Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 282123
AFDIWX

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

.SYNOPSIS...
ISSUED AT 511 PM EDT THU MAY 28 2015

HIGH PRESSURE WILL SHIFT EAST TONIGHT WITH CLEAR 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
NIGHT AND SATURDAY. LOWS TONIGHT WILL BE IN THE 60S...WITH HIGHS
ON FRIDAY IN THE MIDDLE 80S. THE WEEKEND 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 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1250 PM EDT THU MAY 28 2015

VFR CONDITIONS AND LIGHT ESE WINDS WILL PERSIST ON THE STABLE SW
FRINGE OF SFC HIGH PRESSURE THIS AFTERNOON/EVENING. FLOW VEERS MORE
SOUTHERLY IN ADVANCE OF THE NEXT UPPER TROUGH LATER TONIGHT INTO
FRIDAY. COULD SEE SOME STRATUS/BR FILL IN WITH THE ASSOCIATED
MOISTURE ADVECTION DURING THIS TIME. HOWEVER...OPTED TO HOLD WITH
OPTIMISTIC VFR FCST GIVEN WEAK SIGNALS IN MODEL GUIDANCE.


&&

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

$$

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


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