577
FXUS63 KIND 200508
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1208 AM EST FRI DEC 20 2024
KEY MESSAGES
- A HALF INCH TO ISOLATED SPOTS OF 2" OF SNOW EXPECTED FOR AREAS
ALONG AND NORTH OF THE I-74 CORRIDOR 3AM TO NOON FRIDAY
- IMPACTS LIKELY FOR THE FRIDAY MORNING RUSH HOUR FROM SNOW
- WIND GUSTS 25-35 MPH DEVELOPING FOR FRIDAY AFTERNOON/EVENING
- NEXT WEEK WILL SEE A MODEST WARMING TREND ALONG WITH EXTENDED
CHANCES FOR RAIN SHOWERS STARTING MONDAY.
FORECAST UPDATE
ISSUED AT 1011 PM EST THU DEC 19 2024
MINOR ADJUSTMENTS MADE TO SLIGHTLY DELAY PRECIP TIMING AND TIGHTEN
UP POP AND ACCUMULATION GRADIENT SLIGHTLY SOUTH/SOUTHWEST.
LATEST HIGH RES GUIDANCE IS SLIGHTLY LESS AGGRESSIVE WITH SNOWFALL
LATE TONIGHT, PARTICULARLY WITH SOUTHWARD EXTENT, BUT OVERALL THRUST
OF THE FORECAST REMAINS THE SAME, WITH LIGHT SNOW EXPECTED TO BEGIN
LATER TONIGHT AND CONTINUE INTO FRIDAY MORNING. LITTLE INDICATION OF
SIGNIFICANT MESOSCALE FORCING FOR BANDING IS NOTED, BUT PARTICULARLY
NORTH AND NORTHEAST OF INDIANAPOLIS, AT LEAST A FEW HOUR PERIOD OF
FAIRLY STRONG FORCING FOR ASCENT ALONG WITH GOOD SATURATION UP
THROUGH THE DENDRITIC GROWTH ZONE IS SEEN IN FORECAST SOUNDINGS,
WHICH CONTINUES TO SUGGEST A PERIOD OF LIGHT TO MODERATE
ACCUMULATING SNOWFALL WITH IMPACT POTENTIAL FOR THE MORNING COMMUTE,
THOUGH BORDERLINE SURFACE TEMPERATURES WILL HELP, AT LEAST UNTIL
ONSET OF STRONGER COLD ADVECTION AS THE FRONT PUSHES THROUGH AROUND
OR JUST AFTER DAYBREAK.
THERE MAY BE A FAIRLY TIGHT GRADIENT BETWEEN AREAS WHERE LITTLE TO
NO ACCUMULATION OCCURS AND WHERE A HALF INCH TO 1 INCH PLUS OCCURS,
AND THE I-74 CORRIDOR CONTINUES TO LOOK LIKE THE BEST DIVIDING LINE
FOR THIS, WITH AREAS SOUTHWEST OF 74 LOOKING AT A LIGHT COATING AT
BEST, AND NORTHEAST MORE LIKELY TO SEE AMOUNTS NEARING AN INCH OR
SLIGHTLY MORE.
SHORT TERM (THIS EVENING THROUGH FRIDAY)
ISSUED AT 330 PM EST THU DEC 19 2024
THE MAIN FOCUS IN THE SHORT TERM PERIOD IS THE SNOW EXPECTED LATE
TONIGHT THROUGH TOMORROW MORNING FOR PORTIONS OF CENTRAL AND NORTH
CENTRAL INDIANA.
THE SET UP INCLUDES A DIGGING TROUGH OVER THE NORTHERN PLAINS WITH
THE TROUGH AXIS PASSING OVER THE STATE WITHIN THE 09-12Z TIMEFRAME
TOMORROW MORNING. AREA OF LOW PRESSURE STACKED FROM THE SURFACE TO
AROUND 850MB TRACKS FROM SW MINNESOTA INTO NORTH CENTRAL INDIANA BY
SUNRISE FRIDAY PLACING PORTIONS OF CENTRAL INDIANA WITHIN AN AREA OF
WEAK LOW LEVEL "WARM" AIR ADVECTION TONIGHT. BEST FORCING FOR ASCENT
ARRIVES AS THE WIND SHIFT/COLD FRONT APPROACH FROM THE NORTHWEST
DURING THE EARLY MORNING HOURS. CURRENT ACARS SOUNDINGS SHOW QUITE A
BIT OF DRY AIR THROUGH THE COLUMN WHICH WILL LIKELY TAKE MUCH OF THE
NIGHT TO SATURATE ENOUGH TO SUPPORT PRECIPITATION REACHING THE
GROUND. AND WITH THE BEST LIFT AND SATURATION NOT ARRIVING UNTIL
AFTER 08Z, THINKING MOST AREAS WILL REMAIN DRY FOR THE FIRST 12
HOURS OF THE FORECAST.
