Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 160607
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
207 AM EDT TUE SEP 16 2014

.SYNOPSIS...
ISSUED AT 606 PM EDT MON SEP 15 2014

A COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA THIS
EVENING...CONTINUING RAIN SHOWERS THROUGH EARLY TONIGHT. DRY
CONDITIONS WILL RETURN OVERNIGHT BEHIND THE FRONT...WITH A
REINFORCING PUSH OF COOL AIR RESULTING IN CONTINUED BELOW NORMAL
TEMPERATURES THROUGH MID WEEK. LOW TEMPERATURES TONIGHT WILL
RANGE FROM THE MID 40S TO AROUND 50 WITH HIGH TEMPERATURES ON
TUESDAY IN THE LOWER TO MID 60S.

&&

.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 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 159 AM EDT TUE SEP 16 2014

CHALLENGING AVIATION FORECAST FOR THE NEXT 6 TO 9 HOUR PERIOD.
TERMINALS ARE NOW LOCATED WEST OF DEPARTING SURFACE TROUGH WHICH
HAS ALLOWED WINDS TO COME AROUND TO THE NORTH NORTHWEST 5 KNOTS OR
LESS. STRATUS PERSISTS ACROSS MUCH OF THE AREA BEHIND THIS TROUGH
WITH SHALLOW LOW LEVEL MOISTURE REMAINING IN PLACE. SOME PATCHY
AREAS OF CLEARING HAVE ALLOWED FOR LOCALIZED DENSE FOG AND LIFR
CONDITIONS AS EXPERIENCED AT KFWA OVER THE PAST HOUR. IFR AND
POSSIBLY LIFR CONDITIONS CAN BE EXPECTED AT KFWA THROUGH 08Z..AND
HAVE TRENDED KFWA TO IFR AFTER 08Z. SLIGHTLY DRIER LOW LEVEL AIR
IS EXPECTED TO WORK INTO KSBN OVERNIGHT...BUT PATCHY STRATUS OFF
LAKE MICHIGAN SHOULD TEND TO KEEP AT LEAST MVFR CIGS IN PLACE.
EXPECTING IMPROVEMENTS TO VFR BY LATE MORNING...WITH SOME SHORT
TERM MODEL GUIDANCE INDICATING BEST POTENTIAL OF DIURNAL LOW CLOUD
REDEVELOPMENT JUST DOWNWIND OF LAKE MICHIGAN. HOWEVER...WOULD
EXPECT THIS TO BE OF THE VFR VARIETY BY THIS TIME.

&&

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

$$

SYNOPSIS...CEO
SHORT TERM...AGD
LONG TERM...STEINWEDEL
AVIATION...MARSILI


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