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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 161020
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
320 AM PDT TUE SEP 16 2014

.DISCUSSION...LATEST SATELLITE IMAGERY SHOWS A BAND OF HIGH AND MID LEVEL CLOUDS
LIFTING TO THE NORTH AND OUT OF THE AREA. THESE CLOUDS ARE THE LAST
VISUAL CUE TO THE SHORT WAVE TROUGH THAT TRACKED OVER THE REGION
LAST NIGHT. THE COMBINED ENERGY OF THIS LITTLE TROUGH AND THE MUCH
BIGGER ONE BEHIND IT, HAS MANAGED TO BUMP TO THE EAST THE LARGE
UPPER LEVEL RIDGE THAT HAD BEEN IN PLACE OVER THE WEST COAST FOR
ALMOST A WEEK. THE RESULT WILL BE COOLER TEMPERATURES TODAY, WITH
DAYTIME HIGHS MUCH CLOSER, BUT STILL SLIGHTLY ABOVE, NORMAL FOR THIS
TIME OF YEAR. MODELS ARE IN GOOD AGREEMENT CONCERNING THE PATTERN
OVER THE NEXT WEEK, ALTHOUGH THERE ARE SOME DIFFERENCES IN TIMING IN
THE LONG TERM.

WITH THE RIDGE MOVING TO THE EAST AND A VIGOROUS TROUGH APPROACHING
FROM THE WEST, THE MAIN BELT OF WESTERLIES WILL LIE DIRECTLY
OVERHEAD TODAY. AS MENTIONED PREVIOUSLY, THIS WILL LEAD TO COOLER
AND MORE SEASONABLE TEMPS, BUT IT WILL ALSO BRING GUSTY WINDS INTO
THE REGION, PARTICULARLY ALONG AND EAST OF THE CASCADES, AND IN THE
SHASTA VALLEY. FIRE INTERESTS WILL NEED TO PAY CLOSE ATTENTION TO
THIS SCENARIO, AS AFTERNOON MIXING WILL LIKELY BRING THE STRONGER
WINDS ALOFT DOWN TO THE SURFACE, THEREBY REACHING SPEEDS THAT COULD
REACH CRITICAL VALUES, ESPECIALLY IN REGARDS TO ONGOING FIRES.
OTHERWISE, EXPECT CLOUDS TO STEADILY INCREASE THROUGH THE LATTER
HALF OF THE DAY AS THE TROUGH AND ASSOCIATED FRONT APPROACH THE
REGION.

THE UPCOMING SYSTEM ON WEDNESDAY WILL BE THE FIRST OF ITS KIND THIS
SEASON, AND MODEL SOLUTIONS ARE TRENDING WETTER WITH THE PAST
SEVERAL RUNS. HAVE THEREFORE KEPT THE CHANCES FOR PRECIPITATION
WIDESPREAD, WITH AREAS ALONG THE COAST LIKELY TO SEE A GOOD WETTING
RAIN THROUGH THURSDAY. BUT A MAJOR CONSIDERATION SHOULD BE GIVEN TO
THE MOISTURE THIS SYSTEM WILL BRING. COMPARED TO THE PAST SEVERAL
MONTHS, THE MOISTURE FLOW IS IMPRESSIVE, HOWEVER, IN TERMS OF WHAT
WE WOULD EXPECT TO SEE DURING THE WET SEASON, IT IS NOT SO
IMPRESSIVE. ALSO, THIS IS THE FIRST SUCH SYSTEM OF THE SEASON, AND
THERE IS A LOT OF DRY AIR AND TERRAIN TO CONTEND WITH. FOR THESE
REASONS, HAVE KEPT PRECIPITATION AMOUNTS ON THE LOW SIDE. ALSO, WHEN
THE TROUGH AXIS SWINGS OVERHEAD THURSDAY AFTERNOON, THE COLDER AIR
ALOFT IS LIKELY TO RESULT IN SOME DEVELOPING INSTABILITY ALONG AND
EAST OF THE CASCADES. HAVE KEPT THE SLIGHT CHANCE OF THUNDER IN
THESE AREAS FROM THE PREVIOUS FORECAST.

