Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 250633
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
233 AM EDT SAT APR 25 2015

.SYNOPSIS...
ISSUED AT 232 AM EDT SAT APR 25 2015

A LOW PRESSURE CENTER APPROACHING THE REGION EARLY THIS MORNING
WILL BRING WIDESPREAD RAIN TO MOST OF THE AREA. THE LOW WILL MOVE
EAST TONIGHT AS RAIN ENDS ACROSS THE REGION. HIGH TEMPERATURES
TODAY WILL RANGE FROM THE UPPER 40S IN SOUTHERN MICHIGAN TO THE
UPPER 50S IN SOUTHWESTERN INDIANA. LOWS TONIGHT WILL DROP INTO THE
30S.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 350 PM EDT FRI APR 24 2015

RAIN CHANCES TO INCREASE LATE TONIGHT AND ESPECIALLY ON
SATURDAY...WITH NEXT SOUTHERN STREAM SYSTEM TO IMPACT THE AREA.

A VERY DRY LOW LEVEL AIR MASS REMAINS IN PLACE ACROSS THE AREA DUE
TO A RATHER PROLONGED PERIOD OF SYNOPTIC SCALE SUBSIDENCE OVER THE
PAST 36 HOURS. SFC DEW POINT DEPRESSIONS CURRENTLY ARE RUNNING
ANYWHERE FROM 30 TO 45 DEGREES ACROSS MOST LOCATIONS. MID AND HIGH
CLOUDS WILL CONTINUE TO INCREASE THROUGH THE LATE AFTERNOON AS MID
LEVEL WINDS BACK AND MID LEVEL WAA BECOMES MORE PRONOUNCED. A
SMALL SCALE...BUT VIGOROUS SHORT WAVE TRACKING ACROSS EASTERN IOWA
THIS AFTERNOON SHOULD TRACK ACROSS THE SOUTHERN GREAT LAKES REGION
THIS EVENING. A NARROW CORRIDOR OF SOME BETTER LOW LEVEL MOISTURE
POOLING/LOW LEVEL FGEN IS EXPECTED TO SHIFT EASTWARD ACROSS MAINLY
SOUTHERN LOWER MICHIGAN AND EXTREME NORTHERN INDIANA THIS EVENING.
GIVEN VERY DRY LOW LEVELS...CONFIDENCE IS LOW IN MEASURABLE PRECIP
AND ANY CHANCE WILL LIKELY BE CONFINED TO NARROW MOISTURE
POOLING/FGEN AXIS ACROSS THE NORTH. NOT MUCH CHANGE MADE TO
PREVIOUS FORECAST WITH SLIGHT CHANCE LIGHT RAIN/SPRINKLES ACROSS
THE FAR NORTH THIS EVENING.

STRONGER LOW LEVEL THETAE SURGE STILL APPEARS TO BE DELAYED UNTIL
WELL AFTER 12Z FOLLOWING THE EVOLUTION OF SOUTHERN STREAM UPPER
TROUGH CURRENTLY WORKING ACROSS THE SOUTHERN ROCKIES. GUIDANCE STILL
DEPICTS 1 INCH PWATS WORKING ACROSS APPROXIMATELY SOUTHERN TWO
THIRDS OF THE FORECAST AREA SATURDAY MORNING. HAVE MAINTAINED
CATEGORICAL POPS ACROSS MOST LOCATIONS WITH STILL SOME LESSER
CONFIDENCE ACROSS THE EXTREME NORTHEAST IN RAINFALL AMOUNTS AS MORE
ROBUST EASTERLY FLOW SHOULD ALLOW FOR A SOMEWHAT DRIER LOW LEVEL
TRAJECTORY. WILL MAINTAIN A GRADIENT TO LIKELY POPS ACROSS THE FAR
NORTHEAST...WITH EXPECTATION OF AT LEAST SOME MEASURABLE PRECIP DUE
TO THE COMBINATION OF MID/UPPER SYNOPTIC FORCING AND FAVORABLE
PROXIMITY TO LEFT EXIT REGION OF UPPER JET STREAK. PIVOTING LOW
LEVEL THETAE GRADIENT ASSOCIATED WITH PROGRESSION OF LOW LEVEL
CYCLONIC CIRCULATION COULD LEND TO SOME HEALTHY RAINFALL AMOUNTS IN
EXCESS OF ONE HALF INCH ACROSS PORTIONS OF CENTRAL/SOUTHERN CWA.
OTHERWISE...SATURDAY STILL IS SHAPING UP TO BE A RAW DAY WITH BRISK
EASTERLY WINDS AND INFLUENCE OF CLOUDS AND PRECIP KEEPING TEMPS IN
THE UPPER 40S...OR PERHAPS LOWER 50S IF A SLOWER THAN CURRENT FORECAST
EVOLUTION MATERIALIZES IN REGARDS TO SOUTHERN STREAM TROUGH.

