Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 300525
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
125 AM EDT TUE SEP 30 2014

.SYNOPSIS...
ISSUED AT 346 PM EDT MON SEP 29 2014

A STRONG COLD FRONT WILL SWEEP SOUTHEAST ACROSS THE REGION OVER
THE NEXT 24 HOURS BRINGING MORE SEASONABLE TEMPERATURES AND A
CHANCE OF SHOWERS. A BRIEF WARM UP IS EXPECTED MID WEEK BEFORE
AN EVEN STRONGER SYSTEM MOVES IN WITH BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS. LOWS TONIGHT WILL RANGE FROM THE UPPER 40S FAR
NORTHWEST INTO THE MIDDLE 50S SOUTHEAST. HIGHS ON TUESDAY WILL BE
IN THE 60S...EXCEPT ALONG THE LAKESHORE AREAS WHERE TEMPERATURES
WILL STRUGGLE TO REACH 60.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 346 PM EDT MON SEP 29 2014

FOCUS REMAINS ON STRONG COLD FRONT DROPPING SOUTH ACROSS THE
NORTHERN GREAT LAKES. AREA OF MAINLY POST FRONTAL SHOWERS WAS
PERSISTING ACROSS NORTHERN LOWER MICHIGAN WITH MORE SCATTERED
SHOWERS INTO CENTRAL WISCONSIN. VISIBLE SATELLITE DATA SUGGESTED
SOME AGITATED CU RIGHT ON THE FRONT WITH SOME MARGINALLY UNSTABLE
CONDITIONS. THIS FEATURE WILL DROP INTO THE AREA THIS EVENING AND
CLEAR BY TUESDAY MORNING. MAIN QUESTION FOR THE AREA IS AMOUNT OF
RAINFALL/CHANCES FOR THUNDER WITH/BEHIND FROPA. TRACK OF THE
DEEPENING SFC LOW AND UPPER LEVEL SYSTEM WILL BE NORTHEAST OF THE
FORECAST AREA...PLACING LOWER MICHIGAN IN THE BEST AREA FOR
LIFT/DEEPER MSTR. MODES VARY GREATLY ON SW EXTENT OF PRECIP WITH
ONLY PRECIP CONFINED TO FAR NE ON SOME TO A BAND OF SHOWERS (ISOL
STORMS) SWEEPING ACROSS THE ENTIRE AREA. BASED ON UPSTREAM TRENDS
AND STRENGTH OF THE FEATURE HAVE OPTED TO INCREASE POPS SLIGHTLY
INTO LIKELY CATEGORY IN FAR NE. ADDED TEMPORAL RESOLUTION TO KEEP
PERIOD OF HIGHEST POPS TO AN HOUR OR 2 WITH MORE BROAD BRUSHED CHC
BEHIND THE MAIN AREA. WHILE NAM BUFKIT SOUNDINGS SUGGEST SHOWALTER
VALUES DROP TO AROUND ZERO AROUND 6Z AS THE BAND PASSES WILL HOLD
OFF ON ANY THUNDER ADDITION WITH NO INDICATIONS THUS FAR OF
LIGHTNING. RAINFALL AMOUNTS ANOTHER CHANGE TO THE FORECAST WAS
DRAMATIC INCREASE IN CLOUD COVER LATER THIS EVENING INTO MUCH OF
TUESDAY AS MODELS INDICATE MSTR BEING TRAPPED BY STRONG INVERSION IN
POST FRONTAL COLD AIR ADVECTION SETUP. CAN`T RULE OUT SOME CLEARING
AS WE GO THROUGH THE AFTERNOON BUT THINK A MOSTLY CLOUDY FORECAST
HANDLES THIS POTENTIAL FOR NOW.

HIGHS IN TUESDAY WILL DROP BACK TO MORE SEASONABLE LEVELS IN THE
60S. GIVEN EXTENSIVE CLOUD COVER...HIGHS MAY BE A HAIR TOO WARM WITH
SOME SPOTS POSSIBLY NOT CLIMBING OUT OF LOWER 60S ESPECIALLY NW.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 346 PM EDT MON SEP 29 2014

FOR TUESDAY NIGHT...UPPER LEVEL LOW ACROSS THE EASTERN GREAT LAKES
WILL CONTINUE TO SHIFT EASTWARD DURING THE OVERNIGHT HOURS. DESPITE
A TREND TO MORE NEUTRAL LOW LEVEL TEMPERATURE ADVECTION AS THIS
OCCURS...SOME LINGERING STRATOCU IS POSSIBLE ACROSS THE AREA GIVEN
PERSISTENT LOW LEVEL FRONTAL INVERSION AND TRAPPED LOW LEVEL
MOISTURE. THUS...FORECAST CONFIDENCE IN MIN TEMPS TUESDAY NIGHT IS
LOW DEPENDING ON EXTENT OF STRATOCU AND TIMING OF MORE SUBSTANTIAL
CLEARING. AT THIS TIME...SEE NO REASON TO DEVIATE MUCH FROM PREVIOUS
FORECAST WITH LOWS IN THE MID TO UPPER 40S. RETREATING SFC RIDGE
AXIS FOR WEDNESDAY AND UPPER LEVEL RIDGING ACROSS THE REGION WILL
PROVIDE FOR RATHER LIMITED MIXING HEIGHTS WHICH SHOULD TEMPER
MODERATING TREND TO HIGHS IN MID 70S SOUTHWEST TO UPPER 60S
NORTHEAST WEDNESDAY AFTERNOON. IT STILL APPEARS AS THOUGH DRY
CONDITIONS ARE SHAPING UP FOR WEDNESDAY/WEDNESDAY NIGHT AS BULK OF
UPPER LEVEL FORCING REMAINS WEST OF THE AREA DUE TO LEAD UPPER VORT
MAX LIFTING ACROSS MANITOBA.

