Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 290013
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
813 PM EDT THU MAY 28 2015

.SYNOPSIS...
ISSUED AT 811 PM EDT THU MAY 28 2015

HIGH PRESSURE WILL SHIFT EAST TONIGHT WITH PARTLY CLOUDY SKIES
AND MILD TEMPERATURES. A COLD FRONT APPROACHING FROM THE PLAINS
DURING THE DAY FRIDAY WILL BRING INCREASING WINDS...CLOUD COVER
AND HUMIDITY DURING THE DAY AND A RETURN OF SHOWERS AND
THUNDERSTORMS FRIDAY AFTERNOON INTO AND SATURDAY. LOWS TONIGHT
WILL BE IN THE LOWER TO MIDDLE 60S...WITH HIGHS ON FRIDAY IN THE
MIDDLE 80S. SUNDAY WILL BE NOTICEABLY COOLER WITH HIGHS DROPPING
INTO THE 60S BY SUNDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 331 PM EDT THU MAY 28 2015

FAIR WX WILL PREVAIL INTO THE EARLY OVERNIGHT AS THE LOCAL AREA
REMAINS SITUATED ON THE WESTERN EDGE OF A DEPARTING SFC RIDGE.
DEEP LAYER FLOW VEERS MORE SOUTHWESTERLY IN ADVANCE OF THE NEXT
PLAINS MID LEVEL TROUGH BY LATER TONIGHT INTO FRIDAY. RESULTING
MOISTURE ADVECTION WILL BRING AN INCREASE IN CLOUDS AND NON-ZERO
PRECIP CHANCES BACK INTO THE FORECAST DURING THIS TIME.

SUBTLE MID LEVEL SHEAR AXIS AND EMBEDDED VORT ACROSS THE TN
VALLEY AS OF THIS WRITING WILL PROPAGATE NNE INTO OHIO FRIDAY
MORNING/EARLY AFTERNOON. AN ASSOCIATED PLUME OF DEEPER MOISTURE
AND WEAK LOW LEVEL CONVERGENCE MAY CLIP OUR NW OHIO ZONES WITH
SCT SHOWERS/ISO THUNDER DURING THIS TIME. LACK OF CAPPING AND
MODERATE DESTABILIZATION EXPECTED ACROSS THE ENTIRE FORECAST AREA
BY FRIDAY AFTERNOON. BETTER FORCING/FLOW WILL REMAIN WELL WEST IN
ADVANCE OF PRIMARY SYNOPTIC SCALE TROUGH/SFC BOUNDARY...BUT COULD
SEE SCT CONVECTION FIRE INTO WESTERN/CENTRAL ZONES AS
CONVECTIVELY AIDED SHORTWAVE LIFTING INTO THE UPPER MIDWEST
POTENTIALLY DROPS A PRE-FRONTAL BOUNDARY INTO NRN IN/SW LOWER MI
BY PEAK HEATING. SPC CONTINUES TO HAVE THE AREA HIGHLIGHTED IN A
MARGINAL RISK FOR SEVERE STORMS GIVEN POTENTIAL FOR 1500-2000 J/KG
OF MLCAPE AND STEEP LOW LEVEL LAPSE RATES...WITH LACKING DEEP
LAYER SHEAR/FLOW/FORCING LIMITING FACTORS FOR ORGANIZATION (MORE
PULSE TYPE BEHAVIOR ANTICIPATED IF INITIATION OCCURS).

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 331 PM EDT THU MAY 28 2015

OVERALL NO MAJOR CHANGES TO GENERAL IDEA OF PREVIOUS FORECAST
WITH MAIN ITEM OF INTEREST IN THE LONG TERM CENTERING ON
INCREASING RAIN CHANCES FRIDAY NIGHT THROUGH SATURDAY EVENING.

DISJOINTED UPPER LEVEL SYSTEM WILL BEGIN TO AFFECT THE AREA FOR
THE FRIDAY NIGHT THROUGH SATURDAY EVENING PERIOD.
INITIALLY...ATTENTION WILL LIKELY BE ON SMALLER SCALE
CONVECTIVELY ENHANCED DISTURBANCES EJECTING NORTHEAST INTO THE
AREA FROM THE SOUTHERN PLAINS. SOME WEAK INSTABILITY SHOULD
PERSIST THROUGH THE NIGHTTIME HOURS ON FRIDAY/EARLY SATURDAY FOR
SLIGHTLY ELEVATED PARCELS. HAVE MAINTAINED WEST TO EAST POP
GRADIENT FOR FRIDAY NIGHT (LIKELY WEST-CHANCE EAST)...AND JUST
PUSHED BACK TIMING OF HIGHER POPS TO THE OVERNIGHT HOURS WITH
STRONGER HEIGHT FALLS BEGIN TO OVERSPREAD AT LEAST THE WESTERN
GREAT LAKES...AND VEERING LOW LEVEL JET ALLOWS FOR BETTER CHANCE
OF UPSTREAM CONVECTION REACHING ESPECIALLY WESTERN LOCATIONS.
WILDCARD FOR FRIDAY EVENING POPS WILL BE THE SMALLER SCALE
CONVECTIVELY ENHANCED VORTS...WHICH HAVE LOW PREDICTABILITY AT
THIS FORECAST DISTANCE.

