Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 161842
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
142 PM EST TUE DEC 16 2014

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

&&

.SYNOPSIS...
ISSUED AT 142 PM EST TUE DEC 16 2014

LOW PRESSURE OVER THE GREAT LAKES WILL DEPART SLOWLY TO THE EAST
TONIGHT AS HIGH PRESSURE OVER THE UPPER MIDWEST BUILDS INTO THE
OHIO VALLEY THROUGH WEDNESDAY AND THURSDAY.

THE HIGH WILL PROVIDE SOME COOLER CANADIAN AIR TO THE
AREA...RESULTING IN COLDER TEMPERATURES THAN THE PAST FEW DAYS.

THE NEXT BEST CHANCE FOR PRECIPITATION WILL BE FRIDAY NIGHT INTO
SATURDAY AS A LOW PRESSURE SYSTEM AND AN ASSOCIATED UPPER LEVEL
WEATHER DISTURBANCE MOVES THROUGH THE SOUTH.

&&

.NEAR TERM /TONIGHT/...

ISSUED AT 142 PM EST TUE DEC 16 2014

SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS LOW PRESSURE OVER
SOUTHERN LAKE MICHIGAN WITH BROAD CYCLONIC FLOW ACROSS INDIANA AND
THE REST OF THE OHIO VALLEY. SATELLITE CONTINUED TO SHOW
EXTENSIVE CLOUDINESS FOUND ACROSS THE REGION WITH CLOUDS
STRETCHING BACK WEST TO MISSOURI...NEBRASKA AND IOWA. TEMPERATURES
ACROSS THE AREA WERE IN THE 40S...HOWEVER COLDER AIR IN THE 30S
WAS FOUND ACROSS NORTHERN ILLINOIS AND HEADED THIS WAY.

MAIN FORECAST CHALLENGE TONIGHT WILL BE CLOUDS AND ANY FREEZING
PRECIPITATION.

FORECAST SOUNDINGS AND TIME HEIGHTS CONTINUE TO SUGGEST TRAPPED
LOWER LEVEL MOISTURE LINGERING ACROSS THE STATE TONIGHT...SHOWING
SATURATION AND HIGH RH THROUGH THE NIGHT. ALOFT THE GFS 290K
ISENTROPIC SURFACE SHOWS GOOD SINKING AND ASSOCIATED DRYING. THUS
IS THIS AN IDEAL SITUATION FOR DRIZZLE. HOWEVER ONGOING COLD AIR
ADVECTION THROUGH THE NIGHT IS EXPECTED TO RESULT IN TEMPERATURES
FALLING BELOW 32F AFTER 06Z. FORECAST SOUNDINGS SHOW LOWER LEVELS
BELOW FREEZING. THUS WE COULD SEE SOME FLURRIES OR FREEZING
DRIZZLE. WILL MENTION THIS IN THE FORECAST...HOWEVER POPS WILL BE
MINIMAL AS CHANCES MEASURABLE PRECIP IS LOW GIVEN THE WEAK FORCING.

AS FOR TEMPS WILL TREND LOWS AT OR SLIGHTLY ABOVE MAVMOS AS
CLOUDS ARE EXPECTED TO LINGER...AS WELL AS WEST WINDS AT 10-15 MPH
PROVIDING MIXING.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...

ISSUED AT 142 PM EST TUE DEC 16 2014

ON WEDNESDAY THE SLOWLY MOVING SURFACE LOW IS EXPECTED TO REACH
SOUTHEAST ONTARIO...AS HIGH PRESSURE BUILDS ACROSS THE MISSISSIPPI
VALLY THROUGH THE CENTER OF THE CONUS. LOWER LEVEL FLOW LOOKS TO
REMAIN CYCLONIC ON WEDNESDAY AND RIDGING REMAINS IN PLACE ALOFT TO
THE WEST. THIS KEEPS INDIANA ON THE LEE SIDE OF THE RIDGE AND
CONFIDENCE IN CLEARING IS LOW. FURTHER SUPPORT IS SEEN THE THE
TIME HEIGHT SECTIONS WHICH CONTINUE TO DISPLAY A THIN LAYER OF
TRAPPED LOWER LEVEL MOISTURE. THUS WILL TREND SKIES TOWARD MOSTLY
CLOUDY ON WEDNESDAY. WILL ALSO TREND TEMPS AT OR BELOW MAVMOS
GIVEN THE EXPECTED CLOUDS AND ONGOING COLD AIR ADVECTION.

