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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 150541
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
141 AM EDT SAT JUN 15 2013

.SYNOPSIS...
HIGH PRESSURE ACROSS OUR REGION WILL SHIFT EAST ON SATURDAY AS
WEAK LOW PRESSURE APPROACHES FROM THE WEST. THE LOW WILL PASS
NORTH OF OUR AREA SATURDAY NIGHT WHICH WILL DRAG A CONVERGENT
BOUNDARY ACROSS THE AREA. THIS BOUNDARY WILL BE THE FOCUS FOR
SHOWER AND THUNDERSTORM ACTIVITY SATURDAY NIGHT THROUGH SUNDAY
NIGHT.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
NORTHWESTERLY FLOW CONTINUES ALOFT WITH MID LEVEL RIDGING OVER THE
NATIONS MID SECTION AND A TROUGH OFF THE EASTERN SEABOARD. SURFACE
HIGH PRESSURE BETWEEN THESE TWO FEATURES ACROSS THE OHIO VALLEY
WILL KEEP US CLEAR TONIGHT WITH THE EXCEPTION OF SOME PASSING HIGH
CLOUDS IN THE NORTHWESTERLY FLOW. TEMPERATURES TONIGHT WILL DROP
OFF INTO THE MID AND UPPER 50S ACROSS MOST OF OUR ZONES BEFORE
DAYBREAK...WITH A FEW TYPICALLY COOLER LOCATIONS DROPPING TO
AROUND 50.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/...
MID LEVEL RIDGING WILL BEGIN TO BUILD EASTWARD ACROSS OUR AREA AND
FLATTEN OUT ON SATURDAY AS THE SURFACE RIDGE SLIDES EAST OF OUR
REGION. THIS WILL RESULT IN LOW LEVEL RETURN FLOW AND ZONAL FLOW
ALOFT. SURFACE DEWPOINTS WILL INCREASE DURING THE DAY ON SATURDAY
BUT LACK OF ANY FORCING WILL RESULT IN JUST SCATTERED CU AND PASSING
CIRRUS DURING THE DAY. SOME DEBRIS AC ASSOCIATED WITH CONVECTION
TO OUR WEST MAY ALSO SPREAD ACROSS THE AREA DURING THE
AFTERNOON. WITH THICKNESSES INCREASING BY A FEW DECAMETERS ON
SATURDAY...MAXIMUM TEMPERATURES WILL LIKELY END UP A COUPLE OF
DEGREES WARMER THAN FRIDAYS VALUES. THIS WOULD RESULT IN HIGH
TEMPERATURES MAINLY IN THE LOWER 80S WITH A FEW SPOTS ONLY
REACHING THE UPPER 70S.

WEAK LOW PRESSURE EXITING EAST FROM THE CENTRAL PLAINS ON SATURDAY
WILL CROSS THE MIDWESTERN STATES SATURDAY NIGHT. INCREASING
INSTABILITY TO OUR WEST WITH ADVECTED GULF MOISTURE IN PLACE WILL
COMBINE WITH THE FORCING ASSOCIATED WITH THE LOW AND A SUBTLE
COLD FRONT EXTENDING SOUTH OF THE LOW. THIS WILL TRIGGER
CONVECTION OFF TO OUR EAST ON SATURDAY. THIS CONVECTION WILL MOVE
EASTWARD IN THE MEAN ZONAL FLOW AND MAY BE POISED TO ENTER OUR
AREA SATURDAY EVENING. CURRENT THINKING IS THAT THIS ACTIVITY WILL
BE WEAKENING AS IT REACHES OUR NORTHWESTERN ZONES LATE SATURDAY
EVENING. THE LOW WILL PASS TO OUR NORTH OVERNIGHT SATURDAY NIGHT.
AS THIS OCCURS...THE WEAK AFOREMENTIONED FRONTAL BOUNDARY WILL
CROSS INTO OUR AREA. WEAK ELEVATED INSTABILITY AND INCREASING LOW
LEVEL JET OVERNIGHT MAY TRIGGER CONVECTION IN THE VICINITY OF THIS
BOUNDARY AT SOME POINT SATURDAY NIGHT. FOR THIS TIME PERIOD
FAVORED A COMBINATION OF THE 12Z CMC REGIONAL AND ARW FOR THIS
CONVECTION...WHICH WOULD INCREASE POPS TO THE NORTHWESTERN ZONES
SATURDAY EVENING...FOLLOWED BY INCREASING CHANCES FOR POPS EARLY
SUNDAY MORNING ACROSS OUR CENTRAL AND SOUTHERN ZONES.

THE BOUNDARY WILL STALL OUT ACROSS OUR SOUTH DURING THE DAY ON
SUNDAY AS THE WEAK SURFACE LOW EXITS THE REGION. THIS BOUNDARY
WILL SERVE AS THE FORCING MECHANISM FOR ONGOING SHOWERS AND
THUNDERSTORMS INTO SUNDAY AFTERNOON WITH DAYTIME HEATING AND
SOUTHWESTERLY LOW LEVEL FLOW ADVECTING IN ADDITIONAL LOW LEVEL
INSTABILITY...POSSIBLY UP TO 2500 J/KG ACROSS THE SOUTHERN ZONES.
DURING THE SUNDAY AFTERNOON TIME FRAME IF SUFFICIENT INSTABILITY
DOES OCCUR...0-6 KM BULK SHEAR FORECAST TO BE AROUND 30-35 KTS
COULD HELP ORGANIZE STORMS TO MULTI-CELLULAR. THESE STORMS SHOULD
THEY ORGANIZE...COULD PRODUCE LOCALLY HEAVY RAIN...WITH PWATS
NEARING 1.75 INCHES...AND POSSIBLY STRONG DOWNBURST WINDS AND
HAIL. THE POTENTIAL FOR ANY SEVERE WEATHER DURING THE SUNDAY
AFTERNOON AND EVENING WILL BE HIGHLY DEPENDENT ON ANY PREVIOUS
CONVECTION SUNDAY MORNING...WHICH COULD LIMIT THE STRENGTH OF
STORMS DURING THE AFTERNOON. WITH THIS UNCERTAINTY IN MIND
WILL HIGHLIGHT THIS POTENTIAL ACROSS OUR SOUTHERN ZONES IN THE HWO
FOR SEVERE WEATHER ACROSS WITH SOME LOWER CONFIDENCE ATTM.

