Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 020038
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
838 PM EDT SAT AUG 1 2015

.SYNOPSIS...
ISSUED AT 345 PM EDT SAT AUG 1 2015

THERE IS A SLIGHT CHANCE FOR A SHOWER THIS EVENING BUT MOST AREAS
WILL BE DRY AND PARTLY CLOUDY. LOW TEMPERATURES WILL BE IN THE LOW
TO MID 60S. IT WILL BE WARM AND MORE HUMID ON SUNDAY WITH
AFTERNOON HIGHS IN THE MIDDLE 80S. THERE IS A CHANCE FOR
THUNDERSTORMS THROUGH THE DAY.

&&

.UPDATE...
ISSUED AT 813 PM EDT SAT AUG 1 2015

JUST SOME MINOR GRID UPDATES THIS EVENING TO ACCOUNT FOR CURRENT
SKY COVER TRENDS...BUT OTHERWISE TRENDS FROM PREVIOUS FORECAST
REMAIN INTACT. 925-850 HPA THETAE RIDGE ADVECTING ACROSS
PARTICULARLY NORTHEAST HALF OF THE AREA THIS EVENING MAY PROVIDE A
VERY LOW END CHANCE OF AN ISOLATED SHOWER OVER THE NEXT FEW
HOURS...ALTHOUGH WITH VERY WEAK NATURE TO MID/UPPER FORCING THESE
PROBABILITIES APPEAR TO BE DIMINISHING. DIURNAL MIXING APPEARED TO
SQUELCH MORE VIGOROUS CU DEVELOPMENT THROUGH LATE
AFTERNOON...ALTHOUGH EARLY THIS EVENING DID NOTE SOME MORE ROBUST
VERTICAL DEVELOPMENT ALONG ROUTE 30 CORRIDOR ACROSS WEST CENTRAL
PORTIONS OF THE FOERCAST AREA. THUS WILL HOLD SOME 15 TO 20 POPS
OVER THE NEXT FEW HOURS FOLLOWING THIS LOW LEVEL FORCING.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 348 PM EDT SAT AUG 1 2015

DIFFICULT SHORT TERM FORECAST WITH CONVECTIVE TRENDS THE MAIN
ISSUE. SFC DEWPOINTS HAVE MIXED SUBSTANTIALLY THIS AFTERNOON WITH
READINGS INTO THE UPPER 40S ACROSS LOWER MICHIGAN AND LOWER TO
MIDDLE 50S OVER NORTH CENTRAL INDIANA AND NORTHWEST OHIO. THIS
PROBLEMATIC INITIALLY AS THESE DRY LOW LEVELS WILL INHIBIT SHOWER
DEVELOPMENT THIS EVENING AS WEAK THETA E RIDGE AND SOME ELEVATED
INSTABILITY MOVE ACROSS THE AREA. INHERITED LOW CHANCE POPS FOR
THIS EVENING AND HIRES MODELS STILL HINTING AT A FEW POSSIBLE
LIGHT SHOWERS. FOR CONSISTENCY OPTED TO KEEP A SLIGHT CHANCE POP
FOR LIGHT SHRA AND DROPPED THUNDER MENTION.

MODELS HAVE SLOWED APPROACH OF COLD FRONT WITH MAIN AREA OF
CONVECTION EXPECTED SUNDAY NIGHT. MCS EXPECTED TO DEVELOP TONIGHT
UPSTREAM TO OUR NORTHWEST AND LIKELY MOVE EAST. MODELS HINTING THAT
PART OF THIS SYSTEM COULD CLIP OUR NORTH SUNDAY MORNING. OTHERWISE
RESIDUAL CLOUD COVER WILL ONCE AGAIN DICTATE HOW UNSTABLE WE GET
TOMORROW AFTERNOON AND WHETHER ANY CONVECTION DEVELOPS IN WARM
SECTOR. NAM12 SHOWING MUCAPES IN EXCESS OF 3K J/KG WITH INCREASING
DEEP LAYER SHEAR IN AFTERNOON. EML WILL BE MOVING OVER THE REGION
WITH STEEP MID LEVEL LAPSE RATES APPROACHING 9C/KM. INHIBITING
FACTORS FOR AFTERNOON CONVECTION WILL BE CAP...RESIDUAL CLOUD COVER
AND LACK OF STRONG FORCING AHEAD OF COLD FRONT. THETA E MIN ALSO
REMAINS OVER THE REGION UNTIL LATE AFTERNOON. HAVE TRIMMED POPS
BACK...ESPECIALLY SOUTH...BUT DID LEAVE POPS IN ALL AREAS FOR
AFTERNOON.