NORTHERN STREAM SHOULD EVENTUALLY SUPPRESS THIS UPPER WAVE SATURDAY
EVENING...WITH ONSET OF LOW LEVEL DRY AIR ADVECTION AND AN END TO
PRECIP CHANCES FROM NORTH TO SOUTH.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 350 PM EDT FRI APR 24 2015

WILL BE MAINTAINING A DRY FORECAST THROUGH THE PERIOD BUT STILL AT
LEAST ONE FEATURE OF INTEREST TO KEEP AN EYE ON.

RIDGING WILL HOLD ACROSS THE AREA INTO AT LEAST TUESDAY WITH NO
CHANCE OF RAIN AND TEMPERATURES TRENDING BACK TOWARDS NORMAL IN THE
MID 60S. A PIECE OF ENERGY WILL DROP SE OUT OF CANADA IN THE
TUES/TUES NGT TIME FRAME. SOME OF THE MODELS SUGGEST SOME LIGHT
PRECIP...BUT CONCERNED THAT TOO MUCH DRY AIR WILL RESIDE OVER THE
REGION AND LIMIT THE CHANCE FOR SHOWERS. AT THIS POINT WILL MAINTAIN
A DRY FORECAST. THE MORE SIGNIFICANT EFFECT WILL BE EVENTUAL PHASING
WITH A CLOSED SW UPPER LEVEL LOW...RESULTING IN DEEPENING LOW
PRESSURE THAT WILL IMPACT QUICKLY MOVE OFF THE EAST COAST BY THE END
OF NEXT WEEK. THIS WILL PLACE THE REGION BACK INTO RIDGING ALOFT AND
TEMPS REMAINING IN THE 60S...POSSIBLY TRENDING WARMER IF EVERYTHING
COMES TOGETHER CORRECTLY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 209 AM EDT SAT APR 25 2015

AN AREA OF RAIN HAS BEEN TRANSLATING SOUTH AND WAS BEING SUPPORTED
AND ENHANCED BY THE COMBINATION OF THE LEFT EXIT REGION OF AN
UPPER JET ALONG WITH SURFACE CONVERGENCE ALONG A WEAK BOUNDARY.
HAVE ADJUSTED THE TIMING OF THE RAIN AT FT WAYNE GIVEN THESE
CONDITIONS...RADAR TRENDS AND SURFACE OBS. STILL MUCH UNCERTAINTY
CONCERNING THE NORTHERN EXTENT OF THE RAIN SHIELD LATER TODAY...
WITH MOST OF THE HIGH RES MODELS VERY INHIBITED/SUPPRESS WHEREAS
THE SPECTRAL MODELS MUCH MORE PROGRESSIVE AND WET. FOR NOW...
LEFT CONDITIONS BECOMING MVFR LATER IN THE TAF PERIOD...AND THEN
BECOMING VFR AGAIN AFTER THE LOW MOVES EAST.

&&

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

$$

SYNOPSIS...LOTHAMER/SKIPPER
SHORT TERM...MARSILI
LONG TERM...FISHER
AVIATION...SKIPPER


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