000
FXUS63 KIWX 181628
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1228 PM EDT TUE JUN 18 2013

.SYNOPSIS...
ISSUED AT 1227 AM EDT TUE JUN 18 2013

A WEAKENING FRONTAL BOUNDARY WILL SLOWLY DROP INTO CENTRAL INDIANA
BY THIS EVENING. A DISTURBANCE WILL DROP SOUTHEAST ALONG THE FRONT
THIS AFTERNOON...ALLOWING FOR A CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY SOUTH OF US 6. HIGH PRESSURE WILL BUILD IN
ACROSS THE REGION WITH SEASONABLE TEMPERATURES AND DRY CONDITIONS.

&&

.UPDATE...
ISSUED AT 1227 PM EDT TUE JUN 18 2013

CLOUD COVER WILL CONTINUE TO ERODE ACROSS NORTHEASTERN PORTIONS OF
THE AREA OVER THE NEXT HOUR OR 2 AS INCREASED MIXING FINALLY WIPES
OUT THE STRATUS DECK THAT DRIFTING SOUTH FROM MI OVERNIGHT. CLOUD
COVER EXPECTED TO STRUGGLE TO DROP MUCH BELOW US 30 WITH STRONG
DIFFERENTIAL HEATING ONGOING BOTH AHEAD OF THE CLOUDS AND NOW IN
ITS WAKE. WHILE TEMPS HAVE BEEN SLOW TO RISE IN THE
NORTH...FORECAST HIGHS STILL LOOK GOOD WITH SEVERAL HOURS OF
HEATING YET THIS AFTERNOON.

AS FOR PRECIP CHANCES...VORT MAX WAS DROPPING SE ACROSS NE IA/SW
WI. WATER VAPOR LOOP AND VIS SAT APPEAR TO INDICATE SOME OVERALL
WEAKENING OF THE WAVE WITH BOTH CLOUD COVER AND PRECIP COVERAGE ON
THE DECREASE. MARGINAL INSTABILITY DOES EXIST ACROSS SOUTHERN
AREAS WHERE HEATING HAS BEEN UNINTERRUPTED WITH LI`S -2 TO -4 C
AND BETWEEN 500 AND 1000 J/KG OF MUCAPE. WHILE NOT OVERLY
IMPRESSED WITH THE SETUP...CHC/SLGT CHC POPS STILL WARRANTED FOR
SOUTHERN AREAS. WILL MONITOR TRENDS INTO THE AFTERNOON FOR FURTHER
UPDATES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 415 AM EDT TUE JUN 18 2013

