Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 121746
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
146 PM EDT SAT APR 12 2014

.SYNOPSIS...
ISSUED AT 347 AM EDT SAT APR 12 2014

WARM CONDITIONS ARE EXPECTED TODAY INTO TONIGHT AS SOUTHERLY WINDS
INCREASE. THERE IS A CHANCE OF SHOWERS LATE TODAY INTO TONIGHT
ACROSS SOUTHERN LOWER MICHIGAN AND NORTHWEST INDIANA...BUT THE MORE
WIDESPREAD RAIN SHOWER ACTIVITY IS EXPECTED TO REMAIN FURTHER NORTH
ACROSS THE GREAT LAKES REGION. A STRONGER UPPER LEVEL DISTURBANCE
AND FRONTAL BOUNDARY WILL INCREASE THE CHANCES OF RAIN AND SCATTERED
THUNDERSTORMS ACROSS THE REGION SUNDAY NIGHT AND MONDAY. WARM
CONDITIONS WILL PERSIST IN ADVANCE OF THIS SYSTEM SUNDAY...BEFORE
EVENTUALLY TURNING COOLER AND BLUSTERY EARLY NEXT WEEK.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 347 AM EDT SAT APR 12 2014

AN UNSEASONABLY WARM SATURDAY-SATURDAY NIGHT IS IN THE CARDS AS
SOUTHWESTERLY FLOW STRENGTHENS/DEEPENS. THIS TIGHTENING OF THE
HEIGHT FIELD LOCALLY WILL OCCUR AS A WESTERN CANADA MERIDIONAL
UPPER JET DIVES INTO THE PACIFIC NORTHWEST AND HELPS CARVE OUT A
WESTERN CONUS LONGWAVE TROUGH...WITH SUBSEQUENT DOWNSTREAM MID
LEVEL RIDGE AMPLIFICATION ALONG THE EAST COAST. THE INITIAL LOW
LEVEL THETA-E SURGE IN THIS SW FLOW ALONG A NORTHEASTWARD LIFTING
WARM FRONT WILL LIFT QUICKLY THROUGH THE AREA THIS AFTERNOON. HARD
TO COMPLETELY RULE OUT AN ISOLATED SHOWER/STORM ALONG THE THETA-E
GRADIENT IN THE NORTH AND EAST GIVEN WEAK ISENTROPIC ASCENT AND
BUILD UP OF SOME SBCAPE...ALTHOUGH COVERAGE/PROBABILITY REMAINS
TOO LOW IN MOST LOCATIONS FOR A MENTIONABLE POP. BETTER CHANCES
FOR SHOWERS/STORMS WILL RESIDE JUST NORTH/NORTHWEST OF THE IWX CWA
LATER THIS AFTERNOON INTO TONIGHT WHERE LOW/MID LEVEL
MOISTURE/MASS CONVERGENCE WILL BE MAXIMIZED ALONG A DEEPENING
BAROCLINIC ZONE IN RRQ OF A SOUTHEAST ONTARIO/SOUTHWEST QUEBEC
UPPER JET STREAK. LOW AMPLITUDE SHORTWAVE ENERGY...POSSIBLY
AUGMENTED BY CONVECTION...EJECTING OUT THE DIGGING WESTERN CONUS
TROUGH COULD BRING CONVECTION FARTHER SOUTH THAN MODELED TONIGHT
NEAR THETA-E RIDGE. WILL CONTINUE CLOSE TO THE PREVIOUS FCST FOR
POPS TONIGHT (DRY SOUTHEAST AND LOW CHC POPS NORTHWEST) GIVEN LOW
CONFIDENCE ON HOW THIS PLAYS OUT.

AS FOR TEMPS...STRONG WAA, DEEP MIXING TO NEAR 850 MB (11C), AND
NOTHING MORE THAN SOME PESKY HIGH CLOUDS/DIURNAL CU SHOULD SUPPORT
HIGHS INTO THE MID/UPPER 70S FOR MOST LOCATIONS. FORECAST AREA
SHOULD REMAIN ENTRENCHED IN WELL MIXED WARM SECTOR TONIGHT WITH
LOWS 20-25F ABOVE NORMAL. HOWEVER...LOWS IN THE FAR NORTH WILL
TREND COOLER THAN FORECAST IF CONVECTION FORCES RAIN/SFC FRONT
FARTHER SOUTH THAN ANTICIPATED.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 347 AM EDT SAT APR 12 2014

