Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 312205 CCA
AFDIND

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
458 PM EST SAT JAN 31 2015

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

&&

.SYNOPSIS...
ISSUED AT 435 PM EST SAT JAN 31 2015

A SIGNIFICANT STORM SYSTEM WILL IMPACT CENTRAL INDIANA STARTING
TONIGHT...AND CONTINUING THROUGH SUNDAY BEFORE FINALLY COMING TO AN
END EARLY MONDAY MORNING. AS THIS SYSTEM PUSHES AWAY FROM THE AREA
ON MONDAY...FRIGID TEMPERATURES WILL FILTER BACK INTO THE REGION.
THEN AFTER A RETURN TO NORMAL TEMPERATURES BY MID-WEEK...THE BITTER
COLD CONDITIONS WILL RETURN ONCE AGAIN FOR THE END OF THE WORK WEEK
IN THE WAKE OF A COLD FRONT MOVING THROUGH ON WEDNESDAY. THIS COLD
FRONT WILL ALSO BE RESPONSIBLE FOR WINTER PRECIPITATION FROM TUESDAY
NIGHT THROUGH WEDNESDAY NIGHT. COLD HIGH PRESSURE WILL BUILD BACK
OVER THE REGION FOR NEXT THURSDAY AND FRIDAY.

&&

.NEAR TERM /TONIGHT THROUGH SUNDAY NIGHT/...

ISSUED AT 435 PM EST SAT JAN 31 2015

FOCUS FOR THE NEXT 24 TO 36 HOURS IS THE STRONG LOW PRESSURE SYSTEM
DEVELOPING IN THE SOUTHERN PLAINS TONIGHT AND MOVING NORTHEAST INTO
THE OHIO VALLEY BY SUNDAY. FOR THE MOST PART...ALL THE 12Z MODELS
HAVE CONTINUED THE TREND OF PREVIOUS RUNS...WHICH TAKES THE LOW A
LITTLE FARTHER NORTHWARD. THIS IN TURN PULLS MORE WARM AIR INTO THE
REGION. AS STATED IN PREVIOUS FORECAST DISCUSSIONS...THERE WILL BE A
VERY SIGNIFICANT GRADIENT WITH REGARD TO SNOWFALL AMOUNTS ACROSS
CENTRAL INDIANA RANGING FROM LESS THAN AN INCH...POSSIBLY EVEN ZERO
TO A TRACE ACROSS THE FAR SOUTHERN COUNTIES...TO 9-12 INCHES ACROSS
THE NORTH IN CARROLL AND HOWARD COUNTIES!

AHEAD OF THE LOW...ISENTROPIC LIFT DEVELOPS TONIGHT ALLOWING FOR A
MIXTURE OF SNOW AND POSSIBLY SOME RAIN TO OVERSPREAD THE AREA. A
COUPLE OF INCHES OF SNOW ACCUMULATION WILL BE POSSIBLE ACROSS THE
NORTHERN COUNTIES TONIGHT...WITH VERY LITTLE IF ANY ACCUMULATION
WELL TO THE SOUTH OF THE I-70 CORRIDOR.

TEMPERATURES WILL WARM AHEAD OF THE LOW SUNDAY...ALLOWING FOR RAIN
TO MIX IN WITH SNOW...OR EVEN BECOME THE PREDOMINANT PRECIPITATION
TYPE FOR THE SOUTHERN HALF OF THE FORECAST AREA...ESPECIALLY DURING
AN EXTENDED PERIOD SUNDAY AFTERNOON.

THE LOW WILL BEGIN TO MOVE EAST OF THE REGION BY SUNDAY EVENING
AND COLDER AIR WILL THEN QUICKLY WORK IN ON THE BACKSIDE OF THE
SYSTEM...THUS CHANGING ALL THE PRECIPITATION BACK TO SNOW BY
SUNDAY NIGHT. IN ADDITION TO THE PRECIPITATION...THE WINDS WILL
PICK UP STARTING LATE SUNDAY AFTERNOON THANKS TO A STRENGTHENING
TIGHT PRESSURE GRADIENT WITH THIS SYSTEM AND THE SURFACE WINDS
ARE EXPECTED TO GUST UPWARDS OF 30 MPH. THIS WILL HAVE A NEGATIVE
IMPACT ON TRAVEL...AT LEAST FOR THE NORTHERN COUNTIES IN THE
WINTER STORM WARNING AND ADVISORY AREAS AS BLOWING SNOW BECOMES
AN ISSUE WHICH CAN REDUCE VISIBILITIES...IN ADDITION TO
PROBLEMATIC DRIFTING SNOW.

AS FOR TEMPERATURES DURING THIS PERIOD...GENERALLY STUCK WITH A
MOS BLEND BUT WENT SLIGHTLY WARMER AT NIGHT TO ACCOUNT FOR ALL THE
PRECIPITATION AND CLOUD COVER AND WAS MORE CONSERVATIVE WITH HIGHS
AND KNOCKED DOWN THESE TEMPERATURES A NOTCH OR TWO FOR THE SAME
REASONING.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...

