Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 170238
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
938 PM EST TUE DEC 16 2014

.SYNOPSIS...
ISSUED AT 647 PM EST TUE DEC 16 2014

A COUPLE OF UPPER LEVEL SHORT WAVES TRACKING THROUGH THE SOUTHERN
GREAT LAKES REGION WILL CONTINUE TO PROVIDE SOME SCATTERED LIGHT
RAIN SHOWERS OR PATCHY DRIZZLE THIS EVENING. ISOLATED TO SCATTERED
LAKE EFFECT SNOW SHOWERS ARE POSSIBLE LATE TONIGHT INTO
WEDNESDAY...MAINLY ACROSS SOUTHERN LOWER MICHIGAN AND FAR NORTHERN
INDIANA...BUT NO SNOW ACCUMULATION IS EXPECTED. LOW TEMPERATURES
TONIGHT WILL RANGE FROM THE MID 20S ACROSS NORTHEAST ILLINOIS...TO
THE LOWER 30S ACROSS NORTHWEST OHIO. HIGH TEMPERATURES ON
WEDNESDAY WILL REACH INTO THE LOWER TO MID 30S.

&&

.UPDATE...
ISSUED AT 931 PM EST TUE DEC 16 2014

PRECIP COVERAGE IS EXPECTED TO DIMINISH OVER THE NEXT FEW HOURS AS
UPPER VORT LOBE ACROSS SOUTHERN LAKE MICHIGAN CONTINUES TO GET
SHEARED IN STRONG BACKGROUND DEFORMATION FLOW. THIS SHOULD LEAD TO
INCREASING SYNOPTIC SCALE SUBSIDENCE OVERNIGHT...WITH REMAINING
PRECIP AFTER 06Z CONFINED TO LIGHT LAKE EFFECT. LAKE EFFECT SETUP STILL
APPEARS TO BE QUITE UNFAVORABLE GIVEN DRY MID LEVEL
PROFILES/SUBSIDENCE...MARGINAL SATURATION AT DEPTHS SUPPORTIVE OF
ICE INTRODUCTION FOR -SHSN...AND LIMITING WESTERLY FETCH. STILL
SOME CHANCE FOR SOME PATCHY LIGHT FREEZING DRIZZLE IN ASSOCIATION
WITH THIS LAKE EFFECT PRECIP...BUT HAVE OPTED TO CONTINUE TO OMIT
THIS MENTION WITH LOW CONFIDENCE OF OCCURRENCE.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 324 PM EST TUE DEC 16 2014

AFTERNOON WATER VAPOR SHOWS SMALLER SCALE VORT MAXES (ONE NEAR THE
IN/OH BORDER AND ANOTHER OVER CENTRAL LAKE MI) EMBEDDED IN PARENT
GREAT LAKES MID-UPPER LEVEL CIRCULATION/OCCLUSION...WITH A
SEPARATE NORTHERN STREAM SHORTWAVE DROPPING SE INTO THE UPPER
MIDWEST. AT THE SFC (19Z)...THERE IS A 1005 MB SFC LOW CENTERED
OVER SE LOWER MI... WITH A COLD FRONT EXTENDING SW INTO SW LOWER
MI AND WESTERN INDIANA. SCT SHOWERS/DRIZZLE ACCOMPANYING THE
CDFNT/MOIST CYCLONIC FLOW AND MORE ORGANIZED AREA OF LIGHT RAIN
TIED TO IMPULSE NOW WORKING INTO WESTERN OH WILL CONTINUE TO PUSH
EAST RESULTING IN A DOWNTREND IN SHOWER/DRIZZLE COVERAGE THIS
EVENING. ANY LINGERING PCPN COULD END AS A FEW SNOW SHOWERS/SNIZZLE
ACROSS THE NORTH LATE THIS EVENING AS COLDER AIR BEGINS TO
UNDERCUT.

THE AFOREMENTIONED NORTHERN STREAM TROUGH WILL ELONGATE INTO THE
CENTRAL LAKES AND BECOME ORIENTED MORE WEST TO EAST OVERNIGHT INTO
WEDNESDAY. THIS FEATURE WILL HELP KICK THE LOWER LAKES SYSTEM OUT
OF THE AREA WITH DRIER/SUBSIDENT AIR ADVECTING IN ON THE SOUTHERN
FLANK OF A STRUNG OUT CENTRAL LAKES MID LEVEL DEFORMATION AXIS.
THE RESULT WILL BE A TREND TOWARD DRY/COLDER/SOMEWHAT BREEZY
CONDITIONS IN WEAK CAA REGIME. VEERED WNW FLOW WITHIN BOUNDARY
LAYER WITH LAKE-8H DIFFERENTIALS REACHING THE LOW TEENS WILL KEEP
LOW CLOUDS AROUND INTO TOMORROW. MARGINAL DELTA T`S/INVERSION
HEIGHTS AND SHALLOW MOISTURE PROFILES SUPPORT INHERITED LOW-MID
CHC POPS FOR SCT LAKE EFFECT SNOW SHOWERS/FLURRIES AND LITTLE/NO
ACCUMS. QUICK PERUSAL OF FCST SOUNDINGS/XSECTIONS SHOWING BULK OF
MOISTURE BELOW THE -12C LAYER ALSO CONCERNING FOR ANY ICE
PRODUCTION AND DZ/FZDZ POTENTIAL. WILL HOLD OFF ON ADDING DZ/FZDZ
IN THE FCST GIVEN LOW PROBABILITY OF OCCURRENCE. DRY AND FEELING
MUCH MORE LIKE MID DECEMBER OTHERWISE TOMORROW.

