Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 310333
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
833 PM PDT SAT AUG 30 2014

.DISCUSSION...AN EVENING UPDATE TO THE FORECAST IS NOT NEEDED.
THE MOST NOTABLE ASPECT OF OUR CURRENT WEATHER IS THE THICK SMOKE
OVER WESTERN AND CENTRAL SISKIYOU COUNTY DUE TO THE WILDFIRES OF
THE HAPPY CAMP COMPLEX. THE FORECAST FOR SMOKE MOVEMENT LOOKS IN
LINE WITH THE LATEST MODEL DATA WITH TODAYS WESTERLY STEERING
WINDS POISED TO VEER TO THE NORTHWEST ON SUNDAY THEN WEAKEN ON
MONDAY. THIS WILL BRING SOME IMPROVEMENT IN VISIBILITY DURING THE
REMAINDER OF THE HOLIDAY WEEKEND FOR THE NORTHEAST PORTION OF
SISKIYOU COUNTY AND MODOC COUNTY. BUT, AN INCREASING SOUTHWEST
FLOW ON TUESDAY WILL LIKELY SEND SMOKE ACROSS NORTHERN SISKIYOU
COUNTY INTO THE KLAMATH BASIN.

THERE WAS A THUNDERSTORM THAT DEVELOPED OVER NORTHEAST LAKE COUNTY
AROUND 4 PM THIS AFTERNOON AND SENT OUT A FEW LIGHTNING STRIKES.
BUT, WITH SHORTWAVE RIDGING, DRIER AIR ALOFT (ABOVE AROUND 8000 FT
MSL) HAS BEGUN TO FILTER INTO SOUTHERN OREGON AND NORTHERN
CALIFORNIA WITH A DECREASE OF CLOUDS. MEANTIME, LOWER LEVEL
MOISTURE AMOUNTS WILL REMAIN ABOVE NORMAL INTO SUNDAY MORNING WITH
STRATUS EXPECTED TO RETURN TO THE COAST NORTH OF CAPE BLANCO LATER
THIS EVENING AND THEN SPREAD INTO THE UMPQUA VALLEY LATE TONIGHT.
THE LOW CLOUDS ARE EXPECTED TO DISSIPATE DURING THE MORNING.

HIGH TEMPERATURES ON SUNDAY WILL SIMILAR TO THOSE FROM TODAY, BUT
THE BREEZY TO WINDY WEST TO NORTHWEST CONDITIONS OF THIS AFTERNOON
AND EVENING WILL BE NOTICEABLY WEAKER.

THE WEATHER NEXT WEEK WILL BE CHARACTERIZED BY CLEAR SKIES AND
NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES. THERE WILL BE A
THERMAL TROUGH OVER NORTHERN CALIFORNIA WITH OFFSHORE/EASTERLY
NIGHT-TIME WINDS IN THE AREA WEST OF THE CASCADES WHILE THE BROAD
MOISTURE-STARVED SOUTHERN PORTION OF AN UPPER LEVEL TROUGH
PERSISTS OVER THE AREA.

&&

.AVIATION...BASED ON THE 31/00Z TAF CYCLE...ONSHORE FLOW WILL
PERSIST TONIGHT RESULTING MVFR AND OCCASIONAL IFR CIGS DEVELOPING AT
THE COAST...MAINLY NORTH OF CAPE BLANCO. THE MARINE LAYER IS
EXPECTED TO BECOME DEEP ENOUGH TO MOVE INTO THE UMPQUA BASIN
TOWARDS 12Z RESULTING IN MVFR CIGS. ELSEWHERE VFR CONDITIONS WILL
CONTINUE FOR THE NEXT 24 HOURS. THE EXCEPTION WILL BE NEAR THE
LARGE FIRES IN WESTERN SISKIYOU COUNTY WHERE VISIBILITIES HAVE
BEEN IFR IN PLACES. THE NORTHWEST TO WEST UPPER LEVEL WINDS COULD
PUSH THE SMOKE INTO EASTERN SISKIYOU AND MODOC COUNTIES CAUSING
OCCASIONAL REDUCTION IN VISIBILITIES. -PETRUCELLI

&&

.MARINE...UPDATED 230 PM PDT SAT 30 AUG 2014...WINDS WILL REMAIN
RELATIVELY LIGHT THROUGH THE WEEKEND. THE WAVE WATCH AND SWAN OUTPUT
APPEAR TO BE TOO HIGH WITH THE SWELL HEIGHT COMPARED TO WHAT`S BEING
OBSERVED AND HAVE ADJUSTED THOSE DOWN FOR TONIGHT AND SUNDAY. THE
MODELS REMAIN IN FAIRLY GOOD AGREEMENT SHOWING A THERMAL TROUGH
DEVELOPING MONDAY AFTERNOON AND LIKELY PERSISTING INTO AT LEAST THE
MIDDLE OF NEXT WEEK. THIS WILL BRING SMALL CRAFT FOR WINDS FOR THE
SOUTHERN WATERS, POSSIBLY GALES SOUTH OF GOLD BEACH WITH STEEP WIND
DRIVEN SEAS.