THE AFOREMENTIONED "WARM" AIR ADVECTION AHEAD OF THE SYSTEM AND
FRONT WILL KEEP TEMPERATURES RELATIVELY STEADY THIS EVENING AND
TONIGHT IN THE LOWER TO MID 30S WITH INCREASING CLOUD COVER AIDING
IN INSULATING THE BOUNDARY LAYER. DEW POINTS CURRENTLY ARE RUNNING A
DEGREE OR TWO BELOW GUIDANCE, WHICH WILL BE SOMETHING TO WATCH AS
THE LOWER LEVELS SATURATE TONIGHT. THE WET BULB TEMPERATURE (TW)
WILL BE CRITICAL FOR INITIAL SNOWFALL ACCUMULATIONS IN THE 3AM-6AM
TIMEFRAME BEFORE MUCH COLDER AIR RUSHES IN. LATEST FORECAST CALLS
FOR WET BULB TEMPERATURES TO RISE TO THE FREEZING MARK IN NORTH
CENTRAL INDIANA AND IN THE 33-34 DEGREE RANGE ALONG AND SOUTH OF I-
70. THIS MEANS SNOW INITIALLY FALLING LIKELY WILL STRUGGLE TO
ACCUMULATE WITHIN THE FIRST COUPLE HOURS AS GROUND TEMPERATURES WILL
ALSO BE AT OR JUST ABOVE FREEZING. IF DEW POINTS STRUGGLE TO RISE
TONIGHT AND TW ENDS UP BEING JUST A DEGREE COOLER, ACCUMULATIONS MAY
OCCUR SOONER WITH A HIGHER CHANCE OF SLICK SPOTS DEVELOPING. IT IS
LIKELY THAT AREAS ALONG AND SOUTH OF THE I-74 CORRIDOR COULD BEGIN
AS AN LIGHT RAIN DUE TO TEMPERATURES JUST ABOVE FREEZING AND THE DGZ
NOT FULLY SATURATED. PRECIPITATION LIKELY WILL TRANSITION OVER TO
ALL SNOW FOR MOST PLACES THROUGH THE MID MORNING HOURS.
CURRENT FORECAST CALLS FOR THE COLD FRONT TO PUSH EAST THROUGH
INDIANA WITHIN THE 4AM-7AM TIMEFRAME, WHICH IS WHEN SURFACE
TEMPERATURES WILL LIKELY FALL TO OR BELOW FREEZING AND SNOWFALL
RATES WILL BE THE HEAVIEST. CROSS SECTIONAL PROFILES FROM HI-RES
GUIDANCE SHOWING THIS BEING THE PERIOD THE TROUGH AXIS PUSHES
THROUGH WITH THE GREATEST LIFT EXTENDING UP INTO A SATURATED DGZ.
LAPSE RATES ARE ONLY MARGINAL FOR BANDING TO OCCUR, SO MOST OF THE
LIFT WILL BE SYNOPTICALLY DRIVEN FROM THE FRONT PUSHING THROUGH.
STILL, A FEW HOUR PERIOD OF MODERATE SNOW, HEAVY ENOUGH TO
ACCUMULATE, IS EXPECTED TO PUSH WEST TO EAST ALONG AND NORTH OF THE
I-74 CORRIDOR DURING THE EARLY TO MID MORNING HOURS.
