000
FXUS63 KIWX 161722
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
122 PM EDT SUN JUN 16 2013

.SYNOPSIS...
ISSUED AT 1011 AM EDT SUN JUN 16 2013

HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION FOLLOWING
A COLD FRONT. AS HIGH PRESSURE BUILDS, DRIER AND SLIGHTLY COOLER
AIR WILL SETTLE INTO THE REGION TODAY AND TONIGHT. HIGHS TODAY
WILL BE IN THE UPPER 70S TO LOWER 80S. LOWS TONIGHT WILL RANGE
FROM THE UPPER 50S TO LOWER 60S.

&&

.UPDATE...
ISSUED AT 1011 AM EDT SUN JUN 16 2013

PRECIPITATION CONTINUES TO WEAKEN AND SHIFT SOUTHEAST AS SURFACE
HIGH PRESSURE BUILDS INTO THE GREAT LAKES REGION. PRONOUNCED
SUBSIDENCE NOTED ON THE WATER VAPOR IMAGERY ASSOCIATED WITH THE
EXITING SHORTWAVE. WESTERLY FLOW ACROSS THE NORTHERN PLAINS STATES
WILL KEEP COOLER AND DRIER AIR IN PLACE. SEVERAL EMBEDDED
SHORTWAVES IN THE FLOW WILL MOVE RAPIDLY EASTWARD OVER THE NEXT 24
TO 48 HOURS. ENOUGH MOISTURE AND INSTABILITY IN THE AREA FOR
SHOWERS LATE IN THE DAY MONDAY.

UPDATED GRIDS AND FORECAST TO REMOVE SHOWERS...POPS...AND
DECREASE CLOUD COVER. OTHER ELEMENTS GENERALLY UNCHANGED.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM EDT SUN JUN 16 2013

UPPER LEVEL PATTERN HAS FULLY DEAMPLIFIED...ALLOWING DEEP
MOISTURE PLUME TO INFILTRATE OUR REGION. BROAD THETA-E ADVECTION
WILL CONTINUE TODAY BUT LACK OF ANY NOTABLE FORCING MECHANISM
ALOFT WILL LEAD TO ANOTHER PRECARIOUS PRECIP FORECAST. INITIAL
CONVECTION ASSOCIATED WITH SUBTLE VORT MAX/HEIGHT FALLS FROM
SHEARED OUT SOUTHERN PLAINS WAVE WILL CONTINUE TO EXIT THE CWA
DURING THE NEXT FEW HOURS. ENOUGH ELEVATED INSTABILITY TO SUPPORT
SCATTERED THUNDERSTORMS BUT LAPSE RATES APPEAR TOO LOW TO MAINTAIN
SUBSTANTIAL UPDRAFTS. HAVE BEEN A FEW STRONG WIND GUSTS TO OUR
SOUTHWEST THOUGH...ASSOCIATED WITH A FAIRLY IMPRESSIVE MESOHIGH
THAT FORMED OVER MISSOURI EARLIER THIS EVENING. THIS FEATURE HAS
WEAKENED QUITE A BIT IN THE PAST FEW HOURS BUT A FEW GUSTS AROUND
25 MPH MAY STILL BE POSSIBLE THROUGH 6 AM. WILL LIKELY BE A BRIEF
BREAK BEHIND THIS CONVECTION BEFORE ANOTHER ROUND OF SHOWERS AND
STORMS BECOMES POSSIBLE LATER THIS MORNING AND INTO THE AFTERNOON.
THIS IS THE LOW CONFIDENCE ASPECT OF THE FORECAST. THERE ARE SOME
HINTS OF LOW LEVEL CONVERGENCE SETTING UP ACROSS THE AREA THIS
AFTERNOON...MORE OF A MOISTURE GRADIENT THAN TRUE COLD FRONT. THIS
BAND OF CONVERGENCE HAS HELPED SPARK A LINE OF THUNDERSTORMS OVER
WISCONSIN AND SOUTHERN LAKE MICHIGAN AT PRESS TIME. THOUGH THIS
LINE APPEARS TO BE WEAKENING ON LATEST RADAR MOSAIC AND LIGHTNING
DATA...MODEST AFTERNOON CAPE VALUES...AROUND 1500 J/KG ACROSS OUR
SOUTHERN CWA...MAY BE ENOUGH TO TRIGGER A FEW ADDITIONAL
THUNDERSTORMS OVER OUR AREA LATER TODAY. HOWEVER...VERY WEAK
FORCING COMING RIGHT ON THE HEELS OF THIS INITIAL CONVECTION MAY
LIMIT THE SCOPE OF AFTERNOON PRECIP. INSTABILITY VALUES ARE ALSO
PREDICATED ON SURFACE DEWPOINTS REACHING 70F WHICH MAY BE A BIT
OPTIMISTIC AND INTRODUCES CAPPING CONCERNS GIVEN WEAK SUBSIDENCE
INVERSION SETTING UP IN THE WAKE OF PASSING SHORTWAVE. ALL OF THAT
BEING SAID WILL CONTINUE WITH JUST A LOW CHANCE MENTION FOR THE
AFTERNOON...MAINLY ACROSS THE SOUTH. NEGATIVE THETA-E ADVECTION
WILL FINALLY WIN OUT BY TONIGHT AND WITH THE LOSS OF DAYTIME
HEATING WE SHOULD REMAIN PRECIP FREE. TEMPS TODAY WILL BE SOMEWHAT
DEPENDENT ON EVOLUTION OF CONVECTION BUT 850MB TEMPS AROUND 14C
SUPPORT HIGHS AROUND 80F...SIMILAR TO MOS GUIDANCE. TRIMMED
OVERNIGHT LOWS A BIT AS CLEARING SKIES AND LIGHT WINDS SHOULD
ALLOW US TO DROP TO AROUND 60F. STILL RELATIVELY HIGH SURFACE
DEWPOINTS WILL LIKELY PREVENT TEMPS FROM DROPPING MUCH BELOW THIS
LEVEL.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 350 AM EDT SUN JUN 16 2013

