Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 181448
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1048 AM EDT SAT OCT 18 2014

.SYNOPSIS...
ISSUED AT 348 AM EDT SAT OCT 18 2014

COOL CONDITIONS ARE EXPECTED TODAY AS ANOTHER UPPER LEVEL
DISTURBANCE APPROACHES THE AREA. THIS DISTURBANCE WILL BRING A
CONTINUED CHANCE OF RAIN SHOWERS TODAY...WITH SOME LINGERING LAKE
EFFECT RAIN SHOWERS PERSISTING INTO LATE AFTERNOON AND EARLY
EVENING. OUTSIDE OF LAKE EFFECT CLOUDINESS...SKIES WILL CLEAR THIS
EVENING AND WINDS WILL DIMINISH ALLOWING FOR COLD TEMPERATURES TO
NEAR THE FREEZING MARK FOR MANY LOCATIONS...AND THE POTENTIAL FOR
FROST. HIGH TEMPERATURES TODAY WILL RANGE FROM THE UPPER 40S TO
LOWER 50S. LOW TEMPERATURES TONIGHT WILL RANGE FROM THE UPPER 20S
TO MID 30S FOR MOST LOCATIONS. HOWEVER...LAKE EFFECT CLOUDS MAY
KEEP LOWS TONIGHT IN THE MID TO UPPER 30S ACROSS NORTHWEST INDIANA
AND SOUTHWEST LOWER MICHIGAN.

&&

.UPDATE...
ISSUED AT 1038 AM EDT SAT OCT 18 2014

STRENGTH OF DCVA ASSOCIATED WITH UPSTREAM VORTICITY CENTER
FOCUSED ACROSS NERN IL ATTM...ALONG WITH COLLOCATED DEEPER
MOISTURE PER WV IMAGERY...SUGGESTS ARDENT RAMP OF POPS FOR
MIDDAY/EARLY AFTERNOON IN ORDER. NEAR STEADY TEMPS AS WELL WITH
SLIGHT ADJUSTMENTS DOWNARD LEANING TOWARDS NEAR TERM MODEL
CONSENSUS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM EDT SAT OCT 18 2014

TWO FOLD CONCERNS FOR THE SHORT TERM PERIOD WITH MOST SIGNIFICANT
BEING FROST/FREEZE POTENTIAL TONIGHT.

COLD FRONT/INITIAL SHORTWAVE HAS SHIFTED SOUTH OF THE AREA WITH
COLDER AIR CONTINUE TO STREAM INTO THE REGION. NEXT PIECE OF
ENERGY WAS RAPIDLY APPROACHING FROM THE NW. THIS ALONG WITH 850
MB TEMPS DROPPING BELOW ZERO WILL ALLOW FOR A UPTICK IN LAKE
EFFECT CLOUD COVER AND SHOWER ACTIVITY TOWARDS 12Z. UPSTREAM
RADARS SHOWING A FEW NARROW BANDS OF SHOWERS TAKING SHAPE NOW AND
THIS SHOULD EXPAND FURTHER WITH PEAK TIME FRAME IN THE 12 TO 18Z
PERIOD. HAVE ADJUSTED ONSET OF HIGHEST POPS CLOSER TO THE 12Z
TIME FRAME AND EXPANDED INLAND A BIT WITH SUBSEQUENT EXPANSION OF
ALL POPS ACROSS THE AREA FOR AT LEAST A PERIOD OF LIGHT
SHOWERS/DRIZZLE IN MOST LOCATIONS. VERY LITTLE DIURNAL SWING IN
TEMPERATURES TODAY WITH CLOUDY SKIES EXPECTED INTO THIS AFTERNOON
BEFORE DRIER AIR BEGINS TO WORK IN FROM NE.

