Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 102214
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
314 PM PDT THU JUL 10 2014

.DISCUSSION...CONVECTION IS FIRING OFF ON THE EAST SIDE TODAY AS
THE PRELUDE TO THE MORE WIDESPREAD THUNDERSTORMS OVERNIGHT INTO
TOMORROW. AN AREA OF INSTABILITY REMAINS CENTERED OVER THE REGION
TONIGHT INTO TOMORROW MORNING AHEAD OF A STRONG SHORT WAVE THAT
LOOKS TO MOVE THROUGH IN THE MORNING. THERE IS BROAD UPPER LEVEL
DIVERGENCE OVER THE REGION AS A VERY STRONG SHORT WAVE CYCLES
THROUGH THE AREA...SPINNING OFF THE CLOSED LOW MOVING UP THE
COAST. BY 18Z BOTH THE NAM AND GFS ARE INDICATING CAPES IN EXCESS
OF 500 WITH LI`S LOWER THAN -3 OVER THE WEST SIDE...ALMOST TO THE
COAST. THE STEERING FLOW IS SOUTH TO SLIGHTLY SOUTHEAST. THIS AREA
OF INSTABILITY REMAINS OVER THE REGION WITH CAPES REMAINING HIGH
INTO THE EVENING. HOWEVER...THE SHORTWAVE THAT CYCLES THROUGH
15-21Z IS VERY STRONG AND MUCH OF THE INSTABILITY WILL BE MIXED
OUT WITH THIS FIRST SHORTWAVE WITH RESULTING INCREASED HIGH CLOUDS
BLOCKING SURFACE HEATING. THIS WILL DECREASE THE AMOUNT OF
CONVECTION LATER IN THE AFTERNOON AS THE NEXT...WEAKER...SHORT
WAVES MOVES THOUGH FROM THE SOUTH. INSTABILITY REMAINS ON THE WEST
SIDE SATURDAY BUT THERE IS NO STRONG KICKER AND THE UPVALLEY FLOW
SHOULD STABILIZE THE WEST SIDE AND HAVE KEPT ANY CHANCES OF
THUNDERSTORMS ON THE EAST SIDE. THE LATEST 18Z RUNS ARE NOW
BRINGING INSTABILITY DOWN TO THE SOUTHERN EDGE OF THE FORECAST AREA
SUNDAY...BUT THIS IS A BIG DEPARTURE FROM THE 12Z RUN WHICH HAD IT
FROM LAKE OF THE WOODS NORTH. BEING THAT THIS IS A WEAK CUTOFF LOW
SITUATION...DON`T HAVE A LOT OF CONFIDENCE EITHER WAY. THERE IS
MUCH MORE CONFIDENCE IN THE HEAT THAT IS COMING FAIR WEEK...AND AS
USUAL IT IS LOOKING TO BE POSSIBLY THE HOTTEST STRETCH OF THE
SUMMER. SVEN


&&

.AVIATION...BASED ON THE 10/18Z TAFS... EXPECT VFR TO LAST THROUGH
THE AFTERNOON, ALONG WITH GUSTY NORTH WINDS, BEFORE MVFR STRATUS
RETURNS ~03Z AT KOTH. ELSEWHERE, VFR IS EXPECTED THROUGHOUT THE TAF
PERIOD. ISOLATED THUNDERSTORMS ARE EXPECTED DEVELOP THIS AFTERNOON
AND EVENING EAST OF A LINE FROM ABOUT WINTER RIM TO NORTHERN
CALIFORNIA`S MARBLE MOUNTAINS. STORMS MAY DEVELOP OVER THE SISKIYOUS
AS WELL AND CANT RULE OUT ONE DRIFTING INTO SOUTHERN JACKSON COUNTY
LATER THIS AFTERNOON. THE DIURNAL NATURE OF THESE STORMS SHOULD
BRING AN END TO CONVECTION SHORTLY AFTER SUNSET. HOWEVER, A POTENT
SHORTWAVE IS EXPECTED TO MOVE INTO THE AREA FROM THE SOUTH
OVERNIGHT. WITH ALL OTHER INGREDIENTS IN PLACE EXPECT OVERNIGHT
CONVECTION IN NORTHER CAL...SPREADING NORTH BY THE EARLY MORNING
HOURS. DUNCAN

