Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 311720
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1220 PM EST SAT JAN 31 2015

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

&&

.SYNOPSIS...
ISSUED AT 352 AM EST SAT JAN 31 2015

SIGNIFICANT STORM SYSTEM IS STILL EXPECTED TO IMPACT CENTRAL
INDIANA FROM SATURDAY NIGHT THROUGH SUNDAY NIGHT. AS THE SYSTEM
PUSHES AWAY ON MONDAY...FRIGID TEMPS WILL FILTER INTO THE REGION.
AFTER A RETURN TO NORMAL TEMPS AROUND MID-WEEK...THE BITTER COLD
TEMPS WILL RETURN AT THE END OF THE WEEK IN THE WAKE OF A COLD
FRONT. THIS COLD FRONT WILL ALSO BE RESPONSIBLE FOR WINTER
PRECIPITATION FROM TUESDAY NIGHT THROUGH WEDNESDAY NIGHT.

&&

.NEAR TERM /REST OF TODAY/...

ISSUED AT 943 AM EST SAT JAN 31 2015

0935Z UPDATE...MORNING UPDATE FOCUS WAS ON FOR THE REST OF TODAY
WHICH APPEARS TO BE IN GOOD SHAPE. ONLY NEEDED TO MAKE SOME MINOR
MODIFICATIONS BASED ON LATEST TEMP/DEW POINT/SKY TRENDS.

THE TENTATIVE PLAN WITH REGARD TO WINTER WEATHER HEADLINES IS TO
WAIT FOR THE REST OF THE GUIDANCE TO COME IN THIS
MORNING...EVALUATE AND HOPEFULLY MAKE A DECISION(S) BY EARLY THIS
AFTERNOON.

PREVIOUS DISCUSSION FOLLOWS...

CURRENT IR SAT SHOWS SOME INCREASING MID AND HIGH CLOUDS ACROSS
THE SOUTHWEST COUNTIES WITH HIGH PRESSURE CENTERED OVER THE OHIO
VALLEY. THE MAIN TREND FOR THIS MORNING AND TODAY WILL BE THE
INCREASING MID AND HIGH CLOUDS AS STORM SYSTEM APPROACHES FROM THE
WEST/SOUTHWEST. AS SOUTHWEST FLOW STRENGTHENS SLIGHTLY THIS
AFTERNOON...TEMPS WILL WARM INTO THE UPPER 30S/LOW 40S. TRENDED
TOWARD THE SLIGHTLY WARMER GFS FOR TODAY/S HIGHS...FEEL WARM
ADVECTION MAY BE UNDERDONE SLIGHTLY BY MOST MODELS.

&&

.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...

ISSUED AT 457 AM EST SAT JAN 31 2015

THE MAIN FOCUS OF THE SHORT TERM PERIOD CONTINUES TO BE THE STORM
SYSTEM AND SNOWFALL AMOUNTS THIS WEEKEND.

TIMING...LATEST MODEL RUNS OF NAM/GFS/EURO HAVE ALL TAKEN A SLIGHTLY
MORE NORTHERLY ROUTE BUT REMAIN RATHER CONSISTENT IN THE TRACK
AND TIMING OF SYSTEM...THE EURO BEING JUST SLIGHTLY SLOWER THAN
THE NAM AND GFS. LIGHT RAIN SHOWERS SHOULD START ENTERING THE
WESTERN COUNTIES AROUND SUN 00Z...INCREASING SLIGHTLY AROUND SUN
03Z. ISENTROPIC LIFT/BEST DYNAMICS REALLY STRENGTHEN AROUND SUN
06Z AND REMAIN STRONG THROUGH MON 00Z.

PRECIP TYPE...THERE HAVE BEEN MODIFICATIONS TO PRECIP TYPE AND
AMOUNTS WITH LATEST MODEL RUNS. MAIN CONCERN IS THAT WARM
ADVECTION MAY BE UNDERDONE OVER THE SOUTHERN COUNTIES TODAY AND
TOMORROW. DECENT SOUTHWEST FLOW IS GOING TO ALLOW TEMPERATURES TO
CLIMB INTO THE UPPER 30S/LOW 40S OVER MOST OF THE FORECAST AREA
TODAY. COLDER AIR WILL HAVE TIME TO FILTER INTO CENTRAL TIER OF
COUNTIES BY THIS EVENING...BUT DO NOT THINK THE SOUTHERNMOST
COUNTIES WILL BE ABLE TO RECOVER FROM THE WARM TEMPERATURES OF
TODAY AND TOMORROW. BUFKIT SOUNDINGS INDICATE SNOW ACROSS
LAFAYETTE AND INDIANAPOLIS BY EARLY THIS EVENING...BUT NOT
A CHANGE TO SNOW AT TERRE HAUTE UNTIL AFTER SUN 04Z...AND
SOUTHERN COUNTIES NEVER CHANGE OVER FROM RAIN /EXCEPT BRIEFLY
LATE TONIGHT OVER SOUTHEAST COUNTIES/. AS A RESULT...REMOVED
VIGO...CLAY...AND OWEN COUNTIES FROM THE WINTER STORM WATCH.