&&

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 348 PM EDT SAT AUG 1 2015

ON SUNDAY EVENING/00Z MON A 500MB CLOSED LOW LINGERS OVER JAMES
BAY...WITH THE CORRESPONDING SURFACE LOW ACROSS NORTHERN ONTARIO AND
TRAILING TROUGH ACROSS THE GREAT LAKES INTO MISSOURI. THE SFC LOW
FORECAST TO DEVELOP OVER MN/WI EARLIER SUNDAY MORNING IS SITUATED
OVER NORTHERN LAKE MI AND EVENTUALLY WRAPS IN WITH SURFACE LOW TO THE
NORTH AS IT PROGRESSES EASTWARD THROUGH MONDAY. PWATS AROUND 1.3
INCREASE TO NEAR 1.9 INCHES AS A 850MB 45 KT JET PUMPS IN
MOISTURE/INSTABILITY TO THE REGION THROUGH SUNDAY EVENING WITHIN THE
WARM SECTOR. FIRST SHORTWAVE ROUNDING THE BASE OF THE TROUGH IS
FORECAST TO SWING THROUGH SUNDAY AFTERNOON...THEN THE SECOND IS
ASSOCIATED WITH THE COLD FRONT APPROACHING THE WEST AROUND 3-6Z. MID
LEVEL LAPSE RATES ARE DECENT AS WELL...REACHING AROUND 6.5-7 C/KM BY
21Z SUNDAY AFTERNOON AND REMAINING UNTIL THE COLD FRONT PASSES
SUNDAY EVENING. THINKING THERE MAY BE A BRIEF BREAK/LULL IN
PRECIPITATION AROUND 00Z IN THE WAKE OF THE FIRST SHORTWAVE...BUT
LEFT IN CHANCE-SLIGHT CHANCE POPS DUE TO UNCERTAINTY IN
TIMING/DEVELOPMENT OF PRECIPITATION SUNDAY AFTERNOON WITH THE FIRST
WAVE.

AS STRONGER FORCING APPROACHES WITH COUPLED 300 MB
JET/500 MB SHORTWAVE/SFC COLD FRONT AROUND 3-6Z...EXPECT SHOWERS/T-
STORMS. MODELS STILL SUGGEST AROUND 1-2K J/G OF ML CAPE IN THE WEST
BY THIS TIME...WITH ABOUT 30-40 KNOTS OF 0-6 KM SHEAR. THIS WOULD
STILL SUGGEST CHANCES FOR SEVERE WEATHER...THOUGH WITH THE
UNFAVORABLE LATE EVENING/OVERNIGHT TIMING HAVE LOWER CONFIDENCE IN
THIS. IF ANY OCCURS...IT WILL BE IN THE FAR NW NEAR LAKE MICHIGAN AS
THE FRONT APPROACHES. FOR NOW...BUMPED UP POPS TO LIKELY DURING THE
3-9Z TIME FRAME WEST AND CENTRAL...AND TOWARDS 12Z EAST.

THE COLD FRONT WILL CONTINUE TO SINK SOUTHEASTWARD THROUGH THE
MORNING HOURS MONDAY...CLEARING THE REGION BY ABOUT 15Z. IN ITS WAKE
GUSTY NORTHWEST WINDS OF 15-25 KNOTS. THIS WILL LEAD TO WAVES OF 3
TO 6 FEET AND DANGEROUS CURRENTS ALONG LAKE MICHIGAN BEACHES. HAVE
ISSUED A BEACH HAZARDS STATEMENT FOR HAZAROUS CONDITIONS SUNDAY
LASTING INTO EARLY MONDAY TO ACCOUNT FOR THIS.

