Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 230740
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
340 AM EDT WED APR 23 2014

.SYNOPSIS...
ISSUED AT 340 AM EDT WED APR 23 2014

CANADIAN HIGH PRESSURE WILL MAINTAIN COOL AND DRY CONDITIONS ACROSS
THE AREA TODAY. HIGH TEMPERATURES WILL GENERALLY BE IN THE MID TO
UPPER 50S WITH COOLER CONDITIONS NEAR THE LAKE. A WEAK WARM FRONT
WILL APPROACH THE REGION TONIGHT AND MAY GENERATE A FEW SPRINKLES
ACROSS NORTHWEST INDIANA AND SOUTHWEST MICHIGAN. OVERNIGHT LOWS ARE
EXPECTED TO HOLD IN THE UPPER 30S TO LOWER 40S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM EDT WED APR 23 2014

CONFLUENT NORTHWEST FLOW ALOFT AND MIDLEVEL HEIGHT RISES/AVA
ASSOCIATED WITH APPROACHING RIDGE WILL LEAD TO A PLEASANT...ALBEIT
COOL...DAY. LOW LEVEL RIDGE AXIS DOES NOT SHIFT EAST OF OUR
LONGITUDE UNTIL THE EVENING...MAINTAINING LIGHT NORTHERLY FLOW FOR
MUCH OF THE DAY. GRADUAL AIRMASS MODIFICATION UNDER MID APRIL SUN
WILL LEAD TO WARMER CONDITIONS THAN YESTERDAY BUT 850MB TEMPS ONLY
CLIMB TO AROUND 2C BY LATE AFTERNOON. THEREFORE MID TO UPPER 50S
SEEM APPROPRIATE FOR NOW WITH FEW CHANGES NECESSARY TO INHERITED
GRIDS. NOTE THIS IS STILL ALMOST A 30 DEGREE DIURNAL SWING FROM
COLD MORNING LOWS. ONSHORE FLOW/LAKE BREEZE WILL KEEP OUR FAR
NORTHWEST ZONES IN THE UPPER 40S/LOWER 50S. WARM FRONT WILL THEN
APPROACH THE REGION BY TONIGHT. 00Z MODELS STILL TRYING TO PUSH
SOME LIGHT QPF INTO OUR CWA BUT EXPECT ANYTHING MORE THAN A FEW
SPRINKLES WILL BE DIFFICULT GIVEN MAGNITUDE OF DRY/STABLE AIR
PRESENT IN THE LOWER LEVELS. SYSTEM RELATIVE 295K ISENTROPIC
ASCENT IS NOT PARTICULARLY IMPRESSIVE AND THERE IS LITTLE TO NO
UPPER JET SUPPORT. SUPPOSE SOME REMNANTS OF UPSTREAM CONVECTION
COULD WASH OVER THE RIDGE INTO OUR WESTERN COUNTIES AND PRODUCE A
FEW RAIN SHOWERS BUT STILL THINK CHANCE SPRINKLES BETTER REFLECTS
THE EXPECTED NATURE OF THE EVENT. OVERNIGHT LOWS WILL ALSO BE
MILDER TONIGHT GIVEN INCREASING CLOUDS...WEAK WAA...AND A WARMER
START TO THE EVENING. RADIATIONAL COOLING POTENTIAL ALSO APPEARS
LOWER TONIGHT AND PREFER TO SHY AWAY FROM COLD MOS GUIDANCE.
EXPECT GENERALLY UPPER 30S TO LOWER 40S WITH LOW FROST POTENTIAL.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 340 AM EDT WED APR 23 2014

