341
FXUS63 KIWX 181124
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
624 AM EST FRI JAN 18 2019
SYNOPSIS
ISSUED AT 354 AM EST FRI JAN 18 2019
MODERATE SNOW WILL BEGIN ALONG AND NORTH OF THE TOLL ROAD LATE THIS
EVENING AND WILL SPREAD ACROSS THE ENTIRE AREA DURING THE DAY
SATURDAY. SNOWFALL TOTALS OF 4 TO 7 INCHES ARE EXPECTED FOR MOST OF
THE AREA. NORTHEAST WINDS GUSTING TO 25 TO 35 MPH WILL ALSO LEAD TO
CONSIDERABLE BLOWING AND DRIFTING SNOW. ARCTIC AIR WILL ALSO RETURN
WITH WIND CHILLS STEADILY DROPPING THROUGH THE WEEKEND...TO AROUND
15 BELOW ZERO BY MONDAY MORNING.
SHORT TERM
(TODAY THROUGH SATURDAY)
ISSUED AT 354 AM EST FRI JAN 18 2019
APART FROM SOME BR AND PERHAPS SOME LINGERING FLURRIES/DRIZZLE EARLY
THIS MORNING...NO SENSIBLE WEATHER CONCERNS THROUGH TODAY AND WILL
SKIP STRAIGHT TO FEATURE OF INTEREST ON SO MANY MINDS THIS WEEK.
BOTTOMLINE UP FRONT...ONLY MINOR CHANGES TO THE GOING FORECAST WITH
GENERALLY 4-7" FOR MOST OF THE CWA. DID LOWER SNOW AMOUNTS SLIGHTLY
FOR AREAS SOUTH OF THE TOLL ROAD GIVEN SLIGHTLY FASTER/WEAKER 00Z
SOLUTIONS BUT RAISED SNOW AMOUNTS SLIGHTLY IN THE NORTH BASED ON
STRONGER FGEN BAND EXPECTED TONIGHT. SEVERAL LINGERING DOUBTS ON
FINAL SNOWFALL AMOUNTS THAT WARRANT HOLDING ONTO JUST A WATCH FOR
NOW. HEART OF THE EVENT IS STILL OVER 24 HOURS AWAY AND GIVEN
MARGINAL CRITERIA...WOULD RATHER SACRIFICE A BIT OF LEAD TIME THAN
ZIGZAG ON HEADLINES. EVENING WATER VAPOR AND UPPER AIR ANALYSIS SHOW
PACIFIC JET STREAK AND ATTENDANT SHEAR VORT MAX WERE ONLY PARTIALLY
SAMPLED AT 00Z. WILL GET A MUCH BETTER SAMPLE AT 12Z THAT SHOULD
PROVIDE MORE CLARITY AND CONFIDENCE IN FORECAST DETAILS.
FIRST PHASE OF THE EVENT WILL BE CLASSIC RIGHT-ENTRANCE REGION FGEN
BAND TO IMPACT OUR NORTHERN ZONES TONIGHT. 400-300MB JET STREAK IS
DECENT (120+ KTS) BUT PULLS AWAY BY SAT MORNING WITH INCREASINGLY
MUDDLED UPPER LEVEL PATTERN AS SOUTHERN STREAM TROUGH/JET STREAK
APPROACH. NEVER DO GET A TRULY COUPLED UPPER LEVEL JET AND THIS IS
BORNE OUT IN FGEN FIELDS WHICH ARE SIMILARLY DISJOINTED AND OVERALL
UNIMPRESSIVE. AS PREVIOUSLY NOTED...THERE IS SOME REDUCED STATIC
STABILITY ALOFT (ABOVE 500MB) BUT THIS IS WELL ABOVE PRIMARY FGEN
CENTER (GENERALLY FOCUSED AROUND 700MB). CERTAINLY ENOUGH SUPPORT
FOR SOME LIGHT/MODERATE SNOW (ESPECIALLY GIVEN 850-700MB MIXING
RATIOS NEAR 3 G/KG) BUT MORE AGGRESSIVE QPF TOTALS (PARTICULARLY IN
THE NAM12) SEEM SUSPECT. DID UP SNOW AMOUNTS FOR THE TONIGHT PERIOD
BUT STILL GENERALLY IN THE 2-5" RANGE AND FOCUSED IN A MORE NARROW
CORRIDOR ALONG AND NORTH OF THE TOLL ROAD AS SUGGESTED BY HIGHER
RESOLUTION GUIDANCE.
PRECIP THEN TRANSITIONS TO A MORE WIDESPREAD, DEFORMATION DRIVEN
EVENT DURING THE DAY SAT AS LEFT EXIT REGION OF SOUTHERN STREAM JET
MOVES OVERHEAD. ASSOCIATED PV ANOMALY PASSES JUST SOUTH OF OUR AREA
AND DOES EVENTUALLY PHASE WITH NORTHERN STREAM SHORTWAVE BUT THIS
PROCESS HAPPENS A BIT TOO LATE/DOWNSTREAM FOR ANY NOTICEABLE IMPACTS
IN OUR AREA. AGAIN, FGEN FIELDS ARE DECENT BUT NOT SPECTACULAR WITH
A MUDDLED LOOK AND ONLY MODEST/ELEVATED REDUCTION IN STABILITY.
