481
FXUS63 KIWX 192302
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
602 PM EST FRI DEC 19 2025
KEY MESSAGES
- LAKE EFFECT SNOW IS EXPECTED TO DIMINISH THIS EVENING.
- A SEESAW IN TEMPERATURES WILL BE CHARACTERIZED BY WARMING
TEMPERATURES OVERNIGHT INTO SATURDAY BEFORE TEMPERATURES FALL
BACK DOWN FOR SUNDAY AND SUNDAY NIGHT.
- MUCH MILDER WEATHER IS EXPECTED NEXT WEEK WITH HIGHS NEAR 60
ON CHRISTMAS DAY.
DISCUSSION
ISSUED AT 218 PM EST FRI DEC 19 2025
FOR THE PATTERN OUTLOOK DURING THIS PERIOD, THE PACIFIC PATTERN
APPEARS TO BE IN A COMBINATION OF A JET RETRACTION/EQUATORWARD SHIFT
WITH POSITIVE ANOMALIES OVER THE ALEUTIAN ISLANDS AND NEGATIVE
ANOMALIES OVER WESTERN CANADA DOWN INTO WESTERN US. DOWNSTREAM, THIS
SETS UP A RIDGE OVER THE SOUTHERN US WITH SHORTWAVES RIDING OVER THE
TOP AUGMENTING THE RIDGE. A COMBINATION OF A NEGATIVE NAO/AO AND
NEGATIVE PNA ALLOWS FOR A WARMING TREND OF TEMPERATURES AND
BLOCKING, WHICH IS SEEN EAST OF GREENLAND IN THE NORWEGIAN SEA.
FORECAST HOVMOLLER PLOTS OF 200 MB MERIDIONAL WINDS INDICATE A
NEARLY STATIONARY WAVE TRAIN OF POSITIVE ANOMALIES IN THE WESTERN
CONUS WITH A NEGATIVE ANOMALIES IN THE EAST FROM AROUND 12/20 INTO
EARLY JAN. MUCH OF THE MID LEVEL TROUGHING LIKELY EVOLVES TO SET UP
ALONG AND EAST OF THE EASTERN SEABOARD, ESPECIALLY LATER IN THIS
PERIOD.
CLOSER TO HOME, THE TROUGH THAT BROUGHT US THE COLD TEMPS AND RAIN
THAT CHANGED TO SNOW LAST NIGHT PUSHES AWAY THIS AFTERNOON ALLOWING
LES TO COME TO AN END AND WAA TO COME IN BEHIND. WE DO GET A BRIEF
PERIOD FOR WINDS TO RELAX THIS AFTERNOON INTO THE EVENING, BUT
ANOTHER LOW LEVEL JET IS HOT ON ITS HEELS. THE GOOD THING HERE
THOUGH IS THAT BECAUSE OF THE WAA, THE LAPSE RATES ARE MUCH WEAKER
SO GUSTS SHOULD BE CAPPED BETWEEN 20 AND 30 MPH ON SATURDAY.
SATURDAY'S TROUGH IS MUCH FARTHER NORTH THAN THE THURSDAY ONE SO THE
15-20 PERCENT CHANCE FOR RAIN (NOW WITH THE WARMER TEMPS BECAUSE OF
THE WAA) IS DURING THE PM TIME FRAME. SPEAKING OF THE WARMING TEMPS
HERE, APPARENT TEMPS LAST NIGHT WERE IN THE SINGLE DIGITS ABOVE AND
BELOW ZERO, BUT WITH THE WARMING TEMPS AND LIGHTER WINDS, APPARENT
TEMPS WILL BE IN THE SINGLE DIGITS TO LOW DOUBLE DIGITS ABOVE ZERO
TONIGHT. WHILE TEMPS CAP OUT BELOW FREEZING TODAY, WE'LL BE ABLE TO
RISE BACK INTO THE 40S ON SATURDAY.
