000
FXUS63 KIWX 030535
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1235 AM EST TUE DEC 3 2013

.SYNOPSIS...
ISSUED AT 638 PM EST MON DEC 2 2013

A WARM FRONT WILL CONTINUE TO LIFT NORTH INTO TUESDAY...BRINGING A
WARMER AIRMASS TO THE GREAT LAKES REGION. THIS FRONT ALONG WITH THE
PASSAGE OF A WEAK UPPER LEVEL SYSTEM WILL CAUSE CHANCES FOR LIGHT
PRECIPITATION INTO TUESDAY. RAIN IS POSSIBLE... WITH A WINTRY MIX
OR JUST SNOW FURTHER NORTH OVER MAINLY LOWER MICHIGAN TONIGHT INTO
EARLY TUESDAY. THE PRECIPITATION WILL BECOME JUST RAIN AS
TEMPERATURES WARM TUESDAY...AND CLIMB WELL INTO THE 50S WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 321 PM EST MON DEC 2 2013

HIGHLY SHEARED SHRTWV MOVG ESE TO THE NORTH OF WARM FRONT OVER MO
THIS AFTN WILL MOVE ACROSS OUR CWA TONIGHT. RADAR ECHOES/SFC OBS
SUGGEST MOST OF THE PRECIP ASSOCIATED WITH THIS SYSTEM WAS NOT
REACHING THE GROUND ACROSS IA/IL... HWVR LOW LEVEL THETA-E
ADVECTION/ISENT LIFT SHOULD STRENGTHEN OVERNIGHT AS LOW PRESSURE
DVLPS OVER THE NRN PLAINS... PROVIDING ADDITIONAL SUPPORT FOR SOME
LIGHT PRECIP AS THE SHRTWV MOVES THROUGH OUR AREA. THUS... BUMPED
UP POPS FOR TONIGHT BUT KEPT IN THE CHC RANGE GIVEN LACK OF
MEASURABLE PRECIP UPSTREAM THIS AFTN. TOP DOWN METHOD SUGGESTS IF
PRECIP DOES OCCUR IT WILL MAINLY BE RAIN IN OUR AREA... THOUGH LOW
LEVEL EVAPORATIONAL COOLING COULD RESULT IN A PERIOD OF SLEET/SNOW
ESPECIALLY AT ONSET OF PRECIP... AND ACROSS THE NE PORTION OF CWA
A PERIOD OF LIGHT FREEZING RAIN PSBL AS TEMPS FALL TO AOB
FREEZING. LOWS ACROSS THE REMAINDER OF THE CWA EXPECTED TO BE IN
THE M30S.

BY EARLY TUE WAA SHOULD ALLOW TEMPS TO RISE ABOVE FREEZING ACROSS
THE ENTIRE AREA ENDING ANY THREAT OF FREEZING RAIN. WARM FRONT WILL
CONT TO LIFT SLOWLY NORTH ACROSS THE AREA THROUGH THE DAY PSBLY
SUPPORTING SOME LIGHT RAIN...MAINLY ACROSS NRN PORTION OF THE CWA.
CONSIDERABLE LOW CLOUDINESS EXPECTED AS GULF MOISTURE FEEDS NORTH
INTO OUR AREA BUT EXPECT SUFFICIENT BREAKS IN CLOUDS AND DECENT
GRADIENT MIXING TO ALLOW FOR HIGHS IN THE U40S NORTH/L50S SOUTH.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 321 PM EST MON DEC 2 2013

MAIN FOCUS IN LONG TERM ON SYSTEM MIDWEEK AND TIMING OF COLD FRONT.
12Z MODEL SUITE CONTINUES WITH LARGE DIFFERENCES BETWEEN
NAM/GFS/SREF AND NON-NCEP MODELS. CLOSED UPPER LOW CURRENTLY
DROPPING SE INTO NW CONUS THIS AFTERNOON. DISAGREEMENT WITH MODEL
SOLUTIONS ARISE WITH HOW TO HANDLE THIS ENERGY AS IT PROGRESSES
EAST TOWARD THE MIDWEST. NAM/GFS/SREF HAVE FASTER(BY ABOUT 12
HRS)/MORE AMPLIFIED SOLUTION WITH SPLIT FLOW....ALTHOUGH 12Z NAM
HAS SLOWED DOWN A BIT MORE TOWARD NON NCEP SOLUTIONS. THESE
SOLUTIONS DEPICT DEEPENING UPPER LOW OVER UPPER MIDWEST THAT
RESULTS IN STRONG CYCLOGENESIS OF SURFACE LOW PROGGED TO MOVE FROM
CENTRAL PLAINS INTO GREAT LAKES REGION TUES INTO WED. THIS SENDS
ARCTIC FRONT ACROSS LOCAL AREA EARLIER IN THE DAY ON
WEDS...HAMPERING TEMPS DURING THE DAY WITH EARLIER SURGE OF ARCTIC
AIR BEHIND FRONT. ECMWF/GEM/UKMET ON THE OTHER HAND HAVE
SLOWER/LESS AMPLIFIED SOLUTION. EVEN WITH SPLIT ENERGY...FOCUS
NEAR BASE OF LONGWAVE TROUGH ALLOWS FOR WEAKER SW FLOW AND
SLOWER/LESS AMPLIFIED SURFACE REFLECTION. TRAILING COLD FRONT
WOULD NOT MOVE THRU THE AREA UNTIL LATER ON THE DAY ON
WEDS....ALLOWING FOR ANOTHER DAY OF ABOVE NORMAL TEMPS IN THE 50S.
ALTHOUGH THE NAM HAS TRENDED MORE TOWARDS A LESS AMPLIFIED
SOLUTION SINCE 00Z RUN...IT REMAINS ON FASTER/STRONGER SIDE ALONG
WITH OTHER NCEP MODELS. GIVEN PREVIOUS PREFERENCE OF SLOWER
SOLUTION AND THE TREND OF THE NAM TOWARD THE SLOWER/LESS AMPLIFIED
SOLUTION...CONTINUED TO HEDGE TOWARD ECMWF/GEM/UKMET WHICH LIMITS
MAJOR SWINGS IN FORECAST GRIDS. SUSPECT SPREAD MAY LESSEN IN NEXT
COUPLE OF RUNS AS SYSTEM IS BETTER SAMPLED OVER CONUS. AS
MENTIONED BY PREVIOUS SHIFT...CONFIDENCE REMAINS LOW EVEN AS EVENT
IS LESS THAN 36 HOURS OUT. TIMING OF FRONT WILL HAVE DRASTIC
EFFECT ON TEMPERATURES AND TIMING OF PRECIP...WITH BUST POTENTIAL.
MODEL DISPARITY LESSENS FOR REMAINDER OF PERIOD BEHIND ARCTIC
FRONT WITH INTRUSION OF COLD AIR AND WENT WITH GENERAL COMPROMISE
OF ALLBLEND GRIDS.

