Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 290808
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
408 AM EDT FRI MAY 29 2015

.SYNOPSIS...
ISSUED AT 355 AM EDT FRI MAY 29 2015

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AS AN
UNSTABLE AIRMASS OVERSPREADS THE AREA AHEAD OF A COLD FRONT
APPROACHING FROM THE UPPER MIDWEST. COVERAGE OF THE SHOWERS AND
THUNDERSTORMS IS EXPECTED TO INCREASE FROM NORTHWEST TO SOUTHEAST
ACROSS THE AREA LATE TONIGHT AND SATURDAY AS THE FRONT MOVES INTO
THE AREA. HIGHS TODAY WILL BE IN THE LOWER TO MIDDLE 80S... WITH
LOWS TONIGHT MAINLY IN THE MID TO UPPER 60S. MUCH COOLER
TEMPERATURES WILL OVERSPREAD THE AREA BEHIND THE COLD FRONT THIS
WEEKEND... WITH HIGHS BY SUNDAY ONLY IN THE LOWER TO MIDDLE 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM EDT FRI MAY 29 2015

CDFNT OVER THE NRN PLAINS/UPR MIDWEST THIS MORNING IS EXPECTED TO
MOVE SE TO NEAR THE NW BORDER OF OUR CWA BY SATURDAY MORNING.
S-SW FLOW DVLPG AHEAD OF THE FRONT AND ASSOCIATED UPR LEVEL TROF
WAS ADVECTING DEEP MOISTURE BACK INTO OUR CWA WITH PRECIP WATER
FCST TO EXCEED 1.5" TODAY. DIURNAL HEATING SHOULD LEAD TO
1000-1500J/KG MLCAPE THIS AFTN. VORT MAX OVER NRN KY EXPECTED TO
LIFT N-NE ACROSS WRN OH THIS MORNING WHILE WK SHRTWV OVER MO LIFTS
NE ACROSS NWRN PORTION OF OUR AREA LATER TODAY PROVIDING A COUPLE
OF WK FORCING MECHANISMS. GIVEN THE WK-MODERATE DVLPG INSTABILITY
TODAY EXPECT THIS FORCING WILL BE SUFFICIENT TO TRIGGER SCT
SHOWERS/TSTMS WITH STRONGEST CONVECTION DURING THE AFTN. ALTHOUGH
0-6KM SHEAR ONLY EXPECTED TO BE IN THE 20-25KT RANGE TODAY... SOME
LINGERING DRY AIR ALOFT AND STEEP LOW LEVEL LAPSE RATES SHOULD
RESULT IN GUSTY WINDS AND PSBLY SMALL HAIL IN STRONGEST CELLS THIS
AFTN... BUT SVR STORMS ARE NOT EXPECTED. SHOULD BE SUFFICIENT
SUNSHINE/GRADIENT MIXING FOR BOUNDARY LAYER DEPTH UP TO AROUND
850MB AGAIN TODAY RESULTING IN HIGHS IN THE L-M80S.

AS CDFNT/UPR TROF APPROACHES OVERNIGHT COVERAGE OF SHOWERS SHOULD
INCREASE FROM NW-SE ACROSS THE AREA... FCST POPS RANGE FROM LIKELY
NW TO CHC SE. GIVEN VERY MOIST AIRMASS AHEAD OF THE CDFNT/UPR TROF
AND DEEPENING WARM CLOUD LAYER... SOME POTENTIAL FOR LOCALLY HEAVY
RAINFALL... BUT WITH JUST WK INSTABILITY EXPECTED AND STRONGER
FORCING MOVG IN LATE... STAYED CLOSE TO FAIRLY LOW WPC QPF FOR THIS
TIMEFRAME. MODEST SOUTHERLY FLOW AND CONSIDERABLE CLOUD COVER SHOULD
LIMIT TEMP FALLS TONIGHT...FCST MINS IN THE M-U60S...BUT THERE IS
CONSIDERABLE UNCERTAINTY... MAINLY NEAR LAKE MICHIGAN WHERE GFS
IS A LITTLE FASTER WITH FROPA THAN NAM... YIELDING 10F MOS MIN TEMP
DIFFERENCE.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 355 AM EDT FRI MAY 29 2015