NW FLOW WILL REMAIN OFF THE LAKE INTO THIS EVENING WITH 925 MB RH
PLUMES SHOWING GREATER THAN 80 PERCENT RH VALUES DOWNWIND OF THE
LAKE WHICH PERSISTS INTO THE OVERNIGHT HOURS WITH THIS AREA
SHIFTING EAST TOWARDS 12Z SUNDAY AS FLOW BECOMES MORE WESTERLY.
CLEAR SKIES AND LIGHT WINDS LOOK QUITE LIKELY ACROSS THE EASTERN
HALF OR SO OF THE AREA WITH GUIDANCE NUMBERS ALL POINTING TOWARDS
LOWS IN THE LOWER 30S. GIVEN CONFIDENCE IN AREAS TO WIDESPREAD
FROST AND AFTER MUCH COLLABORATION WITH SURROUNDING OFFICES WILL
HOIST FREEZE WATCH FOR AREAS CURRENTLY FORECAST TO DROP TO 33
DEGREES OR LOWER FOR OVERNIGHT LOWS TO ACCOUNT FOR LOCALLY COOLER
POTENTIAL (28 TO 32 DEGREE RANGE) IN BOUNDARY LAYER VS SENSOR
LEVEL MEASUREMENT. MOST IF NOT ENTIRE CWA WILL LIKELY WARRANT
SOME SORT OF HEADLINE BUT WITH CLOUD COVER AMOUNT AND TIMING
STILL A HUGE ISSUE...DON`T WANT TO LOCK DAY SHIFT INTO
ADVISORY/WARNING SITUATION DESPITE CURRENTLY FAVORABLE SETUP IN
PARTS OF THE AREA.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 348 AM EDT SAT OCT 18 2014

MAIN ITEM OF INTEREST IN THE LONG TERM WILL BE A CLIPPER LIKE
SYSTEM DIGGING ACROSS THE GREAT LAKES EARLY IN THE WEEK PROVIDING
FOR THE NEXT CHANCE OF RAIN. QUIETER CONDITIONS WILL FOLLOW FROM
TUESDAY NIGHT THROUGH THE END OF THE FORECAST PERIOD.

ON SUNDAY...LAKE EFFECT CLOUDINESS SHOULD PERSIST ACROSS FAR
NORTHWEST PORTIONS OF THE AREA ALTHOUGH DEPTH OF LAKE INDUCED
INSTABILITY WILL BECOME PROGRESSIVELY MORE SHALLOW WITH LOWERING
INVERSION HEIGHTS UNDER THE INFLUENCE OF SYNOPTIC SCALE
SUBSIDENCE. SOME BACKING OF LOW LEVEL WINDS IS EXPECTED SUNDAY
MORNING WITH APPROACH OF LOW LEVEL RIDGE AXIS WHICH SHOULD YIELD
SOME EASTWARD ADVECTION OF LAKE EFFECT CLOUDINESS. OUTSIDE OF
LAKE EFFECT CLOUDS...MAINLY CLEAR SKIES ARE EXPECTED IN THE
MORNING...BUT STRENGTHENING MID LEVEL WAA SHOULD ALLOW FOR MID
LEVEL DECK TO OVERSPREAD THE AREA FROM WEST TO EAST IN THE
AFTERNOON HOURS. THE LOWER INVERSION HEIGHTS ON SUNDAY SHOULD
RESULT IN MIXING HEIGHTS LIMITED TO AROUND 900 HPA WHICH SHOULD
LIMIT HIGHS FROM LOWER 50S FAR NORTHEAST TO THE MID 50S
SOUTHWEST.

BY SUNDAY NIGHT...ATTENTION WILL SHIFT TO NEXT NORTHWEST FLOW
WAVE SPILLING OVER THE UPPER RIDGE ACROSS THE UPPER MS VALLEY.
SOME WEAK LOW LEVEL MOISTURE POOLING SHOULD COMMENCE ON SUNDAY
ALONG LOW LEVEL TROUGH AXIS DOWNSTREAM OF THIS WAVE...WITH THIS
WEAK MOISTURE AXIS SHIFTING INTO THE WESTERN GREAT LAKES SUNDAY
NIGHT. FAIRLY STRONG MID/UPPER LEVEL BAROCLINICITY SHOULD ALSO
EXIST WELL DOWNSTREAM OF THIS WAVE ACROSS THE OHIO VALLEY WHICH
MAY INDUCE SOME WEAK MID/UPPER LEVEL FRONTOGENETIC RESPONSE
SUNDAY NIGHT. LOW LEVEL MOISTURE WILL BE EVEN MORE MARGINAL
ACROSS AREAS PRONE TO THIS ELEVATED FORCING HOWEVER. GIVEN
COMBINATION OF ABOVE FACTORS HAVE MAINTAINED BROADBRUSH LOW
CHANCE POPS ACROSS ENTIRE CWA SUNDAY NIGHT.

