Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 281826
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
126 PM EST WED JAN 28 2015

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

&&

.SYNOPSIS...
ISSUED AT 126 PM EST WED JAN 28 2015

HIGH PRESSURE OVER OHIO WILL DEPART QUICKLY TO THE EAST TONIGHT AS
A LOW PRESSURE SYSTEM OVER THE DAKOTAS PUSHES TOWARD INDIANA FOR
THURSDAY. AS THE LOW PUSHES ACROSS INDIANA ON THURSDAY...CLOUDS
ALONG WITH A FEW LIGHT RAIN SHOWERS ARE EXPECTED. AN ASSOCIATED
COLD FRONT WILL TRAIL THE LOW...ALLOWING A RETURN OF COLDER
TEMPERATURES AS WE FINISH THE WORK WEEK.

COLD HIGH PRESSURE IS EXPECTED ACROSS THE REGION ON FRIDAY AND
SATURDAY...ALONG WITH LINGERING CLOUDS AND NEARLY SEASONABLE COLD TEMPERATURES.

ANOTHER COLD FRONT AND LOW PRESSURE SYSTEM LOOKS TO PASS ACROSS
INDIANA ON LATE SATURDAY NIGHT INTO SUNDAY...BRINGING CHANCES FOR
ACCUMULATIONS OF SNOW. IT IS TOO SOON TO DETERMINE SNOWFALL
AMOUNTS.

DRY WEATHER IS EXPECTED TO RETURN EARLY NEXT WEEK AS ANOTHER
ARCTIC HIGH PRESSURE SYSTEM BUILDS ACROSS THE OHIO VALLEY.

&&

.NEAR TERM /TONIGHT/...

ISSUED AT 126 PM EST WED JAN 28 2015

SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS HIGH PRESSURE IN PLACE
OVER OHIO AND LOW PRESSURE OVER SOUTH DAKOTA AND NEBRASKA.
SOUTHEAST SURFACE FLOW WAS IN PLACE ACROSS INDIANA...WITH DRY DEW
POINT TEMPS IN THE TEENS. SKIES WERE MOSTLY SUNNY...AS VISIBLE
PICTURES SHOW ONLY SOME HIGH CIRRUS TRYING TO INVADE FROM THE
UPPER MIDWEST...BUT FAILING DUE TO SUBSIDENCE.

MAIN FORECAST CHALLENGE TODAY TONIGHT WILL BE TEMPS. RIDGING ALOFT
IS EXPECTED TO DEPART TO THE EAST THIS EVENING AS THE GFS AND NAM
BOTH DEPICT A MODERATE SHORT WAVE TO PUSH INTO INDIANA SHORTLY
AFTER 12Z THURSDAY. 295K GFS ISENTROPIC SURFACE SHOWS GOOD UPGLIDE
AHEAD OF THIS SYSTEM...MAINLY ARRIVING BETWEEN 06Z AND 12Z.
SPECIFIC HUMIDITIES APPEAR TO HOLDING IN THE 4-5 G/KG AREA DURING
THIS PERIOD. TIME HEIGHT SECTIONS FAIL SHOW SHOW DEEP MOISTURE
ARRIVAL...AND MAINLY SHOW LIFT AMID A DRY COLUMN. BEST MOISTURE
LOOKS TO ARRIVE TOWARD 12Z...IN THE FORM OF MAINLY LOWER CLOUDS.
THUS WILL AIM FOR A LIGHT PRECIP EVENT...WITH HIGHEST POPS ACROSS
THE WESTERN PARTS OF THE STATE TONIGHT.

GOOD WARM AIR ADVECTION IS ONGOING THROUGH THE NIGHT AND A NON-
DIURNAL TEMPERATURE RISE IS EXPECTED. IN FACT FORECAST SOUNDING
REVEAL LOWEST LEVELS WELL ABOVE FREEZING...THUS ANY PRECIP THAT
FALLS WILL BE RAIN. WITH THE ARRIVAL OF CLOUDS EXPECTED LATE
OVERNIGHT...EXPECT LOW TEMPS TONIGHT TO BE REACHED DURING THE
EVENING HOURS...PROBABLY IN THE FIRST 3-4 HOURS AFTER SUNSET. WILL
TREND LOWS TOWARD EXPECTED TEMPS NEAR 02-03Z...AND TREND WARMER
THROUGH THE NIGHT.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...

