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000
FXUS63 KIWX 172027
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
427 PM EDT MON JUN 17 2013

.SYNOPSIS...
ISSUED AT 425 PM EDT MON JUN 17 2013

A WEAK COLD FRONT WILL APPROACH THE REGION THIS EVENING AND BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS OVERNIGHT AND AGAIN TUESDAY
EVENING. HIGH PRESSURE WILL THEN BUILD OVER THE GREAT LAKES BY
MIDWEEK WITH A RETURN TO DRY CONDITIONS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 350 PM EDT MON JUN 17 2013

PERTURBED WNW FLOW ALOFT WILL PERSIST THIS PERIOD BETWEEN AN EASTERN
CANADA NEGATIVE HEIGHT ANOMALY AND AN INTERMOUNTAIN WEST/SOUTHERN
PLAINS UPPER RIDGE. A SHEARED PV FILAMENT EMBEDDED IN THIS FLOW
OVER WISCONSIN WILL TRANSLATE THROUGH THE CENTRAL GREAT LAKES THIS
EVENING...FORCING A BACKDOOR COLD FRONT SOUTHEAST THROUGH THE AREA
TONIGHT. THIS COLD FRONT WILL GET A LITTLE EXTRA BOOST FROM COOL
LAKE MICHIGAN WATERS...FORCING IT INTO FAR NW ZONES BY 00Z. ISOLATED
TO SCATTERED CONVECTION MAY FIRE BTW 23-02Z ALONG THIS BOUNDARY AND
THEN SLOWLY WORK SOUTHEASTWARD OVERNIGHT. KEPT COVERAGE/PROBABILITY
OF CONVECTION LOW (20-30 PERCENT) WITH DEEPER MOISTURE LOCKED UP
SOUTH OF THE AREA AND STRONGER SUPPORT ALOFT PASSING NORTH AND EAST
OF THE IWX CWA. MODERATE DEEP LAYER SHEAR (40-45 KNOTS) AND WEAK
INSTABILITY (500-1000 J/KG OF MLCAPE) MAY SUPPORT AN ISOLATED
WIND/HAIL THREAT IF CONVECTION FIRES EARLY THIS EVENING ACROSS
NORTHERN ZONES.

FRONTAL SLOPE WILL SINK JUST SOUTH OF THE HWY 24 CORRIDOR BY 12Z
TUESDAY...AND THEN CLEARING OUR SOUTHEASTERN ZONES BY MIDDAY. LOW
LEVEL COOL/DRY ADVECTION WILL BE MORE IMPRESSIVE OVER THE NORTHERN HALF
OF THE FA...ESPECIALLY DOWNWIND OF LAKE MICHIGAN INTO NW INDIANA AND
SW LOWER MICHIGAN...WITH GUIDANCE BACKING OFF SOMEWHAT ON THIS
COOL/DRY PUSH INTO SOUTHERN AREAS. 12Z GUIDANCE ALSO CAME IN A LITTLE
STRONGER WITH A MORE PRONOUNCED PV ANOMALY (ACROSS THE NORTHERN
PLAINS AS OF THIS WRITING) PROGGED TO DROP SOUTHEAST THROUGH THE
NORTHERN OHIO VALLEY TUESDAY AFTERNOON. THIS UPPER LEVEL SUPPORT PER
DCVA/7-3H Q VECTOR CONVERGENCE PROGS...COUPLED WITH MODEST BL
DESTABILIZATION (MAYBE 1000-1500 J/KG OF CAPE TO WORK WITH) AND A
POSSIBLE LOW LEVEL FOCUS ALONG A LEFTOVER INVERTED-LIKE TROUGH MAY
COMBINE TO HELP GENERATE SCATTERED SHOWERS/STORMS TUESDAY
AFTERNOON...BEST CHANCES SOUTH OF HWY 30 IN INDIANA. BUMPED UP POPS
A BIT BUT HELD SHY OF LIKELY WITH DEEPER MOISTURE AND MORE UNSTABLE
AIR SUPPRESSED SOUTH OF THE AREA ALONG THE PRIMARY BAROCLINIC
ZONE. THERE DOES APPEAR TO BE A MARGINAL HAIL/WIND THREAT WITH
SUSTAINABLE UPDRAFTS GIVEN PROGGED WEAK TO MODERATE INSTABILITY AND
NEAR 40 KNOTS OF EFFECTIVE DEEP SHEAR.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 350 PM EDT MON JUN 17 2013

A WEAK UPPER LEVEL TROF WILL BE MOVING ACROSS THE SOUTHERN PART OF
THE AREA EARLY IN THE PERIOD. NCEP MODELS HAVE BEEN TRENDING UP THE
CHANCES OF PRECIPITATION OVER SOUTHEAST AREAS AS THE UPPER LEVEL
TROF COMBINES WITH A WEAK FRONT AND MOVES SOUTHEAST. ADDED A CHANCE
FOR SHOWERS AND THUNDER BEFORE MIDNIGHT TUESDAY NIGHT. BULK SHEAR
AND CAPE SHOULD NOT BE SUFFICIENT FOR SEVERE STORMS. THIS SYSTEM
SHOULD MOVE OUT OF THE AREA FAIRLY QUICKLY...WITH DRY WEATHER AND
MODERATING TEMPERATURES THROUGH THE END OF THE WORK WEEK AS AN UPPER
LEVEL RIDGE BUILDS INTO THE AREA. HAVE TRENDED TEMPERATURES WARMER
OVER THE LAST SEVERAL DAYS OF THE THIS PERIOD. CR ALLBLEND LOOKS TOO
COOL AND APPEARS TO HAVE INGESTED SOME OF THE COOLER MODEL DATA.
OVERALL...FAVOR THE GFS WITH AN UPPER RIDGE EXTENDING INTO THE
FORECAST AREA OVER THE WEEKEND. 850 MB TEMPERATURES OVER 20C SUPPORT
HIGHS AROUND OR TOPPING 90 DEGREES. CR ALLBLEND HAS TRENDED
SHOWER/STORM CHANCES LOWER AND APPEARS TO BE ON TRACK AS MID LEVEL
CAP SHOULD BECOME FAIRLY SUBSTANTIAL. SUBSIDENCE FROM THE UPPER
LEVEL RIDGE SHOULD ALSO INHIBIT STORM ACTIVITY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1235 PM EDT MON JUN 17 2013

VFR/DRY CONDITIONS ARE EXPECTED TO PERSIST THIS AFTERNOON WITH
LIGHT WESTERLY WINDS AHEAD OF A COLD FRONT PROGGED TO DROP THROUGH
THE AREA TONIGHT. MOISTURE/LIFT IS LIMITED WITH THIS FEATURE AS
DEEPER MOISTURE REMAINS LOCKED UP SOUTH OF THE AREA AND STRONG
FORCING WITH A WEAK MID LEVEL SHORTWAVE BYPASSES NORTH OF THE IWX
CWA. WITH THIS EXPECT PRIMARILY VFR CIGS/VIS ALONG AND BEHIND THE
FRONT OVERNIGHT INTO TOMORROW MORNING...WITH A LOW CHANCE FOR A
SHOWER/STORM AT THE TERMINALS WITH FROPA. WITH WEAK MOISTURE
POOLING ALONG FRONT INVOF FWA LATER TONIGHT OPTED FOR A TEMPO MVFR
VIS GROUP. ALSO ADDED THIS AT SBN AS MARINE LAYER MAY WORK IN FOR
A BRIEF TIME.


&&

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

$$

SYNOPSIS...NG/KG
SHORT TERM...STEINWEDEL
LONG TERM...SKIPPER
AVIATION...STEINWEDEL


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