Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 021720
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
120 PM EDT MON MAY 2 2016

.SYNOPSIS...
ISSUED AT 407 AM EDT MON MAY 2 2016

ISOLATED LIGHT SHOWERS OR POCKETS OF DRIZZLE WILL DISSIPATE TOWARD
DAYBREAK. ANOTHER WEAK UPPER LEVEL DISTURBANCE APPROACHING FROM
THE WEST MAY PRODUCE AN ISOLATED SHOWER THIS AFTERNOON ACROSS
MAINLY NORTHERN INDIANA. OTHERWISE...CLOUDY AND COOL CONDITIONS
ARE IN STORE TODAY WITH HIGHS IN THE 50S. A FEW ISOLATED LIGHT
SHOWERS MAY PERSIST INTO TONIGHT ACROSS NORTHERN INDIANA BUT
OTHERWISE DRY CONDITIONS ARE EXPECTED FOR MUCH OF THE AREA TONIGHT
INTO TUESDAY. A COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT
LAKES FOR TUESDAY NIGHT AND WEDNESDAY WILL BRING THE NEXT
LIKELIHOOD OF RAIN TO THE REGION.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 407 AM EDT MON MAY 2 2016

AN OVERALL QUIET PERIOD SHAPING UP FOR TODAY THROUGH TUESDAY WITH
SOME LOW CHANCES OF ADDITIONAL RAIN SHOWERS PRIMARILY SOUTHERN TWO
THIRDS OF THE FORECAST AREA.

UPPER VORT MAX IS NOW BEGINNING TO EXIT FAR NORTHEAST PORTIONS OF THE
FORECAST AREA WITH BULK OF RAIN HAVING SHIFTED EAST OF THE AREA AS
OF 07Z. DRY SLOT APPEARS TO HAVE WORKED IN ACROSS MOST OF THE
FORECAST AREA THIS MORNING...BUT SOME SLIGHTLY DEEPER RH SHOULD
LINGER OVER THE NEXT FEW HOURS ACROSS THE NORTH WHERE WILL CARRY
SOME ISOLATED SHOWER MENTION THROUGH DAYBREAK. SOME PATCHY DRIZZLE
WILL ALSO CONTINUE TO BE POSSIBLE FOR LOCATIONS FURTHER SOUTH MORE
IMPACTED BY DRY SLOT. SUBTLE MID/UPPER LEVEL HEIGHT RISES IN THE
WAKE OF THIS SHORT WAVE WILL ALLOW FOR ONLY MODEST SOUTHEASTWARD
DISPLACEMENT OF LOW LEVEL BAROCLINIC ZONE THIS MORNING. ANOTHER
UPSTREAM SHORT WAVE NOW DIGGING ACROSS THE CENTRAL PLAINS SHOULD
ALLOW FOR MINOR NORTHWARD ADVANCEMENT OF WEAK LOW LEVEL THETAE
RIDGING THIS AFTERNOON AND MAY INDUCE SOME WEAK LOW/MID LEVEL
FRONTOGENESIS FORCING ALONG OLD BOUNDARY. PREVIOUS FORECAST
APPEARS TO HAVE THIS WELL IN HAND AND WILL MAINTAIN JUST SOME
SLIGHT CHANCE/LOW CHANCE RAIN SHOWER POPS FOR THIS AFTERNOON. MID
LEVEL LAPSE RATES WILL BE SIGNIFICANTLY LOWER TODAY AND THUS ANY
SURFACE BASED INSTABILITY SHOULD BE OF LIMITED DEPTH. OTHERWISE
FOR TODAY...THE COMBINATION OF FRONTAL INVERSION AND NEXT PV
ANOMALY SHOULD KEEP CLOUDS LOCKED IN WITH LIMITED TEMP RECOVERY
INTO THE MID/UPPER 50S THIS AFTERNOON.

SHORT WAVE WILL BE SLOW TO PROGRESS THROUGH THE AREA TONIGHT...WITH
GUIDANCE DEPICTING WEAK INVERTED SFC TROUGH LAGGING BACK ACROSS
SOUTHERN HALF OF THE AREA WHICH MAY PERPETUATE ISOLD/SCT RAIN
SHOWERS...PARTICULARLY ACROSS SOUTHERN HALF OR SOUTHERN THIRD OF
THE AREA. CLOUDS SHOULD BEGIN TO DECREASE FROM THE NORTH LATE
TONIGHT AS WEAK LOW LEVEL REFLECTION CONTINUES OFF TO THE EAST
WITH LOWS GENERALLY IN THE LOWER-MID 40S.

