Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 231150
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
650 AM EST SUN NOV 23 2014

.SYNOPSIS...
ISSUED AT 410 AM EST SUN NOV 23 2014

A STORM SYSTEM WILL ORGANIZE ACROSS THE CENTRAL UNITED STATES TODAY
AND WILL BRING A WIDESPREAD RAINFALL TO THE REGION FROM LATE THIS
AFTERNOON THROUGH MONDAY MORNING. RAIN SHOWERS WILL CHANGE TO SNOW
SHOWERS MONDAY AFTERNOON AS COLDER AIR RUSHES INTO THE AREA BEHIND
THIS SYSTEM. SOME LIGHT SNOW ACCUMULATIONS WILL BE POSSIBLE FROM
MONDAY AFTERNOON INTO TUESDAY MORNING...MAINLY ACROSS PORTIONS OF
NORTHWEST AND NORTH CENTRAL INDIANA...ALONG WITH SOUTHERN LOWER
MICHIGAN. HIGH TEMPERATURES TODAY WILL REACH MAINLY INTO THE MID
50S. TEMPERATURES WILL NOT DROP MUCH TONIGHT...WITH LOWS FROM THE
UPPER 40S TO LOWER 50S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM EST SUN NOV 23 2014

FORECAST ITEMS TO ADDRESS FOR THE SHORT TERM WILL BE EVOLUTION OF
ONGOING RAIN THIS MORNING...AND THEN A MORE WIDESPREAD RAINFALL
EVENT FOR LATE THIS AFTERNOON AND TONIGHT.

A RELATIVELY NARROW ZONE OF 900-750 HPA MOISTURE CONVERGENCE HAS
SUPPORTED AN AREA OF RAIN THAT HAS AFFECTED PRIMARILY SOUTHEAST HALF
OF THE AREA DURING MOST OF THE OVERNIGHT HOURS. SHORT TERM NAM/RAP
PROGS SUGGEST THAT MAGNITUDE OF THIS MOISTURE CONVERGENCE SHOULD
GRADUALLY WANE OVER NEXT FEW HOURS AND LIFT TO THE NORTHEAST. THIS
IDEA IS SUPPORTED WELL IN HIGHER RES ARW/NMM OUTPUT THIS MORNING.
THUS WILL CARRY CATEGORICAL POPS OVER THE NEXT FEW HOURS ACROSS THE
SOUTHEAST...WITH A FAIRLY STEADY DOWNWARD TREND IN POPS TOWARD
DAYBREAK. DAYBREAK SHOULD ALSO MARK THE APPROXIMATE TIME WEAK VORT
MAX EVIDENT IN WATER VAPOR IMAGERY ACROSS SOUTHWEST LOWER MICHIGAN
DEPARTS TO THE EAST. THUS...STILL EXPECTING A SIZABLE LULL IN
GREATER PRECIP COVERAGE FROM EARLY THIS MORNING THROUGH AT LEAST
EARLY AFTERNOON WITH RELATIVELY WEAK FORCING.

BY MID TO LATE AFTERNOON...LOW LEVEL MOISTURE TRANSPORT SHOULD
STRENGTHEN ONCE AGAIN AS VIGOROUS UPPER LEVEL SHORT WAVE ACROSS THE
LOWER MS VALLEY BEGINS TO LIFT NORTH-NORTHEASTWARD. INITIAL HIGHER
POPS LATER THIS AFTERNOON MAY BE CONFINED TO A RELATIVELY NARROW
ZONE AND DEPEND ON EXACT POSITIONING OF STRONGEST LOW LEVEL MOISTURE
TRANSPORT. HOWEVER...TOWARD EVENING...GUIDANCE IS STILL IN GOOD
AGREEMENT IN DEPICTING SYNOPTIC SUPPORT INCREASING AS SMALLER SCALE
UPPER VORT MAX TRACKS INTO OHIO VALLEY...AND LARGER SCALE UPPER
TROUGH WORKS ACROSS CENTRAL CONUS. COUPLED UPPER JET STRUCTURE ALSO
SHOULD TEND TO AID IN EXPANDING RAIN SHOWER COVERAGE BY EARLY THIS
EVENING. NO CHANGE TO CATEGORICAL POPS FROM LATE AFTERNOON THROUGH
THE EVENING WITH SOME RESPECTABLE RAINFALL AMOUNTS OF AROUND AN INCH
POSSIBLE BY DAYBREAK MONDAY. MOST OF THIS RAIN SHOULD OCCUR IN THE
22Z-06Z TIMEFRAME AS STRONGER UVM SHIFTS NORTHEAST OF THE AREA
OVERNIGHT WITH PASSAGE OF INITIAL SHORT WAVE. POCKET OF SLIGHTLY
DRIER LOW/MID LEVEL AIR BEHIND THIS FEATURE WILL BE SHORT LIVED AS
LARGER SCALE TROUGH APPROACHES FROM THE WEST WITH MORE WIDESPREAD
RAIN SPREADING BACK INTO THE AREA TOWARD DAYBREAK MONDAY.