CONVECTION THAT DOES OCCUR SUNDAY AFTERNOON OR EVENING WILL SLIDE
EAST TO SOUTHEAST OF OUR AREA OVERNIGHT SUNDAY NIGHT...WITH
DECREASING POPS FROM NORTHWEST TO SOUTHEAST EXPECTED DURING THAT
TIME.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
HAVE USED A BLEND OF NCEP/WPC GUIDANCE...14.00Z ECWMF AND 14.12Z CMC
FOR THE IMMEDIATE AND LONGER TERM FORECAST. THE OPERATIONAL 14.12Z
GFS IS SUFFERING SUBSTANTIALLY FROM CONVECTIVE FEEDBACK AND HAVE
DISCOUNTED IT WHILE THE NAM SEEMS TO BE OVERLY ASSERTIVE WITH PCPN
CHANCES ON MONDAY.

IT APPEARS THAT OUR REGION WILL BE BETWEEN TWO SYSTEMS MONDAY
MORNING. A BOUNDARY WILL BE LOCATED NEAR OR SOUTH OF THE OHIO RIVER
WHILE A COLD FRONT WILL BE APPROACHING FROM THE NORTHWEST. CMC AND
ECMWF HAVE BEEN INDICATING THAT OVERALL MOISTURE WILL NOT BE DEEP
OUT AHEAD OF THE APPROACHING COLD FRONT MONDAY AFTERNOON AND THAT
PERHAPS WE MAY STAY DRY FOR THE MOST PART. IT MAY NOT BE UNTIL LATE
MONDAY AFTERNOON AND NIGHT WHEN THE FRONT PUSHES IN FROM THE
NORTHWEST THAT CHANCES OF SHOWERS/STORMS INCREASE. EVEN SO...LOW
LEVEL FORCING IS WEAK AT BEST AND STRONGER UPR LVL FORCING APPEARS
TO STAY TO OUR NE OVER THE ERN GREAT LAKES. AS A RESULT...HAVE
KEPT POPS IN THE CHANCE CATEGORY.

FOR TUESDAY INTO TUESDAY NIGHT...COLD FRONT WILL PUSH SOUTH AND EAST
AWAY FROM THE REGION AS AN EXPANSIVE AREA OF SURFACE HIGH PRESSURE
BUILDS IN FROM THE NORTHWEST. PCPN APPEARS TO BE MAINLY ALONG AND
AHEAD OF THE COLD FRONT SO MOST OF THIS MAY BE OVER WITH BY TUESDAY
MORNING ACRS THE SOUTH WHILE SKIES CLEAR FROM THE NORTH.

FOR THE PERIOD WEDNESDAY THROUGH FRIDAY...OUR REGION WILL BE
DOMINATED BY NORTHWEST FLOW ALOFT. SPRAWLING SURFACE HIGH WILL
GRADUALLY MOVE OFF TO THE EAST. WILL CONTINUE WITH DRY WEATHER
ATTM...ALTHOUGH SOME EMBEDDED DISTURBANCES IN THE FLOW ALOFT MAY
AFFECT THE WRN PARTS OF THE AREA FRIDAY OR SATURDAY.

TEMPERATURES WILL FALL TO BELOW SEASONAL NORMALS INTO MID WEEK THEN
RECOVER TO TYPICAL LATE JUNE READINGS TOWARD THE END OF THE WEEK.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
HIGH PRESSURE SLIDING SOUTHEAST OF FORECAST AREA TONIGHT WILL SEE
WINDS SHIFT SOUTHEAST AND THEN SOUTH AS HIGH CLOUDS STREAM IN FROM
THE NORTHWEST. SCT CU 4-5KFT WILL OCCUR TODAY UNDERNEATH A STRONG
INVERSION AT THIS LEVEL. SHOWERS WILL TAKE SHAPE NORTHWEST OF THE
FORECAST AREA OVERNIGHT TOMORROW AND WILL SEE A MARKED INCREASE
TOWARDS DAYBREAK...OUTSIDE OF THE VALID TAF FORECAST.

VFR CONDITIONS ARE EXPECTED EVEN IF SHOWERS OCCUR AT THE END OF
THE PERIOD AND CIGS GO BROKEN AROUND 4KFT.

OUTLOOK...SHOWERS AND THUNDERSTORMS ARE POSSIBLE SUNDAY MORNING
THROUGH MONDAY NIGHT.
-- End Changed Discussion --

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...LATTO
NEAR TERM...CONIGLIO/LATTO
SHORT TERM...LATTO
LONG TERM...HICKMAN
AVIATION...FRANKS