THURSDAY WILL BE CHARACTERIZED BY STRONG LOW LEVEL WARM ADVECTION IN
ADVANCE OF A PROGRESSIVE EASTERN PACIFIC WAVE THAT WILL IMPACT THE
AREA THURSDAY NIGHT. PLENTIFUL MID/HIGH CLOUDS EXPECTED IN
ASSOCIATION WITH THIS WARM ADVECTION THURSDAY...AND PRESENT
INDICATIONS STILL SUGGEST A RELATIVELY DRY SUBCLOUD LAYER PERSISTING
THROUGH MUCH OF THE DAY. NAM ISENTROPIC ANALYSES DO DEPICT SOME
REDUCED CPD`S ON THE 295K SFC ESPECIALLY ACROSS NORTHERN SECTIONS
THURSDAY MORNING WITH STRONGER WARM ADVECTION WING. NOT COMPLETELY
OUT OF THE QUESTION SOME VERY WEAK ELEVATED INSTABILITY COULD YIELD
A FEW ISOLATED SHOWERS OR SPRINKLES BUT ZONE OF STRONGEST ISENTROPIC
UPGLIDE SHOULD LIFT NORTH OF THE AREA IN THE AFTERNOON. BETTER
CHANCES OF MORE WIDESPREAD RAINFALL WILL HOLD OFF UNTIL EVENING AS
LOW LEVEL THETAE RIDGING/1.25 INCH PWAT AXIS BUILDS IN FROM THE
WEST. GUIDANCE CONTINUES TO DEPICT STRONG LOW LEVEL CONVERGENCE WITH
ASSOCIATED LOW LEVEL TROUGH THURSDAY EVENING...WITH ADDITIONAL
SYNOPTIC SUPPORT FROM A 100 KNOT UPPER JET STREAK NOSING INTO THE MD
MS VALLEY. GIVEN ABOVE FACTORS...AND FAIRLY CONSISTENT RUN TO RUN
SIGNAL...HAVE NUDGED UP TO CATEGORICAL POPS OVERSPREADING THE AREA
WEST TO EAST THURSDAY EVENING. DURATION OF PRECIP SHOULD BE
RELATIVELY SHORT HOWEVER AS PROGRESSIVE NATURE OF THIS SYSTEM ALLOWS
LOW LEVEL MOIST TONGUE TO SHIFT EAST OF THE AREA DURING THE
OVERNIGHT HOURS. STRONG LOW LEVEL CONVERGENCE COULD YIELD SOME
IMPRESSIVE RAINFALL RATES FOR A TIME...BUT ONCE AGAIN PROGRESSIVE
NATURE OF SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO 0.25-0.50 INCHES.
WILL CONTINUE TO LIMIT TS POTENTIAL TO CHANCE AT THIS TIME...WITH
NAM/GFS BUFFER SOUNDINGS CONTINUING TO DEPICT MEAGER INSTABILITY
PROFILES.

WEAK COLD ADVECTION TO ENSUE FOR LATE THURSDAY NIGHT/FRIDAY MORNING
BEHIND SFC FRONT...ALTHOUGH DEEPER POST-FRONTAL MIXING ON FRIDAY
SHOULD OFFSET SLIGHTLY COOLER LOW LEVEL PROFILES...AND THEN
SOME...WITH HIGHS EXPECTED IN THE UPPER 60S TO POSSIBLY LOWER 70S. A
MUCH DRIER AIR MASS WILL OVERSPREAD THE AREA HOWEVER...AIDED BY
STRONG COLUMN LARGE SCALE SUBSIDENCE. MID LEVEL COLD POCKET
ADVECTING INTO THE SOUTHERN GREAT LAKES FOR FRIDAY SHOULD LEND TO
STEEP LOW/MID LEVEL LAPSE RATES...WITH MAIN UNCERTAINTY IN ANY
LOW END PRECIP CHANCE ON DEPTH OF MIXED LAYER AND BOUNDARY LAYER
MOISTURE. SOME WEAK SYNOPTIC FORCING MAY EXIST ACROSS THE FAR NORTH
ALONG SOUTHERN PERIPHERY OF GREAT LAKES DPVA...BUT WILL KEEP
FORECAST DRY AT THIS POINT WITH EXPECTATION OF ONLY AN INCREASE IN
HIGHER BASED CU FRIDAY AFTERNOON WITH SOME VERTICAL EXTENT GIVEN MID
LEVEL LAPSE RATES. SOME LOW END ISOLD SHRA POTENTIAL MAY EXTEND
SOUTHWARD ACROSS THE REMAINDER OF THE AREA THROUGH FRIDAY EVENING AS
STRONGER 850-700 HPA FRONTOGENESIS SHIFTS SOUTHWARD IN ASSOCIATION
WITH SECONDARY FRONTAL BOUNDARY. GIVEN EXPECTED DEPTH TO MIXED LAYER
FRIDAY DID GO AHEAD AND DROP AFTERNOON DEW PTS A FEW DEGREES CLOSER
TO MOS VALUES WHICH COULD POSE SOME FIRE WEATHER CONCERNS GIVEN
BREEZY/WINDY CONDITIONS. HOWEVER...PROBABLE RAINFALL THURSDAY NIGHT
AND WET SOILS SHOULD TEND TO MITIGATE THIS CONCERN.

