Area Forecast Discussion
Issued by NWS Indianapolis, IN

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883
FXUS63 KIND 070433
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1132 PM EST SAT FEB 6 2016

.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW

&&

.SYNOPSIS...
ISSUED AT 317 PM EST SAT FEB 6 2016

DRY AND SEASONABLY MILD WEATHER WILL CONTINUE FOR MOST OF THE REST
OF THE WEEKEND AS HIGH PRESSURE SHIFTS SLOWLY SOUTH. A STRENGTHENING
UPPER LOW AND SURFACE WAVE WILL TRACK FROM THE NORTHERN PLAINS INTO
THE GREAT LAKES BY MONDAY...USHERING IN A MUCH COLDER AND UNSETTLED
PATTERN FOR THE FIRST HALF OF THE WEEK WITH WIDESPREAD SNOW SHOWERS.
HIGH PRESSURE WILL BUILD IN FOR THE SECOND HALF OF THE WEEK WITH
PRIMARILY DRY WEATHER. TEMPERATURES WILL REMAIN BELOW NORMAL ALL
WEEK.

&&

.NEAR TERM /REST OF TONIGHT/...

ISSUED AT 933 PM EST SAT FEB 6 2016

SLOWED ARRIVAL OF CLOUD DECK BASED ON SATELLITE LOOP AND HI RES
GUIDANCE. DROPPED LOW TEMPERATURES A COUPLE DEGREES TO UPPER 20S
WITH CLOUDS BEING A LITTLE SLOWER TO ARRIVE DURING THE OVERNIGHT AND
SOME SITES ALREADY IN THE LOW 30S. PREVIOUS DISCUSSION FOLLOWS...

QUIET WEATHER WILL CONTINUE TONIGHT AS RIDGING ALOFT RETURNS INTO
THE OHIO VALLEY AND HIGH PRESSURE REMAINS THE DOMINANT INFLUENCE AT
THE SURFACE. CLEAR SKIES THIS EVENING WILL GIVE WAY TO A SLOW
INCREASE IN MID AND HIGH LEVEL CLOUDS OVERNIGHT AS A SURFACE TROUGH
APPROACHES THE MID MISSISSIPPI VALLEY.

TEMPS...MOS OVERALL MATCHED LOW LEVEL THERMALS WELL AND KEPT PRETTY
CLOSE TO GUIDANCE. WITHIN THE DRY AIRMASS...TEMPS SHOULD HAVE NO
PROBLEM FALLING INTO THE UPPER 20S AND LOWER 30S.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
ISSUED AT 317 PM EST SAT FEB 6 2016

MAIN FORECAST CHALLENGE THROUGH THE SHORT TERM WILL FOCUS ON A
PROLONGED PERIOD OF SNOW SHOWERS AND SQUALLS FOR THE REGION...LIKELY
CAUSING HIGH IMPACT TO TRAVEL AT TIMES MONDAY THROUGH TUESDAY WHILE
ACCUMULATIONS REMAIN PREDOMINANTLY LOW. NEEDLESS TO SAY...WINTER
POISED TO MAKE ITS RETURN TO BEGIN THE WEEK.

THE MAIN WEATHER FEATURE THROUGH THE SHORT TERM WILL BE A DEVELOPING
UPPER LOW OVER THE NORTHERN PLAINS TONIGHT. THE LOW WILL DEEPEN AS
IT TRACKS INTO THE GREAT LAKES BY MONDAY...CARVING OUT A BROAD
MERIDIONAL TROUGH THAT WILL ENCOMPASS MOST OF THE EASTERN PART OF
THE COUNTRY AS A RIDGE ESTABLISHES ALONG THE PACIFIC COAST. THE
UPPER LOW WILL MOVE SLOWLY EAST THROUGH MIDWEEK...KEEPING CENTRAL
INDIANA WITHIN A BROAD CYCLONIC FLOW UNDER THE DEEP TROUGH AND
ENSURING A COLD SNOWY PATTERN.

