Small Craft Advisory 50, NWS Northern Indiana

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
555 AM EDT SAT OCT 4 2014

.SYNOPSIS...
ISSUED AT 442 AM EDT SAT OCT 4 2014

AN UPPER LEVEL DISTURBANCE WILL BRING ANOTHER CHANCE OF SHOWERS THIS
AFTERNOON...MAINLY ACROSS MICHIGAN AND EXTREME NORTHERN INDIANA.
UNSEASONABLY COOL WEATHER IS ALSO EXPECTED WITH HIGHS TODAY IN THE
UPPER 40S AND LOWS TONIGHT IN THE MID TO UPPER 30S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 442 AM EDT SAT OCT 4 2014

SOUTHERN PIECE OF MIDLEVEL "BOWLING BALL"...WITH 500MB HEIGHTS OF
534 DAM...IS NOW DRIFTING OVER LAKE MICHIGAN PER LATEST WATER
VAPOR IMAGERY. THIS FEATURE WILL PINWHEEL N-NE TODAY AND GET
ABSORBED INTO MORE DOMINANT HEIGHT FALL CENTROID OVER NORTHERN
ONTARIO. THIS WILL LEAVE THE GREAT LAKES IN A SOMEWHAT CONVOLUTED
SYNOPTIC ENVIRONMENT...WITH SHREDS OF VORTICITY AND DEEPER
MOISTURE ROTATING AROUND THE BEHEMOTH CLOSED LOW. OTHER ITEM OF
NOTE FOR THIS FORECAST PACKAGE IS VERY COLD AIR FILTERING OVER
WARM WATERS OF LAKE MICHIGAN...GENERATING SOME LAKE
EFFECT/ENHANCED RAIN SHOWERS. MODELS SHOW 850MB TEMPS AROUND -4C
AND 700MB TEMPS AROUND -13C THIS MORNING...SUPPORTED BY UPSTREAM
00Z SOUNDINGS FROM KMPX AND KDVN. LATEST BUOY OBSERVATIONS SHOW
LAKE MICHIGAN WATER TEMPS STILL AROUND 16C...LEADING TO SOME
IMPRESSIVE LAKE INDUCED CAPE VALUES AND CONVECTIVE DEPTHS BASED ON
NAM BUFKIT DATA. CURRENT LAKE RESPONSE IN OUR CWA IS FIGHTING SOME
DRIER AIR ABOVE 700MB AND AN ALMOST DUE WESTERLY FETCH. MOST OF
THE CWA IS IN A RELATIVE LULL IN PRECIP RIGHT NOW BUT MORE SHOWERS
ARE EXPECTED LATER TODAY AND INTO THIS EVENING.

TROWAL/DEFORMATION AXIS CURRENTLY RESPONSIBLE FOR LIGHT RA/SN OVER
NORTHERN WISCONSIN ON THE NORTHWEST SIDE OF 500MB LOW WILL PIVOT
INTO THE SOUTHERN GREAT LAKES LATER TODAY. THIS FEATURE BECOMES
MUDDLED AS THE SOUTHERN CIRCULATION IS ABSORBED BY THE NORTHERN
ONTARIO CENTROID BUT APPEARS TO BE ENOUGH OMEGA/DEEPER MOISTURE TO
REINVIGORATE LIGHT RAIN SHOWERS IN PARTS OF OUR CWA. THIS IS
ESPECIALLY TRUE IN OUR NORTHERN COUNTIES WHERE LAKE CONTRIBUTION
WILL GREATLY ENHANCE SHOWER COVERAGE/INTENSITY. LATEST MODELS...BOTH
HI-RES AND SPECTRAL...REMAIN CONSISTENT WITH THIS IDEA AND NO MAJOR
QUALMS WITH INHERITED POP FORECAST. ONLY MINOR CHANGE WAS TO CONFINE
HIGHEST POPS TO OUR NORTHERNMOST COUNTIES WITH JUST A LOW CHANCE
ELSEWHERE GIVEN WESTERLY FETCH AND NORTHWARD DISPLACEMENT OF
APPRECIABLE SYNOPTIC FORCING. DRIER CONDITIONS RETURN FOR THE LATTER
HALF OF THE TONIGHT PERIOD.

UNSEASONABLY COLD CONDITIONS EXPECTED TODAY AS THERMAL TROUGH MOVES
DIRECTLY OVERHEAD. MIXING 850MB TEMPS OF -4C TO THE SURFACE YIELDS
ONLY MID TO UPPER 40S FOR HIGHS. CURRENT TEMPS ARE NEAR THESE VALUES
BUT PERSISTENT CAA SHOULD MOSTLY OFFSET ANY DIURNAL CONTRIBUTION
FROM FILTERED INSOLATION. RECORD COLD HIGHS OF 48 AT SBN AND 47 AT
FWA (BOTH SET IN 1935) COULD BE IN JEOPARDY. EXPECT ANOTHER BREEZY
DAY WITH A TIGHT PRESSURE GRADIENT OVER THE GREAT LAKES. MIXING
DEPTHS ARE NOT PARTICULARLY HIGH BUT DO APPROACH 850MB AROUND
MIDDAY. WINDS SPEEDS AT THIS LEVEL ARE ROUGHLY 30 KTS SO A FEW GUSTS
OF 25-30 MPH MAY MIX DOWN TO THE SURFACE. OVERNIGHT LOWS WILL BE IN
THE UPPER 30S FOR MOST PLACES BUT PARTIAL CLEARING IS POSSIBLE IN
OUR SOUTHWEST COUNTIES LATE TONIGHT. SURFACE WINDS WILL ALSO BEGIN
TO RELAX AND THIS COULD LEAD TO A FEW READINGS IN THE LOW TO MID
30S...ALONG WITH SOME PATCHY FROST.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 442 AM EDT SAT OCT 4 2014

