Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 280750
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
250 AM EST WED JAN 28 2015

.UPDATE...
THE LONG TERM SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 213 PM EST TUE JAN 27 2015

TWO SEPARATE SYSTEMS WILL BRING PRECIPITATION CHANCES TO CENTRAL
INDIANA OVER THE FORECAST PERIOD. THE FIRST LOW PRESSURE SYSTEM
WILL RESULT IN PRIMARILY RAIN FROM WEDNESDAY NIGHT THROUGH
THURSDAY AFTERNOON BEFORE CHANGING TO A RAIN/SNOW MIX EARLY
THURSDAY EVENING. AFTER DRY CONDITIONS ON FRIDAY AND
SATURDAY...THE SECOND SYSTEM WILL TRACK FROM THE LOWER MISSISSIPPI
VALLEY THROUGH THE TENNESSEE VALLEY ON SUNDAY...BRINGING SNOW
CHANCES TO THE NORTHERN PORTIONS OF CENTRAL INDIANA AND A
RAIN/SNOW MIX TO THE SOUTHERN HALF.

&&

.NEAR TERM /TONIGHT/...
ISSUED AT 1009 PM EST TUE JAN 27 2015

NO SIGNIFICANT CHANGES REQUIRED AS GOING FORECAST IS IN EXCELLENT
SHAPE. DID MAKE SOME TWEAKS TO SKY GRIDS FOR LATEST SATELLITE TRENDS
BUT OTHERWISE GRIDS LOOK GOOD. PREVIOUS DISCUSSION FOLLOWS.

ISSUED AT 213 PM EST TUE JAN 27 2015

BENIGN WEATHER CAN BE EXPECTED ACROSS CENTRAL INDIANA TONIGHT WITH
HIGH PRESSURE IN PLACE OVER THE GREAT LAKES REGION. MEANWHILE...WINDS
WILL TAKE ON AN EASTERLY COMPONENT AS A STRONG SYSTEM CONTINUES TO
WORK ITS WAY UP THE EAST COAST.

STRONG RADIATIONAL COOLING SHOULD TAKE PLACE TONIGHT AS CLOUDS
SCATTER. OVERNIGHT LOWS WILL DIP INTO THE TEENS OVER THE MAJORITY
OF THE FORECAST AREA...EXCEPT THE SOUTHWEST COUNTIES WHICH WILL BE
IN THE LOW 20S. AS A RESULT...TRENDED TOWARD THE SLIGHTLY COOLER
GFS.

&&

.SHORT TERM /TOMORROW THROUGH FRIDAY/...
ISSUED AT 213 PM EST TUE JAN 27 2015

THE MAIN FOCUS OF THE SHORT TERM PERIOD IS PRECIPITATION IN
ASSOCIATION WITH A LOW PRESSURE SYSTEM PROGGED FOR WEDNESDAY
NIGHT/THURSDAY.

RIDGE OF HIGH PRESSURE WILL RESULT IN DRY CONDITIONS FOR TOMORROW
THROUGH MOST OF WEDNESDAY. HOWEVER...MODELS SHOW RIDGE BREAKING
DOWN BY WEDNESDAY AFTERNOON AS AN UPPER LEVEL LOW APPROACHES FROM
THE UPPER MIDWEST. NAM/GFS/EURO ARE ALL IN AGREEMENT WITH FIRST
WAVE OF ENERGY IMPACTING THE NORTHWEST PORTIONS OF CENTRAL INDIANA
AROUND THU 09Z. ISENTROPIC LIFT REALLY STARTS STRENGTHENING AFTER
THU 12Z...MAKING THE THU 12-18Z TIME FRAME THE BEST FOR
PRECIPITATION CHANCES. FORECAST SOUNDINGS ARE ABOVE FREEZING
DURING THAT TIME THOUGH...SO WILL GO WITH AN ALL RAIN FORECAST.
COOLER AIR WILL START FILTERING IN LATE THURSDAY AFTERNOON...SO
RAIN WILL TRANSITION TO A RAIN/SNOW MIX OVER THE NORTHERN TWO-
THIRDS OF CENTRAL INDIANA AROUND THU 21Z. BY THE TIME THE COLDEST
AIR IS IN PLACE AND ALL PRECIPITATION IS TRANSITIONED TO
SNOW...MOST OF THE MOISTURE AND BEST DYNAMICS WILL BE OUT OF THE
AREA. AS A RESULT...EXPECT LITTLE SNOW ACCUMULATION.

SNOW SHOULD BE OUT OF THE AREA BY THURSDAY NIGHT AS SUBSIDENCE
STRENGTHENS OVER THE MIDWEST.  EXPECT DRY CONDITIONS ON FRIDAY.