&&

.MARINE...UPDATED THURSDAY 10 JULY 500 AM PDT...HIGH PRESSURE
OFFSHORE AND A THERMAL TROUGH ALONG THE SOUTHERN OREGON COAST WILL
BRING MODERATE NORTH WINDS TODAY WITH STEEP TO VERY STEEP SEAS
OVER THE WATERS. HIGHEST SEAS AND STRONGEST WINDS WILL BE SOUTH OF
CAPE BLANCO. THE THERMAL TROUGH WILL WEAKEN TONIGHT THROUGH
SATURDAY RESULTING IN DECREASING WINDS AND SEAS, BUT WILL
REDEVELOP SUNDAY AND STRENGTHEN MONDAY. SPILDE

&&

.FIRE WEATHER...LATEST VISIBLE IMAGE SHOWS MOST OF THE BUILDUPS OVER
FIRE ZONES 625 AND NORTHERN 624 WITH A COUPLE OF ISOLATED
THUNDERSTORMS SHOWING UP ON RADAR. THUNDERSTORMS COULD BECOME
SCATTERED IN PARTS OF THESE AREAS LATE THIS AFTERNOON INTO EARLY
THIS EVENING BEFORE DISSIPATING AROUND SUNSET. CURRENT WATER VAPOR
IMAGE SHOWS AN UPPER LOW CENTERED NEAR 37N/128W AND THIS HAS PUT OUT
SOME LIGHTNING STRIKES DURING THE COURSE OF THE DAY WHICH SUGGEST
ELEVATED CONVECTION. THIS LOW WILL MOVE NORTHEAST INTO NOTHER CAL
AND SOUTHWEST OREGON TONIGHT.  AT THE SAME TIME, A NEGATIVELY
TILTED TROUGH SWINGS NORTHWARD ALONG THE NORCAL COAST AND SHORT WAVE
ENERGY ARRIVES FROM THE SOUTH AND EAST (SIERRA MOUNTAINS). MUCH WILL
DEPEND ON THE TIMING. MODELS ARE SHOWING MONSOONAL MOISTURE ARRIVING
INTO NORTHERN CALIFORNIA BY AROUND 12Z FRIDAY, THEN SPREADING ACROSS
SOUTHWEST OREGON FRIDAY MORNING AND AFTERNOON. MODELS SUGGEST MUCH
OF THE INSTABILITY COULD BE ELEVATED AND JET ENERGY AT 300 MB WILL
MOVE INTO THE AREA WHICH COULD RESULT IN MORE NUMEROUS STORMS.
STEERING WINDS ARE EXPECTED TO BE FROM THE SOUTH AND SOUTHEAST WHICH
IS A FAVORABLE FLOW TO GET STORMS TO SPREAD OUT OVER THE VALLEYS
WEST OF THE CASCADES. GIVEN THE DRY FUELS AND EXPECTED NUMEROUS
LIGHTNING EXPECTED, HAVE ISSUED A RED FLAG WARNING FOR NORTHERN CAL
AND MOST OF OREGON ZONES. THE EXCEPTION WILL BE THE COASTAL ZONES.
EVEN THEN COULD NOT RULE OUT ISOLATED THUNDERSTORMS FOR FIRE ZONES
615 AND 618. MODELS SUGGEST THE BULK OF THE ACTION WILL SHIFT NORTH
DURING THE DAY FRIDAY AND COULD BE OUT OF THE AREA FRIDAY AFTERNOON,
BUT AGAIN MUCH DEPENDS ON THE TIMING. ANOTHER UPPER LOW WILL MOVE
TOWARDS THE AREA SUNDAY, BUT THE MODELS SUGGEST MOST OF THE
INSTABILITY AND THUNDERSTORM POTENTIAL WILL BE FROM AROUND CRATER
LAKE NORTH. -PETRUCELLI


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 6 PM PDT FRIDAY FOR ORZ030-031.
     RED FLAG WARNING FROM MIDNIGHT TONIGHT TO 6 PM PDT FRIDAY FOR
     ORZ021-023>026.
     RED FLAG WARNING UNTIL 6 PM PDT FRIDAY FOR ORZ027>029.

CA...RED FLAG WARNING FROM MIDNIGHT TONIGHT TO 6 PM PDT FRIDAY FOR
     CAZ080>085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT THIS AFTERNOON FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT FRIDAY
     FOR PZZ350-356-370-376.

$$

SBN/SBN/SBN






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