394
FXUS63 KIWX 170813
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
413 AM EDT FRI APR 17 2026
KEY MESSAGES
- AREAS OF FOG THIS MORNING, MANY AREAS WILL BECOME DENSE
ESPECIALLY NEAR LAKE MICHIGAN.
- UNSEASONABLY WARM ON FRIDAY WITH HIGHS NEAR 80 DEGREES.
- A ROUND OF SHOWERS AND THUNDERSTORMS TRACK THROUGH FRIDAY NIGHT
INTO SATURDAY MORNING. A FEW STORMS COULD BECOME SEVERE WITH
DAMAGING WINDS AS THE PRIMARY THREAT.
- COOLER AIR ARRIVES SATURDAY NIGHT INTO EARLY NEXT WEEK. THIS
MAY BRING FROST AND FREEZE CONCERNS, ESPECIALLY EARLY MONDAY
MORNING.
DISCUSSION
ISSUED AT 334 AM EDT FRI APR 17 2026
MARINE AIR FROM LAKE MICHIGAN AND A STILL VERY MOIST SURFACE DUE
TO RECENT RAINS TRAPPED BENEATH AN INVERSION WITH DECENT RADIATIONAL
COOLING CONDITIONS WITH THE CLEARING SKIES HAS ALLOWED FOR AREAS
OF FOG TO BEGIN ENVELOPING THE AREA. MANY LOCATIONS ALREADY AS
OF 07Z HAVE BEEN REPORTING 1/4 MILE OR LESS. A DENSE FOG
ADVISORY IS IN PLACE THROUGH 8 AM EDT THIS MORNING TO ADDRESS
THIS HAZARD. THERE WAS A BIT OF UNCERTAINTY AS TO HOW FAR SOUTH
IN THE CWA THIS WOULD SPREAD BUT PATCHES OF DENSE FOG WILL BE
LIKELY IN ALL AREAS SO OPTED TO INCLUDE THE ENTIRE CWA UNDER THE
ADVISORY OUT OF AN ABUNDANCE OF CAUTION ESPECIALLY WITH THE
THICKER FOG DURING THE MORNING COMMUTE. IF TRAVELLING THIS
MORNING, SLOW DOWN AND ALLOW FOR GREATER FOLLOWING AND STOPPING
DISTANCES.
AFTER 8 AM OR SO DIURNAL WARMING WILL BEGIN AND START TO ALLOW
FOR WINDS TO MIX DOWN AND HELP TO CLEAR OUT THE FOG FOR MOST
AREAS, HOWEVER LOCATIONS NEAR LAKE MICHIGAN MAY TAKE A BIT
LONGER TO MIX OUT.
THE FOCUS THEN TURNS TO THE APPROACHING COLD FRONT FROM THE WEST
ASSOCIATED WITH A SURFACE LOW MOVING THROUGH IOWA INTO SOUTH
CENTRAL WI LATER TODAY. AHEAD OF THE COLD FRONT, WILL BE MUCH
ABOVE NORMAL TEMPERATURES WITH HIGHS ACROSS NORTHERN IN IN THE
UPPER 70S TO LOW 80S AND SURFACE DEW POINTS IN THE UPPER 50S TO
LOW 60S. AROUND 1500 J/KG OF MUCAPE WILL BE AVAILABLE AND BULK
SHEAR VALUES AROUND 35 TO 45 KTS. WITH THE EXPECTED LINEAR
CONVECTIVE LINE PUSHING INTO THE CWA AROUND 11 PM EDT TONIGHT A
FEW POCKETS OF HELICITY WITH VALUES AROUND 200 TO 300 M2/S2
AHEAD OF THE FRONT MAY REMAIN AND ALLOW FOR A FEW TORNADOES
ALONG WITH THE MAIN WIND THREAT BUT WITH THE LESS THAN IDEAL
DIURNAL TIMING MAY LACK THE BETTER SURFACE INSTABILITY WHICH
WILL MINIMIZE THE TORNADO THREAT. WILL NEED TO MONITOR THIS
CAREFULLY LATER TODAY TO GET A BETTER IDEA OF THE ACTUAL
ENVIRONMENTAL INGREDIENTS PRESENT. WITH THE FRONT MOVING THROUGH
OVERNIGHT INTO SATURDAY MORNING THE REMAINING ACTIVITY WILL MOVE
EASTERLY THROUGH THE REST OF THE CWA AND WOULD EXPECT THE
ACTIVITY TO BE ON THE DECREASE INTO THE MORNING HOURS AS THE
STORMS LIKELY BECOME MORE COLD POOL DOMINANT. WILL NEED TO
MONITOR FOR SOME NUISANCE TYPE FLOODING POSSIBLE WITH THE VERY
WET SURFACE STILL IN PLACE AND ANY ADDITIONAL RAINFALL WILL BE
QUICK TO POOL AND POND.
A DRIER PATTER ARRIVES THIS WEEKEND ALONG WITH COOLER
TEMPERATURES (HIGHS IN THE UPPER 40S TO LOW 50S) INTO THE
BEGINNING OF NEXT WEEK. WILL NEED TO MONITOR FOR THE POTENTIAL
FOR SOME FROST AND EVEN FREEZE CONDITIONS ESPECIALLY MONDAY
MORNING WITH LOWS ON SUNDAY MORNING IN THE 30S AND COLDER YET ON
MONDAY WITH LOWS IN THE UPPER 20S TO LOW 30S. BY TUESDAY, BROAD
UPPER LEVEL RIDGING OVER THE CENTRAL CONUS WILL BEGIN PUSHING
EASTWARD INTO THE REGION AND WE WILL SEE A WARMING TREND RETURN
WITH HIGHS ON TUESDAY IN THE UPPER 60S TO LOW 70S. HIGHS IN THE
70S WILL BE EXPECTED THROUGH THE REST OF NEXT WEEK. A FEW
SHOWERS AND THUNDERSTORMS FOR WEDNESDAY AND AGAIN NEXT FRIDAY.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 125 AM EDT FRI APR 17 2026
VFR CONDITIONS INITIALLY THIS FORECAST PERIOD, HOWEVER WITH AN
INVERSION DEVELOPING TRAPPING MOIST LAKE MI MARINE AIR AND
THE MOIST SURFACE CONDITIONS IN PLACE FROM RECENT RAINFALL, WILL
SEE FOG DEVELOP AND GRADUALLY THICKEN OVERNIGHT AS TEMPERATURES
SLOWLY DROP FOR BOTH TAF SITES. MVFR CONDITIONS WILL BECOME
IFR/MVFR IN REDUCED CIGS/VSBYS WITH VSBYS DROPPING AFTER 05Z
FRI FOR BOTH SITES. IMPROVEMENTS IN VSBYS WILL BEGIN AROUND 12Z
FRI WITH INCREASES IN DIURNAL SOUTHERLY WINDS WHICH WILL
INCREASE MIXING. GUSTS AROUND 20 KTS EXPECTED THROUGH THE
EVENING. AN APPROACHING COLD FRONT FROM THE WEST WILL INCREASE
PRECIPITATION CHANCES IN THUNDERSTORMS IN WHICH A FEW OF THE
STORMS MAY BECOME STRONG TO SEVERE AFTER 00Z SAT AND SPREAD
EASTWARD INTO SATURDAY MORNING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...DENSE FOG ADVISORY UNTIL 8 AM EDT /7 AM CDT/ THIS MORNING FOR
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
OH...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR OHZ001-002-
004-005-015-016-024-025.
MI...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MIZ078>081-
177-277.
MARINE...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR LMZ043-046.
DISCUSSION...ANDERSEN
AVIATION...ANDERSEN
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