000
FXUS63 KIWX 230809
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
409 AM EDT THU MAY 23 2013

.SYNOPSIS...
ISSUED AT 407 AM EDT WED MAY 22 2013

A COLD FRONT EXTENDING ACROSS SOUTHERN MICHIGAN AND NORTHERN
ILLINOIS THIS MORNING... WILL MOVE SOUTH TO THE OHIO RIVER VALLEY THIS
EVENING. SHOWERS ARE LIKELY AS THE FRONTAL ZONE MOVES THROUGH THE
AREA. HIGH PRESSURE WILL MOVE SOUTH FROM CENTRAL CANADA INTO THE
GREAT LAKES AND OHIO VALLEY BEHIND THE FRONT TONIGHT... CAUSING
SKIES TO CLEAR AND UNSEASONABLY COOL TEMPERATURES TO OVERSPREAD
THE REGION.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 407 AM EDT THU MAY 23 2013

CUT-OFF UPR LEVEL LOW OVER THE MID MS VALLEY CONTS PROCESS OF
BEING ABSORBED BY TROF DIGGING S-SE ACROSS THE GRTLKS. SFC CDFNT
ASSOCIATED WITH THIS UPR TROF EXTENDED FROM SRN LAKE HURON TO JUST
SOUTH OF LAKE MICHIGAN AND THEN WNW ACROSS NRN IL. AREAS OF FOG
OCRG NEAR FRONT OVER SRN LAKE MICHIGAN AND EXTENDING SLIGHTLY
INLAND. FLOW LIGHT ENOUGH TO KEEP THIS FROM SPREADING VERY FAR
INLAND AND AS WINDS PICK UP...BOUNDARY LAYER MIXING SHOULD ALLOW
VSBYS TO IMPROVE NEAR THE LAKE EARLY THIS MORNING. A FAIRLY
WIDESPREAD AREA OF SHOWERS BEHIND THE FRONT ACROSS NRN IL... WI...
AND NW MI. FORCING RESPONSIBLE FOR THESE SHOWERS MAY WEAKEN SOME
TODAY AS UPR LOW CONTS TO SHEAR OUT... BUT EXPECT DIGGING UPR TROF
AND LIFT ALONG FRONTAL ZONE WILL BE SUFFICIENT TO MAINTAIN POST
FRONTAL SHOWERS MOVG SEWD ACROSS OUR AREA DURING THE DAY. SOME
SHOWERS MAY LINGER OVER SERN PORTION OF THE AREA EARLY THIS EVE
BUT SHOULD BE FOLLOWED BY CLEARING OVERNIGHT AS STRONG
SUBSIDENCE/DRYING OVERSPREADS THE CWA.

RATHER TIGHT PRESSURE GRADIENT BEHIND THE FRONT SHOULD RESULT IN
GUSTS UP TO 30MPH BEHIND THE FRONT TODAY... A LITTLE STRONGER IN
VCNTY OF LAKE MICHIGAN WHERE THERMAL GRADIENT ENHANCED. CONTG WITH
GALE WARNING FOR NSH ZONES AND SINCE BEACH SEASON HAS BEGUN...
ISSUED A BEACH HAZARD STATEMENT FOR THE SURF ZONE.

WITH STRONG CDFNT MOVG ACROSS THE AREA TODAY THERE WILL BE A TIGHT
TEMP GRADIENT WITH HIGHS EXPECTED TO RANGE FROM THE L50S NW TO THE
U60S SE. STRONG CAA TODAY/TONIGHT COMBINED WITH CLEARING SKIES
TONIGHT SHOULD ALLOW TEMPS TO FALL INTO THE U30S NORTH AND L40S
SOUTH. WITH SFC HIGH REMAINING TO THE WEST OF OUR AREA OVERNIGHT...
NORTHERLY GRADIENT EXPECTED TO BE STRONG ENOUGH TO MAINTAIN SOME
LIGHT WIND THROUGHOUT THE NIGHT WHICH SHOULD PREVENT A MORE SGFNT
TEMP DROP AND FROST FROM FORMING.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 407 AM EDT THU MAY 23 2013