LONGEVITY OF UPPER GREAT LAKES VORTEX TO PERSIST INTO EARLY NEXT
WEEK AS SYSTEM RELEASE THWARTED BY DOWNSTREAM EXEMPLARY RIDGE OVR
CNTL/NRN ATL. WHILE OCCASIONAL SHORTWAVES WITHIN THIS FEATURE ALONG
WITH SEVERAL NOTABLE UPSTREAM SHORTWAVES TO ENTER BACKSIDE OF
TROF...FIRST OVER CENTRAL MANITOBA AND ADDITIONAL WAVES WITHIN
STRONG/CONFLUENCY ACRS NERN PAC INTO WRN ALB. STILL SUSPECT AN
OVERALL WANING OF SYSTEMS EFFECT ACROSS CWA...PRIMARILY DUE TO SCOUR
OF LOW LEVEL MOISTURE IN WAKE OF TWO ROBUST SHORTWAVE PASSAGES TODAY
AND EARLY TONIGHT. THIS SHOULD BODE WELL FOR DIURNAL PLUS RISES
AFTER COLD START SUNDAY. DID HOWEVER LEAVE LOW SLIGHT CHC MENTION
SHOULD ANY RESIDUAL MOISTURE FIND ADVANTAGE IN EXTREMELY STEEP 0-1KM
LAPSE RATES SUN AFTN. WEAK CLIPPER FEATURE MOVES UP OHIO VALLEY
SUNDAY NIGHT...HOWEVER NEAR SURFACE CPDS STILL REMAIN HIGH AND
UNDERCUT GOING POPS. SUSPECT CHCS TO INCREASE IN WAKE OF CLIPPER
FEATURE LATE SUN NIGHT INTO MON...WITH DRAWDOWN OF SHORTWAVES
ASSOCIATED WITH NWWD RETROGRADED VORTEX CENTERED IN FAR WRN ONT.
GENERALLY LOW CHC POPS AND LOW QPF /WITH MODEST MOISTURE RECOVERY AT
BEST ANTICIPATED/ CONT INTO TUE AFTERWHICH STRONG CONSENSUS BUILDS
TO NWD LIFTOUT/FILLING OF VORTEX. AIRMASS THERMAL MODERATION
CONTINUES INTO MIDWEEK AND RAISED LOWS MONDAY NIGHT AS LOW LEVEL
THERMAL TROF BEGINS RETREAT. EFFECTIVELY COORDINATED DRY MIDWEEK
AGAINST WET BLEND. CONCEDED THAT SOME HINTS OF SRN PLAINS WARM
FRONTAL LEAF TOWARD SWRN GRTLKS COULD PROVIDE IMPETUS FOR LIGHT RAIN
THU/THU NIGHT..THOUGH ANY SUBSTANTIVE MOISTURE FLUX/NAMELY SIMON
REMNANTS STILL WELL SW OF REGION. RETURN TO NIL WX DY7 AMID
LACKLUSTER/LOW AMPLITUDE ERN CANADIAN TROF WITH REASSERTION OF
PLAINS TO SWRN GRTLKS SURFACE RIDGE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 555 AM EDT SAT OCT 4 2014

TROWAL AXIS CURRENTLY OVER WISCONSIN WILL PIVOT THROUGH THE
SOUTHERN GREAT LAKES LATER TODAY. SYNOPTIC FORCING IS GENERALLY
WEAK BUT SHOWERS WILL BE ENHANCED BY VERY UNSTABLE CONDITIONS OVER
LAKE MICHIGAN. WESTERLY FETCH MAY LIMIT IMPACT TO THE TERMINALS
BUT A BRIEF PERIOD OF FUEL ALTERNATE CONDITIONS MAY BE POSSIBLE AT
KSBN DURING THE LATE AFTERNOON. PRECIP CHANCES AND FUEL ALTERNATE
POTENTIAL ARE MUCH LOWER AT KFWA. OTHERWISE VFR CONDITIONS
EXPECTED WITH GUSTY WESTERLY WINDS BEING THE ONLY OTHER AVIATION
HAZARD.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WARNING UNTIL 10 AM EDT THIS MORNING FOR LMZ043-046.

&&

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...MURPHY
AVIATION...AGD

VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSNORTHERNINDIANA

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