PLENTY OF AVAILABLE MOISTURE IN DEFORMATION ZONE NORTH OF 850MB LOW
TO SUPPORT A QUICK 0.3" OR SO OF QPF BUT FOR ALL BUT OUR FAR SE
ZONES...THIS PRECIP WILL BE IN AND OUT QUICKLY. CENTER PARTS OF OUR
CWA MAY ONLY SEE ABOUT A 9-HOUR WINDOW OF PRECIP THAT WILL LIMIT
SNOWFALL TOTALS. DEFORMATION LINGERS A BIT LONGER IN OUR FAR SE
WHERE AROUND 0.5" QPF IS LIKELY. SNOW RATIOS WILL PROBABLY VARY
QUITE A BIT ACROSS THE CWA WITH A SLIGHTLY WARMER PROFILE IN THE SE
FAVORING MORE RIMING AND LIMITED STELLAR DENDRITES WHERE A SLIGHTLY
COLDER PROFILE IN THE NW (ISOTHERMAL AROUND -10C) COULD FAVOR HIGHER
RATIOS. EXPECT TO AVERAGE AROUND 16:1 IN OUR NW AND CLOSER TO 10:1
IN OUR SE. NET RESULT IS A NEAR-UNIFORM 4-7" SNOWFALL FOR MUCH OF
THE AREA WITH THE LOWEST AMOUNTS IN OUR SOUTHWEST WHERE DURATION IS
MOST LIMITED.
OF COURSE, WIND IS STILL EXPECTED TO BE A MAJOR FACTOR IN WHAT WOULD
OTHERWISE LIKELY BE JUST AN ADVISORY-LEVEL EVENT. SUSTAINED WINDS
WILL BE FROM THE NORTHEAST AROUND 20 MPH DURING THE DAY SAT WITH
GUSTS UP TO 35 MPH POSSIBLE IN OUR SE BASED ON LATEST FORECAST
SOUNDINGS AND TIME/HEIGHT CROSS-SECTIONS OF MIXING HEIGHTS AND
WINDS. THIS WILL LEAD TO CONSIDERABLE BLOWING AND DRIFTING. WIND
CHILLS WILL ALSO DROP INTO THE SINGLE DIGITS DURING THE DAY SAT.
PUTTING EVERYTHING TOGETHER AND AFTER COLLABORATING WITH
NEIGHBORS...FEEL BEST APPROACH IS TO HOLD WITH WATCH FOR ONE MORE
CYCLE. CONFIDENCE IN SNOW AMOUNTS REMAINS ON THE LOWER SIDE AND
COULD EASILY SEE ADJUSTMENTS IN EITHER DIRECTION. THOUGH SNOW WILL
BEGIN IN OUR NORTH LATE THIS EVENING...BULK OF THE IMPACTFUL EVENT
WILL BE SAT WHICH IS STILL A BIT FAR OUT TO UPGRADE WITH SUCH
MARGINAL SNOW AMOUNTS.
LONG TERM
(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 354 AM EST FRI JAN 18 2019
COLD TEMPS STILL THE STORY FOR THE EARLY PART OF NEXT WEEK. HIGHS
WILL BE IN THE LOWER TEENS WITH LOWS WELL BELOW ZERO SUN NIGHT. WIND
CHILL ADVISORY WILL LIKELY BE NEEDED FOR MON MORNING WITH WIND CHILL
VALUES AROUND -15F. SOME LAKE EFFECT SNOW POSSIBLE IN OUR FAR NW
ZONES ON SUN BUT LATEST GUIDANCE KEEPS DOMINANT BAND PRIMARILY WEST
OF OUR AREA.
WITH MAIN FOCUS ON SHORT-TERM CONCERNS...DID NOT MAKE MANY
ADJUSTMENTS TO CONCENSUS INITIALIZATION IN LONG-TERM. ANOTHER SYSTEM
EXPECTED MIDWEEK THOUGH CURRENT TRACK SUGGESTS MORE RAIN
POTENTIAL AS HIGHS QUICKLY REBOUND INTO THE MID/UPPER 30S ON TUE.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 549 AM EST FRI JAN 18 2019
NOT MUCH CHANGE IN FORECAST OF THE 12Z TAF CYCLE. MVFR CEILINGS TO
PREVAIL THROUGHOUT THE DAY WHILE WINDS SLOWLY SHIFT OUT OF THE
WEST TO OUT OF THE EAST. INFLUENCES OF APPROACHING UPPER LOW WILL
START TO BE NOTICED AT KSBN AFTER 02Z AS A BAND OF SNOW STRETCHES
ACROSS LAKE MICHIGAN. THIS SNOW IS NOT EXPECTED TO IMPACT KFWA
UNTIL THE FINAL HOURS OF THIS TAF CYCLE. WHILE SNOW AFFECTS THE
TERMINALS EXPECTED IFR TO LIFR CEILINGS/VISBY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT
FOR INZ008-009-013-015>018-020-022>027-032>034.
WINTER STORM WATCH FROM THIS EVENING THROUGH SATURDAY EVENING
FOR INZ003>007-012-014.
MI...WINTER STORM WATCH FROM THIS EVENING THROUGH SATURDAY EVENING
FOR MIZ077>081.
OH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT
FOR OHZ001-002-004-005-015-016-024-025.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EST SUNDAY
FOR LMZ043-046.
SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...AGD
AVIATION...CM
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