Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 220534
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
134 AM EDT TUE APR 22 2014

.SYNOPSIS...
ISSUED AT 817 PM EDT MON APR 21 2014

A COLD FRONT WILL MOVE ACROSS THE AREA LATE THIS EVENING BRINGING
A CHANCE FOR SHOWERS AND AN ISOLATED THUNDERSTORM. MUCH COOLER AND
DRY WEATHER WILL FOLLOW FOR TUESDAY AND WEDNESDAY AS HIGH PRESSURE
SETTLES IN. LOWS TONIGHT WILL FALL BACK INTO THE 40S WITH HIGHS ON
TUESDAY IN THE 50S.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 333 PM EDT MON APR 21 2014

SLOWLY INTENSIFYING LOW PRESSURE SYSTEM WILL CONTINUE TO TRACK EAST
ACROSS THE GRTLKS TONIGHT. >1" PRECIP WATER MOISTURE PLUME EXTENDING
N-NE THROUGH THE MS VALLEY INTO THE UPR GRTLKS AHEAD OF THIS SYSTEM
AND ITS ASSOCIATED CDFNT. COMBINATION OF THE DEEP MOISTURE AND
MODEST LIFT ASSOCIATED WITH THE APCHG SHRTWV/CDFNT RESULTING IN
NUMEROUS SHOWERS FROM WI TO OK/ARK EARLY THIS AFTN WHICH SHOULD
SPREAD EAST ACROSS OUR CWA TONIGHT. A FEW LIGHTNING STRIKES NOTED
UPSTREAM OVER IL/IA THIS AFTN WHERE MUCAPES GENERALLY 500-1000J/KG
AND WITH MODELS FCSTG THIS WK INSTABILITY TO TRANSLATE EAST ACROSS
OUR AREA TONIGHT... ISOLATED THUNDERSTORMS STILL PSBL ACROSS OUR
AREA THROUGH TONIGHT. STRONG CAA WILL OVERSPREAD THE CWA BEHIND THE
CDFNT LATE TONIGHT AND TUE... ENHANCED BY ONSHORE FLOW OFF LAKE
MICHIGAN. TEMPS BY TUE MORNING EXPECTED TO FALL INTO THE U30S NW TO
THE L50S SE. SUBSIDENCE/DRYING SHOULD ALLOW FOR MOSTLY SUNNY SKIES
TUE... BUT TEMPS SHOULD BE SLOW TO RESPOND WITH ONLY A 5-10F DIURNAL
RISE RESULTING IN HIGHS 20-30F COLDER THAN TODAY WITH BRISK NW WINDS
ADDING TO THE CHILL.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 333 PM EDT MON APR 21 2014

PROGRESSIVE, MORE AMPLIFIED, LONGWAVE PATTERN WILL CONTINUE MID-LATE
WEEK. REBOUNDING HEIGHTS ALOFT BEHIND TUESDAY`S MID LEVEL TROUGH
WILL ALLOW A LOW LEVEL RIDGE AXIS TO BUILD IN TUESDAY NIGHT INTO
WEDNESDAY. DRY CP AIRMASS, NOTHING MORE THAN SOME HIGH CIRRUS, AND
WINDS BECOMING LIGHT/VARIABLE WILL LIKELY SUPPORT OPTIMAL
RADIATIONAL COOLING WITH LOWS NEAR FREEZING. WEDNESDAY`S HIGH TEMPS
SHOULD BE A COUPLE DEGREES WARMER WHEN COMPARED TO TUESDAY...WITH
MIXING TO NEAR 850 MB SUPPORTING UPPER 50S-LOW 60S HIGHS AWAY FROM
LAKE SHADOW...ALTHOUGH GRADUAL INCREASE IN MID-HIGH CLOUDS COULD
LIMIT TEMP RISES SOMEWHAT.