ISSUED AT 126 PM EST WED JAN 28 2015

MAIN FORECAST CHALLENGE DURING THIS PERIOD WILL BE POPS ON
THURSDAY. AS PREVIOUSLY MENTIONED...GFS AND NAM SUGGEST A MODERATE
SHORT WAVE PUSHING ACROSS INDIANA ION THURSDAY. BEST MOISTURE
LOOKS TO ARRIVE NEAR 12Z AND LINGER ACROSS THE AREA THROUGH THE
DAY ON THURSDAY. HOWEVER...BEST FORCING IS ARRIVING EARLIER AHEAD
OF THE SYSTEM IN THE FORM OF ISENTROPIC LIFT. BY 18Z...THE MODELS
SUGGEST THAT THE ISENTROPIC LIFT IS LOST AS THE BULK OF THE SHORT
WAVE FORCING IS EXPECTED TO BE WELL EAST OF OUR FORECAST AREA.
FORECAST SOUNDINGS SHOW SATURATED LOWER LEVEL THROUGH THE DAY WITH
THE LOWEST PARTS OF THE COLUMN HOLDING ABOVE FREEZING UNTIL LATE
IN THE AFTERNOON WHEN THE BULK OF THE MOISTURE WILL BE GONE.

THUS WILL TREND TOWARD A CLOUDY SKY THROUGH THE DAY WITH HIGHEST
POPS IN THE MORNING HOURS...TRENDING TOWARD A DRY FORECAST BY
AFTERNOON. A FLURRY OR SNOWFLAKE CANNOT BE RULED OUT LATE IN THE
AFTERNOON...BUT WITH LIMITED FORCING EXPECTED...MINIMAL TO NO
IMPACT IS EXPECTED. WITH PLENTY OF CLOUDS AND COLD AIR ADVECTION
EXPECTED TO DOMINATE THE AFTERNOON HOURS WILL TREND COOLER THAN
MAVMOS HIGHS. FURTHERMORE AS COLD AIR ADVECTION BEGINS IN THE
AFTERNOON IN THE WAKE OF THE COLD FRONT...TEMPS ARE EXPECTED TO
FALL AND HIGHS WILL PROBABLY BE REACHED IN THE LATE MORNING HOURS
WITH A NEARLY STEADY STATE TEMPERATURE.

NAM AND GFS SUGGEST QUICK NORTHWEST FLOW IN PLACE ALOFT ON
THURSDAY NIGHT THROUGH SATURDAY. TIME HEIGHT SECTIONS SUGGEST
TRAPPED LOWER LEVEL MOISTURE AMID COLD AIR ADVECTION ON THURSDAY
NIGHT AND FRIDAY. FURTHERMORE FORECAST SOUNDINGS SHOW EARLY
CONVECTIVE TEMPERATURES ON FRIDAY IN THE MIDDLE 20S. THUS WILL
TREND TOWARD A CLOUDY SKY ALONG WITH THURSDAY NIGHT LOWS NEAR
MAVMOS AND FRIDAY HIGHS AT OR BELOW MAVMOS.

BY FRIDAY NIGHT SURFACE HIGH PRESSURE AND RIDGING IN PLACE OVER
INDIANA SHOULD ALLOW SKIES TO BECOME A LEAST PARTLY CLOUDY...WITH
LIGHT WINDS. FORECAST SOUNDINGS ALSO INDICATE A DRY COLUMN AMID
SUBSIDENCE. THUS WILL TREND LOWS AT OR BELOW MAVMOS.

WARM AIR ADVECTION BEGIN ON SATURDAY AS RETURN FLOW ON THE
BACKSIDE OF THE HIGH BRINGS SOUTHERLY WINDS TO CENTRAL INDIANA.
FORECAST SOUNDING HERE SUGGEST THE ARRIVAL OF MID CLOUD...TYPICAL
OF WARM AIR ADVECTION. THUS WILL TREND TOWARD AN INCREASING
CLOUDINESS FORECAST WITH HIGHS AT OR ABOVE MEXMOS.



&&

.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 281800Z TAF ISSUANCE/...
ISSUED AT 1150 AM EST WED JAN 28 2015

VFR CONDITIONS WITH HIGH AND MID CLOUDS EXPECTED THROUGH THIS
EVENING. HOWEVER...RAIN AND NEAR MVFR STRATOCU IS POSSIBLE AFTER 08Z
AND THROUGHOUT THE DAY ON THURSDAY AS A COLD FRONT MOVES THROUGH THE
AREA FROM THE WEST. THE FRONT SHOULD REACH LAF AND HUF AROUND 14Z
THURSDAY AND IND AND BMG AROUND 16Z.

WINDS THIS AFTERNOON WILL BE FROM THE SOUTHEAST AND SOUTH TO AROUND
15 KNOTS. THEN...WINDS WILL BE PICK UP LATE EVENING FROM THE SOUTH
WITH GUSTS TO 20 KNOTS OR MORE. FINALLY...WITH THE FRONTAL
PASSAGE...WINDS WILL SHIFT TO THE WEST AND NORTHWEST TO 15 KNOTS AND
GUSTS TO 25 KNOTS.


&&

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

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM...RYAN
AVIATION...MK

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