Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 271041
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
641 AM EDT THU AUG 27 2015

.SYNOPSIS...
ISSUED AT 356 AM EDT THU AUG 27 2015

CLEARING SKIES WILL ALLOW FOR WARMER TEMPERATURES TODAY WITH MOST
LOCATIONS ENJOYING HIGHS IN THE LOWER 70S. TONIGHT LOWS WILL FALL
INTO THE MIDDLE 50S UNDER MOSTLY CLEAR SKIES. THE NEXT CHANCE FOR
SHOWERS AND THUNDERSTORMS WILL ARRIVE SATURDAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 356 AM EDT THU AUG 27 2015

SKIES CONTINUE TO SLOWLY CLEAR ACROSS THE AREA WITH FAR NW AND E
LOCATIONS STILL HOLDING ONTO MOSTLY CLOUDY SKIES. CLEAR AREA HAVE
SEEN MAINLY SHALLOW FOG DEVELOP WITH HIGHLY VARIABLE
VISIBILITIES...INCLUDING LOCALLY DENSE PATCHES. HAVE TRIED TO
CAPTURE AS BEST AS POSSIBLE IN GRIDS THROUGH 13Z. CONDITIONS SHOULD
IMPROVE QUICKLY THROUGH THE DAY WITH HIGH TEMPERATURES SEVERAL
DEGREES WARMER, REACHING THE LOWER 70S.

CLEAR SKIES AND LIGHT WINDS WILL DOMINATE TONIGHT WITH LOWS
BOTTOMING IN THE MIDDLE 50S IN MOST LOCATIONS. CAN`TRULE OUT SOME
PATCHY FOG ONCE AGAIN...BUT COVERAGE WOULD APPEAR TO BE MUCH LESS IF
AT ALL.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 356 AM EDT THU AUG 27 2015


THE PRIMARY FOCUS FOR THE LONG TERM WILL CONTINUE TO BE CENTERED ON
THE SATURDAY-SUNDAY TIMEFRAME AS A SLOW MOVING UPPER TROUGH AFFECTS
THE REGION WITH THE NEXT CHANCE OF SHOWERS/THUNDERSTORMS.

ON FRIDAY AN UPPER LEVEL SHORT WAVE SHOULD BE LIFTING INTO THE
CENTRAL PLAINS WITH CONTINUED INDICATIONS THAT THIS DISTURBANCE
SHOULD GRADUALLY PHASE WITH UPPER LEVEL PV ANOMALY ASSOCIATED WITH
NORTHERN STREAM PERTURBATION ACROSS THE NORTHERN PLAINS. THIS PHASED
SYSTEM WILL BE THE PRIMARY FEATURE OF INTEREST HEADING INTO THE
SATURDAY/SUNDAY TIMEFRAME.  FOR FRIDAY...THE ONLY SENSIBLE WEATHER
IMPACTS FROM THIS CONSOLIDATING SYSTEM WILL BE AN INCREASE IN MID
AND HIGH CLOUD COVER. MODEST LOW LEVEL WARM ADVECTION WILL OFFSET
THIS INCREASE IN HIGH CLOUDS HOWEVER WHICH SHOULD ALLOW FOR
CONTINUED MODERATION OF TEMPS...AND HIGHS INTO THE 75 TO 80 DEGREE
RANGE.

LOW LEVEL FLOW WILL STRENGTHEN FOR FRIDAY NIGHT AND VEER MORE
SOUTHWESTERLY AHEAD OF AFOREMENTIONED UPPER TROUGH. THIS LOW LEVEL
FLOW TRAJECTORY AT LEAST INITIALLY FOR THE FRIDAY NIGHT/EARLY
SATURDAY PERIOD WILL NOT LIKELY BE EFFICIENT FOR SIGNIFICANT
MOISTURE TRANSPORT DUE TO RELATIVELY LONG RESIDENCE TIME OF SYNOPTIC
SCALE SUBSIDENCE ACROSS THE MID MS RIVER VALLEY. A FEW ELEVATED
SHOWERS MAY WORK ACROSS NORTH/NORTHWEST PORTIONS OF THE FORECAST
AREA LATE FRIDAY NIGHT MORE TIED INTO THE ISENTROPIC FORCING.

LARGE SCALE FORCING FOR ASCENT WILL INCREASE ON SATURDAY...WITH TROP
PV ANALYSIS GENERALLY INDICATING STRONGEST FORCING FOR ASCENT ACROSS
NORTHERN HALF OF THE AREA. NAM/GFS DEPICTING TYPICAL BIASES IN TERMS
OF NEAR SFC MOISTURE/INSTABILITY MAGNITUDES DURING THE DAY SATURDAY.
WEAK TO MODERATE INSTABILITY IS POSSIBLE DURING THE AFTERNOON AS
SLIGHTLY MORE IMPRESSIVE MOISTURE PROFILES ADVECT INTO THE AREA.
SEVERE POTENTIAL LOOKS TO BE VERY LOW GIVEN EXPECTED MARGINAL MID
LEVEL LAPSE RATES/WEAK-MODERATE INSTABILITY. HAVE MAINTAINED MID TO
HIGH CHANCE POPS (HIGHEST NORTH)...WITH UNCERTAINTIES IN
TIMING/STRENGTH OF FORCING PRECLUDING LIKELY POPS AT THIS TIME.
UPPER LEVEL FORCING TO GRADUALLY WANE SATURDAY NIGHT INTO SUNDAY AS
THIS PV ANOMALY QUICKLY GETS SHEARED/ATTENUATED. AXIS OF WEAKENING
FORCING WILL PERSIST ACROSS THE AREA INTO SUNDAY HOWEVER...WHICH
ARGUES FOR MAINTAINING LOW CHANCE POPS THROUGH SUNDAY AFTERNOON.

THE REST OF THE LONG TERM LOOKS TO BE RATHER QUIET...AND HAVE PUT
MORE WEIGHT ON MORE CONSISTENT ECMWF DURING THIS PERIOD WITH UPPER
LEVEL RIDGE AMPLIFICATION ACROSS CENTRAL CONUS...AND A TREND TO
ABOVE NORMAL TEMPS TUESDAY AND BEYOND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 620 AM EDT THU AUG 27 2015

IDEAL RADIATIONAL COOLING CONDITIONS HAVE LED TO PATCHY FOG
FORMATION THIS MORNING. WILL LIKELY NEED TO EXTEND TEMPO LIFR
CONDITIONS AT LEAST THROUGH 13Z GIVEN STRENGTH OF LOW LEVEL
INVERSION...BUT CONDITIONS SHOULD BEGIN TO MORE RAPIDLY IMPROVE
IN THE 13Z-14Z TIMEFRAME. OTHER THAN FOG FOR THE NEXT HOUR OR TWO
THIS MORNING...NOT MANY OTHER SIGNIFICANT CONCERNS FOR AVIATION
WEATHER AS A RIDGE OF HIGH PRESSURE SETTLES ACROSS THE AREA.
ANOTHER NIGHT OF GOOD RADIATIONAL COOLING CONDITIONS TONIGHT...BUT
HYDROLAPSE PROFILES DO NOT APPEAR TO BE AS CONDUCIVE FOR
SIGNIFICANT FOG FORMATION...AND IF PATCHY FOG DOES FORM TONIGHT IT
APPEARS AS THOUGH IT WOULD BE MUCH MORE SHALLOW IN NATURE.
THUS...AT THIS FORECAST DISTANCE WILL ONLY INCLUDE MVFR VSBYS
TOWARD THE END OF THE FORECAST VALID PERIOD.

&&

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

$$

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


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