SURFACE HIGH PRESSURE MOVES IN BEHIND SATURDAY'S TROUGH/SFC LOW AND
PROVIDES A DRY DAY FOR SUNDAY. OFTEN, HIGH PRESSURE COMES IN BEHIND
A COLD FRONT AND ONE SUCH FRONT IS ABLE TO MOVE THROUGH SATURDAY
NIGHT THAT BRINGS A FRESH ALLOTMENT OF COLD AIR SO SATURDAY'S
40S ARE CAPPED BELOW FREEZING AGAIN ON SUNDAY. SOME BREEZY WINDS
15 TO 25 MPH WILL BE POSSIBLE FOR SUNDAY, BUT THE LLJ IS
DEPARTING AND LAPSE RATES ARE ON THE WEAKER SIDE KEEPING GUSTS
LOWER THEN.
BEHIND THIS SURFACE HIGH PRESSURE SYSTEM, WAA FOLLOWS FOR MONDAY AND
A WARM FRONT DRAPED ACROSS THE AREA IS BEING TAGGED BY THE GFS TO
PRODUCE SOME LIGHT PRECIPITATION MONDAY. IT IS INTERESTING THAT WE
FINALLY GET MOISTENING ON THE GFS BY AS LATE AS 23Z, SO THIS
RESTRICTS WHAT FALLS AS IT EVAPORATES. THIS EVENING PUSH OF HIGHER
MOISTURE ADVECTION PROBABLY HELPS TO KEEP PTYPES WET AS IT FALLS,
BUT A DRY DGZ COULD ALLOW FOR PERIODS OF DRIZZLE MONDAY NIGHT. WE'LL
HAVE TO SEE WHAT SHAPE ROADS (READ: COLD OR NOT) ARE IN THIS WEEKEND
TO SEE IF DRIZZLE CAN ACCRETE TO ROADWAYS.
THIS MOISTURE PLUME SHOULD BE OUT OF THE AREA TUESDAY MORNING AS
SURFACE HIGH PRESSURE PUSHES THROUGH THE GREAT LAKES OVERTOP THE
RIDGE. THIS ALLOWS FOR A WARMING TREND OF TEMPERATURES SO THAT WE'RE
SECURELY ABOVE FREEZING BY WEDNESDAY 12/24. WE'VE EVEN GOT 60 DEGREE
HIGHS ON CHRISTMAS DAY IN THE FORECAST. THE GEFS HAS 850 AND 700 MB
TEMPERATURES IN THE MAX OF THEIR CLIMATOLOGY ENVELOPE FOR CHRISTMAS,
WHICH PROVIDES ADDITIONAL CONFIDENCE IN SUCH AN OCCURRENCE. ALL OF
THIS CONTRIBUTES TO A BROWN CHRISTMAS THIS YEAR. ONE OTHER THING FOR
12/24 IS A WARM FRONT PUSHES THROUGH. THERE ARE VARYING AMOUNTS OF
MOISTURE BEING FORECAST BETWEEN THE ECMWF AND GFS SO THERE IS STILL
SOME QUESTION ABOUT IF IT'LL PRECIPITATE. HAVE RETAINED THE NBM POPS
THERE TO INDICATE ITS CHANCES.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 550 PM EST FRI DEC 19 2025
THE LARGE AREA OF LIGHT SNOW WAS RETREATING TO THE NORTHEAST AS
WELL AS THE LOWER CLOUDS ACCOMPANYING THE SNOW. COLD, BUT VERY
DRY AIR WAS OVER THE AREA. LOW LEVEL MIXING TONIGHT SHOULD
PREVENT FOG FORMATION. A 60+ LOW LEVEL JET WILL BRING FAVORABLE
CONDITIONS TONIGHT FOR LLWS, SO HAVE INCLUDED IN BOTH TAFS.
WARM AIR ADVECTION OF A RELATIVELY DRY AIRMASS WILL SCATTER OUT
ANY REMAINING LOW CLOUDS. SOUTH WINDS WILL EVENTUALLY BECOME
MORE WEST. VFR CONDITIONS WILL PREVAIL.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST SATURDAY FOR LMZ043-046.
DISCUSSION...COBB
AVIATION...SKIPPER
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