Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 240534
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
134 AM EDT TUE MAR 24 2015

.SYNOPSIS...
ISSUED AT 755 PM EDT MON MAR 23 2015

HIGH PRESSURE WILL BRIEFLY BUILD ACROSS THE REGION TONIGHT AND PRODUCE
DRY CONDITIONS INTO TUESDAY. LOWS TONIGHT WILL GENERALLY RANGE
BETWEEN THE UPPER TEENS AND MID 20S...WITH HIGHS ON TUESDAY
RECOVERING INTO THE LOW TO MID 40S. CHANCES FOR RAIN AND
POTENTIALLY A FEW THUNDERSTORMS WILL INCREASE TUESDAY NIGHT ALONG
A STRONG WARM FRONT...WITH BREEZY AND MILD CONDITIONS ANTICIPATED
BEHIND THIS FEATURE ON WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 327 PM EDT MON MAR 23 2015

SNOW TIED TO WAA/DEEPER MOISTURE CONVERGENCE IN ADVANCE OF A WELL
DEFINED UPPER WAVE WILL EXIT THE LOCAL AREA FROM NW TO SE THIS
AFTERNOON. STILL EXPECT SOME DECENT SNOW RATES AND POTENTIAL FOR
ROADS TO BECOME BRIEFLY SNOW COVERED/SLICK ALONG/SOUTH OF HWY 30
IN NE IN/NW OH THROUGH LATE AFTERNOON GIVEN REDUCTION IN STABILITY
JUST ABOVE THE FGEN CIRC. OTHERWISE...EXPECT AREAS OF LIGHTER
SNOW AND SOME DRIZZLE BEHIND THE MAIN AREA OF WAA PCPN (WITH UPPER
WAVE) INTO THE EARLY EVENING GIVEN LOSS OF MOISTURE ABOVE THE
FRONTAL SLOPE.

ISENTROPIC DESCENT AND WEAK DIFFLUENCE WILL RESULT IN A DRY PERIOD
TONIGHT INTO EARLY TUESDAY AFTERNOON BEHIND THIS AFTERNOON`S SYSTEM.
A SEPARATE VORT MAX SHEARING SE TOWARD THE CENTRAL/LOWER LAKES
TONIGHT MAY AID IN KEEPING MID/HIGH CLOUDS LOCKED IN ACROSS
NORTHERN ZONES...WITH LOWER STRATUS/STRATOCU LIKELY SLOW TO ERODE
UNDER LINGERING FRONTAL INVERSION SOUTH OF HWY 30. GIVEN MODEL AND
SATELLITE TRENDS OPTED TO INCREASE SKY COVER DURING THIS TIME.

A WESTERN CONUS SHORTWAVE WILL EJECT INTO THE PLAINS TOMORROW
WITH HEIGHT FALLS BEGINNING TO OVERSPREAD THE MID MS VALLEY TOWARD
THE END OF THE DAY. INITIAL 850-700 MB THETA-E SURGE ON THE
EASTERN FRINGE OF AN ASSOCIATED MID MS LLJ WILL SUPPORT AN
INCREASE IN CLOUDS AND INCREASING CHANCES FOR RAIN SHOWERS SW OF
HWY 30 BY MID-LATE AFTERNOON.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 327 PM EDT MON MAR 23 2015

AN ACTIVE LONG TERM PERIOD IS IN STORE WITH THE LIKELIHOOD OF RAIN
TUESDAY NIGHT/WEDNESDAY NIGHT...WHICH WILL BE FOLLOWED BY RETURN TO
BELOW NORMAL TEMPS FOR THURSDAY THROUGH THE UPCOMING WEEKEND.

AN UPPER LEVEL WAVE ACROSS THE PACIFIC NORTHWEST COAST WILL BE THE
PRIMARY WAVE TO WATCH FOR TUESDAY NIGHT/EARLY WEDNESDAY. GUIDANCE
HAS BEEN QUITE CONSISTENT DEPICTING A 50-65 KNOT LOW LEVEL JET
DEVELOPING FROM THE MID MS RVR VALLEY INTO THE SOUTHERN GREAT
LAKES. STRONG LOW LEVEL MOISTURE ADVECTION/TRANSPORT ASSOCIATED WITH
THIS LOW LEVEL JET WILL ADVECT A 1 INCH PWAT AXIS INTO NORTHERN
INDIANA TUESDAY EVENING. THE COMBINATION OF THIS DEEPER MOISTURE AND
APPROACH OF AFOREMENTIONED PACIFIC WAVE (ACQUIRING NEGATIVE TILT)
WILL RESULT IN RAIN SHOWERS OVERSPREADING THE FORECAST AREA TUESDAY
EVENING/EARLY PORTIONS OF THE OVERNIGHT HOURS. WHILE ELEVATED
INSTABILITY STILL LOOKS TO BE QUITE MEAGER (GENERALLY LESS THAN 100
J/KG)...THE COMBINATION OF STRONG LLJ/UPPER DYNAMICS MAY BE ENOUGH
FOR ISOLD THUNDER AND HAVE MAINTAINED IN THE FORECAST. WITH
PROGRESSION OF LOW LEVEL WARM FRONT TUESDAY NIGHT...HAVE UTILIZED A
NON-DIURNAL TEMPERATURE CURVE WITH RISING TEMPERATURES OVERNIGHT.

