192
FXUS63 KIWX 190004
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
704 PM EST FRI JAN 18 2019
SYNOPSIS
ISSUED AT 657 PM EST FRI JAN 18 2019
A WINTER STORM WILL AFFECT THE REGION TONIGHT THROUGH SATURDAY
EVENING. SNOW IS EXPECTED TO OVERSPREAD MAINLY EXTREME NORTHERN
INDIANA AND SOUTHERN LOWER MICHIGAN LATER THIS EVENING, AND ACROSS
THE REMAINDER OF THE AREA OVERNIGHT. SNOW WILL GRADUALLY TAPER OFF
FROM NORTHWEST TO SOUTHEAST SATURDAY AFTERNOON. STORM TOTAL SNOW
ACCUMULATIONS OF 4 TO 8 INCHES ARE POSSIBLE. GUSTY NORTHEAST
WINDS WILL ALSO CREATE BLOWING AND DRIFTING SNOW SATURDAY AND
SATURDAY EVENING. BITTERLY COLD CONDITIONS WILL BUILD ACROSS THE
REGION SATURDAY NIGHT THROUGH MONDAY MORNING. WIND CHILLS TO 15
BELOW ZERO ARE POSSIBLE MONDAY MORNING.
SHORT TERM
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 335 PM EST FRI JAN 18 2019
THE WINTER STORM WATCH HAS BEEN UPGRADED TO A WINTER STORM
WARNING.
COMPLICATED FORECAST SCENARIO WILL BEGIN TO UNFOLD THIS EVENING
AS NARROW ELEVATED WARM ADVECTION WING/MID-UPPER LEVEL FGEN
FORCING SHIFTS ACROSS THE SOUTHERN GREAT LAKES. WELL DEFINED RIGHT
ENTRANCE REGION OF GREAT LAKES JET STREAK WILL ALSO SUPPORT
EASTWARD PROGRESSION OF BETTER BANDING CURRENTLY TAKING SHAPE
ACROSS IOWA/MINNESOTA THIS AFTERNOON. STILL SOME UNCERTAINTY AS
TO EXACTLY WHERE THIS BANDING WILL SET UP, BUT CURRENTLY EXPECTING
AREAS ROUGHLY NORTH OF ROUTE 6 TO BE BEST INLINE FOR THE INITIAL
ACCUMULATIONS LATER THIS EVENING INTO THE EARLY OVERNIGHT. THERE
WILL LIKELY BE SHARP SOUTH TO NORTH CUT-OFF WITH THIS INITIAL
BAND. MOST OF NORTHERN INDIANA AND NORTHWEST OHIO WILL HAVE TO
WAIT UNTIL LATE OVERNIGHT OR EARLY SATURDAY MORNING AS STRONGER
LOW/MID LEVEL ADVECTIVE FORCING BEGINS TO SHIFT EAST. IN ADDITION
TO MID/UPPER LEVEL F-GEN BAND TONIGHT, OTHER ITEM OF UNCERTAINTY
WILL BE DETAILS REGARDING EVOLUTION OF PRIMARY SOUTHERN STREAM
UPPER TROUGH. SUBTLE DIFFERENCES IN AMPLITUDE/WAVELENGTH OF THIS
FEATURE AS IT LIFTS EAST/NORTHEAST APPEAR TO BE PLAY A MAJOR ROLE
IN AFFECTING STRENGTH/DURATION OF DEFORMATION FORCING LATER
SATURDAY AFTERNOON INTO EARLY SATURDAY EVENING. CONVECTION ACROSS
THE LOWER/MID MS VALLEY MAY ALSO BE PLAYING SOME ROLE IN
AFFECTING UPPER LEVEL HEIGHT FIELDS IN MODEL GUIDANCE WITH THIS
TROUGH.
IT STILL APPEARS AS THOUGH HEAVIEST SNOWFALL POTENTIAL WILL BE
SOUTH OF US 24 ACROSS NORTHEAST INDIANA AND NORTHWEST OHIO DEPENDING
ON HOW DEFORMATION FORCING EVOLVES. MID/LEVEL FRONTOGENESIS WILL
INCREASE ACROSS THE AREA AGAIN DURING THE DAY SATURDAY AS
DIRECTIONAL CONVERGENCE ASSOCIATED WITH LOW LEVEL JET INCREASES.
MODEL TIME/HEIGHT SECTIONS DO INDICATE GOOD DEAL OF INSTABILITY
ABOVE THIS FORCING WHICH COULD YIELD DECENT RESPONSE. GREATEST
CONFIDENCE FOR 6+ INCH SNOW TOTALS IS ACROSS THE FAR SOUTHEAST
WHERE MORE PROLONGED DEFORMATION FORCING IS EXPECTED INTO SATURDAY
EVENING. SNOW RATIOS WILL VARY QUITE A BIT ACROSS THE AREA WITH
HIGHEST RATIOS ACROSS THE NORTHWEST AND LOWEST RATIOS ACROSS THE
SOUTHEAST WHERE LARGE PORTION OF LOW LEVEL SOUNDING IS IN THE 0 TO
-6 DEG CELSIUS RANGE SATURDAY MORNING WITH INCREASED POTENTIAL OF
RIMING.
