Forecast: Forecast Discussion | 7 Day Forecast

000
FXUS66 KMFR 311557
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
857 AM PDT SAT JUL 31 2010

.DISCUSSION...TEMPERATURES THIS MORNING ARE RUNNING 1 TO 5 DEGREES
COOLER THAN YESTERDAY AT THIS TIME. ONLY CHANGE TO FORECAST WAS TO
DROP UMPQUA BASIN TEMPERATURES SOME DUE TO EXPECTED CLOUDS THERE
THROUGH NOON. VISIBLE SATELLITE IMAGERY DEPICTS A DEEPER MARINE LAYER
THAN YESTERDAY WITH LOW CLOUDS STRETCHING FROM THE COAST INTO MOST
OF DOUGLAS COUNTY. THIS WILL LIKELY KEEP HIGH TEMPERATURES IN THE
MID 70S TODAY IN PLACES LIKE ROSEBURG...AND COASTAL AREAS NORTH OF
CAPE BLANCO WILL REMAIN CLOUDY ALL DAY FOR THE SECOND DAY IN A
ROW. OTHER AREAS WILL REMAIN MOSTLY SUNNY TODAY WITH HIGHS IN THE
MID 80S OVER THE EAST SIDE AREAS AND THE ROGUE VALLEY WITH
READINGS IN THE 90S OVER WESTERN SISKIYOU COUNTY.

THUNDERSTORMS ARE UNLIKELY TODAY FOR A FEW REASONS. 12Z MFR
SOUNDING SHOWS PRECIPITABLE WATER DOWN TO 0.58 INCHES...A 40
PERCENT DROP FROM YESTERDAY. ALSO...ENOUGH COOLING HAS OCCURRED IN
THE LOW LEVELS TO LIMIT INSTABILITY TODAY. SO...JUST SOME CUMULUS
ARE LIKELY OVER LAKE AND MODOC COUNTIES THIS AFTERNOON. GIVEN THAT
MARINE LAYER IS STILL INTACT ALONG THE COAST AND LIKELY DEEPENING
FURTHER...STRATUS COULD MAKE IT EVEN FURTHER INLAND TOMORROW...SO
WILL BE ANALYZING THAT TODAY. OR...THE MARINE LAYER COULD MIX OUT IF
TEMPERATURES DROP FURTHER IN THE LOW LEVELS. THE PREVIOUS
DISCUSSION BELOW DETAILS THE REST OF THE FORECAST PERIOD NICELY.

&&

.AVIATION...CLOUD BASES HAVE RISEN AS THE MARINE LAYER HAS
DEEPENED...SO THERE IS HIGH CONFIDENCE THAT MVFR CEILINGS ALONG
THE MAJORITY OF THE COASTAL TERMINALS WILL LAST FROM THIS MORNING
THROUGH AT LEAST THIS EVENING. A SMALL SECTION OF THE COAST BELOW
CAPE BLANCO MAY REMAIN CLEAR THROUGH THIS AFTERNOON. ROSEBURG WILL
LIKELY NOT CLEAR UNTIL AROUND NOON PER RECENT SATELLITE IMAGERY
AND CEILINGS ARE EXPECTED TO RETURN TONIGHT TO ROSEBURG. MFR AND LMT
WILL REMAIN CLEAR THROUGH TONIGHT WITH WEST TO NORTHWEST WINDS 10
TO 15 KNOTS THIS AFTERNOON.


&&

.PREV DISCUSSION... /ISSUED 311 AM PDT SAT JUL 31 2010/

DISCUSSION...SCATTERED CLOUDS ARE LINGERING OVER FAR NORTHERN
KLAMATH AND NORTHWEST LAKE COUNTY EARLY THIS MORNING...THE LAST
REMNANTS OF THE INSTABILITY THAT PRODUCED A FEW THUNDERSTORMS
YESTERDAY EVENING. THE INLAND AIR MASS WILL STABILIZE AND CONTINUE
TO DRY TODAY AS NOTICEABLY COOLER AIR ARRIVES WITH AN UPPER LEVEL
TROUGH. THE OTHER MAIN IMPACT OF THE TROUGH HAS BEEN TO DEEPEN THE
MARINE LAYER. LOW CLOUDS ALONG THE COAST HAVE SPREAD INTO THE
UMPQUA VALLEY. THIS NIGHTTIME INLAND SPREAD OF THE STRATUS WILL BE
A PERSISTENT OCCURRENCE OVER THE NEXT WEEK BUT IT LOOKS PROBABLE
THAT OUT OF THE NEXT WEEK...IT WILL BE DEEPEST/THE SLOWEST TO
IMPROVE TODAY.

COMPARED WITH LAST NIGHT...THE 00Z GFS AND ECMWF DO HAVE SOME
ALTERATIONS IN THE DETAILS OF THE PROGRESSION OF THE UPPER LEVEL
PATTERN OVER THE NEXT WEEK. BUT THE BIG PICTURE IS THE SAME...WITH
NO THUNDERSTORMS IN THE FORECAST. ONE OF THE CHANGES IS A PERIOD OF
ABOVE NORMAL TEMPERATURES FROM TUESDAY THROUGH THURSDAY WITH SOME
VERY WEAK INSTABILITY THAT SHOULD BE JUST ENOUGH FOR SOME
CAPPED/HIGH BASED CUMULUS OVER THE HIGHER TERRAIN. A WEAK SHORTWAVE
TROUGH SHOULD ENHANCE THE MARINE LAYER A BIT AGAIN ON FRIDAY WITH
TEMPERATURES COOLING CLOSER TO NORMAL. THEN THE NEXT TROUGH MOVING
SOUTHEAST ALONG THE WEST COAST OF CANADA IS EXPECTED TO USHER IN A
STRONGER MARINE PUSH NEXT WEEKEND.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 10 AM PDT THIS MORNING FOR ORZ027-030.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 AM PDT MONDAY FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 AM PDT MONDAY
     FOR PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 PM PDT TUESDAY FOR
     PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 PM PDT TUESDAY
     FOR PZZ376.

$$

SK

NWS MFR Office Area Forecast Discussion