Area Forecast Discussion
Issued by NWS Medford, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KMFR 012151
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
251 PM PDT SUN MAY 1 2016

.SHORT TERM...CLEAR TO PARTLY SUNNY SKIES AND WARM TEMPERATURES ARE
BEING OBSERVED ACROSS THE FORECAST AREA THIS AFTERNOON. TEMPERATURES
ARE 10 TO 15 DEGREES HIGHER THAN THEY WERE 24 HOURS AGO. NORTH BEND
HAS BEAT THE DAILY RECORD HIGH TEMPERATURE THERE BY 2 DEGREES...WITH
81 DEGREES BEING OBSERVED LAST HOUR. MEDFORD`S A WARM 81 DEGREES
TOO BUT FAR FROM THE DAILY RECORD HIGH OF 92.

ONSHORE FLOW RETURNS TO THE COAST TOMORROW...LOWERING TEMPERATURES
THERE BY MORE THAN 10 DEGREES. INLAND TEMPERATURES WILL REMAIN WELL
ABOVE NORMAL AGAIN...WITH SIMILAR READINGS TO TODAY.  MOISTURE ALOFT
INCREASES ACROSS THE AREA TOMORROW AS FLOW TURNS MORE SOUTHERLY.
INSTABILITY INCREASES TOO AND WE HAVE A SLIGHT CHANCE OF
THUNDERSTORMS FOR MOST OF THE FORECAST AREA...EXCEPT TOWARD THE
COAST AND IN FAR EAST LAKE COUNTY. A SIGNIFICANT TRIGGER IS
MISSING BUT MODELS DO SHOW SOME ENERGY MOVING IN FROM EAST TO WEST
DURING THE AFTERNOON...SO THAT MAY BE ENOUGH TO KICK OFF SOME
THUNDERSTORMS. WRF ARW AND NMM REFLECTIVITY AND SPC CALIBRATED
THUNDERSTORM OUTPUT MATCH OUR CONCEPTUAL MODEL FOR CONVECTION
TOMORROW...SO THAT PROVIDES SOME ADDITIONAL CONFIDENCE IN THE
FORECAST.

TUESDAY GETS MORE INTERESTING BECAUSE MOISTURE...INSTABILITY...AND
TRIGGER ALL BECOME MORE FAVORABLE FOR THUNDERSTORMS.
THUS...PRECIPITATION CHANCES ARE HIGHER AND THUNDERSTORM AREAL
COVERAGE IS GREATER. THE UPPER TROUGH NEARS AND SHORTWAVE ENERGY
WILL BE MOVING THROUGH THE AREA DURING THE DAY ON WEDNESDAY...AND
PRECIPITABLE WATERS INCREASE TO ABOUT 0.9 INCHES...WHICH IS IN THE
TOP 10 PERCENT FOR MOISTURE FOR EARLY MAY. THE NAM12 DOES SHOW H7
FLOW OF 20KT...SO STORMS SHOULD MOVE QUICKLY BUT OCCASIONAL
PERIODS OF HEAVY RAIN WILL BE POSSIBLE IN ANY SHOWERS OR STORMS
THAT FORM. ONE KEY TO THUNDERSTORM DEVELOPMENT WILL BE WHERE ANY
CLEAR SKIES OCCUR FOR OPTIMAL SURFACE HEATING. AT THIS POINT IT
LOOKS LIKE THE BEST AREA FOR THIS WILL BE EAST OF THE CASCADES.
FOR THIS REASON WE HAVE ADDED A CHANCE OF THUNDERSTORMS IN MOSTLY
LAKE COUNTY VS. A SLIGHT CHANCE WHICH WE PUT FOR THE REST OF THE
FORECAST AREA.

ON WEDNESDAY THE TROUGH AXIS MOVES CLOSER AND WITH CONTINUED
SOUTHERLY FLOW THIS MEANS MORE ANOTHER DAY WITH HIGH MOISTURE
CONTENT. THERE WILL BE A LOT OF CLOUD COVER AND THIS WILL LIKELY
LIMIT THE AMOUNT OF SURFACE HEATING THE OCCURS...BUT WITH PLENTY
OF FAVORABLE DYNAMICS WE HAVE MAINTAINED THUNDERSTORM CHANCES FOR
THE CASCADES EASTWARD.

.LONG TERM...THURSDAY 12Z UNTIL SATURDAY 12Z...NOT A HUGE CHANGE
OVER THE LAST 24 HOURS OF MODEL RUNS EXCEPT WE GET THE TAIL END OF
THE NAM, WHICH ISN`T THAT DIFFERENT FROM THE GFS OR ECMWF. SAME
STORY AS YESTERDAY WITH BROAD AND STRONG SYNOPTIC LIFT ACROSS OUR
CWA WITH THIS TROUGH.

THIS DEEP TROUGH WILL CONTINUE TO PULL IN MOISTURE FROM THE SOUTH
AND GIVE A CONTINUED CHANCE FOR THUNDERSTORMS DURING THE AFTERNOON
AND EVENING HOURS OVER THE EASTSIDE AND CASCADES. THERE IS STILL
SOME UNCERTAINTY FOR A DECENT FORCING MECHANISM, SO LOW LEVEL
CONVERGENCE ALONG THE SISKIYOUS AND CASCADES SEEMS THE MOST
PROBABLE.

SATURDAY AND SUNDAY...WE ARE STILL EXPECTING TO HAVE A CLOSED LOW
OVER OR WEST OF THE FOUR CORNERS AREA NEXT WEEKEND. IN THE BIG
PICTURE, THE MODELS HAVE CHANGED LITTLE SINCE YESTERDAY, AND THE
ECMWF REMAINS A WET OUTLIER OVER OUR AREA. THE UPPER LOW IS
EXPECTED TO PUSH SOME MOISTURE AND INSTABILITY OUR WAY NEXT
WEEKEND, BUT SINCE WE WILL BE ON THE NORTHWEST PERIPHERY OF THE
SYSTEM, WE CONTINUE TO LEAN TOWARD THE DRIER GFS AND CANADIAN
SOLUTIONS. THIS LEAVES US WITH A CONTINUED CHANCE TO SLIGHT CHANCE
FOR SHOWERS AND AFTERNOON/EVENING THUNDERSTORMS FROM EAST TO WEST
NEXT WEEKEND WITH ABOVE NORMAL TEMPERATURES. -WRIGHT

&&

.AVIATION...FOR THE 01/18Z TAF CYCLE...CONDITIONS WILL REMAIN VFR
AREA-WIDE THROUGH THE TAF PERIOD. SOME GUSTS UNDER 20 KTS ARE
EXPECTED TODAY AS WE EXPERIENCE DEEP MIXING INTO THE BOUNDARY
LAYER... - SMITH


&&

.MARINE...UPDATED 600 AM PDT SUN 1 MAY 2016...WINDS AND SEAS
WILL DIMINISH THROUGH THE REMAINDER OF THE EVENING AS THE THERMAL
TROUGH WEAKENS AND PUSHES NORTH. A COLD FRONT WILL MOVE THROUGH THE
WATERS TUESDAY INTO TUESDAY NIGHT...PRODUCING SOUTHERLY WINDS AS IT
PASSES. BEGINNING WEDNESDAY...THE THERMAL TROUGH RETURNS...AND WITH
HIGH PRESSURE BUILDING OFFSHORE...AN EXTENDED PERIOD OF MODERATE TO
STRONG NORTH WINDS APPEARS LIKELY THROUGH THE REST OF THE WEEK. -BPN

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ350-356-370-376.

$$

NSK/CZS/TRW


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.