Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 241837
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
137 PM EST SAT JAN 24 2015

.SYNOPSIS...
ISSUED AT 400 AM EST SAT JAN 24 2015

ANOTHER DAY WITH MOSTLY CLOUDY SKIES IS EXPECTED. THERE IS A
SLIGHT CHANCE FOR LIGHT RAIN OR SNOW SHOWERS OVER FAR NORTHEAST
INDIANA...NORTHWEST OHIO AND SOUTHERN LOWER MICHIGAN. HIGH
TEMPERATURES TODAY WILL BE IN THE 30S. A CLIPPER SYSTEM WILL
APPROACH THE REGION LATE TONIGHT. THERE IS A CHANCE FOR LIGHT SNOW
AHEAD OF THIS SYSTEM BUT MOST ACCUMULATING SNOW IS EXPECTED ON
SUNDAY. LOWS TONIGHT WILL BE IN THE MID 20S NORTH TO AROUND 30
SOUTH.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 356 AM EST SAT JAN 24 2015

WEAK SHORT WAVE AND ASSOCIATED SURFACE BOUNDARY APPROACHING THE
AREA FROM THE NORTHWEST THIS MORNING. SATELLITE SHOWS CLOUDS WHICH
HAVE PERSISTED OVER THE REGION LAST FEW DAYS FINALLY MOVING OFF TO
THE EAST. HOWEVER...CLOUDS ASSOCIATED WITH SHORT WAVE QUICKLY
APPROACHING FROM THE NORTH. THESE SHOULD SPREAD ACROSS MOST OF THE
CWA THIS MORNING. BASED ON SATELLITE TRENDS...FAR WESTERN AREAS
COULD SEE BREAKS THIS MORNING AS HIGHER RH IN MODEL ANALYSIS
SLIDES SOUTHEAST. FORCING REMAINS WEAK TODAY BUT HAVE ALREADY SEEN
A FEW LIGHT RETURNS ON RADAR AND HIRES GUIDANCE SPITTING OUT A
LITTLE QPF ...ESPECIALLY FAR NORTH AND EAST WHERE SLIGHTLY DEEPER
MOISTURE WILL COINCIDE WITH WEAK SHORT WAVES. WILL KEEP SLIGHT
CHANCE POPS GOING ACROSS THIS AREA. PCPN TYPE POINTS TO MAINLY
LIQUID WITH LACK OF MOISTURE WITHIN THE DGZ. WILL ADD A SLIGHT
CHANCE FOR FREEZING DRIZZLE EARLY THIS MORNING.

BAROCLINIC ZONE TIGHTENS ACROSS THE AREA TONIGHT AHEAD OF CLIPPER
SYSTEM. WARM AIR ADVECTION AND WEAK LIFT MAY ALLOW SOME LIGHT PCPN
TO DEVELOP ACROSS THE NORTHEAST HALF OF THE AREA. WILL HAVE A LOW
CHANCE POP TO START THE NIGHT WITH POPS INCREASING ACROSS THE REST
OF AREA OVERNIGHT. BULK OF PCPN TO FALL IN THE SUNDAY PERIOD BUT
WILL INCREASE POPS TO HIGH CHANCE TOWARD 12Z. WITH CLOUD COVER
EXPECTED AGAIN TODAY LOWERED TEMPS CENTRAL AND NORTHEAST BUT STAYED
WITH  THE WARMER END OF GUIDANCE IN THE SOUTHWEST WHERE SOME SUN
POSSIBLE.


&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 356 AM EST SAT JAN 24 2015

MAIN FOCUS OF LONG TERM PERIOD IS ON SNOWFALL AMOUNTS FOR SUNDAY
WITH FEW CONCERNS THEREAFTER. PARENT JET ENERGY AND ASSOCIATED PV
ANOMALY ARE NOW FULLY ONSHORE THE BRITISH COLUMBIA COAST. LATEST 00Z
NUMERICAL GUIDANCE APPEARS TO BE REACHING A CONSENSUS AND THOUGH
SUBTLE CHANGES ARE STILL CERTAINLY POSSIBLE...CONFIDENCE IN THE
FINER SCALE DETAILS IS INCREASING. AT LEAST TO THE POINT WHERE IT IS
POSSIBLE TO HAVE A MEANINGFUL DISCUSSION OF THE EVENT SPECIFICS.

