Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 281753
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
153 PM EDT FRI AUG 28 2015

.SYNOPSIS...
ISSUED AT 152 PM EDT FRI AUG 28 2015

LOW PRESSURE WILL MOVE THROUGH THE AREA THIS WEEKEND...BRINGING
CHANCES FOR SHOWERS AND THUNDERSTORMS. BY MONDAY...HIGH PRESSURE
MOVING INTO THE REGION WILL BRING ABOVE NORMAL TEMPERATURES. HIGHS
TODAY AND SATURDAY WILL BE IN THE UPPER 70S AND 80S. LOWS TONIGHT
WILL BE IN THE 60S.

&&

.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 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 152 PM EDT FRI AUG 28 2015

A QUIET EVENING IN STORE FOR THE FORECAST AREA BEFORE THE NEXT LOW
PRESSURE SYSTEM MOVES INTO THE REGION. HIGH CLOUDS AHEAD OF THE
SYSTEM HAVE OVERSPREAD BOTH SITES THIS AFTERNOON...AND WILL REMAIN
THROUGH THE TAF PERIOD. PRECIPITATION AHEAD OF A LOW CENTERED OVER
IA/WI WILL SHIFT NORTHEAST OF THE AREA WITH BETTER FORCING TONIGHT.
IT IS POSSIBLE THAT KSBN SEES A STRAY SHOWER...BUT WAS NOT CONFIDENT
ENOUGH TO INCLUDE IN THE TAF.

OTHERWISE...A WARM FRONT WILL MOVE IN LATE TONIGHT/SATURDAY
MORNING...BUT WINDS AT THE SFC AND ALOFT REMAIN FAIRLY LIGHT. GIVEN
LIGHT WINDS AND INCREASING MOISTURE...THERE IS POTENTIAL FOR LOWER
VISIBILITIES AT KFWA. RIGHT NOW THINKING THIS WILL PLAY OUT SIMILAR
TO THIS MORNING...WITH VISIBILITIES AROUND 3-4 MILES. CHANCES FOR
PRECIPITATION WITH THIS SYSTEM ARE PRETTY LOW UNTIL AFTER 18Z
SATURDAY. SOME GUIDANCE SUGGESTS A FEW SHOWERS WITH THE WARM FRONT
NEAR FWA/SBN EARLIER SATURDAY...BUT LEFT OUT FOR NOW GIVEN LOW
CONFIDENCE.


&&

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

$$

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


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