Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 240517
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
117 AM EDT FRI APR 24 2015

.SYNOPSIS...
ISSUED AT 100 AM EDT FRI APR 24 2015

CONDITIONS FAVORABLE FOR FROST AND FREEZING CONDITIONS EARLY
THIS MORNING WILL PREVAIL WITH HIGH PRESSURE OVER THE GREAT LAKES.
THE COLDEST TEMPERATURES WILL BE OVER FAR SOUTHWEST LOWER MICHIGAN
AND INTO ADJACENT AREAS OF NORTHERN INDIANA AND NORTHWEST OHIO.
LOWS OVER THESE AREAS WILL DROP WELL DOWN INTO THE 20. THIS HIGH
WILL MOVE TO THE MID ATLANTIC REGION LATER TODAY. MEANWHILE...LOW
PRESSURE WILL EMERGE FROM THE CENTRAL PLAINS AND SPREAD WIDESPREAD
RAIN TO THE AREA ON SATURDAY. HIGHS TODAY WILL AGAIN BE COOLER THAN
NORMAL...REACHING 55 TO 60 DEGREES.

&&

.UPDATE...
ISSUED AT 1257 AM EDT FRI APR 24 2015

HAVE UPDATED THE FORECAST TO LOWER OVERNIGHT LOWS ABOUT 1 FULL
CATEGORY. AN EXTREMELY DRY AIRMASS...WITH ILX SOUNDING APPARENTLY
SETTING A RECORD FOR THE LEAST PRECIPITABLE WATER SO LATE IN THE
SEASON OF 0.11...HAS ALLOWED LOWS TO DROP INTO THE 20S OVER FAR
SOUTHERN LOWER MICHIGAN WHERE JEROME...NORTHEAST OF
HILLSDALE...WAS ALREADY DOWN TO 26 DEGREES AT 1 AM ACCORDING TO
MESONET OBS. THE SHALLOW BUT SHARP RADIATION INVERSION HAD ALLOWED
LOWS TO FALL WELL BELOW FREEZING AFTER MIDNIGHT OVER NORTHERN
AREAS. THE TRIFECTA OF MOS LOWS INCLUDING THE GFS/MAV...NAM/MET
AND ECMWF OF 26S AT BEH FOR LOWS TONIGHT APPEARS ON TRACK WITH
BENTON HARBOR ALREADY DOWN TO 28F AT 1 AM.

&&

.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 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 828 PM EDT THU APR 23 2015

VFR MET CONDS FOR NRN INDIANA THROUGH THE FCST PD. XTRMLY LOW
XOVER TEMPS /UPR TEENS TO LWR 20S/ TO PRECLUDE BR FORMATION NEAR
SUNRISE. ADVANCE OF NEXT SYSTEM FROM THE CENTRAL PLAINS TO BRING
INCRS AND GRDL LWRNG MID DECK CLOUDS LATE IN FCST PD...WITH
DEGRADED CIGS/VSBYS IN RAFL LKLY HOLDING OFF UNTIL DAYLIGHT HOURS
ON SAT.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZE WARNING UNTIL 9 AM EDT /8 AM CDT/ THIS MORNING FOR
     INZ003>009-012>018-020-022>027-032>034.

MI...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR MIZ077>081.

OH...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR OHZ001-002-004-
     005-015-016-024-025.

LM...NONE.
&&

$$

UPDATE...SKIPPER
SYNOPSIS...MURPHY
SHORT TERM...MARSILI
LONG TERM...NG
AVIATION...MURPHY


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