AMOUNTS...HIGH CONFIDENCE IN LARGE AMOUNTS OF SNOW OVER THE
NORTHERNMOST COUNTIES...SO INSERTED CARROLL AND HOWARD COUNTIES INTO
THE WINTER STORM WARNING AT THIS TIME. DUE TO THE SLIGHT NORTHERLY
SHIFT IN THE STORM TRACK...THESE COUNTIES COULD SEE UP TO 9 TO 12
INCHES OF SNOW ACCUMULATION...AND ANOTHER TIER OF COUNTIES WILL MOST
LIKELY HAVE TO BE ADDED TO THE WARNING WITH NEXT FORECAST ISSUANCE.
MEDIUM CONFIDENCE FORECAST ACROSS THE CENTRAL TIER OF
COUNTIES...WHICH WILL BE RIGHT ALONG SHARP PRECIPITATION GRADIENT.
ONCE AGAIN...THE I-70 CORRIDOR SEEMS TO BE THE BEST CUT-OFF
POINT...WITH THE SOUTHERN SIDE RECEIVING AROUND 3 TO 6 INCHES OF
TOTAL SNOWFALL ACCUMULATION...AND THE NORTHERN SIDE RECEIVING 6 TO 9
INCHES OF SNOW. AGAIN...THESE AMOUNTS COULD STILL CHANGE SINCE MOST
UNCERTAINTY LIES IN THIS PARTICULAR AREA.

SYSTEM WILL WIND DOWN BETWEEN MON 00-06Z WITH MOST OF PRECIP OUT
OF THE AREA BEFORE MONDAY MORNING COMMUTE. THERE WILL BE THE
POSSIBILITY FOR SOME LAKE EFFECT SNOW SHOWERS ACROSS THE FAR
NORTH/NORTHWESTERN COUNTIES ON MONDAY MORNING...BUT NO ADDITIONAL
ACCUMULATIONS ARE EXPECTED FROM THAT. MONDAY NIGHT WILL BE DRY WITH
BITTER COLD TEMPERATURES FALLING INTO THE SINGLE DIGITS ACROSS THE
NORTH...TO TEENS ACROSS THE SOUTH AS CLOUDS SCATTER A BIT.
DAYTIME HIGHS WILL NOT BE MUCH BETTER ON MONDAY EITHER...WITH
READINGS ONLY IN THE TEENS TO LOW 20S.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
ISSUED AT 340 AM EST SAT JAN 31 2015

ALL MODELS CONTINUE A NORTHWEST FAST FLOW ALOFT THROUGH THE LONG
TERM. TEMPERATURES WILL AVERAGE BELOW NORMAL...BUT SIGNIFICANT DAY
TO DAY CHANGES WILL OCCUR AS A COUPLE OF SYSTEMS MOVE RAPIDLY ACROSS
OUR REGION.

MODELS DEVELOP A SOUTHWEST FLOW TUESDAY AS HIGH PRESSURE MOVES OFF
TO THE EAST.  THIS WILL ALLOW TEMPERATURES TO WARM BACK UP INTO THE
30S TUESDAY AFTER A COLD START TUESDAY MORNING.  THERE WILL BE
INCREASING CLOUDS TUESDAY NIGHT WITH A SLIGHT CHANCE OF SNOW LATE
TUESDAY NIGHT IN THE NORTH AS A COLD FRONT APPROACHES.  THIS COLD
FRONT WILL MOVE SOUTH ACROSS OUR REGION WEDNESDAY PRODUCING A SLIGHT
CHANCE OF SNOW OVER NORTHERN SECTIONS AND A SLIGHT CHANCE OF MIXED
PRECIPITATION ELSEWHERE...EXCEPT THE FAR SOUTH WILL REMAINS DRY
UNTIL WEDNESDAY EVENING.

GFS AND GEMNH MODELS INDICATE SLIGHT CHANCE POPS CENTRAL AND SOUTH
WEDNESDAY EVENING...WHILE THE EURO IS DRY.  MEANWHILE ALL MODELS
INDICATE DRY WEATHER REST OF THE LONG TERM AS AN ARCTIC HIGH
PRESSURE SYSTEM BUILDS EAST INTO THE SOUTHERN GREAT LAKES BY
THURSDAY NIGHT.

MODELS HAVE TRENDED A LITTLE WARMER TUESDAY INTO WEDNESDAY MORNING.
HOWEVER IT MAY BE A BIT TOO WARM NORTH WITH SNOW COVER. CUT
TEMPERATURES A LITTLE LATE WEDNESDAY ON...AS ARCTIC AIR MOVES BACK
INTO OUR REGION. SUB ZERO TEMPERATURES ARE POSSIBLE NORTH BY FRIDAY
MORNING.

&&

.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 WATCH FROM 7 PM EST THIS EVENING THROUGH MONDAY
MORNING FOR INZ028>030-035>049-054>057.

WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 AM EST MONDAY
FOR INZ021-031.

&&

$$

SYNOPSIS...TDUD
NEAR TERM...SMF/TDUD
SHORT TERM...TDUD
LONG TERM...JH
AVIATION...MRD

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