BY WEDNESDAY NIGHT THE SURFACE LOW MOVES TO EASTERN NEW ENGLAND
AND HIGH PRESSURE IS FIRMLY ESTABLISHING ITSELF FROM THE UPPER
MIDWEST THROUGH THE OHIO VALLEY TO THE DEEP SOUTH. RIDGING IN THE
MIDDLE LEVEL ARRIVES IN CENTRAL INDIANA AND THE LOWER LEVEL
CYCLONIC FLOW COMES TO AN END. THUS WILL CLEAR SKIES OUT ON
WEDNESDAY NIGHT AS THE HIGH MOVES THROUGH THE AREA. GIVEN THE
IDEAL RADIATIONAL COOLING SET UP WITH CLEAR SKIES AND LIGHT WINDS
WILL TREND LOWS AT OR BELOW MAVMOS.

THURSDAY THROUGH FRIDAY CONTINUE TO LOOK DRY AT THIS TIME WITH
INCREASING CLOUDS THROUGH THE PERIOD. ALOFT A WEAK SHORT WAVE WILL
STREAM THROUGH THE OHIO AND TENNESSEE RIVER VALLEYS ON THURSDAY AND
EXIT ON FRIDAY...BUT NO MOISTURE APPEARS AVAILABLE AS SURFACE
HIGH PRESSURE ACROSS THE AREA KEEPS DRY CONTINENTAL AIR IN PLACE.
SOME WARM AIR ADVECTION IS EXPECTED TO BEGIN ON THE BACKSIDE OF
THE HIGH ON THURSDAY. THE GFS ALSO SUGGESTS WEAK LOW PRESSURE
PUSHING INTO OKLAHOMA AND NORTHERN TEXAS. THE 290K GFS ISENTROPIC
SURFACE REVEALS GOOD LIFT ACROSS OK AND TX...BUT THIS LIFT DOES
RESULT IN THE ARRIVAL OF SOME HIGH CLOUDS ACROSS THE OHIO VALLEY.
FORECAST SOUNDINGS SHOW MID AND HIGHER LEVEL SATURATION BEGINNING
THURSDAY AS THIS WEAK LOW BEGINS ITS TREK THROUGH THE DEEP SOUTH.
OVERALL MOISTURE REMAINS MINIMAL AS SURFACE HIGH PRESSURE REMAINS
IN PLACE OVER INDIANA. THUS WILL JUST TREND TOWARD INCREASING
CLOUDS ON THE THURSDAY THROUGH FRIDAY PERIOD. AS FOR TEMPS WILL
TREND HIGHS CLOSE TO MAV/MEX VALUES GIVEN THE RETURN OF WARM AIR
ADVECTION AND CLOUDS. WILL TREND LOWS THURSDAY NIGHT WARMER GIVEN
THE EXPECTED CLOUDS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
ISSUED AT 332 AM EST TUE DEC 16 2014

MAIN FOCUS FOR THE EXTENDED WILL BE SNOW POTENTIAL ALONG WITH TIMING
AND TEMPERATURES.