MAIN FORECAST ITEMS FOR THE LONG TERM CENTER ON PRECIP CHANCES
MONDAY/MONDAY NIGHT...COOLING TEMPS FOR MID WEEK...AND THEN WARMING
TREND FOR THE LATTER PORTIONS OF THE FORECAST.

UPPER LOW CENTERED ACROSS SOUTHERN SASKATCHEWAN CANADA THIS MORNING
WILL BECOME AFFECTED BY UPPER MIDWEST/GREAT LAKES DEFORMATION FLOW
ON MONDAY...AND THIS WAVE IS STILL EXPECTED TO DAMPEN RAPIDLY AS IT
DROPS SOUTHEAST. UPPER LEVEL STEERING FLOW SHOULD KEEP ANY SOUTHERN
STREAM DISTURBANCES SUPPRESSED SOUTH OF THE AREA ON MONDAY SO MAIN
QUESTION WILL BE STRENGTH OF MID/UPPER LEVEL FORCING FOR CONVECTIVE
CHANCES. LOW LEVEL MOISTURE TRANSPORT PROGS FROM NAM/GFS STILL
DEPICT MUCH MORE FAVORABLE SCENARIO SOUTH OF THE AREA WITH PRIMARILY
WESTERLY FLOW REGIME LIMITING MAGNITUDE OF MOISTURE RETURN ACROSS
THE LOCAL AREA. HOWEVER...STILL SOME WEAK TO MODERATE AFTERNOON
INSTABILITY IS EXPECTED WITH GOOD DEAL OF INSOLATION. DEEP LAYER
BULK SHEAR ALSO EXPECTED TO BE IN THE 30-40 KNOT RANGE...BUT MAIN
LIMITING FACTOR FOR CONVECTIVE CHANCES MONDAY WILL BE A FORCING
MECHANISM. DPVA ASSOCIATED WITH AFOREMENTIONED DAMPENING WAVE SHOULD
BE CONFINED TO SOUTHERN/CENTRAL LOWER MICHIGAN. WHILE SFC BOUNDARY
IS EXPECTED TO DROP SOUTHWARD INTO NORTHERN LOCATIONS DURING THE
AFTERNOON...ANY ASSOCIATED LOW LEVEL CONVERGENCE WITH THIS BOUNDARY
SHOULD BE SHALLOW AND WEAK. MODELS CONTINUE TO HINT AT BETTER
CONVECTIVE CHANCES TIED INTO SLIGHTLY MORE ROBUST 850 HPA
CONVERGENCE FIELDS NORTH OF THE LOCAL AREA MONDAY AFTERNOON/EARLY
EVENING. BY THE TIME DEEPER CONVERGENCE FIELDS REACH THE LOCAL
AREA...PEAK DIURNAL INSTABILITY WILL LIKELY BE WANING SO AT THIS
POINT WILL STAY THE COURSE WITH INHERITED LOW CHANCE POPS MONDAY
AFTERNOON/MONDAY EVENING. NOT COMPLETELY OUT OF THE QUESTION A
PROGRESSIVE SOUTHERN STREAM SHORT WAVE COULD BRING SOME RAIN CHANCES
TO FAR SOUTH MONDAY MORNING...BUT TOO MUCH UNCERTAINTY EXISTS WITH
THIS SCENARIO TO INCLUDE IN FORECAST.