PRONOUNCED DRY SLOT SHOULD OVERSPREAD THE AREA WEDNESDAY MORNING AS
STRONGER DPVA LIFTS ACROSS THE NORTHERN GREAT LAKES. ALL INDICATIONS
STILL POINT TO A LULL IN PRECIP CHANCES PARTICULARLY WEDNESDAY
AFTERNOON AS FORCING AND DEEPER MOISTURE SHIFT EAST OF THE AREA. NEW
SNOWCOVER HAS THROWN SOME COMPLICATIONS IN FOR WEDNESDAY TEMPERATURE
FORECAST...ALTHOUGH WOULD EXPECT THAT STRONG LOW LEVEL THETAE SURGE
TUESDAY NIGHT WILL BE EFFICIENT AT ERODING NEW SNOWPACK. GIVEN
STRENGTH OF ADVECTIVE FIELDS...HAVE MAINTAINED HIGHS FROM THE MID
50S TO LOWER 60S ON WEDNESDAY. WEDNESDAY STILL LOOKS TO BE
BREEZY...ALTHOUGH A SOMEWHAT SLOWER ONSET OF LOW LEVEL CAA APPEARS
TO SUPPORT MORE SHALLOW MIXING HEIGHTS THAT HAVE BEEN ADVERTISED
BY THE NAM.

RAIN CHANCES SHOULD RAMP UP AGAIN WEDNESDAY NIGHT...PARTICULARLY
ACROSS SOUTHEAST HALF OF THE FORECAST AREA AS NEXT UPSTREAM WAVE
INDUCES MID LEVEL FGEN RESPONSE ACROSS THE AREA. BETTER INSTABILITY
MAY BE SUPPRESSED JUST SOUTH OF LOCAL AREA SO HAVE OMITTED THUNDER
MENTION AT THIS TIME...BUT DID INCREASE POPS FOR WEDNESDAY NIGHT.
SFC FRONTAL PASSAGE FOR LATE WEDNESDAY NIGHT INTO THURSDAY WILL BE
FOLLOWED BY REINFORCING SFC TROUGH THURSDAY/THURSDAY EVENING WITH A
RETURN TO BELOW NORMAL TEMPS. TIMING OF LOW LEVEL THERMAL TROUGH
INTO THE GREAT LAKES WOULD SUPPORT FRIDAY AS THE COLDEST DAY OF THE
PERIOD WHEN HIGHS MAY STRUGGLE TO REACH THE MID 30S. TEMPERATURES
SHOULD MODERATE FAIRLY QUICKLY BY SUNDAY HOWEVER AS MEDIUM RANGE
GUIDANCE CONTINUES TO ADVERTISE A STRONGER SHORT WAVE TOPPING THE
UPPER LEVEL RIDGE WITH A PERIOD OF STRONGER ISENTROPIC ASCENT/RAIN
SHOWER CHANCES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 130 AM EDT TUE MAR 24 2015

LOW CLOUD COVER HAS DECREASED AS DRIER AIR IN LOW LEVELS WAS MOVG
INTO THE AREA FROM THE NE. HWVR...VSBYS HAVE BEEN LOWERING AT A
FEW SITES ALONG THE MI/IN BORDER AS WEAKER GRADIENT IN THIS AREA
ALLOWING BOUNDARY LAYER TO DECOUPLE. MAY BE SOME PATCHY BR AT SBN
OVER THE NEXT FEW HOURS BUT BY DAYBREAK GRADIENT SHOULD INCREASE
AS HIGH PRESSURE OVER SE CANADA MOVES SE... ALLOWING FOR VFR CONDITIONS
AT BOTH SITES WHICH SHOULD CONT THROUGH THE REST OF THE TAF
PERIOD. CIGS WILL LOWER TONIGHT AS A LOW PRESSURE SYSTEM AND
ACCOMPANYING WARM FRONT APPROACH FROM THE SW... BUT SHOULD STAY
VFR THROUGH 06Z WITH CONDITIONS DETERIORATING SHORTLY THEREAFTER.

&&

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

$$

SYNOPSIS...STEINWEDEL/LASHLEY
SHORT TERM...STEINWEDEL
LONG TERM...MARSILI
AVIATION...JT


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