ONE MORE DAY OF SPORADIC AFTERNOON CONVECTION EXPECTED THIS SHORT
TERM PERIOD. MUCH BETTER MIDLEVEL SUPPORT WITH THIS EVENT AS A
COMPACT PV ANOMALY CURRENTLY OVER THE UPPER MIDWEST APPROACHES OUR
AREA DURING PEAK AFTERNOON HEATING BUT MOISTURE QUALITY AND
INSTABILITY QUESTIONS REMAIN. LATEST MSAS ANALYSIS SHOWS SURFACE
COLD FRONT HAS CLEARED MOST OUR CWA AND A FAIR AMOUNT OF LOW LEVEL
NEGATIVE THETA-E ADVECTION WILL PERSIST THROUGH THE DAY.
HOWEVER...ELEVATED FRONTAL SLOPE WILL NOT FULLY CLEAR OUR CWA UNTIL
LATE THIS AFTERNOON AND 850-700MB THETA-E FIELDS SHOW A FAIR AMOUNT
OF MOISTURE REMAINS IN PLACE ACROSS OUR SOUTHERN CWA. THIS COMBINED
WITH DIURNAL HEATING...CAPE VALUES CLIMBING TO AROUND 1000
J/KG...AND GOOD PV ADVECTION WILL LIKELY SUPPORT SCATTERED SHOWERS
AND THUNDERSTORMS ACROSS OUR SOUTHERN CWA THIS AFTERNOON/EVENING.
MOST OF THE LATEST 00Z HI-RES RUNS ONLY SHOW CONVECTION CLIPPING OUR
FAR SOUTHERN COUNTIES...WHICH MAKES SENSE GIVEN PLACEMENT OF BETTER
INSTABILITY FIELDS...AND WILL THEREFORE CUT BACK POPS A BIT ACROSS
THE NORTH/CENTRAL WHILE MAINTAINING MID RANGE CHANCE OVER THE FAR
SOUTH. THERE WILL BE AROUND 30 KTS OF 0-6KM BULK SHEAR THIS
AFTERNOON SO IF ANY SUBSTANTIAL UPDRAFTS CAN MATERIALIZE THERE WILL
BE AN ISOLATED THREAT FOR SEVERE WEATHER. HIGH WINDS WOULD PROBABLY
BE THE MAIN THREAT WITH RELATIVELY DRY LOWER LEVELS SUPPORTING HIGH
DCAPE VALUES AND STRONG NEGATIVE BUOYANCY. COULD ALSO BE SOME LARGE
HAIL GIVEN LOW 0C AND -20C LEVELS BUT CAPE DENSITY IS ALSO LOW AND
MAY LIMIT ANYTHING MORE THAN SOME SMALL HAIL IN THE STRONGER
UPDRAFTS. OTHER MAIN STORY WILL BE MUCH COOLER MIN TEMPS TONIGHT.
CANADIAN HIGH WILL SETTLE ACROSS THE GREAT LAKES OVERNIGHT WITH
LIGHT NORTHERLY WINDS/CAA AND CLEARING SKIES SUPPORTING STEEP
DIURNAL LOSSES. THIS AIRMASS IS ALSO UNUSUALLY COLD FOR MID-JUNE AND
AREAS OF THE U.P. OF MICHIGAN HAVE ALREADY DROPPED INTO THE 30S AT
PRESS TIME. WONT BE THAT COLD HERE BUT 40S ARE CERTAINLY IN THE
REALM OF POSSIBILITY...ESPECIALLY ACROSS THE NORTH. APPEARS TO BE
ENOUGH OF A GRADIENT TO KEEP TEMPS FROM TRULY BOTTOMING OUT BUT
STILL TRIMMED A FEW DEGREES OFF INHERITED FORECAST WITH UPPER 40S TO
LOWER 50S...ROUGHLY 10 DEGREES BELOW NORMAL.

&&

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 415 AM EDT TUE JUN 18 2013

WEDNESDAY SHOULD FEATURE QUIET CONDITIONS WITH BROAD SFC ANTICYCLONE
DRIFTING SOUTHEAST ACROSS THE EASTERN GREAT LAKES. COOLEST LOW LEVEL
THERMAL PROFILES SHOULD RESIDE ACROSS THE AREA ON THIS DAY AND HAVE
UTILIZED MIXING NAM/GFS BLENDED 875-850 HPA THERMAL PROGS TO THE SFC
AS FIRST GUESS MAX TEMP FOR WEDNESDAY AFTERNOON. THIS GENERALLY
PROVIDES HIGHS IN THE MID TO POSSIBLY UPPER 70S AND PERHAPS A BIT
COOLER CLOSER TO LAKE MICHIGAN SHORELINE. SOME MODEST LOW LEVEL
WARM/MOIST ADVECTION ON THURSDAY AS SFC ANTICYCLONE SHIFTS EASTWARD
SHOULD ALLOW FOR NEAR SEASONABLE HIGHS. ATTENTION WILL THEN TURN
UPSTREAM TO SHORT WAVE UPPER TROUGH WHICH IS EXPECTED TO EJECT
THROUGH THE BASE OF THE LARGER SCALE UPPER TROUGH JUST OFF THE
PACIFIC NORTHWEST COAST. SOME EVIDENCE OF THIS FEATURE NOTED IN
EARLY MORNING WATER VAPOR IMAGERY ACROSS CENTRAL CALIFORNIA. WITH
JUST SLOW MOISTURE RECOVERY ON THURSDAY...CONFIDENCE IS LOW IN HOW
MUCH LOW LEVEL MOISTURE WILL BE AVAILABLE FOR THIS SHORT WAVE TO
WORK WITH AND WITH SHORT WAVE TRACK STILL OF RELATIVELY LOW
CONFIDENCE WILL KEEP THURSDAY-FRIDAY DRY.