THE TROUGH WILL EXIT TO THE EAST THURSDAY INTO FRIDAY, BUT THE
SOUTHERN PORTION OF THE TROUGH IS EXPECTED TO SEPARATE FROM THE MAIN
WAVE, CUT OFF, AND TAKE UP RESIDENCE OVER SOUTHERN CALIFORNIA, WHERE
IT WILL BIDE ITS TIME UNTIL EARLY NEXT WEEK. MEANWHILE, RIDGING WILL
RETURN TO SOUTHERN OREGON AND NORTHERN CALIFORNIA, ALONG WITH THE THERMAL
TROUGH, WHICH NOT ONLY WILL BRING WARMER TEMPERATURES BACK TO THE
AREA BEGINNING FRIDAY, BUT WILL ALSO BRING A RETURN OF THE OFFSHORE
WINDS THAT HAVE BEEN RATHER COMMON OVER THE PAST SEVERAL WEEKS.

BY MONDAY, WE WILL BE LOOKING AT ANOTHER POSSIBLE TROUGH APPROACHING
FROM THE PACIFIC, BUT MODELS HAVE BEEN INCONSISTENT IN TIMING AND
STRENGTH, SO THERE REMAINS A GOOD DEAL OF UNCERTAINTY REGARDING ITS
EVOLUTION AND PROGRESSION. GIVEN THIS LATEST MODEL CYCLE, IT APPEARS
THAT THINGS MAY PROGRESS IN A SIMILAR MATTER TO THIS WEEK, WITH THE
CUT OFF LOW OVER SOUTHERN CALIFORNIA MOVING BACK NORTH AHEAD OF THE
MAIN TROUGH, THEN THE REST OF THE ACTION FOLLOWING 24 TO 36 HOURS
LATER. GIVEN THE LOW CONFIDENCE, HAVE ONLY INTRODUCED A SLIGHT CHANCE
OF PRECIPITATION TO THE COAST BY MIDWEEK, BUT MAINTAINED ABOVE
NORMAL TEMPERATURES THROUGHOUT THE REMAINDER OF THE FORECAST TERM.
OVERALL, IT APPEARS THAT THERE WILL BE ONE, PERHAPS EVEN TWO, GOOD
CHANCES FOR MUCH NEEDED RAIN OVER THE NEXT WEEK.  -BPN


&&

.AVIATION...BASED ON THE 16/00Z TAF CYCLE...
AT THE COAST- PERSISTENT STRATUS WITH MVFR/IFR CEILINGS VIS WILL
CONTINUE THROUGH THE EARLY MORNING. CEILINGS SHOULD LIFT FULLY TO
MVFR LATER THIS MORNING...LIKELY BECOMING VFR BY EARLY AFTERNOON.
AREAS OF MOSTLY VFR SMOKE WILL AFFECT MUCH OF WESTERN SISKIYOU
COUNTY AND NORTH INTO JACKSON AND JOSEPHINE COUNTIES. SMOKE IS
LIKELY TO BE MORE SUBSTANTIAL- IN THE MVFR TO IFR RANGE- NEAR THE
FIRE POINT SOURCES NEAR HAPPY CAMP AND ONION MOUNTAIN. ELSEWHERE,
VFR CONDITIONS ARE EXPECTED TO CONTINUE. OF NOTE...ANOTHER WINDY
DAY ON TUESDAY IS EXPECTED MAINLY OVER THE HIGH TERRAIN AND FROM
THE CASCADES EASTWARD DUE  TO MODERATE TO STRONG SOUTHWEST FLOW.
-SK/BPN


&&

.MARINE...UPDATED 300 AM PDT TUE 16 SEP 2014...
A LOW WILL APPROACH THE WATERS FROM THE SOUTHWEST TODAY AND
TOMORROW. SOUTH WINDS WILL CONTINUE THROUGH TODAY...AND AFTER A
SLIGHT DECREASE IN WIND SPEEDS WEDNESDAY MORNING...SOUTH WINDS
WILL PEAK AGAIN WEDNESDAY AFTERNOON WITH THE PASSAGE OF THE LOW.
SEAS WILL GRADUALLY INCREASE THIS AFTERNOON THROUGH WEDNESDAY AND
THEN REMAIN AROUND 7 FEET WEDNESDAY INTO WEDNESDAY NIGHT. WINDS
AND SEAS WILL LOWER THURSDAY AS HIGH PRESSURE BUILDS OFFSHORE.
NORTHERLY WINDS MAY RISE TO SMALL CRAFT ADVISORY LEVELS FRIDAY
AFTERNOON AND EVENING WITH STEEP SEAS POSSIBLE AS WELL. -SK/BTL/BPN


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...
CA...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
     EVENING FOR CAZ284-285.

PACIFIC COASTAL WATERS...NONE.

$$

BPN/SK/BTL

NWS MFR Office Area Forecast Discussion