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000
FXUS63 KIWX 210925
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
425 AM EST SAT DEC 21 2013

.SYNOPSIS...
ISSUED AT 418 AM EST SAT DEC 21 2013

A STRONG LOW PRESSURE SYSTEM WILL MOVE RAPIDLY NORTHEAST FROM TEXAS
THIS MORNING... TO INDIANA TONIGHT. HEAVY RAINFALL IS EXPECTED ALONG
THE TRACK OF THE LOW WHICH MAY CAUSE FLOODING. TO THE NORTHWEST OF
THE LOW TRACK... SOME FREEZING RAIN IS POSSIBLE THIS MORNING AND
TONIGHT. HIGHS TODAY WILL RANGE FROM THE MID 30S OVER NORTHWEST
INDIANA AND SOUTHERN MICHIGAN... TO THE LOWER TO MIDDLE 40S OVER
NORTHEAST INDIANA AND NORTHWEST OHIO. LOWS TONIGHT WILL BE IN THE
30S OVER MOST OF THE AREA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 418 AM EST SAT DEC 21 2013

NRLY STNRY FRONTAL BOUNDARY EXTENDS FROM THE LWR GRTLKS TO SRN TX
THIS MORNING. A LOW PRESSURE SYSTEM IS EXPECTED TO LIFT RAPIDLY NE
ALONG THIS STRONG BAROCLINIC ZONE TO NRN INDIANA BY SUNDAY MORNING.
UNSEASONABLY WARM/MOIST AIRMASS SOUTH OF THE FRONT WITH PRECIPITABLE
WATER OF 1-1.5INCHES. AS THE LOW APPROACHES OUR AREA TODAY/TNGT...
VERY STRONG FORCING INCLUDING STRONG UPR LEVEL DIVERGENCE IN RIGHT ENTRANCE
REGION OF A >200KT JET STREAK OVER SE CANADA... STRONG LOW-MID LEVEL
MOISTURE FLUX/THETA-E ADVECTION... AND STRONG SLOPED FRONTOGENESIS
WILL MOVE ACROSS OUR AREA. COMBINATION OF THIS VERY STRONG FORCING
AND ACCESS TO AN UNSEASONABLY WARM MOIST AIRMASS WILL CAUSE RAIN
TO OVERSPREAD THE AREA TODAY... HEAVIEST AND MOST PERSISTENT OVER
SE PORTION OF THE CWA. SREF QPF HAS BEEN VERY LARGE AND FAIRLY
CONSISTENT FOR TODAY/TNGT. FOLLOWED WPC QPF WHICH WAS JUST
SLIGHTLY HIGHER YIELDING 24HR TOTALS AROUND AN INCH NW TO AROUND 3
INCHES SE. THESE WIDESPREAD HEAVY RAINFALL AMOUNTS THIS TIME OF
YEAR SHOULD BE SUFFICIENT TO CAUSE SOME FLOODING... THUS THE FLOOD
WATCH REMAINS IN EFFECT AND EXPANDED SLIGHTLY NORTH ACROSS NE
PORTION OF CWA WHICH ALSO SHOULD GET IN ON THE HEAVY RAIN.

OTHER CONCERN IS ON THE POTENTIAL FOR FREEZING RAIN ACROSS NW
PORTION OF THE CWA WHERE TEMPS THIS MORNING HOVERING JUST ABOVE
FREEZING. AS SFC WINDS TURN NE WITH APCHG LOW TODAY TEMPS MAY FALL
SLIGHTLY THERE. GIVEN THAT IT IS STILL DOUBTFUL IF TEMPS WILL BE BLO
FREEZING AS RAIN MOVES THROUGH THE AREA PLUS UNCERTAINTY ON HOW MUCH
ICE ACCRUAL WILL OCCUR WITH A RELATIVELY WARM RAIN FALLING ON
SURFACES AT OR SLIGHTLY BLO FREEZING... OPTED TO HOLD OFF ON A
FREEZING RAIN HEADLINE ATTM AND JUST CONT WITH THE CHC OF FREEZING
RAIN IN THE GRIDS/ZFP/HWO.

ONLY OTHER CHANGE OF NOTE TO PREVIOUS FCST WAS TO ADD A CHC OF TSTMS
TONIGHT TO SE PORTION OF CWA. MODELS SUGGEST WK ELEVATED INSTABILITY
WILL ACCOMPANY THE STRONG FORCING TONIGHT WHICH COULD LEAD TO A FEW
TSTMS ACROSS THIS AREA. WITH SURFACE BASED INVERSION EXPECTED TO BE
QUITE SHALLOW ACROSS FAR SERN PORTION OF THE AREA... IF STORMS DO
OCCUR THERE IS SOME POTENTIAL THEY COULD TRANSFER SOME OF THE
STRONG WINDS ALOFT TO THE SFC AS FCST IN SPC 5% CONVECTIVE WIND
OUTLOOK CLIPPING THIS AREA.

