Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 020754
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
254 AM EST MON MAR 2 2015

.UPDATE...
THE SYNOPSIS...NEAR TERM...SHORT TERM...LONG TERM AND HYDROLOGY
SECTIONS HAVE BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 248 AM EST MON MAR 2 2015

HIGH PRESSURE IS EXPECTED TO BUILD ACROSS THE AREA TODAY. A LOW
PRESSURE SYSTEM WILL AFFECT THE AREA TONIGHT INTO TUESDAY NIGHT. A
SECONDARY WAVE OF LOW PRESSURE MAY AFFECT THE AREA AROUND WEDNESDAY
INTO WEDNESDAY NIGHT. HIGH PRESSURE WILL AGAIN BUILD INTO THE AREA
BY LATE IN THE WEEK.

&&

.NEAR TERM /TODAY/...
ISSUED AT 248 AM EST MON MAR 2 2015

DRY WEATHER EXPECTED TODAY AS SURFACE HIGH PRESSURE MOVES THROUGH.
SATELLITE AND MODEL DATA SUGGESTS THERE WILL BE QUITE A BIT OF
MID/HI LEVEL CLOUD TODAY...SO WILL OPT FOR PARTLY CLOUDY SKY COVER.

LOW LEVEL THICKNESS PROGS INDICATE THE GFS MOS HIGHS FOR TODAY MAY
BE TOO COOL...ESPECIALLY IN THE NORTH. WILL RAISE THE GUIDANCE ABOUT
A CATEGORY.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
ISSUED AT 248 AM EST MON MAR 2 2015

MODEL DATA SUGGEST A STRONG LOW LEVEL JET IN EXCESS OF 60 KTS WILL
BE NOSING INTO SOUTHERN ILLINOIS BY THE PRE DAWN HOURS OF TUESDAY
AHEAD OF AN EJECTING SHORT WAVE...SO EXPECTING ORGANIZED LIFT AND
RESULTANT PRECIPITATION THREAT TO MOVE INTO THE AREA BY THAT TIME.
APPEARS THERE WILL BE A LARGE ELEVATED WARM LAYER DEVELOPING DURING
THE NIGHT. THIS COMBINED WITH SURFACE TEMPERATURES EXPECTED TO
REMAIN BELOW FREEZING SUGGESTS ANY PRECIPITATION THAT MAY DEVELOP
BEFORE SUNRISE TUESDAY WILL MOST LIKELY BE IN THE FORM OF FREEZING
RAIN...WITH SLEET/SNOW A LESSER THREAT. WILL GO WITH CHANCE POPS
AFTER ABOUT 030800Z.

LOW LEVEL JET IS PROGGED TO PASS OVER THE LOCAL AREA DURING THE DAY
TUESDAY...PROVIDING STRONG LIFT FOR PRECIPITATION. WILL GO WITH
CATEGORICAL POPS AS A RESULT. TEMPERATURE RISE WILL BE TRICKY ON
TUESDAY...WITH THE SNOWPACK LIKELY PREVENTING A GOOD WARM SURGE AT
THE SURFACE. APPEARS FROM MODEL DATA THAT THE SURFACE FREEZING LINE
MAY BE OVER THE FAR SOUTHWEST ZONES AT SUNRISE...WORKING SLOWLY
NORTH INTO THE NORTHEAST ZONES BY EARLY AFTERNOON. HOWEVER
CONFIDENCE IS LOW IN EXACTLY HOW FAST THE FREEZING LINE WILL
PROGRESS NORTH. WILL GO WITH MAINLY FREEZING RAIN IN THE
MORNING...GRADUALLY TRANSITIONING TO RAIN BY EARLY AFTERNOON.
MODEL QFP NOT AS HEAVY AS IT HAS BEEN OVER THE PAST COUPLE OF
DAYS...BUT CONSIDERING THE DEEP SNOWPACK...THERE IS STILL SOME
FLOODING CONCERNS. PARTS OF THE AREA MAY EVENTUALLY NEED HEADLINES
FOR THE FREEZING RAIN THREAT WHEN CONFIDENCE IS BETTER WITH REGARD
TO HOW SURFACE TEMPERATURES WILL BEHAVE ON TUESDAY.