OTHERWISE...A FEW ISOLATED SHOWERS ARE POSSIBLE MONDAY AFTERNOON IN
THE EASTERN CWA WITH A WEAK SHORTWAVE ROUNDING THE BASE OF THE
LOW...BUT HAVE LOW CONFIDENCE IN THIS. KEPT IN SLIGHT CHANCE POPS.
MONDAY NIGHT INTO TUESDAY LOOKS DRY...WITH ZONAL FLOW ALOFT AND WEAK
HIGH PRESSURE AT THE SFC. TEMPERATURES WILL BE COOLER...WITH HIGHS
IN THE 70S.

WEDNESDAY THE UPPER LEVEL LOW OVER NORTHERN ONTARIO BEGINS TO SHIFT
EASTWARD...REACHING THE NEW ENGLAND STATES BY THURSDAY-FRIDAY. MODEL
DISCREPANCIES BECOME LARGER AT THIS POINT...WITH THE GFS BRINGING IN
A SFC LOW FROM THE SOUTH/HAVING A WEAKER HIGH TO THE NORTH WITH
PRECIP OVER THE CWA...AND THE ECMWF BRINGING IN A STRONGER HIGH FROM
THE NORTH AND THUS KEEPING THE SURFACE LOW FAR ENOUGH SOUTH TO KEEP
US DRY. WILL KEEP CONSENSUS POPS FOR NOW. EITHER WAY...TEMPS LOOKING
COOLER THROUGH THE MAINLY IN THE 70S FOR HIGHS.

 &&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 813 PM EDT SAT AUG 1 2015

VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THIS FORECAST VALID
PERIOD. TERMINALS ARE EXPECTED TO REMAIN DRY THROUGH THE REMAINDER
OF THE NIGHT...ALTHOUGH CANNOT COMPLETELY DISCOUNT LOW END
POTENTIAL OF ISOLD SHOWER THROUGH ABOUT 04Z AS LOW LEVEL THETAE
RIDGE ADVECTS INTO THE AREA. OTHERWISE...WINDS TO BACK MORE SOUTH
SOUTHWEST WITH SPEEDS AROUND 5 KNOTS TONIGHT.

A THUNDERSTORM COMPLEX IS EXPECTED TO INITIATE ACROSS THE UPPER MS
VALLEY LATER THIS EVENING AND EVENTUALLY DROP
SOUTHEASTWARD...ALTHOUGH CURRENT THINKING IS THAT UPSTREAM
ACTIVITY WILL BE ON THE DOWNWARD TREND IN INTENSITY/COVERAGE
SUNDAY MORNING AS IT POSSIBLY ENTERS NORTHWEST INDIANA. WITH LOW
CONFIDENCE AT THIS FOERCAST DISTANCE WILL CONTINUE KEEP TAFS DRY.
SFC GRADIENT WILL INCREASE STEADILY SUNDAY MORNING...WITH
SOUTHWEST GUSTS 20 TO 25 KNOTS DURING THE DAY SUNDAY. BETTER
CHANCE OF SHOWERS/THUNDERSTORMS SHOULD HOLD OFF UNTIL AFTER 03Z
SUNDAY NIGHT AS LOW LEVEL FRONT DROPS SOUTHEAST.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...BEACH HAZARDS STATEMENT FROM SUNDAY MORNING THROUGH MONDAY
     MORNING FOR MIZ077.

OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM SUNDAY TO 8 AM EDT MONDAY FOR
     LMZ043.

     SMALL CRAFT ADVISORY FROM 10 AM TO 11 PM EDT SUNDAY FOR LMZ046.

&&

$$

UPDATE...MARSILI
SYNOPSIS...LASHLEY
SHORT TERM...LASHLEY
LONG TERM...MCD
AVIATION...MARSILI


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