UPPER LEVEL FORCING TO INCREASE BY EARLY MONDAY AS UPSTREAM WAVE
AMPLIFIES ACROSS THE GREAT LAKES REGION...ALTHOUGH LATEST
ITERATIONS OF THE EC SEEM TO BE A LITTLE LESS AGGRESSIVE AND MORE
DELAYED IN THIS REGARD. THIS MAY RESULT IN A SLIGHTLY MORE
PROGRESSIVE LOW LEVEL MOISTURE AXIS THAN PREVIOUS
INDICATIONS...SO HAVE HELD TO INHERITED HIGH CHANCE POPS ACROSS
THE EAST. IT IS POSSIBLE POPS WILL NEED TO BE INCREASED ACROSS
THE EAST IN NEXT FEW FORECAST CYCLES DEPENDING ON EVOLUTION OF
UPPER TROUGH. PRECIP MAY END AS A PERIOD OF PATCHY DRIZZLE LATE
MONDAY AFTERNOON INTO MONDAY NIGHT AS UPPER TROUGH TRACKS ACROSS
THE AREA. STILL SOME INDICATIONS OF BETTER PHASING OF UPPER
SYSTEM EAST OF THE AREA ON TUESDAY WHICH COULD LEND TO ISOLD
SHOWER POTENTIAL LINGERING ACROSS THE EAST...SO NO CHANGES MADE
IN THIS REGARD.

TEMPERATURES WILL BE SLOW TO MODERATE THROUGH THE PERIOD AS MORE
PHASED UPPER LOW CONSOLIDATES ACROSS EASTERN CONUS LATER IN THE
WEEK...RESULTING IN ONLY A SLOW EASTWARD MIGRATION OF CENTRAL
CONUS UPPER RIDGING. MORE PRONOUNCED MODERATION IN TEMPERATURES IS
EXPECTED TOWARD THE END OF THE PERIOD HOWEVER.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 632 AM EDT SAT OCT 18 2014

A TEMPORARY LULL IN PRECIP CHANCES TO BEGIN THE PERIOD AS
NORTHERN INDIANA IS SITUATED BETWEEN TWO STRONGER UPPER LEVEL
SHORT WAVES. THE NEXT SHORT WAVE OF INTEREST ACROSS WEST CENTRAL
WISCONSIN WILL DROP SOUTHEAST ACROSS THE OHIO RIVER VALLEY. LIGHT
RAIN SHOWERS ARE EXPECTED TO ACCOMPANY PROGRESSION OF THIS VORT
MAX FROM MID MORNING THROUGH MID AFTERNOON. WILL MAINTAIN
GENERALLY MVFR CIGS THROUGH EARLY AFTERNOON...POSSIBLY TRENDING
TO VFR AT KFWA. STEEP LOW LAPSE RATES SHOULD CONTINUE TO SUPPORT
GUSTS TO AROUND 20 KNOTS THROUGH THIS AFTERNOON...BUT SUBSIDING
THIS EVENING AS LOW LEVEL RIDGE AXIS MOVES IN FROM THE WEST.
STRENGTHENING SYNOPTIC SCALE SUBSIDENCE BEHIND DEPARTING
SECONDARY WAVE TONIGHT SHOULD ALLOW FOR AT LEAST PARTIAL CLEARING
OUTSIDE OF LINGERING LAKE EFFECT CLOUDINESS THAT MAY AFFECT KSBN
THROUGH THE END OF THIS FORECAST VALID PERIOD.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
     INZ005>009-016>018-024>027-032>034.

MI...FREEZE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
     MIZ078>081.

OH...FREEZE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR OHZ001-
     002-004-005-015-016-024-025.

LM...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR LMZ043-046.

&&

$$

UPDATE...MURPHY
SYNOPSIS...MARSILI
SHORT TERM...FISHER
LONG TERM...MARSILI
AVIATION...MARSILI


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