TEMPS...GENERALLY STUCK CLOSE TO A MODEL BLEND DUE TO THE GOOD
MODEL CONSISTENCY WITH AFOREMENTIONED SYSTEM. TEMPS WILL BE AT OR
SLIGHTLY ABOVE NORMAL TOMORROW AND THURSDAY...THEN DROPPING TO
SLIGHTLY BELOW NORMAL LATE IN THE PERIOD AS COLDER AIR FILTERS IN
ON BACK SIDE OF SYSTEM.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
ISSUED AT 249 AM EST WED JAN 28 2015

PRIMARY FOCUS FOR THE EXTENDED PERIOD REMAINS ON THE GROWING POTENTIAL
FOR A HIGH IMPACT WINTER WEATHER SYSTEM ACROSS THE OHIO VALLEY FOR
THE SECOND HALF OF THE WEEKEND. 00Z MODEL GUIDANCE HAS COME IN
GENERALLY WITH A MORE PHASED LOOK TO THE UPPER JET STRUCTURES
CONSEQUENTLY PRODUCING A STRONGER SURFACE WAVE TRACKING THROUGH
THE REGION.

AFTER A DRY DAY SATURDAY AS HIGH PRESSURE MOVES ACROSS THE
AREA...FOCUS WILL TURN TO DEVELOPING LOW PRESSURE OVER TEXAS EARLY
SUNDAY. THIS SYSTEM WILL LIFT NORTHEAST INTO THE OHIO AND
TENNESSEE VALLEYS AS AN UPPER TROUGH AMPLIFIES OVER THE CENTRAL
PLAINS. VARIATIONS ARE PRESENT BETWEEN THE DIFFERENT MODELS WHICH
IS TO BE EXPECTED. THE GGEM AND OP GFS ARE PARTICULARLY AGGRESSIVE
IN PHASING THE UPPER ENERGY OVER THE REGION BY LATE SUNDAY...
CONSEQUENTLY PRODUCING A DEEPENING LOW GOING SUB-1000MB SUNDAY
NIGHT AS IT PASSES THROUGH THE AREA. ECMWF IS FLATTER IN THE UPPER
LEVELS INITIALLY LENDING TO A FASTER MOVING WAVE WITH THE PHASING
ENERGY ALOFT NOT TAKING PLACE UNTIL AFTER THE SYSTEM PASSES. THE
INDIVIDUAL GFS ENSEMBLE MEMBERS HAVE YET TO ORGANIZE INTO A
CONSENSUS SURFACE LOW TRACK AT THIS POINT...SHOWCASING THE
DIFFERENCES WITH RESPECT TO THE DEGREE AND TIMING OF THE POLAR AND
SUBTROPICAL JETS PHASING.

AT THIS POINT...THE FORECAST TRACK IS IN A FAIRLY IDEAL LOCATION
FOR SNOW TO BE A PREDOMINANT PRECIP TYPE FOR MOST OF THE REGION.
AS MENTIONED ON TUESDAY MORNING HOWEVER...THE OVERALL HANDLING OF
LOW LEVEL WARM INTRUSIONS THIS WINTER BY MODELS HAVE BEEN
PROBLEMATIC AND TRACK OF THE 850MB LOW ACROSS CENTRAL INDIANA ON
THE BULK OF THE EXTENDED GUIDANCE DOES NOTHING TO QUELL THAT
CONCERN AT THIS TIME. WITH THIS STORM STILL 4-5 DAYS OUT...IT REMAINS
PREMATURE TO SPECULATE ON DETAILS UNTIL A GREATER MODEL CONSENSUS
CAN BE ACHIEVED.

THE MAIN TAKEAWAY AT THIS EARLY STAGE IS THAT CONFIDENCE IS
GROWING IN A WINTER STORM TO IMPACT THE REGION LATE SATURDAY NIGHT
THROUGH EARLY MONDAY. WILL CARRY MAINLY SNOW OVER THE NORTHERN
HALF OF THE FORECAST AREA WITH A RAIN/SNOW MIX ON SUNDAY ACROSS
SOUTHERN COUNTIES. SHOULD SNOW END UP AS THE PREDOMINANT PRECIP
TYPE...POTENTIAL EXISTS FOR SEVERAL INCHES OF ACCUMULATION. STAY
TUNED.

MUCH COLDER AIR WILL BE DRAWN SOUTH INTO THE REGION FOR EARLY NEXT
WEEK BEHIND THIS SYSTEM WITH POTENTIAL FOR COLDEST TEMPS IN ABOUT
3 WEEKS WITH HIGHS STRUGGLING TO GET OUT OF THE TEENS IN SOME
LOCATIONS MONDAY AND TUESDAY. COULD SEE LOWS NEAR OR JUST BELOW
ZERO IN SPOTS TUESDAY MORNING.

&&

.AVIATION /DISCUSSION FOR THE 280600Z TAFS/...
ISSUED AT 1137 PM EST TUE JAN 27 2015

NO SIGNIFICANT CLOUD COVER...UNRESTRICTED VISIBILITY EXPECTED AT THE
TAF SITES THROUGH 281800Z.

LIGHT SURFACE WINDS OVERNIGHT EXPECTED TO BECOME 140-160 DEGREES AT
7-10 KTS BY MIDDAY WEDNESDAY.

&&

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

&&

$$

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

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