921
FXUS63 KIWX 180512
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1212 AM EST MON NOV 18 2024
KEY MESSAGES
- RAIN CHANCES INCREASE LATER MONDAY INTO EARLY TUESDAY. THERE
ARE SLIGHT CHANCES FOR RAIN TONIGHT.
- ROLLER COASTER OF TEMPERATURES EXPECTED FOR THE PERIOD WITH
WARMEST TEMPERATURES EXPECTED TUESDAY, BUT COOLER TO END THE
WORK WEEK.
- ADDITIONAL PRECIP CHANCES EXIST WEDNESDAY AFTERNOON INTO
FRIDAY, BUT CONFIDENCE ON TIMING AND POSSIBLE PRECIPITATION
TYPES REMAINS VERY LOW.
DISCUSSION
ISSUED AT 230 PM EST SUN NOV 17 2024
AN UPPER LEVEL LOW PRESSURE SYSTEM RIDES NORTHEAST INTO CENTRAL
CANADA. MEANWHILE, A LOW PRESSURE SYSTEM IN MEXICO BECOMES CUTOFF
AND THE VORTICITY BETWEEN THESE TWO SYSTEMS BECOMES STRUNG/SHEARED
OUT. THIS ALLOWS A COLD FRONT TO STALL OUT AND WASH OUT ACROSS THE
AREA TONIGHT. LOW LEVEL MOISTURE LINGERS INTO THIS EVENING AND SO
DOES SOME MID TO UPPER LEVEL CLOUDINESS, BUT THINK IT'S BRIEF ENOUGH
TO REMOVE POPS FROM OVERNIGHT TONIGHT. DRY AIR FILTERS INTO THE AREA
FROM ALOFT AND THIS REMOVES CHANCES FOR DRIZZLE OVERNIGHT. WE START
THE MORNING WITH PEEKS OF SUNSHINE, MONDAY, BUT A RETURN TO
CLOUDINESS TAKES OVER FOR MONDAY AFTERNOON AS THAT SYSTEM IN THE
SOUTHEAST CONUS RISES NORTHEASTWARD. AS THE WARM FRONT SLIDES
NORTHWARD, A SIDE SWIPE BY THE INITIAL WARM ADVECTION WING MAY BRING
US A BRIEF PERIOD OF LIGHT TO MODERATE RAIN MONDAY AFTERNOON, BUT
THE MORE SUBSTANTIAL RAIN COMES FROM THE COLD FRONT LATE MONDAY
NIGHT INTO EARLY TUESDAY MORNING. ONLY VERY WEAK INSTABILITY AT LESS
THAN 500 J/KG OF MUCAPE, EVEN ON THE NAM, AND ITS TIME OF
ARRIVAL SHOULD LIMIT THUNDER ACTIVITY FROM THIS FROPA. AS THE
ENERGY FROM THIS DEEPENING LOW INTERACTS WITH ANOTHER ARRIVING
PACIFIC TROUGH, A STRONG AREA OF VORTICITY RIDES AROUND THE BASE
OF THE TROUGH. PREVIOUS MODEL RUNS PRODUCED SPRINKLES OR
DRIZZLE DURING THIS TIME. THERE'S ENOUGH LOW TO MID LEVEL
MOISTURE TO PRODUCE CLOUDS, BUT THE CHANCE FOR RAIN APPEARS TOO
SMALL TO INCLUDE IN THIS FORECAST.
FROM THIS DANCE OF ENERGY CREATING THIS DEEPENING AREA OF UPPER LOW
PRESSURE, MODELS CONTINUE TO STRUGGLE WITH WHERE ANY SURFACE LOW
PRESSURE FORMS, IF AT ALL. SO, TRYING TO PIN POINT TEMPERATURE AND
ITS GRADIENTS, AND, THEREFORE, BANKING ON ANY PRECIP TYPES AT ANY
ONE TIME IS STILL A DIFFICULT TASK. THERE IS MODEL CONFLUENCE AROUND
BRINGING LOW LEVEL COLD AIR ALONG WITH THE ENERGY FROM THE UPPER LOW
INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY MORNING. THIS COULD BE
WHEN THE FIRST WINTRY PRECIPITATION FALLS. A SECOND SHORTWAVE ROUNDS
THE UPPER LOW AND MOVES SOUTHWARD ACROSS THE LAKE THURSDAY EVENING.
THIS ACTUALLY HELPS TO WRAP IN WARMER AIR AND MAY NOT NECESSARILY
MAKE THE ATMOSPHERE CONDUCIVE TO A LAKE EFFECT SNOW SETUP. IF
LAKE ENHANCEMENT DOES OCCUR, IT COULD ACTUALLY MAKE IT MORE
PREDOMINANTLY RAIN, WITH SOME SNOW POSSIBLE DURING THE OVERNIGHT
AND EARLY MORNING PERIODS. COLD AIR WRAPS IN AGAIN FRIDAY
NIGHT, BUT BY THIS TIME, THE LOW PRESSURE SYSTEM AND ITS
MOISTURE HAS BEGUN TO LEAVE THE AREA SO IT'LL LIKELY BE TOO DRY
TO CREATE PRECIPITATION. IN SUMMARY, COMBINING THE COLD AIR AND
MOISTURE AT THE SAME TIME DURING THIS WEDNESDAY NIGHT THROUGH
FRIDAY NIGHT PERIOD MAY BE DIFFICULT, BUT FURTHER CHANGES WITH
MODELS ARE LIKELY COMING AHEAD. AS THE PREVIOUS FORECASTER
MENTIONED, IT'S STILL THE NIGHT TIME PERIOD THAT BRINGS THE
GREATEST POTENTIAL TO SEE SNOW. THERE'S ALSO SOME QUESTION ABOUT
IF THE SNOW WOULD STICK WITH THE GROUND BEING WARM YET. EITHER
WAY, THIS PERIOD STILL LOOKS FAIRLY BREEZY. TEMP/PRES GRADIENTS
WILL MAKE 25 TO 35 MPH GUSTS MORE POSSIBLE DURING THIS LATE
WEEK PERIOD.
WE'LL THEN HAVE TO WATCH THE LATER SUNDAY/MONDAY TIME PERIOD FOR OUR
NEXT PRECIPITATION CHANCE. GIVEN THE UNCERTAINTY EVEN WITH THE LATE
WEEK SYSTEM, THE WEEKEND SYSTEM BRINGS EVEN MORE UNCERTAINTY WITH
IT.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1207 AM EST MON NOV 18 2024
WEAK/SHALLOW COLD FRONT IN ASSOCIATION WITH LOW AMPLITUDE
SHORTWAVE SPINNING SOUTH OF JAMES BAY WILL STALL OUT ACROSS THE
TERMINALS THIS MORNING. THIS FRONTAL ZONE WILL MIX BACK NORTH
THIS AFTN IN RESPONSE TO STRONG UPSTREAM DISTURBANCE CURRENTLY
EJECTING OUT INTO W TX. LITTLE SENSIBLE WX IMPACT EXPECTED
HOWEVER BOUNDARY LAYER MOISTENING INVOF FRONTAL ZONE MAY YIELD
A BRIEF PERIOD OF THRESHOLD MVFR/VFR CIGS FOR A TIME AROUND
DAYBREAK.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...T
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