&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 324 PM EST TUE DEC 16 2014

INCREASINGLY ACTIVE PATTERN UNFOLDING FOR THE LONG TERM AND BEYOND.
FOCUS WILL BE ON 2 SYSTEMS FOR THE CURRENT PERIOD...ONE FOR THIS
WEEKEND AND THE OTHER ARRIVING PRIOR TO CHRISTMAS.

NW FLOW OFF LAKE MICHIGAN WILL PROVIDE INCREASED CLOUD COVER BUT
QUESTIONABLE IMPACTS IN TERMS OF PRECIPITATION AS COMBINATION OF
MARGINAL DELTA T`S...POTENTIAL FOR DRY AIR ENTRAINMENT AND LOW
INVERSION HEIGHTS ALL LEAD TO LESS THAN IDEAL CONDITIONS FOR
ACCUMULATING SNOWFALL. WILL LIKELY BE AT LEAST SCATTERED SNOW
SHOWERS AROUND...SO WILL MATCH UP WITH COVERAGE WORDING BUT HAVE
LITTLE/NO ACCUMULATIONS. LONGWAVE TROUGH MOVING ACROSS THE
WESTERN STATES WILL DIG INTO TEXAS AND PICK UP A PIECE OF ENERGY
COMING OUT OF THE 4 CORNERS AREA. ALL SIGNS CONTINUE TO POINT
TOWARDS A SUPPRESSED SOLUTION WITH THE LOW TRACKING FROM THE GULF OF
MEXICO NE TO ALONG THE APPALACHIANS SAT/SAT NGT. WHILE PLENTY OF
MSTR WILL EXIST WITH THE SYSTEM...FURTHER EAST TRACK WILL KEEP THE
AREA FROM SEEING ANY MAJOR IMPACTS WITH MAYBE SOME LIGHT
SNOW/FLURRIES.

HIGH PRESSURE WILL BUILD IN FOR SUNDAY INTO MONDAY TO BRING
SEASONABLE TEMPERATURES AND DRY CONDITIONS. FROM THIS POINT
FORWARD...MUCH MORE VOLATILE PATTERN SETS UP WITH NEXT PIECE OF
ENERGY (CLIPPER TYPE) DIVING OUT OF THE PLAINS INTO THE NORTHERN
GREAT LAKES. A COLD FRONT WILL EXTEND FROM THE LOW AND BRING A
CHANCE FOR SNOW SHOWERS TO THE AREA AT THE END OF THE PERIOD. EXACT
COVERAGE AND IMPACTS ARE STILL UNCERTAIN WITH GFS DEEPENING THE SFC
LOW OVER NE WISCONSIN BY TUESDAY AFTERNOON VS MAIN LOW STILL UP BY
THE ARROWHEAD OF MINNESOTA ON THE ECMWF. CONFIDENCE LOW IN EVOLUTION
OF THIS SYSTEM AND ALSO ADDITIONAL ENERGY COMING OUT OF THE 4
CORNERS REGION WITH POTENTIAL FOR PANHANDLE HOOK SYSTEM THAT COULD
BRING ACCUMULATING SNOW JUST OUTSIDE THE PERIOD. POPS WERE INCREASED
SOME BUT KEPT IN CHC FOR AT LEAST SOME CONSISTENCY IN PRECIP ON THE
FRONT ITSELF. TRAVEL INTERESTS OVER THE HOLIDAYS SHOULD MONITOR THE
LATEST FORECASTS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 647 PM EST TUE DEC 16 2014

SCATTERED LIGHT RAIN SHOWERS ALONG WITH SOME PATCHY DRIZZLE WILL
CONTINUE TO AFFECT TERMINALS THROUGH AROUND 03Z. BY LATE EVENING
INTO THE OVERNIGHT SYNOPTIC SCALE SUBSIDENCE WILL BECOME MORE
ESTABLISHED RESULTING IN DIMINISHING PRECIPITATION COVERAGE. SOME
LAKE EFFECT SNOW SHOWERS ARE POSSIBLE LATE TONIGHT INTO
WEDNESDAY...BUT LOW LEVEL WINDS SHOULD FAVOR THIS CHANCE TO THE
NORTH OF KSBN. IFR CIGS TO START THE PERIOD SHOULD IMPROVE TO MVFR
LATE EVENING OR THE EARLY PORTIONS OF THE OVERNIGHT AS DRIER LOW
LEVEL AIR ADVECTS ACROSS NORTHERN INDIANA. STRENGTHENING
SUBSIDENCE OVERNIGHT AND LOWERING INVERSION WILL KEEP IN LOW
CLOUDS HOWEVER THROUGH MUCH OF THIS PERIOD...WITH MVFR CIGS
EXPECTED TO CONTINUE INTO A GOOD PART OF WEDNESDAY. LOW LEVEL COLD
ADVECTION AND A MODERATELY STRONG PRESSURE GRADIENT WILL ALLOW FOR
WEST WINDS OF 10 TO 15 KNOTS THROUGH THE PERIOD...WITH GUSTS TO
AROUND 20 KNOTS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST THURSDAY FOR LMZ043-046.

&&

$$

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


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