Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 282238
AFDIND

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

.UPDATE...

THE AVIATION SECTION HAS 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 NIGHT THROUGH WEDNESDAY/...
ISSUED AT 241 PM EST WED JAN 28 2015

BIG STORY FOR THE EXTENDED CONTINUES TO BE LATE WEEKEND SNOW
POTENTIAL. RUN TO RUN...MODEL TO MODEL AND INDIVIDUAL ENSEMBLE
MEMBER CONSISTENCY CONTINUES TO BE LACKING. THAT BEING SAID...SNOW
ACCUMULATION STILL LOOKS LIKE A GOOD BET SATURDAY NIGHT THROUGH
SUNDAY NIGHT...ESPECIALLY NORTH OF BLOOMINGTON. IT APPEARS TO BE
MORE OF A MATTER OF MINOR SNOWFALL VERSUS SEVERAL INCH SNOWFALL.

THE MAIN HIGHLIGHT OF THE 12Z MORNING RUN WAS THE OPERATIONAL GFS
NOW BEING MUCH WEAKER WITH ITS SURFACE LOW DUE TO LESS PHASING OF
THE NORTHERN STREAM JET WITH AN UPPER SYSTEM OVER THE SOUTHWESTERN
STATES. THIS IS RESULTING IN LESS 24 HOUR HOUR SNOW ACCUMULATION
AMOUNTS FROM THE GFS.

LOOKING AT BUFKIT 12Z MODEL PARTIAL THICKNESSES AND
SOUNDINGS...CONFIDENCE IS PRETTY GOOD THAT THE PRECIPITATION SHOULD
BE MOSTLY SNOW FOR THIS LOOMING SYSTEM EXCEPT THAT THE SNOW COULD
POSSIBLY MIX IN WITH RAIN SOUTH OF BLOOMINGTON BRIEFLY ON SUNDAY.
LESS CONFIDENT IN START TIME...BUT SATURDAY NIGHT CONTINUES TO LOOK
OK FOR NOW PER THE REGIONAL BLEND...CONSIDERING MODEL
UNCERTAINTY.

HIGH PRESSURE BEHIND THIS SYSTEM SHOULD BRING IN MUCH COLDER AIR
ALONG WITH DRY WEATHER. HOWEVER...ANOTHER SYSTEM COULD BRING MORE
SNOW TO THE AREA MIDWEEK. WILL MOSTLY ACCEPT REGIONAL BLEND AS MODEL
AND RUN TO RUN DIFFERENCES DO NOT LEND A LOT OF CONFIDENCE IN
DEPARTING FROM THOSE NUMBERS.

&&

.AVIATION /DISCUSSION FOR THE 290000Z TAFS/...
ISSUED AT 537 PM EST WED JAN 28 2015

SUSTAINED WARM/MOIST ADVECTION TONIGHT SHOULD ALLOW FOR A GRADUAL
LOWERING OF THE CEILINGS WITH TIME...BUT IT APPEARS CEILINGS WILL
PROBABLY REMAIN AT OR ABOVE 050 FOR MOST OF THE NIGHT. MODEL
GUIDANCE SUGGESTS MVFR CEILINGS 015-025 MAY DEVELOP TOWARDS SUNRISE
ON THURSDAY.

SPOTTY LIGHT RAIN MAY DEVELOP IN THE VICINITY OF THE TAF SITES AFTER
ABOUT 290900Z...BUT POTENTIAL FOR DIRECT IMPACTS TOO LOW TO MENTION
IN THE FORECAST AT THIS TIME.

MODEL DATA SUGGEST A LOW LEVEL JET AROUND 50 KTS MAY MOVE INTO THE
AREA AFTER 290600Z. POTENTIAL FOR LOW LEVEL WIND SHEAR EXISTS LATE
TONIGHT...BUT THINK BOUNDARY LAYER WILL REMAIN AT LEAST PARTIALLY
MIXED...SO THE DEVELOPMENT OF A STRONG NOCTURNAL INVERSION DOUBTFUL.

SURFACE WINDS GENERALLY 150-170 DEGREES AT 10-14 KTS FOR MOST OF THE
NIGHT. MAY SEE A FEW LOCAL SURFACE GUSTS 20-25 KTS AFTER 290600Z
WHERE THE LOW LEVEL JET CAN PARTIALLY MIX DOWN.

&&

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

&&

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM...KOCH
AVIATION...JAS

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