ISSUED AT 435 PM EST SAT JAN 31 2015

THE WINTER STORM WILL BE COMING TO AN END ON MONDAY MORNING...WITH
SOME LIGHT ADDITIONAL SNOW ACCUMULATIONS POSSIBLE BETWEEN 12 TO 18Z
MAINLY ACROSS THE EASTERN COUNTIES OF THE FORECAST AREA AS THE LOW
ACCELERATES AWAY FROM THE REGION. ON THE BACK SIDE OF THE
STRENGTHENING SURFACE LOW...GUSTY N/NW FLOW WILL LEAD TO STRONG COLD
ADVECTION AND HIGH TEMPERATURES FOR MONDAY WILL BE WELL BELOW NORMAL
RANGING FROM THE LOW TEENS (NORTH) TO LOW 20S (SOUTH). STRONG
NORTHERLY WINDS WILL ALLOW WIND CHILLS TO DROP TO BELOW ZERO ON
MONDAY AND TUESDAY MORNINGS. HIGH PRESSURE IS QUICK TO REESTABLISH
ITSELF ACROSS THE AREA FOR THE BEGINNING OF THE WORK WEEK AND BY
TUESDAY HIGHS WILL BE BACK IN THE 30S WHICH IS NORMAL FOR THIS TIME
OF YEAR.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...

ISSUED AT 251 PM EST SAT JAN 31 2015

THE EXTENDED TIMEFRAME IS CHARACTERIZED BY A COUPLE OF LIGHT SNOW
PRODUCING UPPER WAVES AND A COUPLE OF WELL BELOW NORMAL TEMPERATURE
DAYS BRACKETED BY A COUPLE SEASONAL DAYS.

A QUICK MOVING WEAK UPPER WAVE WILL MOVE ACROSS THE OHIO RIVER
VALLEY TUESDAY AFTERNOON THROUGH TUESDAY NIGHT...BRINGING LIGHT
SNOW CHANCES TO THE NORTHERN HALF OF CENTRAL INDIANA MAINLY ON
TUESDAY NIGHT. AFTER A COLD FRONT SLIDES SOUTHEAST THROUGH THE
FORECAST AREA WEDNESDAY...TEMPERATURES SOME 10 TO 15 DEGREES
BELOW NORMAL ARE EXPECTED INTO FRIDAY INCLUDING A RETURN OF
SINGLE DIGIT LOWS OVER PORTIONS OF CENTRAL INDIANA. ACCORDING TO
THE 12Z GFS...THE SECOND UPPER WAVE BEGINS TO AFFECT THE OHIO
RIVER VALLEY WEDNESDAY NIGHT WIPING A SWATH OF LIGHT SNOW ACROSS
PORTIONS OF SOUTHERN INDIANA. THERE IS SOME AMBIGUITY AS TO THE
EVOLUTION OF THIS SYSTEM...AS THE 12Z ECMWF SENDS THIS WEAK TROUGH
ACROSS THE NORTHERN PLAINS AND INTO THE AREA WEDNESDAY NIGHT AND
THURSDAY...PRODUCING VERY LITTLE ACROSS THE AREA. THIS STANDS IN
CONTRAST TO THE 12Z GFS DIGGING A MORE AMPLIFIED TROUGH ACROSS THE
CENTRAL AND SOUTHERN PLAINS DURING THE SAME TIMEFRAME. ACCOUNTED
FOR THIS LIGHT SNOW POSSIBILITY WITH SLIGHT CHANCE POP GENERALLY
ACROSS OUR SOUTHERN TWO TIER OF COUNTIES.

&&

.AVIATION /DISCUSSION FOR THE 311800Z TAF ISSUANCE/...

ISSUED AT 1216 PM EST SAT JAN 31 2015

THE MAIN PROBLEM DURING THIS TAF CYCLE WILL BE PRECIPITATION
TYPE...ESPECIALLY ACROSS IND/HUF/BMG.

EXPECT VFR CONDITIONS TO CONTINUE THROUGH THE DAY TODAY WITH
MID/HIGH CLOUDS OVERSPREADING THE TAF SITES EARLY THIS AFTERNOON.
EXPECT TO SEE A SCATTERED DECK AT 2500 TO 3000 FEET ARRIVE LATE
THIS AFTERNOON AS THE SURFACE LOW PRESSURE BEGINS TO TAKE SHAPE
OVER THE CENTRAL PLAINS. AROUND 00Z SUNDAY...PRECIPITATION IS
EXPECTED TO PUSH INTO THE TAF SITES GENERALLY AS A MIX OF SNOW AND
RAIN. HOWEVER...WOULD NOT BE SURPRISED IF PRECIP STARTS AS RAIN
THEN TRANSITIONS TO THE MIX AND THEN TO SNOW LATE TONIGHT. SHORTLY
AFTER 00Z...CEILINGS ARE EXPECTED TO DROP INTO THE MVFR
CATEGORY...AROUND 1500 TO 2000 FEET. EXPECT CEILINGS TO STEADILY
DROP TO IFR SUNDAY AS THE HEAVIEST OF THE PRECIPITATION STARTS TO
FALL AROUND 14 TO 15Z FOR ALL SITES EXCEPT LAF...WHICH WILL OCCUR
A FEW HOURS EARLIER. BUFKIT SOUNDINGS INTRODUCE SOME WARM AIR INTO
THE TEMPERATURE PROFILE UP TO ABOUT 5000 FEET ACROSS THE
IND/HUF/BMG SITES AS THE LOW APPROACHES AND PUSHES EAST INTO
SOUTHERN INDIANA FROM THE WEST. THIS MAY BE ENOUGH TO CHANGE
PRECIPITATION BACK TO A MIX AT IND AND BACK TO RAIN AT HUF/BMG BY
18Z. DUE TO THE RECENT VARIABILITY IN THE TRACK OF THE
LOW...CONFIDENCE IS NOT HIGH ON PRECIPITATION TYPE AT IND/HUF/BMG
FOR SUNDAY AFTERNOON.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR INZ021-028>031-
035>042.

WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR INZ043>049.

&&

$$

SYNOPSIS...SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM....MRD
AVIATION...MRD

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