FXUS66 KMFR 231557
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
857 AM PDT WED MAY 23 2012

.DISCUSSION...
NO UPDATE WILL BE ISSUED THIS MORNING AS THE CURRENT FORECASTS
LOOK WELL ON TRACK. PLEASE REFER TO THE PREVIOUS DISCUSSION,
BELOW, FOR FURTHER DETAILS.

&&

.AVIATION...

BASED ON THE 23/12Z TAF CYCLE.

PLEASE NOTE...MEASURED OBSERVATIONS AT NORTH BEND WILL NOT BE
AVAILABLE UNTIL THURSDAY MAY 24TH. MANUAL OBSERVATIONS WILL BE
TAKEN UNTIL THEN...BUT THEY WILL BE ESTIMATES AND OBSERVATIONS WILL
NOT BE AVAILABLE FROM 9 PM PDT UNTIL 7 AM PDT. TERMINAL FORECAST
FOR KOTH WILL NOT BE AMENDED TONIGHT AND THE 12Z FORECAST FOR KOTH
WILL NOT BE ISSUED. THE FORECAST WILL START AROUND 0800 PDT AFTER
MANUAL OBSERVATIONS HAVE BEEN RECEIVED.

ALONG THE COAST...COAST RANGE...AND IN THE UMPQUA BASIN AREAS OF
MVFR CEILINGS AND ISOLATED IFR CEILINGS WITH ISOLATED MVFR
VISIBILITIES AND THE HIGHER TERRAIN OBSCURED THROUGH AROUND 18Z
THIS MORNING. THERE WILL BE SOME IMPROVEMENT FOR THE REST OF
TODAY BUT THERE WILL BE PERSISTENT AREAS OF MVFR CEILINGS. MVFR
CEILINGS AND SHOWERS WILL BECOME WIDESPREAD AGAIN AT THE COAST
THIS EVENING.

OVER THE REMAINDER OF THE WEST SIDE...LOCAL MVFR CIGS WITH HIGHER
TERRAIN OBSCURED WILL PERSIST THROUGH EARLY MORNING...THEN IMPROVING
TO VFR. EAST OF THE CASCADES...CONDITIONS WILL REMAIN VFR THROUGH
WEDNESDAY...BUT HIGHER TERRAIN WILL BE LOCALLY OBSCURED. GUSTY
WESTERLY WINDS WILL DEVELOP AGAIN WEDNESDAY AFTERNOON. /SVEN

&&

.PREV DISCUSSION... /ISSUED 228 AM PDT WED MAY 23 2012/

DISCUSSION...NORTHWEST FLOW AND EMBEDDED SHORTWAVE TROUGHS ARE
MAINTAINING CLOUDS FROM THE CASCADES WESTWARD WITH PARTLY CLOUDY
SKIES EAST OF THE CASCADES AND OVER NORTHERN CALIFORNIA. RECENT
RAINFALL HAS BEEN SPARSE AND LIGHT...FOCUSED OVER
DOUGLAS...COOS...AND CURRY COUNTIES. LACK OF SIGNIFICANT DYNAMICS OR
INSTABILITY TODAY WILL PROVIDE LITTLE IN THE WAY OF PRECIPITATION
AND WILL AGAIN BE CONFINED MAINLY TO THE AFOREMENTIONED COUNTIES.
HIGH TEMPERATURES TODAY WILL BE GENERALLY SIMILAR TO MONDAY...WITH
50S ON THE EAST SIDE AND 60S ON THE WEST SIDE. LOWS THIS MORNING
WARRANT FROST ADVISORIES NEAR KLAMATH FALLS...AND COLD MORNING
TEMPERATURES WILL CONTINUE THE NEXT SEVERAL NIGHTS. ABUNDANT CLOUDS
WILL PREVENT MOST PLACES FROM DROPPING INTO THE 20S.

ENERGY ARRIVES IN THE FORM OF A POTENT AND ANOMALOUSLY COLD UPPER
LOW DRIVING SOUTHEAST FROM THE GULF OF ALASKA. THIS WILL INCREASE
COVERAGE AND INTENSITY OF PRECIPITATION ACROSS THE FORECAST AREA.
SOME SHOWERS WILL LIKELY BE HEAVY. THE SUITE OF GUIDANCE SUGGESTS
THUNDERSTORMS ARE POSSIBLE THURSDAY AFTERNOON FROM NORTHERN
DOUGLAS COUNTY TO MOST AREAS EAST OF THE CASCADES. LIFTED INDICES
ARE GENERALLY BELOW ZERO WITH LITTLE TO NIL CONVECTIVE INHIBITION
FOR THOSE LOCATIONS. SOME THUNDERSTORMS WILL LIKELY DROP SMALL HAIL.
THE LIMITING FACTOR TO ANY THUNDERSTORM DEVELOPMENT WILL LIKELY BE
LACK OF SURFACE HEATING.

THE UPPER LOW CENTER TRAVERSES SOUTHERN OREGON THURSDAY NIGHT...AND
PLENTY OF MOISTURE AND INSTABILITY WILL MAINTAIN SHOWERS ON FRIDAY
WITH THE POTENTIAL OF THUNDERSTORMS. SUBSIDENCE WEST OF THE LOW WILL
DIMINISH PRECIPITATION WEST OF THE CASCADES...WHILE VERY DRY AREAS
EAST OF THE CASCADES MAY SEE SOME BENEFICIAL PRECIPITATION...SOME OF
WHICH WILL BE SNOW. FOLKS HEADING INTO THE MOUNTAINS FRIDAY
MORNING...GETTING AN EARLY START ON THE HOLIDAY WEEKEND...WILL BE
MET WITH COLD AND BREEZY CONDITIONS AND AN INCH OR MORE OF SNOW AT
ELEVATIONS ABOVE 5000 FEET.

THE CHANCE OF SHOWERS LINGERS ON SATURDAY...ESPECIALLY IN THE HIGHER
TERRAIN...BUT A NOTICEABLE WARM UP IS EXPECTED. SUNDAY SHOULD BE
MOSTLY DRY WITH SEASONABLE TEMPERATURES UNDER SHORTWAVE RIDGING.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FROST ADVISORY FROM 2 AM TO 8 AM PDT THURSDAY FOR ORZ029.

CA...FROST ADVISORY FROM 2 AM TO 8 AM PDT THURSDAY FOR CAZ084.

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THIS
MORNING FOR PZZ350-356-370-376.

$$

BTL/SK

Aviation Portion of Forecast Discussion