT MONDAY...BUT WILL START TO COOL
TUESDAY. TEMPERATURES WILL APPROACH SEASONAL VALUES TOWARD THE END
OF THE WEEK. /SVEN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 11 PM PDT THIS
     EVENING FOR ORZ617-621>625.

CA...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 11 PM PDT THIS
     EVENING FOR CAZ280-281-284-285.

PACIFIC COASTAL WATERS...NONE.

$$

MAS/MAP/SBN



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