&&

.PREV DISCUSSION... /ISSUED 242 PM PDT SAT AUG 30 2014/

DISCUSSION...SUBSTANTIAL SMOKE AND SUBSEQUENT FUMIGATION IS
OCCURRING FROM THE WILDFIRES BURNING IN SISKIYOU COUNTY. A
VISIBILITY OF 1 MILE OR LESS TYPICALLY RELATES TO VERY UNHEALTHY
AIR QUALITY. THE MT. SHASTA CITY OBSERVATION HAD DROPPED TO 3/4
MILE AT 1 PM. THE SISKIYOU AIRPORT IN MONTAGUE IS DOWN TO 4 MILES
VISIBILITY WHICH IS UNHEALTHY FOR SENSITIVE GROUPS. THE AREAS MOST
IMPACTED ARE THE WESTERN SISKIYOU MOUNTAINS...SCOTT AND SHASTA
VALLEYS...AND THE I-5 CORRIDOR DOWN TO DUNSMUIR.

THE SMOKE IS EXPECTED TO WORSEN NEAR THE FIRES AS THE ATMOSPHERE
STABILIZES OVERNIGHT. THE SMOKE IS EXPECTED TO BLOW TOWARD THE
SOUTHEAST ON SUNDAY AND THEN MORE TO THE SOUTH ON MONDAY. WINDS
MAY BEGIN TO BACK ON TUESDAY AHEAD OF AN APPROACHING TROUGH
RESULTING IN THE SMOKE BLOWING TOWARD THE EAST AND NORTHEAST.

ONE OF OUR METEOROLOGISTS BASED IN ETNA TOOK A TEMPERATURE READING OF
ONLY 71 DEGREES AT 2 PM WHILE IT WAS 81 IN MEDFORD. THE SMOKE WILL
KEEP HIGH TEMPERATURES DOWN AT LEAST 5 DEGREES COMPARED TO SMOKE-
FREE AREAS SO HAVE LOWERED HIGH TEMPERATURES AROUND THE SCOTT
VALLEY FOR THE NEXT COUPLE OF DAYS.

THE BIG WEATHER FEATURES IN THE FORECAST HAVE NOT CHANGED. THE
MARINE LAYER AND ASSOCIATED CLOUDS AND COOLING WILL EXPAND INTO
SUNDAY MORNING BUT THEN RETREAT ON MONDAY AS A MORE OFFSHORE FLOW
PATTERN DEVELOPS. TEMPERATURES WILL WARM INLAND MONDAY AND
TUESDAY AS UPPER RIDGING AND A MORE OFFSHORE LOW LEVEL FLOW
PERSISTS.

AN DRY UPPER TROUGH WILL THEN LINGER ACROSS THE REGION WEDNESDAY
INTO NEXT WEEKEND. A DRY FRONT WILL ADVANCE TO AROUND THE
CALIFORNIA-OREGON BORDER BY EARLY WEDNESDAY. COOLER SURFACE HIGH
PRESSURE WILL BUILD ACROSS NORTHERN AREAS OF THE PACIFIC NORTHWEST
WITH A STRONGER OFFSHORE FLOW POSSIBLE THURSDAY. DESPITE THE UPPER
TROUGH IT DOES NOT LOOK LIKE THUNDERSTORMS WILL DEVELOP AS THE
AIRMASS IS DRY...SLIGHTLY STABLE...AND SOLAR HEATING IS DIMINISHING
IN SEPTEMBER. SANDLER


FIRE WEATHER...AFTER A COOLER DAY WITH SOMEWHAT HIGHER HUMIDITIES,
A BRIEF PERIOD OF WARMER AND DRIER CONDITIONS WILL RETURN
LATE THIS WEEKEND INTO EARLY NEXT WEEK. THERE IS AN ONGOING CONCERN
THAT THE SUBSIDENCE INVERSION WILL DESCEND TO THE LEVEL OF SOME OF
THE RIDGELINES WITHIN NORTHERN CALIFORNIA AND ALONG THE CASCADES
TONIGHT AND AGAIN SUNDAY NIGHT. SHOULD THIS OCCUR, IT WILL RESULT IN
SLIGHTLY WARMER, VERY DRY AIR SETTLING IN OVERNIGHT, ACCOMPANIED BY
A SHIFT IN THE WIND. THIS COULD LEAD TO AN INCREASE IN NOCTURNAL
FIRE ACTIVITY. THERE IS A LOT OF UNCERTAINTY REGARDING THE EXACT
ELEVATION THIS COULD OCCUR, BUT ANY SITES ABOVE 4000 FT IN NORTHERN
CALIFORNIA, OR ROUGHLY 5000 FT IN THE OREGON CASCADES COULD BE
AFFECTED. THIS SAME SCENARIO COULD ALSO RETURN LATER IN THE WEEK.
THEREFORE, HAVE LOWERED THE FORECAST HUMIDITIES NEARLY ACROSS THE
BOARD FOR THE NEXT WEEK.

ANOTHER DRY COLD FRONT IS EXPECTED MIDWEEK, ONCE AGAIN PROVIDING
GUSTY WINDS AND SOME TEMPERATURE AND HUMIDITY RELIEF. HOWEVER, THE
THERMAL TROUGH IS ALSO LIKELY TO RETURN THIS WEEK, AND IF MODEL
SOLUTIONS ARE ANY INDICATION, IT WOULD RESULT IN RATHER SIGNIFICANT
OFFSHORE FLOW. WE CAN THEREFORE EXPECT OVERNIGHT RECOVERIES TO
SUFFER, ESPECIALLY ALONG RIDGELINES AND HIGHER TERRAIN.

THERE IS NO INDICATION OF ANYTHING MORE THAN A VERY SLIGHT CHANCE OF
PRECIPITATION NORTH OF THE UMPQUA DIVIDE FOR AT LEAST THE NEXT WEEK.
-BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

DW/MAP






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