REMARKABLY PLACID CONDITIONS TO BEGIN THIS LONG TERM PERIOD AS
BLOCKY HIGH AMPLITUDE WAVE TRAIN SLOWLY PROPAGATES
EASTWARD...LEAVING THE SOUTHERN GREAT LAKES ON SUBSIDENT SIDE OF
IMPRESSIVE MID/UPPER LEVEL RIDGE. 1030MB SURFACE ANTICYCLONE WILL BE
FIRMLY IN PLACE BY FRIDAY...LEADING TO A PLEASANT...ALBEIT SOMEWHAT
COOL...DAY. WILL BE INTERESTING TO SEE HOW WARM WE ACTUALLY GET WITH
THE STRONG LATE MAY SUN ANGLE ACTING ON CHILLY CP AIRMASS. THERMAL
TROUGH WILL BE PUSHING EASTWARD DURING THE DAY AND 850MB TEMPS LOOK
TO RECOVER TO AROUND 5C BY THE AFTERNOON. THIS WOULD USUALLY SUPPORT
HIGHS ONLY IN THE LOW 60S BUT FULL SUN SHOULD ALLOW FOR A GOOD
SUPERADIABATIC RESPONSE AT THE SURFACE...PUSHING HIGHS A FEW DEGREES
WARMER. WENT WITH GENERALLY MID 60S...SAVE FOR THE LAKESHORE AREAS
WHERE LIGHT NORTHERLY WINDS WILL ALLOW FOR DECENT MARINE INFLUENCE.
GOOD RADIATIONAL COOLING EXPECTED FRIDAY NIGHT. SURFACE HIGH WILL BE
DIRECTLY OVERHEAD WITH CALM WINDS AND FULL BOUNDARY LAYER
DECOUPLING. COULD BE SOME INCREASING CIRRUS TOWARD DAYBREAK BUT THE
EFFECT SHOULD BE MINIMAL AND EXPECT LOWS AROUND 40F ONCE AGAIN.
FROST IS NOT LIKELY GIVEN MARGINAL TEMPS AND VERY DRY AIRMASS.

FORECAST BECOMES A BIT MORE MUDDLED HEADING INTO THE HOLIDAY
WEEKEND. SEVERAL WEAK VORTICES ARE EXPECTED TO CASCADE DOWN THE
LONGWAVE RIDGE AND INCITE A DECENT WAA/FGEN RESPONSE TO OUR WEST.
QUESTION WILL BE WHETHER OR NOT THIS FORCING CAN CLIP OUR WESTERN
CWA. GIVEN THE STRENGTH OF CONFLUENCE ALOFT AND PERSISTENCE OF
GENERAL AVA IN SLOWLY PROGRESSING LARGE SCALE PATTERN...EXPECT
PRECIP WILL REMAIN CLOSELY TIED TO LOW LEVEL THETA-E GRADIENT DRAPED
OVER THE MIDWEST. PREPONDERANCE OF DRY AIR AND EFFECT OF COLD LAKES
THIS TIME OF YEAR SHOULD MAINTAIN HIGH PRESSURE AND DRY NORTHEAST
FLOW LOCALLY...AS SEEN IN THE LAST FEW ECMWF RUNS. WOULDNT RULE OUT
A FEW SPRINKLES OVER OUR SOUTHWEST AT TIMES THIS WEEKEND BUT
CONFIDENCE IS MUCH TOO LOW TO INCLUDE IN THE FORECAST. BAROCLINIC
ZONE WILL EVENTUALLY WORK ITS WAY EAST AS PACIFIC JET FORCES
DOWNSTREAM RIDGE TO SHIFT EASTWARD EARLY NEXT WEEK. LARGE
DISAGREEMENT IN LATEST MODELS ON HOW AND WHEN THIS WILL HAPPEN
THOUGH. WILL KEEP WITH PREVIOUS ECWMF PREFERENCE FOR NOW AND HOLD
OFF ON POPS UNTIL MIDWEEK. AFTER ANOTHER COOL DAY ON
SATURDAY...EXPECT A SLOW MODERATING TREND THROUGH EARLY NEXT WEEK AS
RIDGE AXIS PASSES OVERHEAD. TEMPS SHOULD RETURN TO AT OR ABOVE
NORMAL BY TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 133 AM EDT THU MAY 23 2013

CDFNT ACCOMPANIED BY IFR CONDITIONS DROPPING S-SE ACROSS
WI-MI EARLY THIS MORNING. EXPECT FLYING CONDITIONS TO DETERIORATE
RATHER QUICKLY BEFORE DAWN AT SBN AS LAKE MICHIGAN MARINE LAYER
PUSHES INLAND. CONDITIONS THERE SHOULD IMPROVE TO MVFR THIS AFTN AND
VFR AGAIN BY THIS EVE. SLOWER DOWNWARD TREND FCST AT FWA WITH VFR
CONDITIONS LOWERING TO MVFR THIS MORNING AND PERSISTING THROUGH THE
AFTN BEFORE IMPROVING TO VFR THIS EVE. POST FRONTAL -SHRA UPSTREAM
OVER MI-WI ALSO EXPECTED TO SPREAD ACROSS NRN INDIANA TODAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...BEACH HAZARDS STATEMENT FROM 10 AM CDT THIS MORNING THROUGH
     FRIDAY EVENING FOR INZ003.

MI...BEACH HAZARDS STATEMENT FROM 11 AM EDT THIS MORNING THROUGH
     FRIDAY EVENING FOR MIZ077.

OH...NONE.
LM...GALE WARNING FROM 10 AM THIS MORNING TO 8 PM EDT THIS EVENING
     FOR LMZ043-046.

&&

$$

SYNOPSIS...CEO/KG
SHORT TERM...JT
LONG TERM...AGD
AVIATION...JT


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