CLOSED UPPER LOW OVER CALIFORNIA NOW GETTING RAPIDLY ABSORBED INTO
DIGGING WEST COAST TROUGH ASSOCIATED WITH A 100+ KT MERIDIONAL UPPER
JET. UPSTREAM HEIGHTS WILL CONTINUE TO FALL AS THIS TROUGH
DEEPENS...FORCING DOWNSTREAM AMPLIFICATION OF THE PATTERN ALOFT AND
A GRADUAL INCREASE IN SOUTHWEST FLOW/THETA-E ADVECTION THROUGH THE
WEEKEND. LARGE SCALE PATTERN AMPLIFICATION WILL RESULT IN A VERY
STRONG BAROCLINIC ZONE DRAPED FROM THE CENTRAL GREAT LAKES TO THE
SOUTHERN PLAINS. RIGHT ENTRANCE DYNAMICS IN DEVELOPING 140+ KT JET
STREAK OVER EASTERN CANADA WILL FAVOR STRONG LOW LEVEL FRONTOGENESIS
AND UPPER LEVEL DIVERGENCE AS SEVERAL SMALL SCALE EMBEDDED
SHORTWAVES EJECT OUT OF THE WESTERN CONUS TROUGH. SYNOPTIC
ENVIRONMENT WILL BE PRIMED FOR PERIODS OF MODERATE TO HEAVY RAIN
ACROSS THE REGION AS PWATS CLIMB ABOVE 1.25 INCHES ALONG VERY SLOWLY
PROGRESSING BOUNDARY. THE GOOD NEWS IS THAT LATEST 00Z MODELS
CONTINUE TO KEEP THE AXIS OF HEAVIEST RAIN CONFINED NORTHWEST OF OUR
CWA THROUGH SUNDAY NIGHT. FRONT WILL ARRIVE BY EARLY MONDAY WITH THE
POTENTIAL FOR MODERATE TO HEAVY RAIN BUT MEAN FLOW VECTORS BECOME
ALIGNED A LITTLE MORE ORTHOGONAL TO THE BOUNDARY BY THIS TIME AS
MAIN TROUGH AXIS APPROACHES. THIS LOWERS THE POTENTIAL FOR STORM
TOTAL QPF AMOUNTS IN EXCESS OF 0.5-0.75 INCHES AS THE MAIN SURFACE
WAVE/FRONTAL BOUNDARY PASSES. QUESTION THEN BECOMES WILL A SECONDARY
SURFACE WAVE DEVELOP ALONG THE FRONT MONDAY NIGHT AND IMPACT OUR
CWA. THE POTENTIAL IS CERTAINLY THERE AS MAIN PV RIBBON DOESN`T
CROSS THE AREA UNTIL TUESDAY MORNING. STILL...THERE IS A GREAT DEAL
OF UNCERTAINTY REGARDING EXACT TIMING/PLACEMENT OF FRONTAL BOUNDARY
AND AVAILABLE MOISTURE. LATEST GFS...GEM...AND ECMWF KEEP SECONDARY
WAVE OF PRECIP MAINLY OVER OHIO WITH A MORE PROGRESSIVE TROUGH/LOW
LEVEL FRONT COMPARED TO THE NAM AND 11.12Z ECMWF. INCLINED TO FAVOR
LATEST CONSENSUS ON A SLIGHTLY MORE PROGRESSIVE EVENT BUT CONFIDENCE
IS LOW AND WILL MAINTAIN LOW CHANCE POPS FOR MOST OF THE CWA WITH
HIGHER CHANCES IN OHIO. IF PRECIP DOES OCCUR...EXPECT A HODGEPODGE
OF PRECIP TYPES. CAA WILL FAVOR AN EVENTUAL CHANGEOVER TO ALL SNOW
BY LATE MONDAY NIGHT BUT A BRIEF PERIOD OF TRANSITORY SLEET AND
FREEZING RAIN WILL ALSO BE POSSIBLE. EFFICIENT ACCUMULATION OF SNOW
WILL BE DIFFICULT GIVEN VERY WARM/WET GROUND CONDITIONS BUT COULD
SEE SOME LIGHT ACCUMULATION ON GRASSY/ELEVATED SURFACES IF RATES ARE
HIGH ENOUGH. DRY/TRANQUIL WEATHER RETURNS FOR THE MIDDLE OF NEXT
WEEK AS MIDLEVEL HEIGHTS BUILD AND SURFACE HIGH PRESSURE REMAINS
OVER THE REGION.

ROLLER COASTER TEMPS STILL EXPECTED THROUGH THE PERIOD. MOST OF OUR
CWA WILL REMAIN FIRMLY IN THE WARM SECTOR ON SUNDAY WITH 850MB TEMPS
HOLDING AROUND 10-12C. WILL PROBABLY HAVE A FEW MORE
CLOUDS...ESPECIALLY IN THE NORTHWEST...BUT HIGHS SHOULD STILL REACH
THE MID TO PERHAPS EVEN UPPER 70S IN OUR SOUTHEAST HALF.
THUNDERSTORMS REMAIN POSSIBLE BUT LIMITED INSTABILITY THIS FAR NORTH
PRECLUDES SEVERE WEATHER POTENTIAL. SUNDAY NIGHT LOWS AND MONDAY`S
HIGHS WILL DEPEND ON EXACT FRONTAL PLACEMENT AT 12Z AS TEMPERATURES
WILL PROBABLY STEADILY FALL IN STRONG POSTFRONTAL CAA. EXPECT
AFTERNOON TEMPS IN THE 40S FOR MOST LOCATIONS BEFORE DROPPING INTO
THE 20S OVERNIGHT. HIGHS ON TUESDAY WILL STRUGGLE TO GET ABOVE 40F
GIVEN 850MB TEMPS AROUND -10C. STEADY WARMING THEN EXPECTED THROUGH
THE END OF THE WEEK AS SOUTHERLY FLOW RETURNS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 145 PM EDT SAT APR 12 2014

VFR CONDS XPCD TO PERSIST THROUGH THE PD. TIGHTENING SFC GRADIENT
BTWN RIDGE NOW CNTRD ALG THE EAST COAST AND DVLPG LOW OVR WRN KS
WILL YIELD GUSTY S/SW WINDS BOTH THIS AFTN AND AGAIN LT TONIGHT/SUN
AS SFC LOW LIFTS INTO IA. DIURNAL CU DVLPMNT SLOWED BY PRIOR PATCH
OF ACCAS THAT HAS MOSTLY MIXED OUT. HWVR MOST LOCATIONS NEARING CONV
TEMPS AND XPC MORE VIGOROUS CU DVLPMNT WILL OCCUR THROUGH THIS AFTN.

OTRWS SHRA/TSRA ACTIVITY XPCD TO REMAIN NW OF THE TERMINALS THROUGH
THE PD INVOF OF SFC FNTL ZONE/LL THETA-E RIDGE.

&&

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

$$

SYNOPSIS...MARSILI/STEINWEDEL
SHORT TERM...STEINWEDEL
LONG TERM...AGD
AVIATION...T


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