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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 210535
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
135 AM EDT TUE MAY 21 2013

.SYNOPSIS...
A WARM AND HUMID AIRMASS WILL REMAIN IN PLACE BEFORE A COLD FRONT
ARRIVES ON THURSDAY. MID LEVEL RIDGING WILL SLIDE EAST OF OUR AREA
TONIGHT AS LOW PRESSURE SLOWLY MOVES SOUTH AND EAST ACROSS THE
NORTHERN PLAINS. CHANCES FOR PRECIPITATION WILL INCREASE AS THIS
LOW APPROACHES OUR AREA OVER THE NEXT COUPLE OF DAYS.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
MID LEVEL RIDGE OVER OHIO KEPT THE REGION DRY TODAY. ILN/S 00Z
SOUNDING SHOWED INSTBY AROUND 2100 J/KG BUT ALSO A SUBSIDENCE
INVERSION CAP AROUND 800 MB. WITH A LAKE OF SIGNIFICANT FORCING...THIS
CAP COULD NOT BE OVERCOME TO TAP INTO THIS INSTBY AND PRODUCE DEEP
CONVECTION. SKIES WILL BE MOSTLY CLEAR THIS EVENING WITH JUST SOME
THIN HI LEVEL CLOUDS PASSING THRU.

THE MID LEVEL RIDGE AXIS TO SHIFT A LTL EAST OVERNIGHT WITH THE
FLOW BACKING. LOW LEVEL JET HAS INITIATED DEEP CONVECTION TO OUR
WEST OVER THE MID MS VLY. AS THIS JET SHIFTS NE THE CONVECTION WILL
HEAD EAST TO NE. WITH PLENTY OF ELEVATED INSTABILITY IN PLACE EXPECT
THAT SOME OF THIS CONVECTION COULD MAKE IT INTO OUR NORTHWESTERN ZONES
LATE. HAVE ADJUSTED TIMING A LTL SLOWER WITH THESE STORMS INTO THE
NW AND FOLLOWED PREV FCST TRENDS...GRADUALLY WEAKENING THEM AS THEY
SHIFT EASTWARD ACROSS OUR AREA TUESDAY MORNING.

ANOTHER MILD NIGHT IS EXPECTED TONIGHT WITH OVERNIGHT LOWS IN THE
MID TO UPPER 60S.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
OVERALL PATTERN FOR THE SHORT TERM TIME PERIOD IS FOR A LOW OVER
THE NORTHERN PLAINS TO SLOWLY SHEAR EASTWARD TUESDAY THROUGH
TUESDAY NIGHT...BEFORE GETTING ABSORBED INTO A DEEPENING TROUGH
ACROSS THE GREAT LAKES. AS THIS SYSTEM BEGINS TO GET SHEARED INTO
SOUTHWESTERLY FLOW ACROSS OUR REGION...TIMING OF INDIVIDUAL PIECES
OF ENERGY AND ASSOCIATED CONVECTION BECOMES UNCERTAIN.

BASED ON THE NEAR TERM FORECAST DECAYING CONVECTION ACROSS OUR
ZONES TUESDAY MORNING...THERE WOULD BE A PORTION OF THE DAY
TUESDAY WHERE THE BOUNDARY LAYER WILL BE WORKED OVER. THEREFORE
THERE MAY BE SEVERAL HOURS DURING THE FIRST PART OF THE DAY
TUESDAY WHERE LITTLE TO NO CONVECTION IS OCCURRING IN OUR FORECAST
AREA. THIS SOLUTION IS BEING INDICATED BY THE MAJORITY OF COMPUTER
MODELS. BY LATE TUESDAY AFTERNOON INSTABILITY WOULD HAVE INCREASED
AND SUFFICIENT RECOVERY OF THE BOUNDARY LAYER IS EXPECTED TO HAVE
OCCURRED. FORCING ASSOCIATED WITH ANY SHORTWAVE ENERGY EJECTING
EAST FROM THE LOW OVER THE PLAINS WILL HELP TO TRIGGER CONVECTIVE
DEVELOP LATE TUESDAY AFTERNOON. ALTHOUGH EXACT TIMING AND
PLACEMENT OF THE CONVECTION IS HIGHLY UNCERTAIN AT THIS TIME...UP
TO 45 KT OF 0-6 KM SHEAR MAY BE PRESENT ACROSS THE NORTHWESTERN
HALF OF OUR FORECAST AREA. THEREFORE...IF CONVECTION DOES GET GOING
TUESDAY AFTERNOON AND EVENING ACROSS OUR NORTHWEST...THERE WILL
BE THE POTENTIAL FOR SOME OF THESE STORMS TO BECOME SEVERE. THE
MAIN THREAT FROM THESE STORMS WOULD BE DAMAGING WIND AND ISOLATED
LARGE HAIL. THIS THREAT IS BEING HIGHLIGHTED IN THE HWO.

CHANCES FOR SHOWER AND THUNDERSTORMS WILL CONTINUE INTO TUESDAY
NIGHT AND INTO THE DAY ON WEDNESDAY AS THE LOW PROGRESSES NEARER
TO OUR AREA. SHEAR AND INSTABILITY WILL DECREASE ON TUESDAY NIGHT
AND WEDNESDAY....WHICH SHOULD LESSEN THE OVERALL SEVERE THREAT.
HOWEVER...ON WEDNESDAY THERE MAY STILL BE SUFFICIENT INSTABILITY
TO COMBINE WITH ABOUT 35 KT OF 0-6 KM SHEAR TO PRODUCE ISOLATED
CHANCES FOR DAMAGING WINDS AND LARGE HAIL SHOULD STORMS GET
ORGANIZED.