ATTENTION WILL THEN SHIFT TO SERIES OF MORE PROGRESSIVE UPPER LEVEL
WAVES AFFECTING THE AREA FROM PACIFIC NORTHWEST/SOUTHWEST CANADA FOR
THE THURSDAY-SUNDAY PERIOD. ONE CONSISTENT THEME AMONG MEDIUM RANGE
MODELS OVER PAST SEVERAL RUNS HAS BEEN TO DEPICT A SOMEWHAT
DISJOINTED NATURE TO UPPER FORCING...WITH LACK OF SIGNIFICANT
PHASING THROUGH THURSDAY NIGHT. BULK OF UPPER FORCING SHOULD REMAIN
WEST OF LOCAL AREA DURING THE DAY THURSDAY...BUT INCREASING
ISENTROPIC LIFT/LOW LEVEL THETAE ADVECTION THURSDAY
AFTERNOON...PARTICULARLY ACROSS THE WEST...ARGUES FOR LEAVING LIKELY
POPS THURSDAY AFTERNOON ACROSS THESE LOCATIONS. BETTER UPPER LEVEL
DYNAMICS SHOULD COME INTO PLAY THURSDAY NIGHT INTO EARLY FRIDAY AS A
PAIR OF MORE DISTINCT UPPER LEVEL WAVES AFFECT GREAT LAKES/MS VALLEY
REGIONS...AND WILL CONTINUE TO FOCUS HIGHEST POPS FOR THIS PERIOD.
THURSDAY NIGHT INTO EARLY FRIDAY SHOULD ALSO COINCIDE WITH BEST
THUNDER POTENTIAL...ALTHOUGH INSTABILITY PROGS APPEAR TO BE A BIT
MORE TEMPERED FROM PREVIOUS INDICATIONS. SOME LOWER FORECAST
CONFIDENCE STILL EXISTS FOR FRIDAY IN TIMING POP DIMINISHMENT GIVEN
POTENTIAL OF BETTER PHASING BY THIS TIME. HAVE OPTED TO CONTINUE
WITH GFS/EC BLENDED APPROACH IN THIS REGARD...MAINTAINING LIKELY
POPS ACROSS THE EAST INTO FRIDAY MORNING.

MUCH COOLER AIR TO ADVECT INTO THE REGION FRIDAY NIGHT AND SATURDAY
WITH LITTLE CHANGE MADE TO PREVIOUS FORECAST IN MUCH BELOW NORMAL
TEMPERATURES BY SATURDAY. WHILE RESOLVING SMALLER SCALE DETAILS IN
NORTHWEST FLOW PATTERN DIFFICULT AT THIS FORECAST DISTANCE...LOCAL
AREA WILL BE PRONE TO WEAKER...SMALLER SCALE WAVES AND PERIODIC WAA
EPISODES FOR THE WEEKEND...AND THUS DID INCLUDE SOME SLIGHT CHANCE
RAIN SHOWER POPS FOR MUCH OF THIS PERIOD. SOME MODERATION IN TEMPS
EXPECTED TOWARD THE END OF THE PERIOD AS UPPER FLOW DEAMPLIFIES TO
SOME DEGREE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 117 AM EDT TUE SEP 30 2014

KIWX 88D FINE LINE INDICATES CDFNT MOVG THROUGH FWA ATTM. IFR CIGS
LAG THE FRONT A BIT BUT SHOULD MOVE INTO FWA IN THE NEXT FEW
HOURS. WIDESPREAD POST FRONTAL SHRA SHOULD STAY NE OF THE
TERMINALS BUT STILL A FEW MOVG INTO NRN INDIANA SO MAINTAINED A
PERIOD OF VCSH THIS MORNING. POST-FRONTAL LOW CLOUD DECK IS
RATHER EXTENSIVE ACROSS THE GRTLKS. CIGS SHOULD RISE TO MVFR
DURING THE MORNING AND MVFR THIS AFTN... WITH CIGS PRBLY
SCATTERING OUT THIS EVE. NW-N WINDS BEHIND THE FRONT MAY BE GUSTY
AT TIMES EARLY THIS MORNING BUT SHOULD GRDLY SUBSIDE DURING THE
DAY AND VEER LIGHT NE THIS EVE AS A HIGH PRESSURE RIDGE BUILDS IN
FROM THE NW.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ043-046.

&&

$$

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


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