Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 231930
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
330 PM EDT THU APR 23 2015

.SYNOPSIS...
ISSUED AT 328 PM EDT THU APR 23 2015

A RIDGE OF HIGH PRESSURE EXTENDING FROM THE UPPER MIDWEST TO THE
MID MISSISSIPPI RIVER VALLEY WILL OVERSPREAD THE GREAT LAKES INTO
THE OHIO VALLEY BY FRIDAY MORNING. AS THIS HIGH APPROACHES...WINDS
WILL DIMINISH EARLY THIS EVENING AND CLOUDS WILL DECREASE. QUIET
WEATHER WILL CONTINUE INTO FRIDAY BEFORE THE NEXT SYSTEM BRINGS
THE LIKELIHOOD OF RAIN ON SATURDAY. LOW TEMPERATURES TONIGHT WILL
DROP INTO THE UPPER 20S AND LOWER 30S. HIGH TEMPERATURES ON FRIDAY
WILL RANGE FROM 55 TO 60.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 328 PM EDT THU APR 23 2015

QUIET WEATHER EXPECTED THROUGH THE SHORT TERM PERIOD WITH THE MAIN
CONCERN ON THE POSSIBILITY OF SUB-FREEZING TEMPERATURES ONCE AGAIN
TONIGHT.

MID LEVEL COLD CORE ACROSS SOUTHEAST LOWER MICHIGAN HAS ALLOWED AN
EXTENSIVE STRATOCU DECK TO FORM THIS AFTERNOON. LOSS OF PEAK
DIURNAL HEATING AND CONTINUED EASTWARD PROGRESSION OF MID LEVEL COLD
CORE AND SHEARED UPPER VORTICITY MAXIMUM WILL RESULT IN RAPID
CLEARING LATE THIS AFTERNOON/EARLY EVENING. REGIONAL AMDAR SOUNDINGS
SUGGEST MIXING UP TO ABOUT 850 HPA THIS AFTERNOON...WHICH HAS
PROMOTED PEAK WIND GUSTS INTO THE 25 TO 30 MPH RANGE OVER THE PAST
SEVERAL HOURS. DECOUPLING SHOULD OCCUR RAPIDLY THIS EVENING...WITH
GUSTS SUBSIDING AROUND 22Z...AND WINDS BECOMING LIGHT AND VARIABLE
SHORTLY AFTER 00Z. WHILE LOW LEVEL THERMAL TROUGH WILL BE DEPARTING
TO THE EAST TONIGHT...THE COMBINATION CLEARING SKIES AND DIMINISHING
WINDS SHOULD ALLOW FOR GOOD RADIATIONAL COOLING CONDITIONS AND MIN
TEMPS FROM THE UPPER 20S TO LOWER 30S FOR MOST LOCATIONS. HAVE
ISSUED ANOTHER FREEZE WARNING FOR ALL OF THE FORECAST AREA IN EFFECT
FROM 05Z-13Z.

TRANQUIL WEATHER FOR FRIDAY AS LOW LEVEL ANTICYCLONE SLOWLY BEGINS
TO SHIFT OFF TO THE EAST. ATTENTION WILL THEN SHIFT TO APPROACHING
SOUTHERN STREAM TROUGH. HOWEVER...THROUGH THE SHORT TERM
PERIOD...THE ONLY LOCAL EFFECTS FROM THIS SYSTEM WILL BE INCREASING
MID/HIGH CLOUDS DURING THE MID-LATE AFTERNOON HOURS. TEMPERATURES
WILL CONTINUE TO MODERATE ON FRIDAY WITH HIGHS FROM THE MID 50S
NORTHEAST TO AROUND 60 SOUTHWEST.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 328 PM EDT THU APR 23 2015

MAIN FOCUS OF THE LONG TERM PERIOD WILL BE RAIN CHANCES ACROSS THE
AREA LATE FRIDAY NIGHT THROUGH SATURDAY NIGHT.