GIVEN STRONG LLJ/UPPER DYNAMICS/MOISTURE TRANSPORT...REALLY
CANNOT RULE OUT ISOLD THUNDER ANY TIME FROM LATE THIS AFTERNOON
THROUGH TONIGHT BUT PROBABILITIES STILL APPEAR TO BE VERY LOW FOR
ANY GIVEN LOCATION AND WILL NOT ADD ANY MENTION AT THIS TIME.
PERHAPS THE BEST CHANCE OF ISOLD THUNDER WILL BE VERY LATE TONIGHT
ACROSS THE WEST WHERE DIFFERENTIAL TEMP ADVECTION SHOULD SETUP
POCKET OF WEAK INSTABILITY FROM NORTHERN ILLINOIS INTO NORTHWEST
INDIANA. IN TERMS OF TEMPERATURES....HIGHS TODAY SHOULD REACH INTO
THE LOWER TO MID 50S...WITH NEARLY STEADY TEMPERATURES TONIGHT DUE
TO CONTINUED WAA/LLJ/CLOUD COVER.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 410 AM EST SUN NOV 23 2014

MAIN FOCUS REMAINS ON PTYPE/STRONG WINDS/FALLING TEMPS WITH DYNAMIC
PHASED LOW LIFTING THROUGH THE GREAT LAKES REGION MONDAY-MONDAY
EVENING. UNSEASONABLY CHILLY/DRIER THEREAFTER...

00Z GUIDANCE OVERALL PICKING UP ON STRONGER SHEARED SHORTWAVE ENERGY
NOW INTO THE FOUR CORNERS IN LEFT EXIT REGION OF A 140 KT UPPER JET.
THE RESULT HAS BEEN A TREND TOWARD A MORE ROBUST DEFORMATION/FGEN
AXIS LIFTING NE THROUGH THE MID MS VALLEY/WESTERN LAKES MON-MON EVE
AS THIS JET COUPLING/SHORTWAVE ENERGY ROUNDS THE BASE OF AN
AMPLIFYING CENTRAL CONUS LONGWAVE TROUGH. STRONG COLD ADVECTION
FOLLOWING THE PASSAGE OF THE SYSTEM COLD FRONT SHOULD ALLOW RAIN TO
CHANGE OVER TO SNOW WITHIN THIS BURGEONING DEFORMATION AXIS MON
AFTN. FAVORED ECMWF/GFS GUIDANCE SUGGEST THAT THIS FEATURE WILL
PIVOT INTO OUR NORTHWESTERN ZONES DURING THIS TIME WITH LIGHT
ACCUMULATIONS POSSIBLE...ESPECIALLY SW LOWER MI THANKS TO LAKE
ENHANCEMENT. MID LEVEL DRY SLOT SHOULD IMPINGE ON SOUTHEASTERN ZONES
SUPPORTING A DOWNTREND IN RAIN SHOWER COVERAGE DURING THE DAY...WITH
LATER CHANGEOVER TO LIGHT SNOW SHOWERS/FLURRIES (LITTLE TO NO ACCUM)
DELAYED TO LATE MON EVE HERE AS PRIMARY HEIGHT FALL AXIS SETTLES IN.
HEADLINE WORTHY WIND GUSTS (>45 MPH) ALSO REMAINS A POSSIBILITY FOR
THE ENTIRE CWA BY LATER MON MORNING-AFTN. STILL CONSIDERABLE
DIFFERENCES NOTED IN GUIDANCE ON JUST HOW DEEP SFC REFLECTION WILL
BE ONCE REACHING THE NRN LAKES...RESULTING IN SOME UNCERTAINTY.
IMPRESSIVE PRESSURE RISES AND SLIGHT DEEPENING OF MIXED LAYER IN
RESPONSE TO THE COLD ADVECTION PROCESS MAY BE ENOUGH TO TAP INTO
40-50 KT 900 MB JET CORE (LOW CONFIDENCE).

