Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 022311
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
611 PM EST MON MAR 2 2015

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

&&

.SYNOPSIS...
ISSUED AT 306 PM EST MON MAR 2 2015

AN ELONGATED LOW PRESSURE SYSTEM DEVELOPING FROM THE CENTRAL
CANADIAN PROVINCES SOUTHWARD INTO THE CENTRAL PLAINS WILL PUSH
INTO THE GREAT LAKES TONIGHT INTO TUESDAY NIGHT...ALLOWING WINTRY
PRECIPITATION TO OVERSPREAD CENTRAL INDIANA LATE TONIGHT INTO
TUESDAY MORNING. A SEVERAL HOUR PERIOD FROM JUST PRIOR TO THE
TUESDAY MORNING RUSH THROUGH LATE MORNING WILL FEATURE THE THREAT
FOR FREEZING RAIN AND SLEET. PRECIPITATION WILL CHANGE OVER TO
SNOW BY MIDDAY TUESDAY AND RAIN WILL FALL THROUGH THE AFTERNOON
AND INTO THE EVENING HOURS...BEFORE THE COLD FRONT MOVES THROUGH
THE AREA AND RESULTS IN ANY LINGERING PRECIPITATION CHANGING OVER
TO A MIX AND THEN ALL SNOW.

THE FRONTAL ZONE WILL BECOME QUASI-STATIONARY FOR A TIME TO OUR
SOUTH WEDNESDAY INTO WEDNESDAY NIGHT...WHICH MAY ALLOW FOR SOME
ACCUMULATING SNOW MAINLY ACROSS FAR SOUTHERN PORTIONS OF CENTRAL
INDIANA. THE LATTER PORTION OF THE WEEK WILL BE COLD AS HIGH
PRESSURE PUSHES BACK INTO THE AREA.

&&

.NEAR TERM /TONIGHT THROUGH TUESDAY MORNING/...
ISSUED AT 306 PM EST MON MAR 2 2015

MODELS ARE IN FAIR AGREEMENT ON PRECIPITATION OVERSPREAD THE AREA
VERY LATE TONIGHT...LIKELY JUST PRIOR TO THE START OF THE EARLY
MORNING RUSH. POOR TIMING OBVIOUSLY AS THERMAL PROFILES ARE
SUPPORTIVE OF PERHAPS A SNOW/SLEET/FREEZING RAIN MIX NORTHEAST...A
FREEZING RAIN/SLEET MIX CENTRAL...AND MOSTLY FREEZING RAIN
SOUTHWEST INITIALLY. THERE ARE SOME SUBTLE DIFFERENCES IN THE LOW
LEVEL THERMAL PROFILES WITH THE NAM/SREF A BIT WARMER AND A BIT
FASTER WITH THE OVERALL TRANSITION THAN THE GFS AND OTHER
GUIDANCE...BUT BETWEEN WETBULB EFFECTS INITIALLY AND THE PRESENCE
OF A DEEP EXPANSIVE SNOWPACK...AM SKEPTICAL OF THE WARMER SIDE OF
THE SOLUTIONS AND WILL LEAN MORE TOWARD THE COOLER SOLUTIONS EARLY
ON.

AS WARM ADVECTION CONTINUES INTO THE AREA ON THE BACK OF A 60+ KT
LOW LEVEL JET...PRECIPITATION WILL TRANSITION FROM SOUTHWEST TO
NORTHEAST. EXPECT FREEZING RAIN TO BE THE PREDOMINANT
PRECIPITATION TYPE ACROSS MOST OF THE AREA AROUND 12Z...SAVE FOR
PERHAPS THE FAR SOUTHWEST. WITHIN THE FIRST FEW HOURS OF THE
MORNING...FREEZING RAIN WILL TRANSITION TO RAIN ACROSS THE
SOUTHWEST...WITH THIS TRANSITION OCCURRING IN THE INDY METRO
AROUND THE 16Z OR 11 AM EST TIME FRAME.