SOME WEAK ELEVATED INSTABILITY IS POSSIBLE OVER THE SOUTHERN ZONES
BY TUESDAY AFTERNOON...SO WILL RETAIN THE SMALL THREAT FOR
THUNDERSTORMS.

PRECIPITATION SHOULD GRADUALLY DIMINISH LATER IN THE NIGHT TUESDAY
AS COLD FRONT PASSES THROUGH.

OPERATIONAL MODELS DIFFER QUITE A BIT LATE IN THE SHORT TERM PERIOD
WITH REGARDS TO A POTENTIAL SECONDARY WAVE DEVELOPING ON THE FRONT
BY WEDNESDAY. IF THIS WAVE COMES TO FRUITION...THERE MAY BE SEVERAL
INCHES OF SNOW ACROSS PARTS OF THE AREA WEDNESDAY AND WEDNESDAY
NIGHT. AT THIS TIME...THE ENSEMBLES SEEM TO BE LEANING IN THIS
DIRECTION...BUT THERE ARE STILL QUITE A FEW MEMBERS THAT SUPPRESS
THIS WAVE AS WELL. FOR NOW...WILL GO WITH CHANCE POPS FOR SNOW
WEDNESDAY AND WEDNESDAY NIGHT TO COVER THE MORE AGGRESSIVE SOLUTIONS.

LOW LEVEL THICKNESSES SUGGEST THE GFS MOS TEMPERATURE GUIDANCE FOR
TONIGHT AND TUESDAY AS PROBABLY TOO COOL. WILL BUMP UP THE NUMBERS
IN THOSE PERIODS. WITH THE POSSIBILITY OF A SECONDARY WAVE
DEVELOPMENT LATER THIS WEEK...WILL ALSO RAISE THE GFS MOS IN THE
LATER PERIODS ABOUT 5 DEGREES.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
ISSUED AT 248 AM EST MON MAR 2 2015

THE EXTENDED WILL BE HIGHLIGHTED BY A BREAK FROM THE ACTIVE PATTERN
AS OF LATE. THE WEST COAST RIDGE ALOFT WILL ATTEMPT TO REESTABLISH
DURING THE PERIOD...RESULTING IN A DOWNSTREAM LONGWAVE TROUGH OVER
MUCH OF THE EASTERN U S...RESULTING IN COOL DRY WEATHER THROUGH THE
WEEKEND.

DEPENDING ON HOW FAR NORTH SNOW IMPACTS THE REGION WITH SECONDARY
FRONTAL WAVE WEDNESDAY NIGHT...MAY EVENTUALLY NEED TO INTRODUCE
LINGERING LOW POPS THURSDAY MORNING TO ACCOUNT FOR DEPARTING SNOWS.
AS OF NOW...GOING TO RUN WITH A DRY FORECAST FROM 12Z WITH YET
ANOTHER STRONG ARCTIC HIGH BUILDING INTO THE MISSISSIPPI AND OHIO
VALLEYS. 850MB TEMPS WILL DROP INTO THE -15 TO -20C RANGE...SETTING
THE STAGE FOR ANOTHER SHARP BLAST OF COLD AIR FOR THURSDAY/THURSDAY
NIGHT. THE REMNANT SNOWPACK WHICH IS LIKELY TO BE REFRESHED TO SOME
DEGREE WEDNESDAY NIGHT IN PARTS OF THE FORECAST AREA WILL AGAIN HAVE
AN INFLUENCE ON SURFACE TEMPS.

AS WE NOW ENTER MARCH...THESE COLD SURGES ARE BECOMING INCREASINGLY
ANOMALOUS FROM A CLIMATOLOGICAL STANDPOINT. VERY LIKELY INDY BREAKS
A LOW MAX TEMP ON THURSDAY WITH HIGHS STRUGGLING TO GET TO THE
MIDDLE TEENS AND MAY THREATEN THE RECORD LOW FOR FRIDAY MORNING AS
WELL. WITH THE HIGH OVERHEAD EXPECT SOME LOCATIONS TO GO SUBZERO
FRIDAY MORNING. SHOULD INDY SLIP BELOW ZERO...IT WOULD BE THE FIRST
OCCURRENCE OF SUBZERO TEMPS IN MARCH SINCE MARCH 9 1984.

