967
FXUS63 KIND 201416 AAA
AFDIND
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
916 AM EST MON JAN 20 2025
KEY MESSAGES
- COLD WEATHER ADVISORY IN EFFECT THROUGH WEDNESDAY MORNING
- FREQUENT WIND CHILLS OF 10 BELOW WITH BRIEF PERIODS AS LOW AS 20
BELOW EXPECTED THROUGH WEDNESDAY
- SCATTERED FLURRIES WITH A FEW SNOW SHOWERS TONIGHT
- MODERATING TEMPERATURES WEDNESDAY ONWARD, THOUGH STILL BELOW
NORMAL.
- SLIGHT CHANCE OF FLURRIES OR LIGHT SNOW SHOWERS THURSDAY INTO
THURSDAY NIGHT.
FORECAST UPDATE
ISSUED AT 916 AM EST MON JAN 20 2025
ARCTIC AIR MASS IS IN PLACE WITH TEMPERATURES CURRENTLY EITHER SIDE
OF ZERO AREA WIDE. WIND CHILLS RANGE FROM AROUND -10F TO -20F, AND
SHOULD STAY BELOW ZERO ALL DAY. WILL KEEP THE COLD WEATHER ADVISORY
DESPITE WIND CHILLS RISING ABOVE CRITERIA TODAY, JUST FOR SIMPLISTIC
MESSAGING SINCE WIND CHILLS WILL AGAIN FALL BELOW -10F. ALL OTHER
WEATHER ELEMENTS APPEAR TO BE IN GOOD SHAPE WITH NO CHANGES NEEDED
FOR THIS MORNING UPDATE.
SHORT TERM (TODAY AND TONIGHT)
ISSUED AT 300 AM EST MON JAN 20 2025
EARLY THIS MORNING...
THE BANDS OF CLOUDS WITH SOME FLURRIES CONTINUE TO ERODE THIS
MORNING AS DRIER AIR FLOWS INTO THE AREA. EVEN THOUGH WINDS ARE
DIMINISHING, WIND CHILLS AT OR BELOW -10 REMAIN COMMON.
WINDS WILL STILL REMAIN UP ENOUGH TO PREVENT GREAT RADIATIONAL
COOLING, BUT TEMPERATURES WILL STILL FALL TO AROUND ZERO
OR BELOW ZERO BY AROUND SUNRISE.
TODAY...
SUNSHINE WILL COMBAT THE COLD AIRMASS TODAY AND SHOULD BRING
TEMPERATURES BACK TO AROUND 10 TO NEAR 15 DEGREES. WINDS OF 5 TO 15
MPH WITH SOME HIGHER GUSTS WILL MAKE IT FEEL COLDER. WIND CHILLS
WILL WARM ABOVE COLD WEATHER ADVISORY CRITERIA FOR SOME AREAS TODAY,
BUT WILL LET THE ADVISORY CONTINUE TO KEEP MESSAGING SIMPLE.
LATER THIS AFTERNOON, CLOUDS WILL INCREASE AHEAD OF ANOTHER UPPER
WAVE AND REINFORCING SHOT OF COLD AIR.
TONIGHT...
FORCING WILL MOVE IN THIS EVENING AND CONTINUE OVERNIGHT AS AN UPPER
TROUGH WORKS ITS WAY INTO THE AREA. A REINFORCING SHOT OF COLDER AIR
WILL ACCOMPANY IT. MOISTURE IS LIMITED WITH THIS SYSTEM, BUT WITH
SOME LIFT AND MOISTURE IN THE DENDRITIC GROWTH ZONE, SCATTERED
FLURRIES AND A FEW SNOW SHOWERS WILL LIKELY BE SQUEEZED OUT.