FOCUS WILL REMAIN ON COLD FRONT WHICH WILL SWEEP SOUTHEAST ACROSS
THE REGION SATURDAY. PLENTY OF LOW LEVEL MSTR WILL RESIDE ALONG AND
AHEAD OF THE FRONT WITH PWATS IN EXCESS OF 1.5 INCHES. INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS SHOULD OCCUR...BUT MAY END UP
MORE BEHIND THE FRONT WHERE BEST FORCING RESIDES. AHEAD OF THE
FRONT...CLOUD COVER AND EARLY TIMING OF THE FRONT MAY LIMIT
CONVECTIVE DEVELOPMENT AND ORGANIZATION. IN ADDITION...ONLY A NARROW
WINDOW OF SLIGHTLY INCREASED LAPSE RATES AND INSTABILITY IS POSSIBLE
AHEAD OF THE FRONT ACROSS MAINLY THE SE HALF. THIS APPEARS TO LINE
UP WITH NEW DAY 2 SEVERE WEATHER OUTLOOK DEPICTING A MARGINAL RISK
OF SEVERE STORMS. PUTTING IT ALL TOGETHER YIELDS CONTINUATION OF
LIKELY POPS ALL AREAS IN THE MORNING AND CONFINED TO SE AFTERNOON
WITH A PASSING MENTION OF STG STORMS IN THE HWO.

COLDER AIR WILL MOVE IN AS 2 SURGES...THE FIRST BEING THE LARGEST
DROP AS 850 MB TEMPS DROP TO AROUND 10 C. FRONT MAY STALL OUT SAT
NGT INTO SUNDAY IN FAR SE SECTIONS AS A SECOND TROUGH AND SOMEWHAT
COLDER AIR DROP INTO THE AREA. SHOWERS AND MAYBE A RUMBLE OF THUNDER
COULD LINGER UNTIL THE FRONT FINALLY CLEARS THE AREA. TONED DOWN
POPS IN THIS PERIOD AND TRIED TO ADD A BIT MORE TIMING DETAIL.

DRY FORECAST WILL BE IN STORE SUNDAY NIGHT INTO AT LEAST WEDNESDAY
NIGHT WITH TEMPS SOMEWHAT SLUGGISH TO INCREASE AT FIRST. STRONG
EARLY JUNE SUN AND INCREASING UPPER LEVEL HEIGHTS SHOULD ALLOW FOR A
RAPID UPTICK IN BOTH TEMPERATURES AND MOISTURE MID TO LATE WEEK.
AFTERNOON/EVENING CONVECTION WILL BECOME POSSIBLE STARTING AS EARLY
AS THURSDAY AS INSTABILITY BUILDS. HOWEVER...MED RANGE MODELS ALL
SUGGEST NO STRONG SIGNALS FOR TRIGGERS FOR MORE WIDESPREAD
CONVECTION AT THIS TIME WITH WARM FRONT WELL NORTH OF THE AREA.
SUPERBLEND OF MODELS TRIES TO INCREASE PRECIP CHANCES AND AT THIS
TIME WILL HOLD OFF ON RAISING AS CHANCES WILL LIKELY BE MORE KEYED
IN ON OUTFLOW BOUNDARIES AND LEFT OVER COMPLEXES THAT MAY MOVE IN
FROM UPSTREAM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 115 AM EDT FRI MAY 29 2015

LOW LEVEL FLOW VEERING S-SW THIS MORNING ADVECTING MOISTURE BACK
INTO NRN INDIANA. DIURNAL HEATING SHOULD RESULT IN MODERATE
INSTABILITY DVLPG TODAY WITH WK DISTURBANCES MOVG NE ACROSS THE AREA
EXPECTED TO TRIGGER SCT TSRA THIS AFTN. VFR CONDITIONS SHOULD
PREVAIL THROUGH THE PERIOD THOUGH CIGS AROUND 4KFT EXPECTED
TODAY/TNGT. POTENTIAL FOR BRIEF MVFR/IFR CONDITIONS AND STRONG/GUSTY
WINDS IF TSRA MOVE OVER THE TERMINALS BUT FOR NOW STUCK WITH VFR
FORECAST AND VCTS AS COVERAGE OF STORMS SHOULD BE LIMITED GIVEN WK
FORCING.

&&

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

$$

SYNOPSIS...JT
SHORT TERM...JT
LONG TERM...FISHER
AVIATION...JT


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