WARM ADVECTION WILL COMMENCE AS THE HIGH PASSES BY ON FRIDAY...WITH
TEMPS WARMING INTO THE 30S AND LOWER 40S FOR THE WEEKEND. A FRONTAL
BOUNDARY TRACKS THROUGH THE REGION LATE SATURDAY AND EARLY SUNDAY
BUT WITH MOISTURE LIMITED...WILL MAINTAIN A DRY FORECAST. 00Z ECMWF
PRESENTING AN INTERESTING WRINKLE WITH THIS FEATURE...BRINGING A
SOUTHERN STREAM SYSTEM MUCH FURTHER NORTH THAN OTHER MODELS SUNDAY
WITH PHASED JET INTERACTION ALOFT. COULD BE SOMETHING TO WATCH GOING
FORWARD.

&&

.AVIATION /DISCUSSION FOR THE 020600Z TAF ISSUANCE/...
ISSUED AT 1145 PM EST SUN MAR 1 2015

THE WIDESPREAD MVFR CEILINGS FROM EARLIER THIS EVENING ACROSS ARE
STARTING TO IMPROVE TO VFR ALREADY VERY EARLY THIS MORNING. AFTER
LOOKING AT CONDITIONS UPSTREAM APPEARS KLAF WILL REMAIN AT VFR FOR
THE REST OF THE PERIOD. THEN ALL SITES WILL SCATTER OUT IN THE LOW
LEVELS FOR GOOD BY 08-11Z THIS MORNING. LIGHT NORTHWEST WINDS WILL
SHIFT TO THE NORTHEAST EARLY THIS AFTERNOON AS HIGH PRESSURE BUILDS
INTO OUR REGION.

MID LEVEL CLOUDS WILL BEGIN TO INCREASE ACROSS THE AREA AGAIN
LATER THIS AFTERNOON AND EVENING AS A STRONG LOW PRESSURE SYSTEM
ADVANCES TOWARD THE AREA. PUT IN A MVFR GROUP AT THE TAIL OF THE
THE KIND TAF PERIOD AROUND 10Z FOR A WINTRY MIX...-FZRAPL WITH
MVFR CEILINGS AND VISIBILITIES. CONDITIONS ARE EXPECTED TO
RAPIDLY DETERIORATE AFTER 12Z TUESDAY WITH A WIDESPREAD AREA OF
HEAVY WINTRY MIX PRECIPITATION FORECAST FOR CENTRAL INDIANA ON TUESDAY.
THIS IS OUTSIDE OF THE OTHER TAF FORECAST PERIODS BUT LIKELY WILL BE
INCLUDED IN SUBSEQUENT AVIATION FORECAST UPDATES.

&&

.HYDROLOGY...

RIVER FLOODING MAY DEVELOP BY THE MIDDLE OF THE WEEK IN CENTRAL AND
SOUTHERN INDIANA.

AS OF SUNDAY EVENING...SNOW DEPTHS WERE ESTIMATED TO BE AROUND 8 TO
10 INCHES ACROSS THE NORTHERN PARTS OF THE WABASH AND WHITE RIVERS.
CENTRAL PORTIONS APPEAR TO BE HIGHER...ESTIMATED AROUND ONE FOOT.
ESTIMATED WATER CONTENT OF THE SNOWPACK RANGE FROM 0.50 TO 1.00 INCH
ACROSS THE NORTH TO POSSIBLY 1.00-1.50 INCHES OVER PARTS OF CENTRAL
INDIANA.

THE FAIRLY DEEP FROZEN GROUND...INDICATED BY AN OBSERVED FROST DEPTH
OF 8 INCHES AT INDIANAPOLIS...WILL HINDER THE ABSORPTION OF MELTING
SNOW AND RAINFALL. THEREFORE...ANY RAINFALL IS EXPECTED TO QUICKLY
BECOME RUNOFF INTO AREA RIVERS AND STREAMS.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....RYAN
AVIATION...SMF
HYDROLOGY...JAS/LEE

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