COLD/MOIST CYCLONIC FLOW WITHIN DEEP LAYERED EASTERN CONUS TROUGH
AXIS WILL KEEP CLOUDS AND SPORADIC SNOW SHOWERS/FLURRIES AROUND
LATER MONDAY NIGHT INTO TUESDAY...ESPECIALLY NORTHWEST ZONES AS 850
MB DELTA T`S DROP INTO THE MID TEENS. A GRADUAL TRANSITION TO LOWER
AMPLITUDE WNW FLOW IS EXPECTED WED THRU SAT...BUT EXPECT THE LOCAL
AREA TO MAINLY REMAIN ON COLD SIDE OF A PLAINS TO MID MS VALLEY
BAROCLINIC ZONE...RESULTING IN AN EXTENDED PERIOD OF BELOW NORMAL
TEMPS. SEVERAL MOISTURE STARVED SHORTWAVES WILL RIPPLE THROUGH IN
THIS FLOW...ONE LATER WED-THU AM AND ANOTHER POSSIBLE TOWARD END OF
PERIOD...BRINGING A COUPLE CHANCES FOR LIGHT SYSTEM SNOW AND RENEWED
LAKE RESPONSES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 631 AM EST SUN NOV 23 2014

A WEAK UPPER LEVEL SHORT WAVE ACROSS SOUTH CENTRAL LOWER MICHIGAN
WILL SHIFT INTO THE EASTERN GREAT LAKES THIS MORNING. AS THIS
OCCURS...STRONG LOW/MID LEVEL MOISTURE CONVERGENCE WHICH AIDED
BETTER RAIN COVERAGE DURING THE OVERNIGHT HOURS WILL ALSO SHIFT
EASTWARD...RESULTING IN DIMINISHING RAIN COVERAGE OVER THE NEXT
SEVERAL HOURS. THIS LULL SHOULD LAST THROUGH THE MORNING WITH JUST
SOME ISOLATED OR SCATTERED LIGHT SHOWERS EXPECTED. A MORE POTENT
SHORT WAVE ACROSS THE LOWER MS VALLEY WILL LIFT NORTH-
NORTHEASTWARD TONIGHT WITH A STRONG LOW LEVEL JET OVERSPREADING
NORTHERN INDIANA TONIGHT. THIS WILL RESULT IN WIDESPREAD RAIN
AFFECTING TERMINALS LATE THIS AFTERNOON AND ESPECIALLY TONIGHT. AN
ISOLATED THUNDERSTORM REMAINS A VERY LOW PROBABILITY AND WILL
CONTINUE TO REFRAIN FROM ANY MENTION IN TERMINAL FORECASTS AT THIS
TIME. TREND TO MVFR CIGS EXPECTED BY MID AFTERNOON...WHICH SHOULD
DETERIORATE RAPIDLY TOWARD 00Z. IFR CONDITIONS ARE A GOOD
POSSIBILITY AT BOTH TERMINALS TONIGHT AS SFC WARM LIFTS INTO
CENTRAL INDIANA. SOUTH WINDS TO CONTINUE THROUGH THE PERIOD AT 10
TO 15 KNOTS WITH PERIODIC HIGHER GUSTS POSSIBLE. ALONG WITH THE
AFOREMENTIONED LOW LEVEL JET TONIGHT WILL COME INCREASED LLWS
POTENTIAL BY 00Z AND HAVE CONTINUED THIS MENTION FOR THE 12Z TAFS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR
     LMZ043-046.

     SMALL CRAFT ADVISORY UNTIL 9 AM EST MONDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...STEINWEDEL
AVIATION...MARSILI


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