Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 280723
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
323 AM EDT FRI AUG 28 2015

.SYNOPSIS...
ISSUED AT 1257 AM EDT FRI AUG 28 2015

HIGH PRESSURE OVERHEAD WILL MOVE EAST THROUGH THE LOWER GREAT
LAKES TO THE MID ATLANTIC REGION OVER THE NEXT FEW DAYS. THIS WILL
ALLOW TEMPERATURES TO WARM ABOVE NORMAL BY EARLY NEXT WEEK. IN THE
MEANTIME...A WEAK UPPER LEVEL SYSTEM WILL BRING A CHANCE FOR
SHOWERS AND THUNDERSTORMS THIS WEEKEND. HIGHS TODAY WILL REACH THE
MID TO UPPER 70S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 320 AM EDT FRI AUG 28 2015

LIGHT WINDS AND MAINLY CLEAR SKIES ASSOCIATED WITH SFC HIGH
PRESSURE CENTERED OVER THE EASTERN LAKES HAS ALLOWED TEMPS TO NEAR
XOVER VALUES EARLY THIS MORNING. NOT SEEING ANY BR/FG RESTRICTIONS
IN LATEST OBSERVATIONS BUT WOULD NOT BE SURPRISED TO SEE SOME
PATCHY FOG (NOT AS WIDESPREAD AS YESTERDAY) BETWEEN 10-13Z GIVEN
LINGERING BOUNDARY LAYER MOISTURE. ANY PATCHY FOG SHOULD LIFT OUT
TO A SCT STRATO CU DECK BY MID MORNING.

WINDS SHIFTING MORE SOUTHERLY BY LATER THIS MORNING/AFTERNOON IN
RESPONSE TO EASTWARD SHIFT OF THE ABOVE MENTIONED SFC HIGH WILL
SUPPORT A WARMER DAY (YET STILL BELOW NORMAL FOR LATE AUGUST) WITH
HIGHS INTO THE MID-UPPER 70S. EXPECT ANOTHER QUIET DAY OTHERWISE
WITH INCREASING MID-HIGH LEVEL CLOUDS IN ADVANCE OF A CONVECTIVELY
ENHANCED SHORTWAVE (OVER EASTERN NEBRASKA AS OF 07Z) AND ATTENDANT
SFC REFLECTION MODELED TO TRACK SLOWLY EAST THROUGH IOWA. ELEVATED
THETA-E ADVECTION (WITHIN 20-30 KNOTS OF CROSS ISOBARIC FLOW ON THE
305K SFC) IN ADVANCE OF THIS FEATURE MAY BE ENOUGH TO SPREAD SHOWERS
INTO OUR NORTHWESTERN ZONES BY LATER TONIGHT...ALTHOUGH KEPT POPS
LOW GIVEN EXPECTATIONS FOR BULK OF PRECIPITATION TO ALIGN WEST-
NORTHWEST OF THE IWX CWA ALONG SLOWLY ADVANCING MOISTURE AXIS/
PV ANOMALY.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 320 AM EDT FRI AUG 28 2015