SREF PROBABILITIES ARE GENERALLY SUPPORTIVE OF THIS PROGRESSION IF
SLIGHTLY FASTER THAN THE FORECAST GRIDS OWING TO THE THERMAL
DIFFERENCES ARTICULATED EARLIER.

WILL REQUIRE A WINTER WEATHER ADVISORY FOR A MIX OF FREEZING RAIN
AND SLEET AS LIGHT ICE ACCUMULATIONS APPEAR TO BE A GOOD BET...BUT
SHOULD GENERALLY BE NO MORE THAN A TENTH OF AN INCH. WILL RUN THE
ADVISORY FROM 08Z THROUGH 17Z OR 3 AM THROUGH 12 PM EST FOR THE
ENTIRE AREA. LIKELY WILL BE ABLE TO CANCEL PORTIONS OF THIS EARLY
FROM THE SOUTHWEST BUT WILL MAKE THIS SIMPLER WITH A ONE SEGMENT
PRODUCT.

&&

.SHORT TERM /TUESDAY AFTERNOON THROUGH WEDNESDAY NIGHT/...
ISSUED AT 306 PM EST MON MAR 2 2015

FOCUS THEN TRANSITIONS TO RAINFALL TOMORROW AFTERNOON AND
EVENING...FOLLOWED BY THE POTENTIAL FOR LIGHT SNOW ACCUMULATIONS
MAINLY ACROSS SOUTHERN PORTIONS OF CENTRAL INDIANA WEDNESDAY INTO
WEDNESDAY NIGHT.

MODELS KEEP THE HEAVIER RAIN ACROSS SOUTHERN INDIANA AND INTO
KENTUCKY BUT BRING PRECIPITABLE WATER VALUES OF BETWEEN 2 AND 3
STANDARD DEVIATIONS ABOVE THE CLIMATOLOGICAL NORM INTO PORTIONS OF
CENTRAL INDIANA TOMORROW AFTERNOON AND EVENING.

A QUARTER INCH OF RAIN NORTH...HALF INCH CENTRAL...AND UP TO AN
INCH SOUTH...COMBINED WITH FROZEN GROUND...WHICH WILL EFFICIENTLY
CONVERT RAINFALL TO RUNOFF...AND A MELTING SNOWPACK WHICH LIKELY
CONTAINS ON THE ORDER OF A HALF INCH TO AN INCH OF LIQUID
EQUIVALENT...MAY RESULT IN A FLOOD THREAT TOMORROW AFTERNOON AND
OVERNIGHT. ADDITIONALLY...REMAINING SNOW AND ICE MAY CLOG STREET
DRAINS AND RESULT IN URBAN FLOODING ALONG ROADWAYS.

LOW LEVEL THERMAL PROGS AGREE FAIRLY WELL WITH ONLY SLIGHT
DIFFERENCES IN FRONTAL PASSAGE AND RESULTANT COLD ADVECTION
WEDNESDAY NIGHT. EXPECT TO SEE THINGS TRANSITION TO A RAIN/SNOW
MIX AND FINALLY ALL SNOW BY 12Z WEDNESDAY. ANY AMOUNTS WILL BE
LIGHT THROUGH THIS TIME...MAYBE UP TO HALF AN INCH IN THE SOUTH.

GUIDANCE...EVEN THE MORE AGGRESSIVE AND FURTHER NORTH NAM...KEEP
THE BULK OF THE DEFORMATION ZONE TO OUR SOUTH ALONG THE RIVER AND
INTO KENTUCKY WEDNESDAY INTO WEDNESDAY NIGHT. EXPECT THIS TO BE
THE AXIS OF HEAVY SNOW WITH A FAIRLY TIGHT GRADIENT TO THE NORTH.
WILL CARRY LIKELIES ACROSS THE FAR SOUTH ON WEDNESDAY...DROPPING
TO CHANCES AT BEST WEDNESDAY NIGHT.

