Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 280618
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
218 AM EDT TUE APR 28 2015

.SYNOPSIS...
ISSUED AT 218 AM EDT TUE APR 28 2015

CLEAR SKIES AND LIGHT WINDS WILL SET THE STAGE FOR FROST ACROSS
MUCH OF THE REGION. THE GREATEST RISK FOR FROST IS ACROSS MUCH OF
NORTHERN INDIANA INTO SOUTHWESTERN LOWER MICHIGAN AS LOWS FALL
INTO THE LOWER TO MIDDLE 30S. TEMPERATURES WILL REBOUND LATER
TODAY WITH HIGHS REACHING INTO THE LOWER 60S IN MOST LOCATIONS.
AREAS ALONG THE LAKE SHORE WILL SEE HIGHS AROUND 50 TO THE MID
50S. LOWS TONIGHT WILL BE AROUND 40.

&&

.UPDATE...
ISSUED AT 734 PM EDT MON APR 27 2015

CURRENT HEADLINES APPEAR ON TRACK FOR THE TIME BEING.

SKIES WERE CLEARING AS EXPECTED ACROSS WESTERN AREAS WHERE THE
FROST ADVISORY WAS ALREADY IN PLACE. SOME CONCERNS THAT SKY COVER
MAY CLEAR OUT MORE THAN PREVIOUSLY THOUGHT IN THE EAST WHICH COULD
INCREASE THE THREAT. PATCHY FROST SHOULD WORK FOR THE MOST
PART...BUT SOME SHELTERED AREAS COULD SEE LARGER COVERAGE OF FROST
BY MORNING.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 350 PM EDT MON APR 27 2015

CLOUD COVER AND ASSOCIATED IMPACT ON OVERNIGHT LOWS/FROST
POTENTIAL ARE THE MAIN CONCERNS FOR THIS SHORT TERM PERIOD.
COOL/MOIST LOW LEVEL CYCLONIC FLOW IN THE WAKE OF ROBUST SHORTWAVE
DIVING THROUGH THE EASTERN GREAT LAKES HAS LED TO A FAIR AMOUNT OF
STRATOCU THIS AFTERNOON. LOW LEVEL FLOW DOES BECOME MORE
ANTICYCLONIC OVERNIGHT BUT FORECAST SOUNDINGS INDICATE A DECENT
SUBSIDENCE INVERSION AROUND 850-700MB THAT WILL SLOW THE DIURNAL
DISSIPATION OF PRESENT CLOUD COVER. STILL EXPECT SOME CLEARING
OVERNIGHT...ESPECIALLY IN OUR WESTERN COUNTIES WHERE CLOUDS ARE
ALREADY SCATTERED...BUT WILL TAKE SOME TIME IN OUR EASTERN CWA
BASED ON LATEST MODEL RH FIELDS. THIS MAKES THE PRECISE OVERNIGHT
LOWS DIFFICULT TO PREDICT...ESPECIALLY GIVEN WEAK PGF WINDS OF 5
MPH OR LESS. LATEST CONSENSUS GUIDANCE IS AROUND MID 30S BUT A
DEGREE OR TWO IN EITHER DIRECTION WILL MEAN THE DIFFERENCE BETWEEN
FROST OR NO FROST. STAYED CLOSE TO PRIOR FORECAST OF UPPER 30S IN
THE EAST AND LOW/MID 30S IN THE WEST BASED ON EXPECTED CLOUD
TRENDS. GIVEN LIGHT WINDS...CLEARING SKIES...AND MIN TEMPS IN THE
LOW-MID 30S...FEEL FROST ADVISORY IS NECESSARY FOR AT LEAST OUR
NORTHWEST THIRD. MUCH LOWER CONFIDENCE OUR E/SE COUNTIES WILL
CLEAR OUT AND SEE ANY FROST SO WILL HOLD OFF ON THOSE FOR NOW AND
JUST MENTION PATCHY FROST. LATER SHIFTS CAN MAKE ADJUSTMENTS
BASED ON CLOUD/TEMP TRENDS OVERNIGHT.