DETERMINISTIC MODELS ARE NOW ATTEMPTING TO CONVERGE ON A SIMILAR
SOLUTION...ALTHOUGH THE ECMWF LOOKS A BIT SLOW BRINGING QPF ACROSS
THE FORECAST AREA. THE 00Z GEM AND GFS BOTH HAVE QPF ACROSS OUR
SOUTHERN COUNTIES FRIDAY NIGHT AS ENERGY LIFTS NORTHEAST FROM THE
LOWER MISSISSIPPI VALLEY AHEAD OF AN APPROACHING UPPER TROUGH OVER
THE SOUTHERN PLAINS. STILL...THIS MARKS A CHANGE AS PREVIOUS MODEL
RUNS SUGGESTING THE PRECIPITATION WOULD BE FURTHER NORTH AND ENVELOP
OUR ENTIRE FORECAST AREA. FURTHER SOUTHERLY TRACK SUGGESTS AREAS
NEAR AND NORTH OF INTERSTATE 70 SHOULD BE DRY FRIDAY NIGHT. AS THE
UPPER TROUGH PASSES THROUGH ON SATURDAY...PRECIPITATION SHOULD
SPREAD FAR ENOUGH NORTH TO KEEP CHANCE POPS IN ALL OF CENTRAL
INDIANA. FINALLY...SYSTEM TO DAMPEN SATURDAY NIGHT AS IT MOVES EAST
AND BECOMES ABSORBED IN NORTHERN STREAM LOW OVER THE UPPER MIDWEST
AND ONTARIO. THE REST OF THE EXTENDED LOOKS TO BE DRY AS SURFACE
HIGH PRESSURE SETTLES SOUTHEAST OVER THE GREAT LAKES AND OHIO
VALLEY. PRECIPITATION TYPE SHOULD BE MOSTLY SNOW BASED ON MODEL
SOUNDINGS AND CRITICAL THICKNESSES...ALTHOUGH WOULD NOT RULE OUT
SOME SLEET OR FREEZING RAIN AT THE ONSET FRIDAY NIGHT...FAR SOUTH AS
WARM LAYER ALOFT MOVES INTO THAT AREA. WILL KEEP IT JUST SNOW FOR
NOW...HOWEVER AND TAKE ANOTHER LOOK AT IT AFTER SUBSEQUENT MODEL
RUNS.

NOT EXPECTING MUCH ACCUMULATION WITH THIS SYSTEM BASED ON THE
CURRENT TRACK CONSENSUS. EVEN IN THE SOUTHERN SECTIONS...IT DOES NOT
LOOK LIKE MORE THAN AN INCH AT THIS POINT.

WITH THE SYSTEM TRENDING FURTHER SOUTH PER THE MORE CONSISTENT ECMWF
AND ITS ENSEMBLE MEANS...PREFER THE COOLER GFS ENSEMBLE MEMBERS
ALONG WITH THE ECMWF ENSEMBLE MEANS WHICH MATCH NICELY WITH THE 00Z
REGIONAL BLEND.

&&

.AVIATION /DISCUSSION FOR 161800Z TAF ISSUANCE/...
ISSUED AT 1218 PM EST TUE DEC 16 2014

IFR CONDITIONS CONTINUE THIS AFTERNOON...GRADUAL IMPROVEMENTS IN
CEILINGS TO MVFR BY WEDNESDAY MORNING.

LOW PRESSURE SLOWLY TRACKING EAST ACROSS THE GREAT LAKES THIS
AFTERNOON WITH ABUNDANT LOW LEVEL MOISTURE AND LIGHT SHOWERS
ACCOMPANYING IT. CEILINGS HAVE BEEN HOVERING BETWEEN 500 AND
1500FT FOR THE MOST PART AS THE NEAR SURFACE LAYER REMAINS
SATURATED. EXPECT SCATTERED LIGHT PRECIP TO LINGER THROUGH THE
AFTERNOON WITH IFR CONDITIONS PERSISTING. WINDS WILL VEER TO
WESTERLY AND GUST TO 20-25KTS WITH THE PASSAGE OF A WEAK BOUNDARY
THIS AFTERNOON AS WELL.

DRIER AIR WILL FILTER INTO THE REGION THIS EVENING BUT MODEL
SOUNDINGS SHOW THE CONTINUED PRESENCE OF A SHALLOW INVERSION WHICH
WILL MAINTAIN THE STRATUS DECK BETWEEN 1000-2000FT. FLURRIES ARE
POSSIBLE THIS EVENING AS DEEP MOISTURE IS LOST AND THE AIRMASS
COOLS. COULD EVEN SEE A BRIEF PERIOD WITH FREEZING DRIZZLE AFTER
06Z AS FURTHER DRYING OCCURS ABOVE THE INVERSION. NOT MAKING A
MENTION OF FREEZING DRIZZLE AT THIS POINT...BUT WILL BE SOMETHING
TO MONITOR. MVFR STRATUS WILL REMAIN ON WEDNESDAY MORNING DESPITE
HIGH PRESSURE BUILDING IN. GUSTS WILL DIMINISH THIS EVENING...WITH
W/NW WINDS PERSISTING AT 10-15KTS FOR MUCH OF THE REST OF THE
FORECAST PERIOD.


&&

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

$$

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

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