Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 151936
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
336 PM EDT MON SEP 15 2014

.SYNOPSIS...
ISSUED AT 1046 AM EDT MON SEP 15 2014

A COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA TODAY...BRINGING
RAIN SHOWERS AND ISOLATED THUNDERSTORMS TO THE REGION. DRY
CONDITIONS WILL RETURN LATER THIS EVENING BEHIND THE FRONT...WITH
A REINFORCING PUSH OF COOL AIR RESULTING IN CONTINUED BELOW NORMAL
TEMPERATURES THROUGH MID WEEK. HIGH TEMPERATURES THIS AFTERNOON
WILL REACH INTO THE 60S. LOW TEMPERATURES TONIGHT WILL RANGE FROM
THE MID 40S TO AROUND 50.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 335 PM EDT MON SEP 15 2014

AFTERNOON WATER VAPOR IMAGERY SHOWS WELL DEFINED SHORTWAVE CURRENTLY
APPROACHING THE SOUTHERN GREAT LAKES...EMBEDDED IN BROAD TROUGHING
OVER EASTERN NOAM. FOCUSED PV CENTROID...RESPONSIBLE FOR RAIN
CURRENTLY OVER SOUTHERN WISCONSIN...WILL SWING JUST NORTH OF OUR CWA
LATER THIS EVENING AND ASSOCIATED QG FORCING WILL LEAD TO AN
EXPANSION OF RAIN SHOWERS ACROSS OUR AREA. ELEVATED FRONTAL ZONE
WILL BE SUPPORTED BY DECENT MIDLEVEL HEIGHT FALLS BUT ALSO RIGHT
ENTRANCE DYNAMICS OF ATTENDANT 100+ KT UPPER LEVEL JET STREAK. I-80
CORRIDOR HAS BEEN LARGELY SPLIT SO FAR TODAY BY BETTER 300K
ISENTROPIC ASCENT TO THE SOUTH AND CVA FORCING TO THE NORTH. SOME
CONCERN THAT WILL CONTINUE TO BE THE CASE THROUGH THE EVENING BUT
ALL OF THE LATEST HI-RES GUIDANCE INDICATES THIS AREA WILL FILL IN
BY THIS EVENING AS MID/UPPER LEVEL WAVE AND ASSOCIATED 700-600MB
FGEN APPROACH. 16Z RUN OF THE HRRR FINALLY SEEMED TO GET A DECENT
HANDLE ON EVOLVING PRECIP AND SUGGESTS LINE OF SHOWERS CURRENTLY IN
NORTHEAST ILLINOIS WILL EXPAND EASTWARD AS TROUGH AXIS APPROACHES.
BETTER MOISTURE IS BEING ROBBED BY CONVECTION TO OUR SOUTH THOUGH
AND EXPECT JUST OCCASIONAL LIGHT RAIN SHOWERS THROUGH THE EVENING.
PRECIP SHOULD EXIT QUICKLY WITH DRY CONDITIONS THEN PERSISTING
THROUGH TOMORROW.

DESPITE EXITING PRECIP...SKIES WILL LIKELY NOT BEGIN TO CLEAR UNTIL
LATE TOMORROW MORNING GIVEN NOCTURNAL BOUNDARY LAYER COOLING WITH
LINGERING LOW LEVEL MOISTURE AND A DEVELOPING INVERSION. SOME
POTENTIAL FOR PATCHY FOG BUT FORECAST SOUNDINGS...AND PERSISTENT
GRADIENT WIND...SUGGEST BETTER POTENTIAL FOR LOW STRATUS. ADDED
PATCHY FOG MENTION TO OUR WESTERN COUNTIES BASED ON MORE SHALLOW
MOISTURE AND LIGHTER WINDS BUT WILL HOLD OFF IN THE EAST FOR NOW AND
MONITOR TRENDS OVERNIGHT. THESE CONDITIONS SHOULD ALSO KEEP A BIT OF
A FLOOR ON OVERNIGHT LOWS. EXPECTING VALUES GENERALLY IN THE MID TO
UPPER 40S BASED ON LATEST RAW AND MOS GUIDANCE. APPROACHING AIRMASS
IS NOT MUCH COLDER THAN WHAT IS CURRENTLY IN PLACE AND HIGH TEMPS
TOMORROW SHOULD BE VERY CLOSE TO TODAY`S VALUES. DID INCREASE SKY
COVER THOUGH...BASED ON EXPECTATION FOR A SLOW EROSION OF MORNING
STRATOCU.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 335 PM EDT MON SEP 15 2014

PATTERN MID-LATE WEEK WILL BE CHARACTERIZED BY COOL NORTHWEST FLOW
ALOFT AND RIDGING AT THE SFC. THERE WILL LIKELY BE A FEW WEAK WAVES
EMBEDDED IN THIS FLOW. HOWEVER...ANY SUCH FEATURE WILL STRUGGLE TO
PRODUCE ANYTHING MORE THAN SCATTERED CLOUDS GIVEN DEARTH OF MOISTURE
AND STABLE MID LEVELS.

BRIEF RELAXATION OF EASTERN CONUS TROUGHING WITH WINDS VEERING
SOUTHWESTERLY SHOULD ALLOW HIGHS TO WARM NEAR OR JUST ABOVE SEASONAL
AVERAGES BY SATURDAY. ASSOCIATED WARM ADVECTION PRECIP ALONG A
DEVELOPING WARM FRONT MAY CLIP FAR NORTHERN ZONES LATER FRIDAY
NIGHT-SATURDAY WHERE LOW CHC POPS WERE RETAINED.

MODELS HAVE REMAINED CONSISTENT IN TRANSLATING AN UPPER TROUGH/CDFNT
EAST THROUGH THE AREA SATURDAY NIGHT INTO SUNDAY MORNING. POSSIBLE
ABSORPTION OF HURRICANE ODILE REMNANT MOISTURE INTO THIS FEATURE MAY
AID IN BRINGING SOME HEAVIER RAINFALL/ISO THUNDER TO THE AREA DURING
THIS TIME. OTHERWISE...DRIER/COOLER AIR EXPECTED IN WAKE OF THIS
SYSTEM LATER SUNDAY-MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 145 PM EDT MON SEP 15 2014

SHORTWAVE TROUGH IS CURRENTLY APPROACHING THE AREA AND EXPECT
SHOWERS TO GRADUALLY EXPAND ACROSS NORTHERN INDIANA BY LATE THIS
AFTERNOON. UPSTREAM OBSERVATIONS SUGGEST IT WILL TAKE SOME TIME
FOR BETTER LOW LEVEL MOISTURE...AND MVFR CONDITIONS...TO DEVELOP.
PUSHED BACK THE TIMING A BIT BUT FORECAST SOUNDINGS STILL SUPPORT
FUEL ALTERNATE CONDITIONS AS THE RAIN MOVES THROUGH THIS EVENING.
PATCHY FOG WILL ALSO BE POSSIBLE LATE TONIGHT GIVEN RESIDUAL LOW
LEVEL MOISTURE...DEVELOPING INVERSION...AND LIGHT SURFACE WINDS.
CONFIDENCE IS STILL LOW HOWEVER AND A STRATUS DECK CANNOT BE
RULED OUT. INTRODUCED MVFR CONDITIONS FOR KFWA BASED ON MOS
GUIDANCE AND BETTER MOISTURE SEEN IN FORECAST SOUNDINGS BUT LEFT
KSBN VFR FOR NOW.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...MCD
SHORT TERM...AGD
LONG TERM...STEINWEDEL
AVIATION...AGD


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