Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 230547
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1247 AM EST TUE DEC 23 2014

.SYNOPSIS...
ISSUED AT 1244 AM EST TUE DEC 23 2014

A WARM FRONT WILL LIFT NORTH THROUGH THE AREA EARLY THIS MORNING
BRINGING PERIODS OF RAIN. DRIER AND MUCH MILDER AIR WILL FILTER IN
BY THIS AFTERNOON WITH LOW CLOUDS AND SOME PATCHY LIGHT RAIN OR
DRIZZLE POSSIBLE. HIGHS THIS AFTERNOON WILL BE UNSEASONABLY MILD
INTO THE UPPER 40S AND LOW 50S. A STRENGTHENING LOW PRESSURE
SYSTEM WILL THEN TRACK DUE NORTH INTO INDIANA WEDNESDAY.
TEMPERATURES WILL LIKELY BE WARM ENOUGH FOR PRECIPITATION TO FALL
AS MAINLY RAIN ACROSS THE LOCAL AREA. CHRISTMAS DAY WILL FEATURE
DRIER AND COOLER CONDITIONS AS HIGH PRESSURE BUILDS IN.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 408 PM EST MON DEC 22 2014

AREA OF RAIN ASSOCIATED WITH LOW LEVEL THETA-E ADVECTION/ISENT
LIFT/MOISTURE CONVERGENCE AHEAD OF DEEPENING CENTRAL PLAINS LOW
SHOULD CONT TO OVERSPREAD OUR CWA FROM WEST-EAST LATE THIS AFTN/EVE.
ANOTHER BATCH OF WIDESPREAD RAIN EXPECTED OVERNIGHT AS VORT MAX
ROTATING AROUND THE UPR LOW LIFTS NE THROUGH NRN IL AND OCCLUDING
SFC FRONT APPROACHES FROM THE WEST. RAINFALL SHOULD BE LIFTING NE
OUT OF OUR CWA TUE MORNING AS DRY SLOT WRAPPING AROUND THE LOW
SPREADS NE INTO OUR AREA. LOW LEVELS WILL LIKELY REMAIN SATURATED
WITH SOME WK LIFT CONTG UNTIL OCCLUDED FRONT PASSES... SO EXPECT
SOME LIGHT RAIN OR DRIZZLE WILL PERSIST UNTIL MIDDAY...ESPECIALLY
ACROSS NRN/ERN PORTIONS OF CWA. WITH WARM FRONT MOVG THROUGH THE
AREA THIS PERIOD... TEMPS SHOULD CONT ON A SLOW CLIMB OVERNIGHT AND
TUE... REACHING HIGHS IN THE M-U40S TUE AFTN.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 408 PM EST MON DEC 22 2014

...MAIN FOCUS OF THE LONG TERM IS THE STORM SYSTEM EXPECTED
CHRISTMAS EVE...

UNFORTUNATELY NEW MODEL RUNS CONTINUE TO DISAGREE ON THE SECONDARY
SFC LOW TRACK FOR CHRISTMAS EVE/CHRISTMAS DAY. THE 12Z GFS/GEM HAVE
A STRONGER SYSTEM MOVING FROM KY AT 12Z WED...TO NE IN/NW OH BY 18Z
WED...AND THE THUMB REGION/LAKE HURON BY 00Z THU. THE 00Z ECMWF/12Z
NAM HAVE A WEAKER SURFACE LOW ALONG THE GULF 12Z WED WITH A TROUGH
ACROSS THE OHIO VALLEY...THEN DEVELOP THE SURFACE LOW AND LIFT IT
INTO KY BY 18Z WED...WITH THE ECMWF A BIT STRONGER WITH THE LOW. AT
00Z THU BOTH MODELS HAVE THE SURFACE LOW SITUATED OVER WESTERN
OHIO...WITH THE NAM A BIT FURTHER NORTH. ALL OF THE MODELS HAVE A
CLOSED/CUT OFF LOW AND NEGATIVELY TILTED TROUGH IN THE MID
LEVELS...THOUGH THE NAM IS THE OUTLIER KEEPING THE CUT OFF LOW OVER
SOUTHERN ILLINOIS VERSUS THE GEM/GFS/ECMWF HAVE IT OVER SW LOWER MI.
AS MENTIONED IN PREVIOUS DISCUSSIONS...WITH THE DEEPENING LOW AND
THE NEGATIVELY TILTED TROUGH WANT TO LEAN TOWARDS THE SLIGHTLY
WESTWARD SOLUTIONS OF THE GEM/GFS. OVERALL WENT WITH A GEM/GFS/ECMWF
COMPROMISE GIVEN THESE SIGNIFICANT DIFFERENCES.

TUESDAY NIGHT AS THE FIRST SYSTEM MOVES OUT CUT POPS FOR THE FIRST
SIX HOURS AS DRY SLOT MOVES OVER THE AREA. AFTER 6Z HAVE INCREASING
TRENDS AGAIN AS SECONDARY LOW APPROACHES THE AREA. EXPECT RAIN
THROUGH THE LATE AFTERNOON ACROSS A MAJORITY OF THE CWA BEFORE THE
CHANGE OVER TO SNOW OCCURS...STARTING IN THE NORTHWEST NEAR LAKE MI.
EXPECT A MAJORITY OF THE SNOW ACCUMULATION TO BE IN THE 00Z TO 6Z
TIME FRAME AS TEMPERATURES FALL AND THE DEFORMATION ZONE OF THE
DEEPENING LOW SWINGS OVERHEAD. GENERALLY THINK THE GOING FORECAST OF
1 TO 3 INCHES IS STILL ON TRACK...MAINLY IN THE WEST AND CENTRAL CWA
GIVEN MIXED PRECIP/WARM GROUND CONCERNS WHEN THE FORCING IS STRONGEST.
AGAIN THOUGH...UNCERTAINTY REMAINS AS TO WHERE THE STRONGEST FORCING
WILL BE. TAKING A QUICK PEEK AT THE 12Z ECMWF...IT HAS COME IN LINE
CLOSER TO THE GEM/GFS SOLUTIONS...WHICH MAY FORCE THE AXIS OF
HEAVIER PRECIP FURTHER TO THE NORTHWEST. THOSE TRAVELING ON
CHRISTMAS EVE SHOULD CONTINUE TO MONITOR THE LATEST FORECASTS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1244 AM EST TUE DEC 23 2014

AREA OF MORE ORGANIZED RAIN TIED TO STRONG MOISTURE/PV SURGE
WILL LIFT NE THROUGH NRN IN EARLY THIS MORNING. HIGH END MVFR TO
VFR CONDITIONS AT ISSUANCE WILL DETERIOTE TO IFR BY DAYBREAK GIVEN
THE LOW LEVEL MOISTURE SURGE AND UPSTREAM OBSERVATIONS. LOW IFR
STRATUS/HAZE WILL LIKELY LINGER AT THE TERMINALS THROUGH LATE
MORNING/EARLY AFTERNOON AS SFC OCCLUSION LIFTS THROUGH...WITH
POCKETS OF DRIZZLE/LIGHT RAIN POSSIBLE. IMPROVEMENT TO MVFR-VFR
POSSIBLE BY THIS AFTN/EVE AS DRY SLOT OVERSPREADS.

&&

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

$$

SYNOPSIS...STEINWEDEL
SHORT TERM...JT
LONG TERM...MCD
AVIATION...STEINWEDEL


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