WILL HAVE SOME SLIGHT CHANCE POPS FOR PARTS OF THE AREA WITH A
MENTION OF FLURRIES ELSEWHERE, SPREADING FROM NORTHWEST TO SOUTHEAST
DURING THE NIGHT. THE LIGHT AND FLUFFY SNOW MAY ACCUMULATE A COUPLE
OF TENTHS IN SOME AREAS.
CLOUDS WILL HELP KEEP TEMPERATURES A LITTLE WARMER THAN THE PREVIOUS
NIGHT, BUT WINDS WILL STILL PRODUCE WIND CHILLS OF AT OR BELOW -10
FOR MUCH OF THE AREA. THUS WILL CONTINUE THE ADVISORY AS IS.
LONG TERM (TUESDAY THROUGH SUNDAY)
ISSUED AT 300 AM EST MON JAN 20 2025
WE'LL BE TRANSITIONING OUT OF THE ARCTIC PATTERN CURRENTLY IN PLACE
WITH TEMPERATURES TO RETURN TO NORMAL BY THE END OF THE WEEK.
TUESDAY NIGHT INTO WEDNESDAY LOOKS TO BE OUR LAST NIGHT OF TRULY
COLD CONDITIONS. THERE REMAINS QUITE A SPREAD WITHIN GUIDANCE
REGARDING HOW COLD IT GETS, WITH ONE CAMP SHOWING LOWS WELL INTO THE
NEGATIVES (ECMWF AND GEM) AND THE OTHER KEEPING LOWS NEAR OR ABOVE
ZERO (GFS AND ASSOCIATED MODELS). RIGHT OFF THE BAT THE GEM APPEARS
WAY TOO COLD, SO IT WILL BE DISCOUNTED. THE FACTORS CONTRIBUTING TO
THE TEMPERATURE FORECAST WILL BE HOW EFFICIENT RADIATIVE PROCESSES
(DEPENDENT ON CLOUD COVER AND WIND SPEED) ARE AND HOW QUICKLY WARM
AIR ADVECTION BEGINS DURING THE NIGHT.
RIGHT NOW, THE SURFACE HIGH CENTER LOOKS TO PASS THROUGH INDIANA
LATE IN THE DAY TUESDAY AND EARLY WEDNESDAY. RETURN FLOW ON THE BACK
SIDE OF THE HIGH ALLOWS WINDS TO BECOME SOUTHERLY. WARM AIR
ADVECTION BEHIND THE HIGH APPEARS QUITE ROBUST...WITH 850MB TEMPS
CLIMBING FROM -25C TUESDAY AFTERNOON TO -10C BY 12Z WEDNESDAY.
ADDITIONALLY, A POTENT LOW-LEVEL JET (LLJ) DEVELOPS AS A PASSING
WAVE TO OUR NORTH TIGHTENS THE MLSP GRADIENT AND INDUCES A STRONG
MASS RESPONSE. RADIATIVE PROCESS MIGHT BE STRONG EARLY IN THE NIGHT
AS WINDS REMAIN LIGHT AND LINGERING DAYTIME CLOUDS DISSIPATE...BUT
THESE PROCESSES COULD BE COUNTERED MORE EFFECTIVELY (BY MIXING AND A
LIGHT SOUTHERLY WIND) AS THE NIGHT PROGRESSES. THEREFORE,
TEMPERATURES COULD PLUNGE SHARPLY AFTER SUNSET TUESDAY BEFORE
LEVELING OFF. WE WILL KEEP OUR EASTERN AND NORTHEASTERN COUNTIES THE
COLDEST SINCE THEY WILL FEEL THE EFFECTS OF THE LLJ AND WARM AIR
ADVECTION THE LEAST...AND WE WILL KEEP OUR CENTRAL AND SOUTHWESTERN
COUNTIES A BIT WARMER THAN PREVIOUS FORECAST CYCLES. REGARDLESS,
TEMPERATURES ARE STILL EXPECTED TO BE VERY COLD WITH LOWS BETWEEN 0
TO 5 DEGREES ABOVE FROM INDY SOUTHWESTWARD AND -8 TO 0 NORTH AND
EAST.
