Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 030729
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
229 AM EST TUE MAR 3 2015

.UPDATE...
THE LONG TERM 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 /REST OF TONIGHT/...

ISSUED AT 934 PM EST MON MAR 2 2015

UPDATE...
RADAR IS CURRERENTLY QUIET OVER MUCH OF THE REGION. ALL PRECIP SO
FAR IS LOCATED OVER KANSAS AND MISSOURI. LATEST IR SATELLITE IS
SHOWING A RAPID INCREASE IN MID AND HIGH CLOUDS THOUGH OVER THE
LOWER MIDWEST...AND PRECIPITATION SHOULD START AFFECTING CENTRAL
INDIANA LATE TONIGHT. WILL NOT MAKE ANY CHANGES TO FORECASTED
START TIME OF 3AM EST TUESDAY.  UPDATED GRIDS HAVE BEEN SENT.

PREVIOUS DISCUSSION...
MODELS ARE IN FAIR AGREEMENT ON PRECIPITATION OVERSPREADING 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 /FRIDAY THROUGH NEXT TUESDAY/...
ISSUED AT 227 AM EST TUE MAR 3 2015

ENSEMBLES INDICATE A SLOWLY PROGRESSIVE NATURE TO THE LONG WAVE
FEATURES DURING THIS PERIOD. MEAN TROUGHING INITIALLY OVER THE
EASTERN PARTS OF THE COUNTRY IS EXPECTED TO LIFT OFF TO THE
NORTHEAST BY EARLY NEXT WEEK AS AN UPPER RIDGE MOVES INTO THE
PLAINS.

A COUPLE OF SHORT WAVE TROUGHS MAY PASS THROUGH THE AREA DURING THIS
PERIOD...ONE AROUND SATURDAY AND ANOTHER AROUND SUNDAY NIGHT INTO
NEXT MONDAY. A FEW ENSEMBLE MEMBERS INDICATE VERY LIGHT QFP WITH
EACH OF THESE FEATURES...SUGGESTING MINOR CHANCES FOR SOME LIGHT
SNOW. HOWEVER...CHANCES FOR MEASURABLE NOT HIGH ENOUGH TO INCLUDE
IN THE FORECAST AT THIS TIME. WILL KEEP THE EXTENDED DRY.

INITIALLY COLD TEMPERATURES SHOULD MODERATE WITH TIME AS HEIGHTS
GRADUALLY RISE.

&&

.AVIATION /DISCUSSION FOR THE 030600Z TAFS/...
ISSUED AT 1208 AM EST TUE MAR 3 2015

VFR UNTIL VERY EARLY THIS MORNING. DROPPING TO MVFR AROUND 10Z THIS
MORNING WITH A WINTRY MIX OF -FZRAPL. THIS WILL CHANGE OVER TO
FREEZING RAIN AND FINALLY BY AROUND NOON JUST RAIN FOR ALL THE
TERMINALS. WIDESPREAD IFR FLYING CONDITIONS WILL COMMENCE BY LATE
MORNING...AND THIS WILL HANG ON FOR THE REST OF THE TAF
PERIOD...UNTIL POSSIBLY AROUND 06Z WEDNESDAY WITH A SLIGHT
IMPROVEMENT TO LOW END MVFR.

LOOK FOR INCREASING MID CLOUDS OVER THE NEXT SEVERAL HOURS AND AS
STATED ABOVE...FREEZING RAIN AND POSSIBLY SOME SLEET BEGINNING
AROUND 09Z-11Z THIS MORNING. LOWERING CEILINGS AND VISIBILITIES
EXPECTED AS WE TREND TOWARDS IFR BY LATE MORNING...12-14Z. MODELS
INDICATE WARMER AIR WILL SPREAD INTO OUR REGION BY MIDDAY AND
PRECIPITATION WILL BECOME ALL RAIN..HOWEVER GUIDANCE INDICATES THIS
WILL NOT IMPROVE FROM THE IFR...POSSIBLY SOME LIFR(?) FLIGHT
CATEGORY.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...NIELD
NEAR TERM...NIELD/TDUD
SHORT TERM...NIELD
LONG TERM....JAS
AVIATION...SMF

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