Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 200617
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
117 AM EST THU NOV 20 2014

.SYNOPSIS...
ISSUED AT 352 PM EST WED NOV 19 2014

COLDER AIR WILL ARRIVE BEHIND A DEPARTING COLD FRONT...ALLOWING
FOR RENEWED LAKE EFFECT SNOW SHOWER DEVELOPMENT ACROSS WESTERN
LOWER MICHIGAN INTO PORTIONS OF NORTHERN INDIANA. WINTER WEATHER
WARNINGS AND ADVISORIES ARE IN EFFECT. OVERNIGHT LOWS WILL DROP
INTO THE TEENS TONIGHT WITH HIGHS ON THURSDAY STRUGGLING BACK INTO
THE 20S. BREEZY CONDITIONS WILL PREVAIL...CAUSING AREAS OF BLOWING
AND DRIFTING SNOW.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 352 PM EST WED NOV 19 2014

...LAKE EFFECT SNOW SHOWERS TO PLAGUE THE AREA...

WINTER WEATHER HEADLINES WILL REMAIN UNCHANGED FOR THE TIME BEING AS
EXACT EVOLUTION/POSITION OF HEAVIEST BAND(S) STILL NOT FULLY CLEAR.

COLD FRONT WAS SWEEPING ACROSS THE AREA WITH TEMPERATURES
ALONG/AHEAD OF IT IN THE UPPER 20S TO LOWER 30S. SURGE OF COLDER AIR
WILL BEGIN TO ARRIVE BEHIND THE FRONT BUT WILL ARRIVE IN 2 BATCHES.
THE FIRST WILL MOVE IN QUICKLY WITH LK TO 850 MB DELTA T`S CLIMBING
INTO THE LOW TO MID 20S. FLOW WILL BE VERY SIMILAR TO THE LAST EVENT
WITH GROWING CONCERNS THAT A PERSISTENT BAND COULD SET UP IN THE
VICINITY OF THE IN/MI STATE LINE TOWARDS THE INDIANA TOLL ROAD AS
STRONGLY SUGGEST BY THE LAST COUPLE OF RUNS OF THE LOCAL WRF MODEL.
OTHER FINER RESOLUTION MODELS HINTING AT A SIMILAR SETUP WITH NAM
NOT QUITE AS FAR SOUTH. OVERALL INSTABILITY...MSTR DEPTH AND
INVERSION HGT ARE LESS THAN WITH THE MOST RECENT EVENT BUT STILL
MORE THAN SUFFICIENT FOR EFFICIENT LAKE EFFECT SNOW SHOWER
PRODUCTION. HOWEVER...FLOW IS NOT AS STRONG WHICH MAY ALLOW FOR MORE
PRODUCTIVE/BETTER ORGANIZED SNOW BANDS. GIVEN THE SIGNALS OF A MORE
SOUTHERLY TRANSITION OF THE HEAVIER BAND HAVE INCREASED SNOWFALL
AMOUNTS CLOSER TO THE STATE LINE AND AS FAR SOUTH AS THE TOLL ROAD.
AT THIS POINT WILL NOT UPGRADE TO A WARNING ALTHOUGH POTENTIAL FOR
SIGNIFICANT IMPACTS IN NE LA PORTE...FAR NORTHERN ST JOE AND ELKHART
COUNTIES ARE INCREASING. WILL BEEF UP THE WORDING ON THE RESPECTIVE
SEGMENT OF THE ADVISORY TO REFLECT CONCERNS AND DEFER TO EVE SHIFT
TO SEE HOW THE BAND SETS UP. IT SHOULD BE NOTED AS OF WRITING THAT
REGION RADAR LOOP OVER THE SOUTHERN PART OF THE LAKE ALREADY
INDICATING AT LEAST ONE BAND TAKING SHAPE...MATCHING WELL WITH
PLACEMENT OF THE MORE FAVORABLE MODELS. REST OF THE WARNING/ADVISORY
HEADLINES ON TRACK ALTHOUGH WILL NUDGE TOTAL AMOUNTS UP IN THE
ACTUAL WARNING TO BETTER REFLECT TRENDS. AWAY FROM THE LAKE SCT
FLURRIES WILL OCCUR IN THE WAKE OF THE FRONT PER UPSTREAM OBS AND
RADAR TRENDS. IMPACT SHOULD BE LIMITED TO NIL BUT GUSTY WINDS WILL
CAUSE SOME LOW DRIFTING AND BRIEF PERIODS OF REDUCED VISIBILITY IN
ANY HEAVIER SNOW SHOWERS.

ON THURSDAY...FLOW TRIES TO BECOME MORE WESTERLY AS A SHORT WAVE
APPROACHES. SOMEWHAT COLDER AIR WILL ARRIVE WITH THIS FEATURE IN THE
AFTERNOON ALLOWING INVERSION HEIGHTS TO INCREASE. AS A RESULT OF THE
ADJUSTMENT IN FLOW...THE BAND MAY TRANSITION BACK NORTH IN THE
MORNING BEFORE RETURNING SOUTH AGAIN IN THE AFTERNOON. NO SIG
CHANGES TO THIS PERIOD. HIGHS WILL BE A GOOD 20 DEGREES BELOW NORMAL
WITH READINGS ONLY IN THE LOW TO MID 20S.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 352 PM EST WED NOV 19 2014