TEMPS SHOULD BE FAIRLY STEADY ACROSS THE AREA TODAY AND TONIGHT WITH
HIGHS RANGING FROM THE M30S NW TO THE M40S SE... AND LOWS RANGING
FROM THE L30S NW TO THE L40S SE.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 418 AM EST SAT DEC 21 2013

PRECIP CHANCES WILL BEGIN TO DECREASE BY SUNDAY MORNING AS A DRY
SLOT NUDGES INTO THE REGION. RAIN WILL GRADUALLY CHANGE OVER TO SNOW
BY SUNDAY AFTERNOON...WITH MUCH COOLER AIR WRAPPING AROUND THE BACK
OF THIS WEEKENDS HEAVY RAIN PRODUCING SYSTEM AS IT SHIFTS EAST.
TEMPERATURES LOOK TO BEGIN DROPPING OFF SUNDAY AFTERNOON...DIPPING
INTO THE LOW/MID 20S BY SUN NIGHT. HAZARDOUS CONDITIONS COULD
DEVELOP AS STANDING WATER LEFT OVER FROM THE WEEKEND RAIN EVENT
FREEZES. THE COLD AIR IS ALSO EXPECTED TO LINGER KEEPING
TEMPERATURES STUCK BELOW NORMAL LEVELS THROUGHOUT THE MAJORITY OF
THE PERIOD.  HIGHS WILL BARELY MAKE IT TO THE 20S EARLY THIS WEEK
WITH LOWS DROPPING INTO THE LOW TEENS AND EVEN SINGLE DIGITS.

A SHORTWAVE WILL MOVE THROUGH THE REGION JUST TO OUR NORTH
MONDAY...PROVIDING ANOTHER CHANCE FOR SNOW SHOWERS LATE MONDAY INTO
TUESDAY MORNING BEFORE HIGH PRESSURE PUSHES INTO THE REGION. SNOW
CHANCES CONTINUE ON WEDNESDAY AHEAD OF THE NEXT APPROACHING SYSTEM
WITH THE GREATEST PROBABILITY ONCE AGAIN TO OUR NORTH. ANY SNOWFALL
AMOUNTS IN OUR CWA APPEAR TO REMAIN LIGHT AT THIS TIME. TEMPS COULD
REBOUND INTO THE LOW TO MID 30S CHRISTMAS DAY BEFORE ANOTHER SHOT OF
ARCTIC AIR SHOOTS DOWN FROM CANADA WITH THE PASSAGE OF A COLD
FRONT.  THIS BRINGS ANOTHER SMALL CHANCE FOR SNOWFALL...HOWEVER THE
AMOUNT OF MOISTURE DOES NOT LOOK OVERLY PROMISING AT THIS TIME.
MODELS ARE CONTINUING TO SHOW SUBSTANTIAL DISAGREEMENT AS TO THE
TIMING AND EXTENT OF THE COLD AIR DURING THE LATTER PART OF THIS
PERIOD...THEREFORE OPTED TOWARD ALLBLEND VALUES UNTIL MODELS CAN
COME TO A BETTER CONSENSUS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED
AT 1215 AM EST SAT DEC 21 2013

SWLY SFC WINDS HAVE PICKED UP A BIT IN WAKE OF A LOW PRESSURE
SYSTEM MOVG NE ACROSS SERN MI. THIS HAS ALLOWED VSBYS TO IMPROVE
ACROSS MUCH OF INDIANA THOUGH STILL IFR ACROSS NW INDIANA. AS THE
LOW CONTS MOVG AWAY FROM THE AREA WINDS WILL DIMINISH OVERNIGHT
WHICH SHOULD ALLOW FOG TO DVLP AGAIN AT FWA BY MORNING AS LOW
LEVELS REMAIN VERY MOIST. IFR CONDITIONS AND RAIN EXPECTED ACROSS
THE AREA SATURDAY CONTG INTO THE EVE AS A LOW PRESSURE SYSTEM
MOVES NE FROM TX TO INDIANA.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FLOOD WATCH FROM 1 PM EST /NOON CST/ THIS AFTERNOON THROUGH
     SUNDAY MORNING FOR INZ007>009-012>018-020-022>027-032>034.

MI...FLOOD WATCH FROM 1 PM EST THIS AFTERNOON THROUGH SUNDAY MORNING
     FOR MIZ081.

OH...FLOOD WATCH FROM 1 PM EST THIS AFTERNOON THROUGH SUNDAY MORNING
     FOR OHZ001-002-004-005-015-016-024-025.

LM...NONE.
&&

$$

SYNOPSIS...JT
SHORT TERM...JT
LONG TERM...KG
AVIATION...JT


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