BY WEDNESDAY EVENING THE BEST CHANCES FOR PRECIPITATION WILL SHIFT
EAST OF OUR AREA ALONG WITH THE BEST FORCING.

TEMPERATURES WILL BE ON A DOWNWARD TREND THROUGHOUT THE SHORT TERM
TIME PERIOD. ON TUESDAY EXPECT UPPER 80S ACROSS THE EAST TO LOWER
80S ACROSS THE WEST. BY WEDNESDAY...CLOUD COVER AND PRECIPITATION
WILL KEEP TEMPERATURES LOWER THAN TUESDAY. OVERNIGHT LOWS WILL
CONTINUE TO BE MILD BOTH TUESDAY AND WEDNESDAY NIGHT AS WE REMAIN
IN THIS WARM AND HUMID AIRMASS.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE UPPER LEVEL TROUGH WILL PIVOT EAST ACROSS OUR AREA THROUGH THE
DAY ON THURSDAY. THIS COMBINED WITH SOME LINGERING
INSTABILITIES...WILL KEEP THE THREAT OF SHOWERS AND A FEW
THUNDERSTORMS GOING THROUGH THE AFTERNOON. AS THE TROUGH BEGINS TO
SHIFT EAST AND WE LOSE THE INSTABILITY...PCPN SHOULD TAPER OFF TO A
FEW SHOWERS THURSDAY NIGHT. COOLER AIR WILL BEGIN FILTERING INTO THE
AREA THROUGH THE DAY ON THURSDAY WITH HIGHS RANGING FROM THE UPPER
60S NORTHWEST TO LOW TO MID 70S SOUTHEAST.

SURFACE HIGH PRESSURE WILL BUILD DOWN FROM THE NORTH AND INTO OUR
AREA FRIDAY INTO SATURDAY...KEEPING A SEASONABLY COOL AIRMASS IN
PLACE THROUGH THE START OF THE WEEKEND. HIGHS ON FRIDAY WILL BE IN
THE MID TO UPPER 60S AND WITH THE SURFACE HIGH OVERHEAD...LOWS
SATURDAY MORNING WILL DIP INTO THE LOW TO MID 40S. THE SURFACE HIGH
WILL BEGIN TO SHIFT OFF TO THE EAST THROUGH THE REMAINDER OF THE
WEEKEND AS MID LEVEL RIDGING BEGINS TO ESTABLISH ITSELF ALOFT. THIS
WILL RESULT IN A GRADUAL RETURN TO WARMER TEMPERATURES THROUGH THE
REST OF THE HOLIDAY WEEKEND. MODELS ARE STILL TRYING TO SUGGEST THE
POSSIBILITY OF SOME ENERGY DROPPING DOWN FROM THE NORTHWEST LATE IN
THE WEEKEND. HOWEVER...TIMING AND PLACEMENT ARE HIGHLY VARIABLE SO
WILL MAINTAIN A DRY FORECAST AT THIS POINT.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
LARGE SCALE UPPER LEVEL LOW CENTERED OVER THE NORTHERN PLAINS WILL
MAKE LITTLE EASTWARD PROGRESSION OVER THE NEXT 24 HOURS. REGION
WILL BE LOCATED IN A WARM...MOIST SOUTH/SOUTHWEST FLOW AT THE SFC
AND ALOFT.

FIRST ITEM OF CONCERN WILL BE THE QLCS TO OUR WEST ACROSS WESTERN
INDIANA AND EASTERN ILLINOIS. SOME MODELS WEAKEN THIS FEATURE TO
THE POINT THAT IT IS GONE BY THE TIME IT GETS NEAR OUR WESTERN TAF
SITES BETWEEN 09Z AND 12Z. OTHER MODELS TRY TO HOLD IT TOGETHER
INTO OUR WESTERN TAF SITES BEFORE COMPLETELY WEAKENING IT. AT THIS
TIME...HAVE NOT PLACED ANY CONVECTION IN THE TAFS AND WILL MONITOR
LINE/TRENDS AND UPDATE/AMEND ACCORDINGLY IF NECESSARY.

OTHERWISE...THE TIMING OF CONVECTION FOR TODAY IS FAIRLY MURKY AS
MODELS ARE NOT HANDLING MESOSCALE FEATURES AT THE SURFACE AND
ALOFT WELL. KEPT PREVIOUS FORECAST TREND TO ALLOW FOR SHOWERS AND
THUNDERSTORMS DURING THE PEAK HEATING OF THE DAY FOLLOWED BY A
LULL IN ACTIVITY THIS EVENING. FOR LATE TONIGHT INTO WEDNESDAY...A
MORE BONAFIDE DISTURBANCE AND DEVELOPING LOW LEVEL JET WILL LIKELY
BRING WIDESPREAD PRECIPITATION TO OUR AREA...BUT EXACT TIMING IS
STILL IN QUESTION AT THIS POINT. WINDS TODAY WILL BE LOCALLY GUSTY
FROM THE SOUTHWEST TO 25 KNOTS WITH GUSTINESS SUBSIDING TOWARD
SUNSET.

OUTLOOK...THUNDERSTORMS WILL BE POSSIBLE FROM TUESDAY NIGHT THROUGH
THURSDAY.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...LATTO
NEAR TERM...AR
SHORT TERM...LATTO
LONG TERM...JGL
AVIATION...HICKMAN