MID/UPPER LEVEL JET STREAK AND VORTICITY MAXIMUM WILL DIG INTO THE
MIDWEST SUNDAY MORNING AND SEND SURFACE REFLECTION THROUGH SOUTHERN
INDIANA DURING THE AFTERNOON. SYNOPTIC SCALE DYNAMICS ARE DECENT BUT
SYSTEM STARTS TO OCCLUDE FAIRLY QUICKLY. LOW LEVEL CYCLONE IS STEADY
OR EVEN FILLING SLIGHTLY BY THE TIME IT ARRIVES IN OUR REGION.
NEVERTHELESS...A HEALTHY MESOSCALE RESPONSE IS STILL NOTED IN THE
LOWER LEVELS. INCREASING 285K WAA/ISENTROPIC ASCENT AND COLD AIR
FILTERING SOUTH FROM SURFACE HIGH OVER ONTARIO WILL HELP TIGHTEN THE
THERMAL GRADIENT IN PLACE AND LIGHT UP A MODEST BAND OF 925-850MB
FRONTOGENESIS. MODEL CROSS SECTIONS OF EPV AND THETA-E...AS WELL AS
REGULAR FORECAST SOUNDINGS...ALSO SHOW REDUCED STATIC STABILITY IN
THE MIDLEVELS FROM ROUGHLY 700 TO 400MB. FGEN SIGNAL IS PRETTY
SHALLOW SO AM NOT SURE IT WILL BE ABLE TO FULLY CAPITALIZE ON
REDUCED STABILITY ALOFT BUT THE POTENTIAL FOR MESOBANDING IS THERE
AND THIS WILL BE THE KEY FACTOR TO WATCH FOR GREATER SNOWFALL
TOTALS. OTHER FACTOR SUPPORTING HIGHER QPF IS AVAILABLE MOISTURE. AS
PREVIOUSLY NOTED...SPECIFIC HUMIDITIES OF OVER 3 G/KG EXTEND THROUGH
ALMOST 700MB AND PW VALUES APPROACH 0.6 INCHES. GIVEN THESE
FACTORS...MODEL QPF TOTALS OF UP TO A HALF INCH ARE DEFINITELY
WITHIN THE REALM OF POSSIBILITY. SNOW TO LIQUID RATIOS WILL
DETERMINE FINAL ACCUMULATIONS AND THIS REMAINS THE BIGGEST NEGATIVE
FACTOR FOR THE EVENT. SEVERAL ASPECTS SUPPORT A LOWER THAN AVERAGE
SNOW RATIO. BULK OF THIS EVENT WILL FALL DURING DAYLIGHT HOURS AND
ALTHOUGH SUN ANGLE IS STILL PRETTY LOW THIS TIME OF YEAR...IT STILL
HAS AN EFFECT WHEN SURFACE TEMPERATURES HOVER NEAR FREEZING AS THEY
WILL THROUGH THE EARLY AFTERNOON. SECONDLY...DGZ IS VERY SHALLOW AND
HIGHLY ELEVATED. UVM EXTENDS THROUGH A DEEP LAYER AND WILL PRODUCE A
HODGEPODGE OF DIFFERENT CRYSTAL TYPES. THE 0 TO -10C LAYER IS ALSO
VERY DEEP AND WILL PROMOTE A HIGH DEGREE OF RIMING. COUPLED WITH
SURFACE/GROUND TEMPS RIGHT AROUND OR JUST ABOVE FREEZING...ALL OF
THESE FACTORS SHOULD SUPPORT A WET/HEAVY SNOW WITH RATIOS PROBABLY
NEAR 10:1. (AVERAGE RATIOS FOR OUR CWA ARE AROUND 15:1.)

THEREFORE STILL THINK GENERALLY 3-5 INCHES WILL FALL ALONG AND SOUTH
OF US-30. (2 TO 4 INCHES NORTH OF THERE AND MAYBE JUST AN INCH OR
TWO IN OUR FAR NORTHERN ZONES.) HIGHER QPF TOTALS IN THE FAR
SOUTHERN COUNTIES SHOULD LARGELY BE OFFSET BY LOWER RATIOS AND
HIGHER POTENTIAL FOR MELTING. A FEW ISOLATED LOCATIONS MAY SEE
ENHANCED BANDING PUSH TOTALS TOWARD WARNING CRITERIA OF 6 INCHES IN
12 HOURS. HOWEVER...CONFIDENCE IN THIS OCCURRING IS NOT HIGH ENOUGH
FOR THE ISSUANCE OF A WATCH. LACKLUSTER MID/UPPER LEVEL DYNAMICS
WITH A SLOWLY FILLING SYSTEM AND WARM THERMAL PROFILES RAISE TOO
MANY CONCERNS. ANY 6+ INCH TOTALS SHOULD ALSO BE FAIRLY ISOLATED AND
IT IS DIFFICULT TO NAIL DOWN PRECISE LOCATIONS THIS FAR IN
ADVANCE...ESPECIALLY GIVEN HOW THIS SYSTEM HAS BEEN HANDLED BY THE
MODELS THUS FAR. LESS IMPACTS ALSO ANTICIPATED GIVEN THAT IT IS THE
WEEKEND. WILL THEREFORE FORGO ANY HEADLINE ISSUANCE AT THIS JUNCTURE
AND ALLOW DAY SHIFT ONE FINAL LOOK WITH THE BENEFIT OF 12Z DATA.

REST OF THE FORECAST FAIRLY QUIET. WEAK CLIPPER COULD BRING SOME
LIGHT SNOW MONDAY NIGHT BUT AMOUNTS LOOK LIMITED. A STRONGER WAVE
WILL PUSH THROUGH THE REGION ON THURSDAY BUT CONFIDENCE IN TRACK AND
PRECIP TYPES IS VERY LOW. TEMPERATURES DURING THIS UPCOMING WEEK
WILL START OFF ON THE COLD SIDE BUT WILL SLOWLY MODERATE THROUGH
MIDWEEK AS FLOW BECOMES MORE W/SW FOR AT LEAST A SHORT TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 116 PM EST SAT JAN 24 2015

SKIES WERE TEMPORARILY CLEARING AHEAD OF THE CLIPPER SYSTEM EARLY
THIS AFTERNOON WITH WEAK SUBSIDENCE BEHIND THE TROF. MADE THE TAFS
MORE OPTIMISTIC WITH VFR CONDITIONS AT THE START OF THE PERIOD AT
SBN. OTHERWISE...LOW CLOUDS SHOULD RETURN THIS EVENING WITH SNOW
SPREADING ACROSS THE AREA EARLY SUNDAY. AT THIS POINT...IT LOOKS
LIKE THE HEAVIEST SNOW WILL FALL SOUTH OF BOTH TERMINALS...
HOWEVER...IFR CONDITIONS ARE LIKELY AFTER DAYBREAK.

&&

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

$$

SYNOPSIS...LASHLEY
SHORT TERM...LASHLEY
LONG TERM...AGD
AVIATION...SKIPPER


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