MODELS REMAIN IN GOOD AGREEMENT IN TRANSLATING THE NEXT AMPLIFIED
NORTHEAST PACIFIC UPPER TROUGH EAST INTO THE INTERMOUNTAIN WEST
WEDNESDAY AND CENTRAL US THURSDAY. SHORTWAVE/JET ENERGY ROUNDING THE
BASE OF THIS TROUGH NORTHEAST INTO THE MID/UPPER MS VALLEY BY LATER
THURSDAY WILL EVENTUALLY HELP CARVE OUT A VERTICALLY
STACKED/OCCLUDED SYSTEM OVER THE NORTHERN LAKES BY FRIDAY. BULK OF
SHOWER ACTIVITY IN ISENTROPIC/WAA WING OF THIS APPROACHING SYSTEM
SHOULD PASS WEST OF THE IWX CWA LATE WEDNESDAY AFTERNOON INTO
THURSDAY MORNING GIVEN DRY LOW LEVELS. MAYBE A FEW SPRINKLES AT BEST
ACROSS OUR NORTHWEST ZONES. OTHERWISE...RETURN FLOW ON BACKSIDE OF
HIGH PRESSURE SHOULD ENSURE A SOLID WARM UP WED NIGHT/THU. RAIN
CHANCES INCREASE LATER THURSDAY AFTN-EVE GIVEN MODEST LOW LEVEL
MOISTURE SURGE AND RESPECTABLE MID LVL PV ADVECTION/UPPER LEVEL
DIFFLUENCE ALONG THE SFC OCCLUSION. DRY SLOT WITH NEGATIVE HEIGHT
ANOMALY EMERGING OVER THE NORTHER LAKES SHOULD ENSURE A MAINLY
DRY/SEASONABLY MILD/BREEZY FRIDAY. A STRONGER SECONDARY COLD FRONT
WITH PV FILAMENT ROTATING AROUND THE PRIMARY UPPER LOW SHOULD DROP
THROUGH THE AREA LATER FRIDAY AFTERNOON-FRIDAY EVENING MAINTAINING A
LOW CHANCE FOR SHOWERS DURING THIS TIME.

CONFIDENCE IN ANY MODEL SOLUTION REMAINS VERY LOW THIS WEEKEND INTO
EARLY NEXT AS INCREASED HIGH LATITUDE BLOCKING LEAVES SLOW MOVING
(ALMOST CUT-OFF) MID TROPOSPHERIC CIRCULATIONS INVOF THE CENTRAL
HIGHS PLAINS AND ANOTHER OVER THE NORTHEAST US/SE CANADA. IN
BETWEEN...SFC HIGH PRESSURE WILL ATTEMPT TO NUDGE SOUTH INTO THE
GREAT LAKES REGION...WITH THE GFS AND MANY OF ITS MEMBERS (12Z ECMWF
ALSO TRENDING THIS WAY) KEEPING AN ACTIVE BAROCLINIC ZONE SOUTH AND
WEST OF THE LOCAL AREA FOR MUCH OF THE SATURDAY-MONDAY PERIOD. GIVEN
LOW CONFIDENCE AND 12Z ECMWF TRENDS FELT PERSISTENCE (A MAINLY DRY
OPTIMISTIC FCST) WAS THE WAY TO GO THIS WEEKEND. OTHERWISE...EXPECT
BELOW NORMAL TEMPS SAT-MON.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 134 AM EDT TUE APR 22 2014

SURFACE COLD FRONT IS CURRENTLY APPROACHING THE AREA WITH SCT RAIN
SHOWERS ALONG/AHEAD OF IT. PATCHY BR HAS ALSO BEEN REPORTED AT
SEVERAL SITES IMMEDIATELY ALONG AND AHEAD OF THE FRONT. THESE MVFR
CONDITIONS...POSSIBLY BELOW FUEL ALTERNATE CRITERIA...ARE EXPECTED
TO IMPACT THE TERMINALS THROUGH ROUGHLY 09Z AS THIS FRONT PASSES.
VFR CONDITIONS EXPECTED BY 12Z THOUGH AS HIGH PRESSURE AND DRY AIR
ADVECTION SCOUR OUT LOW LEVEL MOISTURE. MOSTLY CLEAR SKIES
EXPECTED TODAY BUT STRONG PRESSURE GRADIENT AND DECENT MIXING
HEIGHTS WILL LEAD TO GUSTY NORTHWEST WINDS FOR MUCH OF THE DAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 6 AM THIS MORNING TO 8 PM EDT THIS
     EVENING FOR LMZ043-046.

&&

$$

SYNOPSIS...CEO/T
SHORT TERM...JT
LONG TERM...STEINWEDEL
AVIATION...AGD


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