RISING HEIGHTS AND INCREASED BACKING/RMS WITHIN STEERING FLOW TO VEX
LES PRODUCTION THROUGH THU NIGHT. WHILE STILL GOOD INITIAL LES EVENT
ONGOING THU EVENING PER LK/8H THERMAL DIFFERENTIALS NEAR 23C WITHIN
A SLIGHTLY MORE VEERED CBL FLOW...290 DEGREES INITIALLY VEERING
FURTHER TO 315 BY DAYBREAK FRIDAY...WHEN INVERSION HEIGHTS LOWER.
FURTHERMORE LESS FAVORABLE UVM WITHIN A DIMINISHED DGZ DEPTH BECOME
INCREASED NEGATIVES THROUGH THE NIGHT. HEREAFTER ATTENTION FOCUSES
ON SRN TRACKED STREAM SYSTEM /CURRENTLY NEAR 40N/140W. THIS SYSTEM
TO DIG ACROSS SOCAL/SRN AZ FRIDAY...THEN EMERGE OFF EDWARDS PLATEAU
MIDDAY SATURDAY/TO MID MS VLY 18 UTC SUN. GOOD CONSENSUS OF SYSTEM
TRACKING WEST OF CWA IN AN INCREASINGLY NEGATIVELY TILTED FASHION
TOWARDS LAGGED ALEUTIAN/GULF OF AK VORTEX. THIS ALONG WITH COHESION
OF SURFACE RIDGING INTO MID OHIO VALLEY FRIDAY...SLIDING OFF MID
ATLANTIC POSITIONED DISFAVORABLY FOR SHALLOW COLD AIR RETENTION ACRS
CWA. NON DIURNAL TRENDS ADDED FOR FRIDAY NIGHT WITH MINS REACHED
EARLY WITH INCRSD CLOUD COVER ALONG WITH RAMPING/DEEPENING SOUTHERLY
FLOW THROUGH THE NIGHT. DRY SUBCLOUD LAYER PER EXTREME 200-300 MB
925 MB CONDENSATION PRESSURE DEFICITS TO EFFECTIVELY ERODE LEADING
EDGE SENSIBLE WX THROUGH THE NIGHT. KEPT SPATIAL/TEMPORAL DETAIL OF
WX BROAD IN LIGHT OF ANTICIPATED FUTURE MODEL TRENDS/VARIANCES AND
GIVEN DY4 TIMEFRAME. SMALL CHC LIGHT ZR EARLY...THOUGH QUICKLY
TRANSITIONING TO ALL LIQUID PTYPE AS SHALLOW COLD POOL QUICKLY
DISSOLVES/RETREATS NEWD TO A PRIMARILY RAIN EVENT THIS WEEKEND AS
SYSTEM CONTS TO WRAP/DEEPEN ON NWD TRACK INTO NRN GRTLKS MON AM.
AGAIN A NOD TO ATYPICAL DIURNAL/FALLING AFTERNOON TEMPS WITH AGAIN
BROAD RAIN/SNOW...CONCEDING A RAIN TO MIX TO SNOW MOST PROBABLE
SCENARIO...FOLLOWED BY EPISODIC LES WITH AT LEAST MODEST LK/8H
DIFFERENTIALS EXPECTED BEFORE UPPER LOW AND ASSOCD LAKE AGGREGATE
TROF LIFTS OUT NEWD INTO MIDWEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1255 AM EST THU NOV 20 2014

LAKE INDUCED INSTABILITY TO INCREASE OVERNIGHT AS LOW/MID LEVEL
COLD ADVECTION CONTINUES ACROSS THE SOUTHERN GREAT LAKES REGION.
SHEARED UPPER LEVEL WAVES WILL ALSO BE DIVING SOUTHEASTWARD INTO
THE REGION AIDING IN LAKE EFFECT SNOW. WESTERLY FETCH SHOULD KEEP
BULK OF SNOW SHOWERS NORTH OF KSBN...ALTHOUGH TOWARD MIDDAY...SOME
VEERING OF FLOW IS EXPECTED THAT COULD BE MORE FAVORABLE FOR LAKE
EFFECT SNOW SHOWERS AT KSBN. NOT MUCH CHANGE MADE TO PREVIOUS
TAFS...WITH IFR CONDITIONS AT KSBN IN THE 19Z-23Z TIMEFRAME.
SLOWING BUILDING MID LEVEL HEIGHTS TOWARD THE END OF THE PERIOD
SHOULD GRADUALLY SUBSIDE LAKE EFFECT SNOW THREAT. OUTSIDE OF LAKE
EFFECT SNOW SHOWERS...MVFR CIGS OF 2-3K FT ARE EXPECTED TO IMPACT
KSBN FOR MUCH OF THE PERIOD...WHILE GENERALLY VFR CONDITIONS ARE
ANTICIPATED AT KFWA WHERE ONLY SCATTERED FLURRIES ARE EXPECTED.
WEST WINDS TO REMAIN GUSTY TO 20 TO 25 KNOTS THROUGH THE PERIOD.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 4 AM EST /3 AM CST/ FRIDAY FOR
     INZ003>006.

MI...WINTER WEATHER ADVISORY UNTIL 4 AM EST FRIDAY FOR MIZ079-080.

     WINTER STORM WARNING UNTIL 4 AM EST FRIDAY FOR MIZ077-078.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EST FRIDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...FISHER
SHORT TERM...FISHER
LONG TERM...MURPHY
AVIATION...MARSILI


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