GREATEST SNOWFALL ACCUMULATIONS ARE EXPECTED TO BE IN PORTIONS OF
EASTERN AND NORTH CENTRAL INDIANA WHERE UP TO 1 TO 2 INCHES OF SNOW
COULD FALL... THIS INCLUDES AREAS LIKE RUSH COUNTY, MUNCIE,
ANDERSON, AND KOKOMO. A FEW FACTORS GOING AGAINST HIGHER SNOWFALL
TOTALS ARE WARMER GROUNDS, MARGINAL LAPSE RATES, AND NOT ENOUGH
SATURATION WITHIN THE DGZ LEADING TO INEFFICIENT SNOW PRODUCTION AND
LOWER SNOW TO LIQUID RATIOS. THE 1 TO 2 INCHES MAY NOT BE VERY
WIDESPREAD AS MOST LOCATIONS LIKELY WILL RECEIVE A HALF INCH TO AN
INCH. NEVERTHELESS, JUST A HALF INCH OF SNOW IS MORE THAN ENOUGH TO
CAUSE TRAVEL IMPACTS, ESPECIALLY DURING THE FRIDAY MORNING RUSH
HOUR; THEREFORE A SPECIAL WEATHER STATEMENT HAS BEEN ISSUED FOR
AREAS ALONG AND NORTH OF THE I-74 CORRIDOR FOR EXPECTED IMPACTS DUE
TO SNOW.
AS THE LOW PASSES BY AND THE FRONT EXITS TO THE EAST, CENTRAL
INDIANA WILL BE LEFT WITHIN A CYCLONIC FLOW PATTERN AROUND THE LOW
WITH ENOUGH MOISTURE PRESENT FOR ISOLATED SNOW SHOWERS TO PERSIST
THROUGH THE AFTERNOON HOURS WITH ONLY MINOR ADDITIONAL ACCUMULATIONS
EXPECTED.
THE FOCUS SHIFTS TO THE STRONGER WINDS DEVELOPING DURING THE DAY
FRIDAY AS COLDER AIR RUSHES IN ALOFT AND WINDS WITHIN THE LOW LEVEL
JET MIX DOWN TO THE SURFACE. WINDS SHIFT TO THE WEST NORTHWEST IN
THE MORNING AND INCREASE TO 10 TO 15 MPH HOWEVER STRONGER GUSTS OF
25 TO 35+ MPH ARRIVE MID AFTERNOON AND EVENING. SNOW SHOWERS WILL
LIKELY BE TAPERING OFF BY THIS TIME, SO BLOWING SNOW IS NOT MUCH OF
AN ISSUE. FEELS LIKE TEMPERATURES WILL BE ONLY IN THE TEENS AND 20S
THOUGH, MAKING IT FEEL NOTICEABLY COLDER.
LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 PM EST THU DEC 19 2024
FRIDAY NIGHT THROUGH SUNDAY NIGHT...
SEASONABLY STRONG NORTHWESTERLY UPPER LEVEL FLOW WILL OVERSEE MAINLY
DRY CONDITIONS SLIGHTLY BELOW NORMAL TEMPERATURES THROUGH THE
WEEKEND. FLURRIES AND A FEW SNOW SHOWERS ARE POSSIBLE ACROSS THE
NORTHERN TIER OUT OF WHAT SHOULD BE A MORE IMPRESSIVE AREA OF LAKE-
EFFECT SNOW SHOWERS NORTH OF THE LAFAYETTE AREA. ROBUST COLD
ADVECTIVE BREEZES FRIDAY EVENING WILL STEADILY WANE INTO THE WEEKEND.
OVERNIGHT LOWS AROUND THE LOW 20S FOR MANY LOCATIONS BOTH FRIDAY
NIGHT AND SATURDAY NIGHT WILL BRING MINIMUM WIND CHILLS INTO THE
TEENS TO AROUND 20F EARLY ON BOTH SATURDAY AND SUNDAY. SUNDAY WILL
THEN SEE THE SLOW START OF SOUTHEASTERN RETURN FLOW THAT WILL
MAINTAIN A THIRD DAY REACHING THE 30S...BUT ALSO PREVENT READINGS
FROM DROPPING BELOW THE LOW 20S SUNDAY NIGHT.
MONDAY THROUGH THURSDAY...
