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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 172152
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
252 PM PDT THU APR 17 2014

.DISCUSSION...THE LEADING EDGE OF THE COLD FRONT IS STILL OFFSHORE,
BUT CLOUDS AND LIGHT PRECIPITATION ARE MOVING IN AHEAD OF IT.
CURRENT VISIBLE IMAGE SHOWS SOME CUMULUS BUILDING UP IN MODOC AND
SOUTHEAST LAKE COUNTY. MODELS CONTINUE TO SHOW WEAK INSTABILITY AND
COULD NOT RULE OUT A FEW ISOLATED STORMS, BUT THERE IS A BETTER
CHANCE NOTHING HAPPENS.

THE FRONT WILL REACH THE COAST THIS EVENING, THEN PUSH INLAND
TONIGHT. SNOW LEVELS REMAIN HIGH THROUGH THIS EVENING WHEN MOST OF
THE PRECIPITATION IS EXPECTED, THEREFORE NOT EXPECTING MUCH IF ANY
ACCUMULATING SNOW. AN UPPER TROUGH SWINGS THROUGH IN THE WAKE OF THE
FRONT TONIGHT AND SHOWERS WILL CONTINUE, BUT THEY`LL TEND TO
DECREASE OVERNIGHT TONIGHT ONE THE UPPER TROUGH MOVES THROUGH. WERE
NOT EXPECTING A LOT OF QPF FROM THIS FRONT. THE HIGHEST AMOUNTS WILL
BE WEST FACING SLOPES OF THE CASCADES FROM CRATER LAKE NORTH WITH
0.10-0.20 OF AN INCH POSSIBLE AND MOST THIS WILL BE FROM NOW INTO
THIS EVENING. SNOW LEVELS WILL LOWER TO AROUND 5000 FEET BY FRIDAY
MORNING, BUT MOST OF THE PRECIPITATION WILL BE GONE BY THEN.

DRY WEATHER RETURNS FRIDAY. COULD NOT RULE OUT A FEW ISOLATED
SHOWERS ALONG THE NORTHERN CASCADES EARLY FRIDAY, BUT THAT`S IT.
TEMPERATURES FRIDAY SHOULD REBOUND AND END UP IN THE UPPER 60S TO
LOWER 70S FOR WESTSIDE VALLEYS.

THE MODELS ARE FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE NEXT
FRONT SATURDAY WHICH SHOULD BE LATE IN THE MORNING AT THE COAST,
THEN INLAND IN THE AFTERNOON. THE NAM IS STILL WEAKER COMPARED TO
THE GFS/EC AND GEM, BUT THE LATTER ARE ALSO TRENDING WEAKER COMPARED
TO PREVIOUS RUNS. SO WE`LL CONTINUE TO LEAN TOWARDS THE WEAKER NAM
SOLUTION WITH THE IDEA THAT THE FRONT WILL WEAKEN AS IT MOVES
INLAND. DRY CONDITIONS RETURN SATURDAY NIGHT WITH ANY PRECIPITATION
CONFINED TO THE NORTHWEST PART OF THE FORECAST AREA. EASTER SUNDAY
LOOKS DRY WITH DECREASING CLOUDS AND MILDER TEMPERATURES.
-PETRUCELLI

.EXTENDED DISCUSSION...FROM MONDAY MORNING ONWARD. OTHER THAN SOME
TIMING ISSUES THE ECMWF AND GFS ARE IN GOOD AGREEMENT FOR THE
EXTENDED PORTION OF THE FORECAST. MONDAY MORNING STARTS WITH A COLD
FRONT OFFSHORE POISED TO ENTER THE COASTAL WATERS. THIS FRONT COMES
ONSHORE MONDAY AFTERNOON BUT SOME SHOWERS ARE LIKELY ON THE CASCADE
CREST AND EAST SIDE WITH THE GFS INDICATING WEAK INSTABILITY ALONG
AND JUST EAST. WITH THE ANTECEDENT FLOW FROM THE SOUTH NOT SETTING
IN UNTIL THAT MORNING AM NOT ADDING AND THUNDERSTORMS IN THAT TIME
FRAME AS THERE WILL NOT BE THE USUAL DAY AHEAD SOUTHERLY FLOW
NORMALLY NEEDED TO "PRIME THE PUMP" FOR DEEP CONVECTION. THIS FIRST
FRONT COMES IN ON THE LEFT EXIT REGION OF THE JET THAT IS CURVED
AROUND FROM THE NORTHWESTERLY JET WELL OFFSHORE. THE CORE OF THE JET
IS AROUND 140W. SHOWERS REMAIN IN COOL ONSHORE FLOW AS THE CORE OF
THE 120KT JET APPROACHES THE WEST COAST TUESDAY..BRINGING
ANOTHER..MORE POTENT FRONT INTO THE REGION TUESDAY. THE FLOW THEN
BECOMES ZONAL..AND WITH TIMING DIFFERENCES IN A PATTERN THAT IS
ALREADY DIFFICULT TO TIME FRONTS IN THE EXTENDED...HAVE BROAD
BRUSHED POPS THROUGH THE REMAINDER OF THE EXTENDED.

&&

.AVIATION...BASED ON 17/18Z TAF CYCLE...FROM THE CASCADES WEST...
MVFR AND LOCAL IFR CIGS/VSBYS IN RAIN AT THE COAST WILL CONTINUE TO
SPREAD INLAND TO THE CASCADES DURING THROUGH THE AFTERNOON. HIGHER
TERRAIN OBSCURATIONS WILL SPREAD TO THE CASCADES INTO THIS EVENING
WITH ONLY SLIGHT IMPROVEMENT AS PRECIPITATION BECOMES MORE SHOWERY
AND ENDS OVERNIGHT. EAST OF THE CASCADES...LOCAL MVFR CIGS WILL
DEVELOP THIS AFTERNOON WITH AREAS OF HIGHER TERRAIN BECOMING
OBSCURED IN SHOWERS. AN ISOLATED THUNDERSTORM CANNOT BE RULED OUT
OVER THE FAR EAST SIDE IN PORTIONS OF MODOC AND SOUTHERN LAKE
COUNTIES. LOWER CONDITIONS WILL IMPROVE OVERNIGHT.
SVEN


&&

.MARINE...A COLD FRONT WILL MOVE THROUGH THE WATERS TODAY THEN
HIGH PRESSURE WILL BRIEFLY BUILD FRIDAY. ANOTHER STRONGER FRONT
WILL MOVE THROUGH SATURDAY THEN HEAVY LONG PERIOD WESTERLY SWELL
WILL DEVELOP SATURDAY NIGHT INTO SUNDAY. THE SWELL...WHICH WILL BE
THE HIGHEST IMPACT EVENT OVER THE NEXT WEEK...WILL BUILD RAPIDLY
TO 16 TO 18 FEET SATURDAY NIGHT WITH A DOMINANT PERIOD OF 16
SECONDS. IT WILL SUPPORT HIGH SURF ALONG THE COAST ALONG WITH
SNEAKER WAVES. IT MAY ALSO RELOCATE CRAB GEAR. SEAS WILL SLOWLY
SUBSIDE SUNDAY.


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 11 PM SATURDAY TO 11 AM PDT SUNDAY FOR
     ORZ021-022.

CA...NONE.

PACIFIC COASTAL WATERS...HIGH SURF ADVISORY FROM 11 PM SATURDAY TO 11 AM PDT
     SUNDAY FOR PZZ310.
     HAZARDOUS SEAS WATCH FROM SATURDAY EVENING THROUGH SUNDAY
     MORNING FOR PZZ350-356-370-376.

$$

NWS MFR Office Area Forecast Discussion