COOLER AND LESS HUMID CONDITIONS IN STORE FOR TUESDAY AS LOCAL AREA
BECOMES POSITIONED ON WESTERN PERIPHERY OF LOW LEVEL THERMAL TROUGH
OVERSPREADING NORTHEAST CONUS. SOME RUN TO RUN CONSISTENCY OVER THE
PAST SEVERAL DAYS FOR TUESDAY WITH LOW AMPLITUDE SHORT WAVE MOVING
INTO THE AREA ON THE HEELS OF MONDAY NIGHTS DISTURBANCE. WEAK MID
LEVEL THERMAL TROUGHING SHOULD LEND TO SOME RESPECTABLE LAPSE RATES
WITH PRIMARY QUESTION/UNCERTAINTY AT THIS TIME OF ANY ISOLD
AFTERNOON PRECIP CHANCES FOCUSED ON LOW LEVEL DEW PT TRENDS. 00Z NAM
WOULD SUGGEST SBCAPES ON THE ORDER OF 500-1000 J/KG...BUT SUSPECT
NAM IS A BIT OVERDONE WITH LOW LEVEL MOISTURE. WHILE CANNOT
COMPLETELY DISCOUNT ISOLD AFTERNOON SHOWER DEVELOPMENT...FEEL THAT
JUST SOME BETTER CU DEVELOPMENT IS THE MORE LIKELY SCENARIO AND WILL
KEEP TUESDAY DRY.

1020 MB HIGH TO DROP SOUTHWARD ACROSS SOUTHERN GREAT LAKES REGION
TUESDAY NIGHT WITH EVEN DRIER LOW LEVEL AIR MASS SPREADING SOUTHWARD
WHICH SHOULD ALLOW FOR RELATIVELY COOLER LOWS. MODELS ARE IN DECENT
AGREEMENT IN SMALL SCALE WAVE EJECTING OUT OF NEXT EASTERN PACIFIC
TROUGH THROUGH MEAN CENTRAL CONUS RIDGING MID WEEK.
HOWEVER...NOTHING MORE THAN JUST INCREASING HIGH CLOUDS EXPECTED
WITH THIS SHORT WAVE GIVEN DRY PROFILES. FLOW AMPLIFICATION IS
EXPECTED THURSDAY AND BEYOND AS ACTIVE EASTERN PACIFIC JET CARVES
OUT LARGE NEGATIVE UPPER HEIGHT ANOMALY ACROSS THE PACIFIC
NORTHWEST...INDUCING DOWNSTREAM RIDGE AMPLIFICATION. THIS SHOULD
ALLOW FOR STEADY MODERATING TEMP TREND TOWARD THE END OF THE PERIOD
WITH LOW LEVEL THERMAL PROGS SUGGESTING TEMPS WELL INTO THE 80S
TOWARD THE END OF THE PERIOD WHICH IS ALREADY CAPTURED IN PREVIOUS
FORECAST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 114 PM EDT SUN JUN 16 2013

HIGH PRESSURE EXTENDS FROM SOUTHERN IOWA INTO KENTUCKY. WESTERLY
FLOW CONTINUES ACROSS THE NORTHERN PLAINS INTO THE GREAT LAKES
WITH EMBEDDED SHORTWAVES AND SURFACE TROFS. SURFACE
FRONT/DEFORMATION AXIS EXTENDS FROM NRN MI-ACROSS LAKE MI TO NEAR
KANSAS CITY. THIS BOUNDARY WILL GRADUALLY SHIFT EAST AND SOUTHEAST
THROUGH THE FORECAST PERIOD. WITH POOL OF COOLER AIR OVER THE
REGION...CU/SC HAVE FORMED AND EXPECT TO SEE CLEARING SKIES AFTER
SUNSET. VERY LIGHT AND ISOLD SHRA ARE POSSIBLE...HOWEVER NOT
EXPECTED TO IMPACT TERMINALS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

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


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