LACK OF UPSTREAM RIDGING WILL ALLOW A PROGRESSIVE BARRAGE OF
ASSORTED SHORT WAVES INTO THE CONUS AMID AN OVERALL ZONAL OR SPLIT
UPPER PATTERN. THERMAL PROFILES IN TIMES OF PRECIPITATION SHOULD
MAINLY PROMOTE RAIN...WITH MODERATE CONFIDENCE IN WARM ENOUGH
SURFACE CONDITIONS TO PREVENT ANY IMPACTS.
THE EARLY WEEK WILL FIND A SHORT WAVE CROSSING THE GREAT LAKES, WITH
THE TRAILING WEAK COLD FRONTAL ZONE SLOWING AND DRAGGING INTO THE
OHIO VALLEY...WHICH SHOULD EXTEND RAIN CHANCES THROUGH AT LEAST 2-3
PERIODS. THE NEXT VORT IS EXPECTED TO PLUNGE DOWN THE HIGH PLAINS,
WHICH SHOULD ENCOURAGE AT LEAST WEAK LOW PRESSURE OVER THE LOWER
MISSISSIPPI VALLEY...YET MORE IMPORTANTLY BRING A RIBBON OF GULF
MOISTURE NORTHWARD INTO THE REGION THROUGH THE MID-WEEK. WHILE
GUIDANCE INDICATES OVERALL RAIN POTENTIAL TO BE DISORGANIZED, THE
QUASI-STAGNANT PATTERN COUPLED WITH PRECIPITABLE WATER VALUES OVER
1.00 INCH COULD LEND TO AT LEAST ADDITIONAL MODERATE PRECIPITATION
VALUES OVER PORTIONS OF THE REGION.
THE TIMING FOR ANY LULL IN RAIN COVERAGE BETWEEN THE EARLY WEEK
FRONT AND MID-WEEK SOUTHERN INFLUENCE WOULD MOST LIKELY OCCUR AROUND
PM HOURS OF THE 24TH...WITH ANY OCCASIONALLY ORGANIZED RAIN ON THE
25TH MORE LIKELY FOCUSED SOUTH OF I-70.
LESS CONFIDENCE SURROUNDING A LARGER WAVE ARRIVING TOWARDS THE END
OF THE LONG TERM...WHICH SHOULD AT LEAST ACT AS A KICKER TO PUSH THE
DAMP MID-WEEK CONDITIONS TO OUR NORTH. WHETHER THE ARRIVING WAVE'S
BROAD NEGATIVE-TILTING WOULD HELP BRING MORE RAINFALL TO MOST OF THE
REGION IS UNCERTAIN AT THIS TIME...WITH THIS POTENTIAL PERHAPS
FOCUSED MORE TO OUR NORTH. EITHER WAY TEMPERATURES WILL EXHIBIT A
SUBTLE MODERATION THROUGH SLIGHTLY ABOVE TO ABOVE NORMAL LEVELS. THE
NORMAL MAX/MIN AT INDIANAPOLIS THROUGH THE LONG TERM IS 38/24.
AVIATION (06Z TAF ISSUANCE)
ISSUED AT 1208 AM EST FRI DEC 20 2024
IMPACTS:
- SNOW SHOWERS WILL INCREASE IN COVERAGE EARLY THIS MORNING;
POSSIBLY BRIEFLY MIXED WITH RAIN AROUND ONSET
- CEILINGS WILL LOWER EARLY THIS MORNING TO IFR
- WINDS WILL GRADUALLY VEER TO SOUTHWESTERLY AND EVENTUALLY
NORTHWESTERLY, BECOMING GUSTY
DISCUSSION:
MAIN CHANGE WAS TO REFINE TIMING, AND DELAY CEILING IMPROVEMENTS
LATER TODAY. PRECIPITATION MAY BE PERIODIC WITH VARYING IMPACTS TO
VISIBILITY THROUGH THE MORNING. SNOW SHOWERS MAY LINGER THROUGH THE
AFTERNOON BRIEFLY REDUCING VISIBILITIES. WINDS WILL GRADUALLY VEER
AND STRENGTHEN THROUGHOUT THE DAY. SUB-VFR CEILINGS WILL PERSIST
THROUGH THE ENTIRE TAF PERIOD.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...NIELD
SHORT TERM...CM
LONG TERM...AGM
AVIATION...BRB
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