ANOTHER DRY DAY ON TAP FOR TOMORROW AS MID/UPPER LEVEL RIDGING
SLIDES OVER THE GREAT LAKES. ANOTHER ROUND OF DIURNAL CU WILL LEAD
TO JUST PARTLY SUNNY SKIES DURING THE AFTERNOON BUT 850MB TEMPS DO
CLIMB A DEGREE OR TWO ABOVE ZERO AND THIS SHOULD ALLOW HIGHS TO
REACH THE 60 DEGREE MARK.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 350 PM EDT MON APR 27 2015

FOCUS OF THE LONG TERM PERIOD IS PRECIP CHANCES WEDNESDAY NIGHT
THROUGH THURSDAY...AND A WARMER MORE ACTIVE PATTERN NEXT WEEKEND.

NORTHERN STREAM VORT/JET MAX WILL DIG SOUTHWARD FROM EASTERN
MANITOBA/WESTERN ONTARIO TUESDAY NIGHT THROUGH THE GREAT LAKES
WEDNESDAY/WEDNESDAY NIGHT. UPPER SHORTWAVE WILL DEEPEN AND CUT OFF
OVER THE GREAT LAKES REGION...WHICH WILL THEN DIG SOUTHEASTWARD
TOWARDS THE SE ATLANTIC COAST THURSDAY NIGHT...PHASING WITH SHEARING
SOUTHERN STREAM SHORTWAVE. AS THIS LOW TRAVERSES ALMOST DIRECTLY
OVER THE AREA...PRECIP CHANCES WILL INCREASE LATE WEDNESDAY THROUGH
THURSDAY. GFS HAS BEEN MOST AGGRESSIVE/DEEPER W/ CUTOFF LOW
EVOLUTION THAN OTHER MODELS...HOWEVER 12Z ECMWF/NAM/GEM STARTING TO
TREND TOWARD THIS MORE AGGRESSIVE SOLUTION. THEREFORE INCREASED POPS
ACROSS THE EASTERN HALF OF THE FORECAST AREA WEDNESDAY NIGHT AND
THURSDAY...AND INTRODUCED SLIGHT CHANCE POPS IN THE WEDNESDAY PERIOD.

AFTER THIS SYSTEM MOVES SOUTHEAST OF THE REGION THURSDAY
NIGHT...RIDGING WILL WORK EASTWARD INTO THE AREA ON FRIDAY...WITH
DRY CONDITIONS AND A WARMING TREND INTO THE WEEKEND. BACKED OFF WITH
SLIGHT CHANCE POPS FRIDAY NIGHT AND SATURDAY...WITH AN INCREASE IN
POPS INTO SUNDAY THROUGH MONDAY...AS SHARP MOISTURE INCREASE ACROSS
THE AREA AND WEAK DISTURBANCES IN QUASI ZONAL FLOW WILL INCREASE
PRECIPITATION CHANCES. HOWEVER...WITH WEAKER OVERALL FORCING
SIGNAL...WILL NEED TO CONTINUE TO WATCH THIS PERIOD FOR PRECIP
TRENDS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 130 AM EDT TUE APR 28 2015

WINDS HAD DECOUPLED TO CALM WINDS OVER NEARLY ALL OF NORTHERN
INDIANA EARLY THIS MORNING. UPSTREAM SOUNDINGS SHOWED THE
SUBSIDENCE INVERSION WAS STRENGTHENING WITH THE BASE OF THE
INVERSION ABOVE 850 MB. KEPT VFR CIGS TODAY AS MOISTURE UNDER THE
BASE OF THE INVERSION WILL FORM CLOUDS WITH DAYTIME MIXING. SBN
MAY BE MORE SCATTERED TODAY GIVEN THE 12 NAM WAS VERIFYING TOO
COOL AND TOO MOIST IN THE LOW LEVELS BASED ON AIRCRAFT SOUNDINGS.
OTHERWISE...WINDS SHOULD REMAIN LIGHT WITH WEAK RIDGING OVER THE
AREA.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FROST ADVISORY UNTIL 9 AM EDT /8 AM CDT/ THIS MORNING FOR
     INZ003>006-012>016-020-022.

MI...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR MIZ077>080.

OH...NONE.
LM...NONE.
&&

$$

UPDATE...FISHER
SYNOPSIS...JT
SHORT TERM...AGD
LONG TERM...NG
AVIATION...SKIPPER


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