AT THIS TIME...HAVE AMOUNTS IN THE GRIDS OF ROUGHLY 1-4 ACROSS THE
FAR SOUTHERN TWO TIERS OF COUNTIES...WITH THE HIGHEST AMOUNTS ON
THE FAR SOUTHERN FRINGE. LESS THAN AN INCH ELSEWHERE. SMALL
CHANGES IN THE GUIDANCE COULD HAVE A SIGNIFICANT IMPACT ON
EXPECTED ACCUMULATIONS DURING THIS TIME FRAME.

CONSENSUS NUMBERS APPEARED REASONABLE ON TEMPS THROUGH THE PERIOD
AND WERE ACCEPTED WITH A FEW MINOR TWEAKS...MAINLY ON WEDNESDAY
WITH COLD ADVECTION CONTINUING THROUGHOUT THE DAY AND THUS LITTLE
TO NO DIURNAL WARMING ANTICIPATED.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
ISSUED AT 306 PM EST MON MAR 2 2015

MUCH QUIETER WEATHER WILL BE THE RULE DURING THE LONG TERM. THE MAIN
ISSUES WILL BE VERY COLD TEMPERATURES THURSDAY AND THURSDAY NIGHT AS
COLD ARCTIC HIGH PRESSURE MOVES EAST ACROSS OUR REGION.  SOME MODELS
INDICATE VERY LOW CHANCES OF PRECIP EARLY NEXT WEEK...BUT THE NEW
EURO IS DRY SUNDAY AND MONDAY...ALTHOUGH THEY GIVE LOW CHANCES
ACROSS OUR NORTHEAST LATE SUNDAY NIGHT.  WILL MENTION A CHANCE OF
FLURRIES THEN. OTHERWISE...IT WILL BE DRY THROUGH THE LONG TERM.

CONCERNING TEMPERATURES...MODEL 850 MB TEMPERATURES WILL BE AS COLD
AS -17 CELSIUS ON THURSDAY AND NEAR OR SLIGHTLY BELOW ZERO REST OF
THE LONG TERM.   EXPECT HIGHS FROM 15 TO 20 THURSDAY AND NEAR OR
SLIGHTLY BELOW ZERO SOME AREAS FOR LOWS THURSDAY NIGHT. HIGHS WILL
BE UPPER 20S TO LOWER 30S FRIDAY AND UPPER 30S TO LOWER 40S MOST
OTHER PERIODS.   IN MOST CASES MODEL BLEND ON TEMPERATURES SEEM
REASONABLE. BUT THEY MAY BE A TAD LOW FRIDAY INTO SATURDAY AS MODELS
INDICATE GOOD WARM ADVECTION. ONLY MINOR TWEAKS MADE.

&&

.AVIATION /DISCUSSION FOR 030000Z TAF ISSUANCE/...

ISSUED AT 607 PM EST MON MAR 2 2015

VFR UNTIL LATE TONIGHT...FOLLOWED BY MVFR AROUND 10Z WITH A WINTRY
MIX OF -FZRAPL...TURNING TO FREEZING RAIN AND THEN BY AROUND NOON
JUST RAIN FOR ALL THE TERMINALS AND IFR FLYING CONDITIONS WILL
COMMENCE BY LATE MORNING...AND THIS WILL HANG ON FOR THE REST OF
THE TAF PERIOD.

LOOK FOR INCREASING MID CLOUDS TONIGHT AND FREEZING RAIN AND
POSSIBLY SOME SLEET BEGINNING AROUND 09Z-11Z TUESDAY. LOWERING
CEILINGS AND VISIBILITIES EXPECTED TUESDAY MORNING AS WE
TREND TOWARDS IFR BY LATE MORNING. MODELS INDICATE WARMER AIR WILL
SPREAD INTO OUR REGION BY MIDDAY TUESDAY AND PRECIPITATION WILL
BECOME ALL RAIN.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST TUESDAY FOR INZ021-
028>031-035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...NIELD
NEAR TERM...NIELD
SHORT TERM...NIELD
LONG TERM...JH
AVIATION...SMF

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