MUCH COOLER DAY SHAPING UP FOR SATURDAY...PARTICULARLY ACROSS THE
FAR NORTHWEST WHERE SOUTH CENTRAL CANADIAN HIGH PRESSURE PROVIDES
ONSHORE FLOW...LIKELY KEEPING AFTERNOON HIGHS IN THE MID-UPPER 40S.
MID/UPPER LEVEL FLOW PATTERN TO BECOME LESS PROGRESSIVE/BLOCKY BY
LATER THIS WEEKEND WHICH WILL ALLOW MID LEVEL RIDGING TO MAINTAIN
ITS GRIP ON THE REGION THROUGH MUCH OF THE WEEKEND. WITH MAIN UPPER
TROUGH CUTTING OFF ACROSS THE CENTRAL PLAINS BY LATE
WEEKEND...SOUTHEAST LOW LEVEL FLOW SHOULD TEND TO DELAY SIGNIFICANT
MOISTURE RETURN UNTIL VERY LATE WEEKEND/OR EARLY NEXT WEEK
PARTICULARLY ACROSS THE FAR NORTHEAST. THUS HAVE LOWERED CR ALLBLEND
POPS ACROSS THE NORTHEAST...AND HAVE PUT MORE WEIGHT ON PREVIOUS
FORECAST WITH MAINTENANCE OF LOWER POPS THROUGH SUNDAY AFTERNOON
BEFORE DEEPER MOISTURE ONCE AGAIN ADVECTS INTO THE AREA.

THE LATE SUNDAY THROUGH TUESDAY PERIOD STILL LOOKS TO BE UNSETTLED
AS BROAD UPPER LEVEL NEGATIVE HEIGHT ANOMALY SHOULD PERSIST ACROSS
THE LOWER/MID MS VALLEY WITH OCCLUDED SYSTEM STALLING ACROSS THE
REGION. WHILE SYSTEM WILL BE VERTICALLY STACKED TOWARD THE END OF
THE PERIOD...PRECIP CHANCES TO PERSIST THROUGH THE MIDDLE OF NEXT
WEEK WITH LOCAL AREA POSSIBLY BECOMING POSITIONED IN FAVORABLE FGEN
REGION NORTH OF THE MID LEVEL HEIGHT MINIMUM. WEAK THERMAL RIDGE
SHOULD BE CONTINUE TO WRAP BACK INTO THE LOCAL AREA THROUGH THE END
OF THE PERIOD...BUT INFLUENCES OF CLOUDS/PRECIP SHOULD KEEP TEMPS
BELOW NORMAL FOR MON/TUE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 130 AM EDT WED APR 23 2014

VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD AS APPROACHING
MIDLEVEL RIDGE AXIS ENSURES A DRY/SUBSIDENT ENVIRONMENT THROUGH
MOST OF THE DAY. GRADUAL TOP-DOWN SATURATION EXPECTED LATER TODAY
THOUGH AS WAA SLOWLY INCREASES AHEAD OF NEXT TROUGH. A FEW
SPRINKLES ARE POSSIBLE AT KSBN TOWARD THE END OF THE PERIOD BUT
VERY DRY CONDITIONS IN THE LOWER LEVELS WILL LIMIT RAINFALL
POTENTIAL AND KEEP CEILINGS WELL ABOVE 3 KFT.

&&

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

$$

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


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