ON WEDNESDAY, THE WARM AIR ADVECTION AND LLJ MENTIONED ABOVE FULLY
ENTER INTO INDIANA. DIURNAL MIXING AND A TIGHTENING MSLP GRADIENT
SHOULD PROMOTE GUSTY SSW WINDS. SUCH PATTERNS TEND TO BE A BIT
WINDIER THAN WHAT BLENDED GUIDANCE SUGGESTS, SO WE WILL BUMP WINDS
AND WIND GUSTS UP SLIGHTLY DURING THE DAYLIGHT HOURS WEDNESDAY. WITH
THIS IN MIND, OUR FORECAST NOW SHOWS WIND GUSTS UP NEAR 30MPH FROM
INDY NORTHWESTWARD. EVEN WITH THE ROBUST WARM AIR ADVECTION
MENTIONED ABOVE, OUR HIGH TEMPERATURES WILL "ONLY" REACH LOW TO MID
20S. WITH THOSE TEMPERATURES A 20-30MPH WIND CREATES WIND CHILLS IN
THE SINGLE DIGITS, SO WEDNESDAY WILL STILL FEEL VERY COLD.
THE WAVE MENTIONED ABOVE SHOULD DO MORE THAN JUST INDUCE WARM AIR
ADVECTION. SOME MOISTURE LOOKS TO BE PRESENT AND ENOUGH LIFT MAY
MATERIALIZE TO GENERATE ISOLATED SNOW SHOWERS AND FLURRIES ACROSS
OUR NORTHWESTERN COUNTIES. MOST OF THIS ACTIVITY CURRENTLY APPEARS
TO BE IN ILLINOIS AND NORTHERN INDIANA, HOWEVER. ADDITIONALLY, A
SECONDARY WAVE IS MODELED TO PASS THROUGH ON THURSDAY WITH ANOTHER
ROUND OF LIGHT SNOW SHOWERS OR FLURRIES. WE MAINTAIN LOW POPS ADDED
BY THE DAY SHIFT.
ENSEMBLES ARE SHOWING A MORE ACTIVE PATTERN BY THE WEEKEND WITH
POSSIBLE PRECIPITATION CHANCES. BY THIS POINT, CONTINUED BREAKDOWN
OF THE UPPER-LEVEL TROUGH AND AIR MASS MODERATION SHOULD ALLOW HIGHS
TO BE BACK TO NORMAL. AS SUCH, PRECIPITATION TYPE ISSUES COULD COME
INTO PLAY SHOULD A SYSTEM APPROACH FROM THE SOUTHWEST. THERE REMAINS
LITTLE COHERENCY WITHIN GUIDANCE SO CONFIDENCE IS VERY LOW FOR ANY
PARTICULAR MODEL SOLUTION.
AVIATION (12Z TAF ISSUANCE)
ISSUED AT 554 AM EST MON JAN 20 2025
IMPACTS:
- SOME GUSTS NEAR 20KT POSSIBLE TODAY
- ISOLATED SNOW SHOWERS TONIGHT
DISCUSSION:
CLEAR SKIES WILL EVENTUALLY GIVE WAY TO CLOUDS AROUND 5000FT LATER
THIS AFTERNOON AND EVENING, WHICH WILL PERSIST THROUGH THE NIGHT.
ISOLATED SNOW SHOWERS WILL BE AROUND TONIGHT, ESPECIALLY IN THE KLAF
AREA. BRIEF MVFR CONDITIONS WOULD BE POSSIBLE IN THESE.
WIND GUSTS NEAR 20KT MAY RETURN THIS AFTERNOON AND TONIGHT.
IND WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR INZ021-
028>031-035>049-051>057-060>065-067>072.
UPDATE...BRB
SHORT TERM...50
LONG TERM...ECKHOFF
AVIATION...50
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