FOR SATURDAY...A SOMEWHAT DISJOINTED UPPER LEVEL TROUGH WILL BE
MAKING ITS WAY THROUGH THE AREA AS NORTHERN STREAM PV ANOMALY
ATTEMPTS TO PARTIALLY PHASE WITH PACIFIC SHORT WAVE TRACKING ACROSS
THE WESTERN GREAT LAKES REGION. BROAD ISENTROPIC LIFT ASSOCIATED
WITH WARM FRONT LIFTING THROUGH THE AREA WILL PRECEDE THIS FORCING
ALTHOUGH LOW LEVEL MOISTURE RETURN IS EXPECTED TO BE SOMEWHAT
LIMITED AT THE ONSET ON SATURDAY MORNING. TWO DISTINCT POCKETS OF
BETTER INSTABILITY MAY DEVELOP SATURDAY AFTERNOON...ONE ACROSS
SOUTHEAST PORTIONS OF THE AREA MORE DIVORCED FROM STRONGER MID/UPPER
LEVEL FORCING AND ANOTHER AREA IN CLOSER PROXIMITY TO ASSOCIATED SFC
TROUGH/LOW LEVEL CONVERGENT AXIS ACROSS NORTHEAST ILLINOIS/EXTREME
NORTHWEST INDIANA. LEAD VORT MAX ASSOCIATED WITH PACIFIC WAVE SHOULD
TEND TO OUTRUN THIS BETTER LOW LEVEL CONVERGENCE DURING THE DAY
SATURDAY...SO SOME QUESTION AS TO EASTWARD EXTENT OF PRECIP
COVERAGE. SECONDARY SHORT WAVE ASSOCIATED WITH NORTHERN STREAM
SHOULD BE ON THE HEELS OF THIS LEAD WAVE WITH A BETTER CHANCE OF
CONVECTIVE DEVELOPMENT ACROSS THE WEST/NORTHWEST SATURDAY
AFTERNOON/EARLY EVENING WHERE LOW LEVEL MOISTURE MAY BE MORE
EFFECTIVELY POOLED. PREVIOUS POPS SEEM TO CAPTURE CURRENT TRENDS
WELL SO NO DRAMATIC CHANGES MADE FOR THIS FORECAST CYCLE WITH HIGH
CHANCE POPS NORTHWEST TAPERING TO LOW CHANCE SOUTHEAST ON SATURDAY
AFTERNOON. ANY NOTABLE BELTS OF STRONGER DEEP LAYER SHEAR SHOULD BE
SHIFTING EAST OF THE AREA BY SATURDAY AFTERNOON IN ASSOCIATION WITH
40 KNOT MID LEVEL SPEED MAX...AND OVERALL LIMITED NATURE TO SURFACE
BASED INSTABILITY/MARGINAL MID LEVEL LAPSE RATES SUGGEST LITTLE TO
NO SEVERE THREAT AT THIS TIME.

MAINTAINED LOW CHANCE POPS INTO THE OVERNIGHT HOURS SATURDAY AS
SURFACE TROUGH ENTERS NORTHERN INDIANA...BUT BY THIS TIME MID/UPPER
FORCING SHOULD BE ON THE DECLINE AS UPPER VORT MAX BECOMES MORE
ATTENUATED. THIS WEAK FORCING WILL PERSIST INTO SUNDAY AND HAVE THUS
CONTINUED LOW CHANCE POPS THROUGH EARLY SUNDAY EVENING. DESPITE LOW
LEVEL WAA...IMPACTS OF GOOD DEAL CLOUD COVER/PRECIP SHOULD LIMIT
HIGH TEMPS FROM UPPER 70S TO LOWER 80S FOR BOTH SATURDAY/SUNDAY.

EVENTUAL DECAY OF THIS PV ANOMALY EARLY NEXT WEEK WILL BE FOLLOWED
BY BUILDING MID/UPPER LEVEL HEIGHTS SUPPORTIVE OF PREVIOUSLY
ADVERTISED WARMING TREND FOR THE TUESDAY/WEDNESDAY TIMEFRAME.
WEATHER SHOULD BE RATHER UNEVENTFUL FOR MUCH OF THE UPCOMING WEEK
UNDER THE INFLUENCE OF THIS UPPER RIDGING WITH HIGHS GENERALLY IN
THE MID TO UPPER 80S AND LOWS IN MID 60S. SOME POSSIBILITY MAY EXIST
FOR A FEW WEAK WAVES TO MEANDER THROUGH MEAN UPPER RIDGING IN THE
WED/THU TIMEFRAME...BUT OVERALL UNSUPPORTIVE BACKGROUND
THERMODYNAMIC ENVIRONMENT SUGGESTS MAINTAINING DRY FORECAST IS MOST
PRUDENT AT THIS TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1257 AM EDT FRI AUG 28 2015

GOOD RADIATIONAL COOLING WILL ALLOW TEMPS TO NEAR XOVER VALUES
EARLY THIS MORNING. RESULTING PATCHY FOG MAY IMPACT THE TERMINALS
TOWARD DAYBREAK (MAINTAINED MVFR BR TEMPO GROUP BTW 10-12Z).
LIGHT/CALM WINDS WILL VEER MORE SOUTHERLY BY LATE
MORNING/AFTERNOON AS SFC RIDGE CENTERED OVER THE LOWER/EASTERN
LAKES PUSHES EAST. VFR OTHERWISE WITH INCREASING MID-HIGH CLOUDS
AS SYSTEM APPROACHES FROM THE WEST (EXCEPTION MAY BE A PERIOD OF
MVFR STRATOCU IN THE 13-16Z WINDOW BEFORE MIXING UP/OUT).

&&

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

$$

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


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