FIRST THOUGH...SUNDAY WILL CONTINUE THE RECENT STRETCH OF DRY AND
SEASONABLY MILD WEATHER AS HIGH PRESSURE AND RIDGING ALOFT SLOWLY
GET PUSHED TO THE SOUTH WITH THE STRENGTHENING OF THE UPPER LOW
OVER THE UPPER MIDWEST. EXPECT CLOUDS TO SLOWLY BUT STEADILY INCREASE
THROUGH THE COURSE OF THE DAY AS A LOW LEVEL JET ADVECTS MOISTURE
INTO THE REGION AHEAD OF A SURFACE TROUGH. OP GFS REMAINS MOST
AGGRESSIVE MODEL IN DEVELOPING SHOWERS WITHIN A BAND OF ISENTROPIC
LIFT ALIGNED WITH DEEPER MOISTURE AS THE TROUGH MOVES INTO THE
FORECAST AREA LATE DAY SUNDAY. MOST ALL OTHER MODEL GUIDANCE
INCLUDING THE HI-RES ARW AND NMM HOLD BULK OF ANY LIGHT RAIN
IMPACTING THE FORECAST AREA UNTIL AROUND 00Z OR LATER INTO SUNDAY
EVENING. CONSIDERING THE POOR MOISTURE RETURN INITIALLY IN THE LOW
LEVELS WITH NO GULF FETCH PRESENT...WILL CONTINUE WITH A DRY
FORECAST INTO THE EVENING BEFORE INTRODUCING CHANCE POPS.

THE GREATER FOCUS FOR ANY LIGHT RAIN SUNDAY NIGHT WILL LIKELY RESIDE
OVER THE EASTERN HALF OF THE FORECAST AREA IN CLOSER PROXIMITY TO
THE LOCATION OF THE SURFACE TROUGH. MODEL CONSENSUS HAS THIS
BOUNDARY EAST OF THE FORECAST AREA BY 06Z...WITH A NARROW DRY SLOT
COINCIDING WITH A SUBTLE AND BRIEF SURFACE RIDGE. MAY ACTUALLY SEE A
FEW HOURS WITH DRY CONDITIONS AND POSSIBLY EVEN A BRIEF PERIOD WHERE
CLOUD COVERAGE DIMINISHES DURING THE PREDAWN HOURS MONDAY. ANY LIGHT
PRECIP WILL BEGIN TO TRANSITION FROM RAIN TO SNOW AS THE INITIAL
SURGE OF COLD ADVECTION ARRIVES BEHIND THE SURFACE TROUGH.

AS THE DRY SLOT QUICKLY SHIFTS EAST BY 12Z MONDAY...BROAD CYCLONIC
FLOW WILL TAKE OVER AS THE UPPER LOW AND AN ATTENDANT SURFACE WAVE
PINWHEEL INTO THE GREAT LAKES. EXPECT SNOW SHOWERS TO QUICKLY BECOME
WIDESPREAD IN COVERAGE MONDAY MORNING AND CONTINUE FOR THE REST OF
THE SHORT TERM AS VARIOUS FACTORS CONTRIBUTE TO PERIODS WITH
MODERATE TO HEAVY SQUALLS AT TIMES.

MODEL SOUNDINGS SHOW AN INCREASINGLY FAVORABLE THERMODYNAMIC PROFILE
FOR SNOW SQUALLS MONDAY AFTERNOON AS CONDITIONAL INSTABILITY AND
STEEPENING LAPSE RATES ENHANCE THE FORCING ALOFT AND COINCIDES WITH
THE MORE SUBSTANTIAL SURGE OF MORE INTENSE COLD ADVECTION. IN
ADDITION...THE SNOW GROWTH ZONE INCREASE TO NEAR 100MB AT TIMES
BEGINNING MONDAY AFTERNOON AND PERSISTING INTO TUESDAY...LIKELY
CONTRIBUTING TO LARGE DENDRITES WITHIN HEAVIER SQUALLS.

EVEN THOUGH THE THERMODYNAMIC PROFILES BECOME SOMEWHAT LESS
FAVORABLE MONDAY NIGHT...EXPECT SNOW SHOWERS AND SQUALLS TO CONTINUE
IN ABUNDANCE AS MAIN MODEL GUIDANCE ALL HINTING AT THE TAIL OF AN
850MB TROWAL FORMING AND ROTATING THROUGH THE FORECAST AREA AS THE
SECONDARY LOW BECOMES MORE ORGANIZED OFF THE MID ATLANTIC COAST. THE
TROWAL WILL SWING ACROSS THE AREA IN TANDEM WITH THE STRONGEST PIECE
OF ENERGY ASSOCIATED WITH THE UPPER LOW. FURTHERMORE...LOW LEVEL
WIND FLOW AT 290-310 DEGREES WILL LIKELY ADD A LAKE ENHANCEMENT
POTENTIAL TO SNOW AS WELL.

BY TUESDAY...THE TROWAL WILL SHIFT EAST OF THE REGION BUT THE
COMBINATION OF PERSISTENT CYCLONIC FLOW...FORCING ALOFT...A RENEWED
PERIOD OF STEEPER LAPSE RATES AND HIGHER SNOW RATIOS PUSHING 20 TO 1
IN AN INCREASINGLY COLDER AIRMASS WILL CONTINUE THE THREAT FOR SNOW
SHOWERS AND SQUALLS...ESPECIALLY ACROSS THE EASTERN HALF OF THE
FORECAST AREA.