GIVEN SLOWER SOLUTION...RAIN SHOWERS WILL BE LINGERING TUES NIGHT
INTO WEDS FOR START OF PERIOD AS WARM FRONT LIFTS NORTH AND STALLS
OUT NEAR CWA BOUNDARY. SOUTHERN PORTIONS OF CWA MAY REMAIN DRY LATE
TUES NIGHT INTO WEDS MORNING AHEAD OF FRONTAL APPROACH. PRECIP THEN
RETURNS AHEAD AND ALONG FRONT WEDS EVENING INTO OVERNIGHT HOURS WITH
WARM AIR ALLOWING FOR ALL RAIN. EVEN THEN DEPTH OF MOISTURE IS
FAIRLY SHALLOW SO NOT EXPECTING MORE THAN A TENTH OR TWO OF QPF.
SOME SNOW MAY MIX IN WITH LINGERING SHOWERS BEHIND FRONT AS COLDER
AIR BEGINS TO FILTER IN. TEMPS COULD ACTUALLY FALL DURING THE DAY ON
THU WITH CAA AS 850MB TEMPS PLUMMET FROM THE +8C RANGE INTO THE
NEGATIVE TEENS BY FRI. SEVERAL WAVES PROGGED TO MOVE IN JET ALONG
LOW LVL BAROCLINIC ZONE AS IT MOVES SE OUT OF AREA THU INTO FRI. AS
OF NOW...IT APPEARS BULK OF PRECIP SHIELD WILL REMAIN SOUTH OF AREA
WITH HIGHEST POPS IN SE CWA. HAVE KEPT LOWER POPS IN NW TO ACCOUNT
FOR A POSSIBLE NW SHIFT IN SOLUTIONS OVER TIME. THERMAL PROFILES
COLD ENOUGH FOR ANY PRECIP TO REMAIN AS SNOW THU NIGHT INTO FRI.

SECONDARY SURGE OF COLD AIR THEN ARRIVES FRIDAY WITH TEMPS NEARLY 10
DEG COLDER THAN THU. SPRAWLING ARCTIC HIGH PRESSURE WILL SHIFT EAST
TOWARD REGION AS WEEKEND BEGINS. DAYTIME HIGHS WILL STRUGGLE TO
REACH THE LOWER TO MID 20S WITH NIGHTTIME LOWS IN THE TEENS TO
POSSIBLY SINGLE DIGITS IN COLD BIAS AREAS. LAKE EFFECT SNOW SHOWERS
POSSIBLE THRU THE WEEKEND IN NW FLOW AND INSTABILITY GIVEN VERY COLD
AIR. AMTS UNCERTAIN THIS FAR OUT BUT WILL BE SOMETHING TO WATCH.
ANOTHER SHORTWAVE WILL THEN APPROACH BY END OF WEEKEND/MON BRINGING
A CHANCE FOR LIGHT SNOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1235 AM EST TUE DEC 3 2013

PERIODS OF IFR CONDITIONS WILL REMAIN POSSIBLE THROUGH THE MORNING
HOURS AS WARM FRONT LIFTS NORTH ACROSS THE REGION. UPSTREAM
OBSERVATIONS HAVE BEEN FAIRLY CHAOTIC THOUGH AND EXPECTED BRIEF
MVFR CONDITIONS TO MIX IN AT TIMES. STEADY IMPROVEMENT EXPECTED BY
LATER TODAY AS FOCUS OF WARM FRONT SHIFTS NORTH. CONFIDENCE IN
EXACT CEILING HEIGHTS IS LOW FOR THE AFTERNOON AND EVENING
HOWEVER. NAM FORECAST SOUNDINGS SEEM TO STILL BE OVER SATURATING
THE NEAR SURFACE ENVIRONMENT AND PREFER THE DRIER VIEW SEEN IN
THE GFS. MOS GUIDANCE IS STILL FAIRLY PESSIMISTIC THOUGH AND WILL
MAINTAIN JUST A HIGH END MVFR CEILING HEIGHT FOR NOW.

&&

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

$$

SYNOPSIS...SKIPPER
SHORT TERM...JT
LONG TERM...CEO
AVIATION...AGD


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