ROCKIES UPPER LEVEL TROUGH TO EVENTUALLY SHEAR AS IT BEGINS TO
PARTIALLY PHASE WITH NORTHERN STREAM WAVE...WHICH WILL ALLOW
ASSOCIATED COLD FRONTAL BOUNDARY TO APPROACH THE FORECAST AREA
SATURDAY. NAM STILL ON THE SLOWER SIDE WITH FRONTAL PROGRESSION
IN COMPARISON TO GFS...WITH SREF GENERALLY A REASONABLE
COMPROMISE AT THIS POINT. FRONTAL PROGRESSION SHOULD GET A MORE
SUBSTANTIAL PUSH SOUTHWARD ACROSS RELATIVELY COLD LAKE MICHIGAN
WATERS...RESULTING IN FALLING TEMPERATURES SOMETIME SATURDAY
MORNING OR EARLY SATURDAY AFTERNOON FOR AREAS DOWNWIND OF LAKE
MICHIGAN. AREAS ACROSS THE FAR SOUTHEAST MAY FLIRT WITH 80 IF A
MORE DELAYED TIMING TO THICKER CLOUD COVER OCCURS. UPPER LEVEL
SUPPORT TO ALSO INCREASE IN ASSOCIATION WITH THIS FRONT...WITH
SOUTHERN GREAT LAKES IN FAVORABLE RIGHT EXIT REGION QUADRANT OF
UPPER JET BY SATURDAY MORNING. ASSOCIATED FGEN FORCING AND THE
ABOVE FACTORS STILL ARGUE FOR LIKELY POPS FORECAST AREA-WIDE ON
SATURDAY. ANAFRONT CHARACTERISTICS OF THIS BOUNDARY SHOULD KEEP
PLENTY OF ELEVATED MOISTURE IN PLACE AFTER SFC FRONTAL
PASSAGE...AND A VERY LOW SOUTHWARD PROGRESSION OF 850 HPA THETAE
GRADIENT ARGUES FOR THE POSSIBILITY OF SOME DECENT RAINFALL
AMOUNTS. SEVERE WEATHER CHANCES STILL APPEAR TO BE RELATIVELY LOW
GIVEN WEAK WARM SECTOR WEAK DEEP LAYER SHEAR AND THE POSSIBILITY
OF EXTENSIVE CLOUD COVER THROUGH THE DAY. CONTINUED TO CARRY
LIKELY POPS ACROSS MUCH OF SOUTHEAST HALF SATURDAY EVENING...WITH
CONDITIONS DRYING OUT SUNDAY. OF LOW CONFIDENCE AT THIS TIME IS
POSSIBILITY OF ANOTHER SOUTHERN STREAM VORT LIFTING ACROSS OHIO
RIVER VALLEY LATE SATURDAY NIGHT INTO EARLY SUNDAY THAT COULD
PROLONG RAIN CHANCES GIVEN PROXIMITY OF LOW LEVEL BOUNDARY. MUCH
COOLER CONDITIONS BEHIND THE FRONT FOR SUNDAY...WITH HIGHS
GENERALLY MID 60S.

ALL INDICATIONS STILL POINT TO BUILDING UPPER LEVEL HEIGHTS AGAIN
BY THE TUESDAY TIMEFRAME SUGGESTING THE COOL DOWN SHOULD BE
FOLLOWED IN SHORT ORDER BY MODERATING TEMPERATURE TREND.
MID/UPPER LEVEL RIDGING SHOULD ALLOW FOR MAINLY DRY AND
UNEVENTFUL CONDITIONS FOR TUESDAY-WEDNESDAY. UPPER RIDGE AXIS MAY
TEND TO PUSH JUST EAST OF THE AREA TOWARD THE END OF THE
PERIOD...WHICH COULD ALLOW FOR MAINLY DIURNALLY ENHANCED LOW END
SHOWER/STORM CHANCES BY THE END OF THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 812 PM EDT THU MAY 28 2015

CONTD VFR MET CONDS THROUGH THE FORECAST PD. INCRSD POTNL FOR
CONVECTION BY MID/LATE AFTN AS MID 60S SFC DPS ACRS SRN IL BEGIN
TO STREAM NNEWD INTO NRN IN...TIMED WITH EJECTION OF MID LEVEL
SHORTWAVE ENERGY. FOR NOW WILL COVER WITH VCTS AS POINT/AIRFIELD
PROBABILITIES/IMPACT APPEAR LOW AT THIS TIME.

&&

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

$$

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


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