ALL OF THE FACTORS ABOVE SUPPORT A HIGH IMPACT/LOW ACCUMULATION
SCENARIO FOR MONDAY...MONDAY NIGHT AND TUESDAY ACROSS CENTRAL
INDIANA. STILL SOME QUESTIONS TO BE IRONED OUT REGARDING SNOWFALL
AMOUNTS...BUT A GENERAL 1 TO 3 INCHES SEEMS QUITE PLAUSIBLE OVER THE
36 HOUR PERIOD WITH THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS
COINCIDING WITH HEAVIER SQUALLS. HIGHEST AMOUNTS OVERALL ARE
LIKELY TO BE LOCATED MORE OVER THE NORTHEAST HALF OF THE FORECAST
AREA. EXPECT PLENTY OF TRAVEL DIFFICULTIES THROUGH THE PERIOD AS
GUSTY WINDS LEAD TO BLOWING SNOW IN ADDITION TO RAPID DROPS IN
VISIBILITY WITHIN SQUALLS AND ICY AND SNOW COVERED ROADS. WILL
CONTINUE TO HIGHLIGHT VIA THE HWO.

TEMPS...WITH A QUICK SHOT OF WARM ADVECTION SUNDAY...WENT SLIGHTLY
ABOVE MOS FOR HIGHS IN THE UPPER 40S AND LOWER 50S. GENERALLY LEANED
TOWARDS THE COLDER METMOS THE REST OF THE WAY. MONDAY WILL SEE MOST
HIGHS BY MIDDAY WITH FALLING TEMPS THEREAFTER AS THE STRONGER COLD
ADVECTION ARRIVES.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
ISSUED AT 317 PM EST SAT FEB 6 2016

LINGERING SNOW SHOWERS WILL IMPACT THE EASTERN TWO-THIRDS OF CENTRAL
INDIANA THROUGH TUESDAY NIGHT FROM THE REMNANTS OF A STORM SYSTEM.
AS THE UPPER LOW PUSHES FARTHER EAST...SNOW SHOWERS WILL BECOME
CONFINED TO JUST THE EASTERN PORTIONS OF THE FORECAST AREA ON
WEDNESDAY. AFTER THAT...A LARGE RIDGE OF HIGH PRESSURE ALOFT WILL
STRENGTHEN OVER THE WESTERN U.S...AND SURFACE HIGH PRESSURE OVER THE
CENTRAL U.S. WILL KEEP CONDITIONS DRY ACROSS CENTRAL INDIANA THROUGH
THE END OF THE EXTENDED PERIOD.  THE ONLY CAVEAT WILL BE A SLIGHT
CHANCE FOR SNOW SHOWERS ACROSS THE NORTHERN THIRD OF CENTRAL INDIANA
ON FRIDAY AS A SURFACE LOW PASSES OVER THE GREAT LAKES REGION.
TEMPERATURES THROUGH THE PERIOD WILL BE BELOW NORMAL WITH HIGHS IN
THE UPPER 20S TO MID 30S AND LOWS IN THE TEENS.

&&

.AVIATION /DISCUSSION FOR THE 07/0600Z TAF ISSUANCE/...
ISSUED AT 1132 PM EST SAT FEB 6 2016

VFR THROUGH FOR AT LEAST THE NEXT 24 HOURS...WITH LOWERING FLIGHT CONDITIONS
TOWARDS DAYBREAK MONDAY.

HIGH PRESSURE RIDGE OVER TENNESSEE AND KENTUCKY WILL RETREAT SOUTHEASTWARD
AS LOW PRESSURE OVER SOUTHERN MANITOBA MOVES TO THE NORTHERN GREAT LAKES
BY END OF FORECAST PERIOD. MOSTLY CLEAR OVERNIGHT FOLLOWED BY SOME MID/HIGH
CLOUDS AFTER 10Z-12Z SUNDAY.  MID CLOUDS WILL GRADUALLY INCREASE AND MODEL
SOUNDINGS HINT AT FEW-SCT CU SOME AREAS BY LATE SUNDAY ON.  CEILINGS WILL LOWER
MORE AFTER COLD FRONT MOVES THROUGH BY DAYBREAK MONDAY.

WINDS WILL BE FROM THE SOUTHWEST 8 KNOTS OR LESS OVERNIGHT AND EARLY
SUNDAY INCREASING TO 12 KNOTS WITH GUSTS BY 20 KNOTS BY LATE SUNDAY MORNING.
WINDS SUNDAY NIGHT WILL BECOME WEST 10 KNOTS OR LESS.



&&

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

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/CP
SHORT TERM...RYAN
LONG TERM....TDUD
AVIATION...JH



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