768
FXUS63 KIWX 201843
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
143 PM EST SAT DEC 20 2025
KEY MESSAGES
- BREEZY CONDITIONS PERSIST THROUGH THIS EVENING.
- SHARPLY COLDER OVERNIGHT THROUGH SUNDAY WITH MORNING LOWS NEAR
20.
- TRENDING WARMER MONDAY THROUGH AT LEAST FRIDAY WITH CHANCES
FOR RAIN.
DISCUSSION
ISSUED AT 140 PM EST SAT DEC 20 2025
RIDGING OVER THE EASTERN US AND ASSOCIATED WARM AIR ADVECTION HAS
PROPELLED HIGH TEMPERATURES WELL INTO THE 30S AND INTO THE 40S AS OF
THIS MIDDAY WRITING. WIND GUSTS HAVE BEEN STEADILY INCREASING BUT
LOW-LEVEL MIXING HAS BEEN LIMITED DUE TO MOSTLY CLOUDY SKIES. A COLD
FRONT IS ARRIVING OVER NORTHWEST ILLINOIS AND PRESENTS ONE MORE
OPPORTUNITY FOR BREEZY CONDITIONS AS WIND BECOME NORTHWESTERLY AFTER
SUNSET. COLD AIR ADVECTION BENEATH MOSTLY CLEAR SKIES WILL ALLOW
TEMPERATURES TO FALL INTO THE 20S OVERNIGHT. CANNOT RULE OUT A BRIEF
PERIOD OF LIGHT LAKE EFFECT SNOW FOR BERRIEN COUNTY LATE TONIGHT
AMID STIFF WESTERLY FLOW. FORECAST SOUNDINGS REVEAL POOR SATURATION
AND EQUILIBRIUM LEVELS, BOTH OF WHICH WILL LIMIT SNOWFLAKE SIZE AND
ANY ACCUMULATION POTENTIAL.
AFTER A COLD SUNDAY, A MILD WEEK LIES AHEAD WITH A PROGRESSIVE UPPER-
AIR PATTERN IN PLACE AND A STEADILY AMPLIFYING RIDGE OVER THE
SOUTHERN US. AN EMERGING SHORTWAVE FROM THE NORTHERN PLAINS
REPRESENTS ONE TARGET OF OPPORTUNITY IN THIS FORECAST PACKAGE. HIGH
PRESSURE NOW OVER THE EASTERN SEABOARD OFFERS WEAK MOISTURE
ADVECTION FROM THE GULF INTO A DEVELOPING WARM SECTOR THROUGH THE
MID-MISSISSIPPI VALLEY. ANTECEDENT COLD AIR OVER THE GREAT LAKES
REGION PRESENTS SOME PRECIPITATION-TYPE CONCERN, THOUGH DETAILS ARE
HIGHLY UNCERTAIN AT THIS DISTANCE. I'VE STAYED CLOSE TO THE EXISTING
FORECAST OF SNOW SHOWERS CHANGING TO RAIN MONDAY NIGHT INTO TUESDAY.
UPPER-LEVEL RIDGING CONTINUES TO AMPLIFY BY MIDWEEK WITH HIGHS IN THE
50S ANTICIPATED WEDNESDAY WHEN OUR NEXT CHANCE OF RAIN ARRIVES. HOW
LONG THIS WARMTH LASTS IS SOMEWHAT UNCERTAIN AS A CANADIAN LOW
PRESSURE SYSTEM LOOKS TO DROP IN AT SOME POINT NEXT WEEKEND, MARKING
A PERIOD OF RAIN PERHAPS CHANGING TO SNOW, BEFORE RIDGING
RESUMES.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1232 PM EST SAT DEC 20 2025
THE MAIN LOW LEVEL JET IS TRANSLATING EASTWARD AWAY FROM THE AREA
THIS AFTERNOON AND THIS WILL ALLOW LLWS TO DISAPPEAR FROM THE
TAFS. ADDITIONALLY, GUSTS WILL DROP BACK BELOW 20 KTS THIS
AFTERNOON AS DIRECTIONS VEER MORE NORTHWESTERLY BY SUNDAY
MORNING.
OTHERWISE, HIGH CLOUDS PROVIDE ONLY A 10-15% CHANCE FOR LIGHT RAIN
LATER THIS AFTERNOON AS A LOW PASSES TO OUR NORTH, BUT GIVEN THE DRY
AIR, AM NOT COMPLETELY CERTAIN THIS HAPPENS. AT THE VERY LEAST,
FLIGHT CONDITIONS ARE EXPECTED TO STAY IN VFR THROUGH THE PERIOD.
ONE OTHER POSSIBILITY IS THAT CONDITIONS DIP DOWN INTO MVFR AS
HAZE/FOG FORMS UNDER THE INVERSION SUNDAY MORNING OR THAT CIGS DIP
INTO MVFR. IT IS INTERESTING TO SEE LAV GUIDANCE KEEP SUSTAINED
WINDS AROUND 10 KTS OR ABOVE, WHICH WOULD POINT TO MORE OF A CIG
ISSUANCE THAN FOG. BUT HAZE COULD STILL BE POSSIBILITY IN THIS
SCENARIO. GIVEN THE LOW CONFIDENCE THAT THESE HAZARDOUS CONDITIONS
HAPPEN, WILL ONLY MENTION THEM HERE AND NOT IN THE TAF
THEMSELVES.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR LMZ043-046.
DISCUSSION...BROWN
AVIATION...ROLLER
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page