THE FOCUS OF THE REMAINDER OF THE FORECAST WILL CENTER ON THE
EVOLUTION OF THE PACIFIC NORTHWEST UPPER TROUGH AND EXPECTED
DOWNSTREAM MID/UPPER RIDGE AMPLIFICATION ACROSS CENTRAL CONUS IN THE
LATE FRIDAY THROUGH WEEKEND PERIOD. STRENGTHENING SOUTHWESTERLY LOW
LEVEL FLOW AND INCREASED LOW LEVEL THETAE ADVECTION SHOULD TAKE HOLD
BY LATER FRIDAY AND PATTERN DOES SEEM CONDUCIVE FOR AT LEAST THE
POSSIBILITY OF SOME ELEVATED THUNDER AT LEADING EDGE OF THIS THETAE
ADVECTION AND JUST AHEAD OF PRONOUNCED EASTWARD ADVANCING MID LEVEL
THERMAL RIDGE. FORCING SHOULD BE RELATIVELY WEAK HOWEVER SO HAVE
JUST INCLUDED SOME LOW END CHANCE POPS ACROSS WESTERN HALF OF AREA
FRIDAY NIGHT.

LATEST 00Z EC APPEARS TO BE SHOWING SOME TREND TO THE PAST SEVERAL
RUNS OF THE GFS IN ADVERTISING A MORE ROBUST UPPER RIDGE ACROSS THE
REGION FOR THE WEEKEND. POP PREDICTABILITY AT THIS FORECAST DISTANCE
IS QUITE LOW GIVEN THE POTENTIAL OF RIDGE RIDING SHORT WAVES TO
INDUCE CONVECTIVE DEVELOPMENT THAT COULD DROP SOUTHEAST ACROSS THE
AREA DURING THIS PERIOD. STRENGTH OF ANY CAPPING ALSO WILL BE HIGHLY
DEPENDENT ON LOW LEVEL DEW PT TRENDS WHICH REMAIN UNCERTAIN. HAVE
OPTED TO STAY CLOSE TO PREVIOUS FORECAST IN MAINTAINING SLIGHT TO
LOW END CHANCE POPS ACROSS THE AREA FOR SAT-TUE WITH HIGHEST CHANCE
TSRA POPS ACROSS THE NORTH WHERE IT WOULD AT LEAST APPEAR POTENTIAL
MAY EXIST FOR PERIODS OF A WEAKER MID LEVEL CAP. BUT
AGAIN...CONFIDENCE IS LOW AND DETAILS ON CONVECTIVE POTENTIAL ARE
VERY MUDDLED AT THIS POINT. HAVE ALSO MAINTAINED IDEA OF PREVIOUS
FORECASTS IN STAYING MUCH ABOVE CRALLBLEND FOR HIGHS THROUGH THIS
PERIOD FAVORING HOTTER MEX NUMBERS NEAR 90 WHICH ARE ON THE HIGHER
END OF ENSEMBLE SPREAD. IF CAP DOES HOLD THROUGH MUCH OF THIS
PERIOD...A POSSIBILITY DOES EXIST FOR EVEN WARMER CONDITIONS LATE
WEEKEND/EARLY NEXT WEEK THAN CURRENTLY FORECAST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1227 PM EDT TUE JUN 18 2013

MVFR/IFR CIGS SHOULD NO LONGER BE AN ISSUE BY VALID TIME AS MIXING
CONTINUES TO ERODE THE STRATUS DECK DRIFTING SOUTH. CONFIDENCE IN
THUNDER CHANCES AT BOTH TAF SITES REMAINS LOW TO VERY LOW WITH
MAIN FOCUS LOOKING TO REMAIN SOUTH OF THE AREA. MAY ADD A VCTS
MENTION FOR A FEW HOURS AT KFWA TO REPLACE THE PROB30 BUT MAY ALSO
REMOVE COMPLETELY AND MONITOR TRENDS WITH ANY CONVECTION LIKELY OF
SHORT DURATION.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...BEACH HAZARDS STATEMENT THROUGH LATE TONIGHT FOR INZ003.

MI...BEACH HAZARDS STATEMENT THROUGH LATE TONIGHT FOR MIZ077.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EDT WEDNESDAY FOR LMZ043-046.

&&

$$

UPDATE...FISHER
SYNOPSIS...FISHER
SHORT TERM...AGD
LONG TERM...MARSILI
AVIATION...FISHER


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