UPPER TROUGH WILL SWING FROM THE SOUTHERN PLAINS FRIDAY NIGHT
THROUGH THE OHIO VALLEY SATURDAY AND SATURDAY NIGHT. SFC LOW WILL
ORGANIZE AND TRACK TOWARDS THE AREA FRIDAY NIGHT...WITH MOISTURE
RICH FLOW.../PWATS OVER 1.00 IN/...INCREASING TOWARDS THE AREA.
STRONG ASCENT THROUGH A SATURATED LAYER UP THROUGH AT LEAST 600 MB
WILL BRING WIDESPREAD RAIN INTO THE AREA FROM THE WEST/SOUTHWEST
LATE FRIDAY INTO SATURDAY MORNING. BACKED OFF SLIGHTLY WITH THE
ARRIVAL OF RAIN...REMOVING POPS IN THE 00Z TO 06Z TIMEFRAME
SATURDAY. INCREASED POPS TO CATEGORICAL ON SATURDAY...MAINLY ACROSS
THE SOUTHWEST HALF OF THE FORECAST AREA...MIRRORING STRONG 850MB
THETA E BOUNDARY THAT WILL BE LAYED ROUGHLY ALONG THE US 30
CORRIDOR. NORTHEAST OF THIS 850 MB THETA E BOUNDARY...RAIN MAY
STRUGGLE TO OVERCOME FAIRLY DRY 850 MB LAYER...AIDED BY EASTERLY
FLOW. HOWEVER...STILL WENT WITH LIKELY POPS ON SATURDAY...WITH A
LATER ARRIVAL TIME EARLY SATURDAY MORNING AND A SHARPER QPF GRADIENT
NORTHEAST OF U.S. 30. CONSIDERED POTENTIAL ISO THUNDER MENTION IN
THE FAR SOUTHWEST W/ MID LVL LAPSE RATES NEAR 6 C/KM AND STRONG
FORCED ASCENT...BUT LEFT OUT OF GRIDS AT THIS TIME.

STRONG 850MB INVERSION AND CLOUD COVER/PRECIPITATION WILL KEEP MAX
TEMPS IN THE MID 40S TO AROUND 50S RANGE. WENT TOWARDS RAW MODEL
GUIDANCE TEMPS...WHICH YIELDED A DROP OF A FEW DEGREES FOR MAX TS
NORTH OF U.S. 30...WHERE LOW LEVEL DRY LAYER/EVAPORATIVE COOLING
WILL HELP KEEP TEMPS LOWER THROUGH THE DAY.

RAIN CHANCES WILL SUBSIDE LATE SATURDAY NIGHT ACROSS THE AREA AS SFC
LOW TRACKS EAST TO THE ATLANTIC SEABOARD. SFC RIDGING WILL NUDGE
SOUTHEAST FROM CANADA INTO THE GREAT LAKES REGION ON SUNDAY. MAINLY
DRY WEATHER EXPECTED FOR MUCH OF THE WEEK AS SOUTHERN STREAM CUT
OFF LOW KEEPS SUPPRESSED ACROSS THE SOUTHERN TIER OF THE U.S. AND
MID/UPPER LEVEL RIDGING INCREASES INTO THE AREA TOWARD THE END OF
THE PERIOD. THIS WILL RESULT IN A MODERATING TEMPRATURE TREND
THROUGH THE END OF THE PERIOD...WITH THE RETURN TO NEAR NORMAL
TEMPERATURES BY LATE NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 202 PM EDT THU APR 23 2015

LOW LEVEL ANTICYCLONE TO OVERSPREAD THE REGION THROUGH FRIDAY
MORNING. DECOUPLING SHOULD OCCUR FAIRLY EARLY THIS EVENING.
CURRENT GUSTS TO AROUND 25 KNOTS SHOULD DIMINISH IN THE 22-23Z
TIMEFRAME...BEFORE WINDS BECOME LIGHT AND VARIABLE TOWARD 01Z.
MAINLY CLEAR SKIES ARE EXPECTED TONIGHT WITH SOME INCREASE IN MID
CLOUDS TOWARD THE END OF THE PERIOD AS MID LEVEL WARM ADVECTION
INCREASES. LIGHT AND VARIABLE WINDS SHOULD ALSO BECOME LIGHT
WESTERLY BY MID MORNING FRIDAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZE WARNING FROM 1 AM EDT /MIDNIGHT CDT/ TO 9 AM EDT /8 AM
     CDT/ FRIDAY FOR INZ003>009-012>018-020-022>027-032>034.

MI...FREEZE WARNING FROM 1 AM TO 9 AM EDT FRIDAY FOR MIZ077>081.

OH...FREEZE WARNING FROM 1 AM TO 9 AM EDT FRIDAY FOR OHZ001-002-004-
     005-015-016-024-025.

LM...NONE.
&&

$$

SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...NG
AVIATION...MARSILI


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