TUESDAY SHOULD FEATURE MAINLY DRY CONDITIONS ALTHOUGH WITH BROAD
SHEARING POSITIVELY TILTED UPPER TROUGH MAY NOT BE ABLE TO
COMPLETELY RULE OUT ISOLD SHOWER/SPRINKLE FAR SOUTH/SOUTHEAST...BUT
WILL OMIT FROM FORECAST AT THIS TIME. SOME MODERATION IN TEMPS IS
ANTICIPATED FOR TUESDAY WITH HIGHS BACK IN THE LOWER TO MID 60S.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 407 AM EDT MON MAY 2 2016

THE PRIMARY FEATURE OF INTEREST TO BEGIN THE LONG TERM WILL BE A
RATHER POTENT UPPER PV ANOMALY PROGGED TO DIG ACROSS THE GREAT
LAKES/OHIO VALLEY. UPPER DYNAMICS LOOK TO BE FAIRLY IMPRESSIVE WITH
COMPACT UPPER JET STREAK/UPPER DIVERGENCE OVERSPREADING THE SOUTHERN
GREAT LAKES. THE COMBINATION OF THE ABOVE AND SHARP LOW LEVEL
CONVERGENCE WITH THE ASSOCIATED WITH THE FRONTAL BOUNDARY STILL
SUPPORTS PREVIOUSLY FORECASTED LIKELY POPS SPREADING FROM
NORTHWEST TO SOUTHEAST ACROSS THE AREA LATE TUESDAY NIGHT INTO
WEDNESDAY. INSTABILITY WILL BE LIMITED WITH NOT MUCH IN THE WAY OF
ANY LOW LEVEL MOISTURE RETURN AHEAD OF THE FRONT...AND INITIALLY
DRY SUBCLOUD LAYERS. HOWEVER GIVEN DYNAMICS OF THIS SYSTEM AND
STEEPENING MID LEVEL LAPSE RATES WOULD SUSPECT THAT SOME ISOLATED
THUNDER IS A POSSIBILITY. UNSETTLED CONDITIONS TO CONTINUE INTO
WEDNESDAY WITH MID/UPPER LEVEL COLD CORE OVERHEAD AND STRONGEST
SYNOPTIC FORCING SETTING UP ACROSS EASTERN HALF FOR THE AFTERNOON.
BASED ON TIMING OF THESE FEATURES SOME SURFACE BASED INSTABILITY
IS POSSIBLE ACROSS EASTERN HALF OR THIRD OF THE AREA INTO
WEDNESDAY AFTERNOON AND DID ADD AN ISOLD THUNDER MENTION.
OTHERWISE COOLER AND BREEZY CONDITIONS IN STORE FOR WEDNESDAY AS
LOW LEVEL COLD ADVECTION OVERSPREADS THE AREA.

THE ONLY CHANGE OF NOTE FROM PREVIOUS FORECAST FOR THE REMAINDER OF
THE LONG TERM DEALS WITH THIS WEEKEND. LARGE SCALE BLOCKING PATTERN
TO GENERALLY REMAIN IN PLACE THROUGH NEXT WEEKEND...BUT DPROG/DT OF
BULK OF MEDIUM RANGE GUIDANCE NOW BEGINNING TO INDICATE SLIGHTLY
FASTER EASTWARD DEPARTURE OF MID WEEK NEGATIVE UPPER HEIGHT ANOMALY
WHILE NEXT SUBSTANTIAL UPPER TROUGH DIGS ACROSS SOUTHEAST CANADA.
THIS PATTERN WOULD ALLOW FOR ANOTHER BACKDOOR COLD FRONT SOME TIME
DURING THE WEEKEND AND HAVE LIMITED POPS TO SLIGHT CHANCE/LOW CHANCE
FOR LATER SATURDAY/SUNDAY WITH THIS FEATURE. FRONT MAY WASH OUT
ACROSS THE AREA ON SUNDAY GIVEN STRONGER UPPER FORCING WOULD REMAIN
WELL NORTHEAST OF THE AREA...SO CONFIDENCE IN POPS REMAINS QUITE LOW
FOR THE WEEKEND. WITH THIS TREND IN THE MEDIUM RANGE MODELS...HAVE
INCREASED MAX TEMPS FOR FRI/SAT AHEAD OF THIS FRONT TO AT OR ABOVE
SEASONAL NORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 120 PM EDT MON MAY 2 2016

SLOW BUT STEADY IMPROVEMENT ANTICIPATED FOR THE REST OF THE
AFTERNOON AS DIURNAL MIXING INCREASES SLIGHTLY. TREND SHOULD
CONTINUE INTO THE OVERNIGHT AS WEAK HIGH PRESSURE AND SLIGHTLY
DRIER AIR ARE ADVECTED INTO THE AREA. VFR EXPECTED AT KSBN BUT
KFWA MAY BE JUST FAR ENOUGH SOUTH TO REMAIN MVFR THROUGH THE
NIGHT...AS SUGGESTED BY SOME OF THE LATEST HI-RES FORECAST
SOUNDINGS. ADJUSTED THE TAF ACCORDINGLY BUT SUSPECT THERE MAY
STILL BE PERIODS OF VFR OVERNIGHT. HIGH CONFIDENCE IN VFR
CONDITIONS AT BOTH SITES BY LATE TOMORROW MORNING.

&&

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

$$

SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...MARSILI
AVIATION...AGD


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