OPTED TO GO WITH A WARNING WITH THIS EVENT GIVEN COMBINATION
SNOW/WIND THREAT, BUT AS MENTIONED ABOVE CONFIDENCE IS ON THE LOW
SIDE IN ACCUMULATIONS GIVEN MULTI-FACETED ASPECT OF THIS STORM AND
POTENTIAL THAT DEFORMATION BAND MAY END UP JUST SOUTH OF THE
LOCAL AREA. IMPACTS WILL BE LIKELY EVEN IF LOWER END AMOUNTS
VERIFY WITH GUSTS TO 25 TO 35 MPH, WITH BLOWING/DRIFTING CONCERNS
GREATEST SATURDAY AFTERNOON/SATURDAY EVENING.
BITTERLY COLD TEMPERATURES WILL BE THE OTHER CONCERN WITH SINGLE
DIGIT LOWS ABOVE ZERO FOR SATURDAY NIGHT AND WIND CHILLS OF 5
BELOW TO 10 BELOW ZERO.
LONG TERM
(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 335 PM EST FRI JAN 18 2019
NOT MUCH CHANGE TO THE EXTENDED FORECAST WITH LOW CONFIDENCE IN
LAKE EFFECT FOR SUNDAY. CONTINUED INDICATIONS THAT TRAJECTORIES
AND LAKE AGGREGATE TROUGHING MAY FAVOR NE ILLINOIS/EXTREME NW
INDIANA FOR BETTER LAKE EFFECT BANDING. GIVEN THIS UNCERTAINTY,
WILL LIMIT POPS TO LOW TO MID CHANCE ACROSS NW INDIANA. BITTERLY
COLD TEMPERATURES FOR SUNDAY-MONDAY WITH HIGHS ONLY REACHING 10
TO 15 SUNDAY, AND LOWS SUNDAY NIGHT BELOW ZERO AWAY FROM LAKE
EFFECT CLOUDS. WIND CHILLS MAY FLIRT WITH ADVISORY CRITERIA SUNDAY
NIGHT/MONDAY MORNING, ALTHOUGH WINDS WILL BE DIMINISHING IN THE
EVENING.
ACTIVE PATTERN CONTINUES NEXT WEEK WITH RETREAT OF ARCTIC AIR AND
ADDITIONAL EASTERN PACIFIC WAVES. ON TUESDAY INDICATIONS STILL
POINT TO STRONG LOW LEVEL JET AHEAD OF ONE OF THESE WAVES AND
STRONG THERMAL ADVECTION LEADING TO A BRIEF PERIOD OF SNOW LIKELY
CHANGING TO RAIN. ADDITIONAL CHANCES OF SNOW WERE MAINTAINED FOR
MID-LATE NEXT WORK WEEK.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 656 PM EST FRI JAN 18 2019
DIFFICULT AVIATION FORECAST WITH TIMING OF LOWERING CIGS AND VIS
WITH SNOW MAIN ISSUES. A NARROW AREA OF LIGHT SNOW WAS OVER KSBN
AND OVER PERFORMING EARLY THIS EVENING. HAVE INCLUDED A TEMPO
GROUP FOR EARLY EVENING BUT EXPECT THIS TO LIFT NORTH. BETTER
FORCING ARRIVES LATE EVENING AND CONTINUES THROUGH SATURDAY
AFTERNOON. SNOW WILL SPREAD INTO KFWA AFTER 10Z AND CONTINUE
SATURDAY. IFR EXPECTED WITH LIFR POSSIBLE BRIEFLY AT TIMES WITH
HEAVIER SNOW SHOWERS. CONDITIONS IMPROVE MID AFTERNOON KSBN AND
LATE AFTERNOON OR EARLY EVENING KFWA.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER STORM WARNING FROM 4 AM TO 10 PM EST SATURDAY FOR INZ026-
027-032>034.
WINTER STORM WARNING FROM 4 AM EST /3 AM CST/ TO 7 PM EST /6 PM
CST/ SATURDAY FOR INZ008-009-012>018-020-022>025.
WINTER STORM WARNING UNTIL 2 PM EST /1 PM CST/ SATURDAY FOR
INZ003>007.
MI...WINTER STORM WARNING UNTIL 2 PM EST SATURDAY FOR MIZ077>081.
OH...WINTER STORM WARNING FROM 4 AM TO 10 PM EST SATURDAY FOR OHZ016-
024-025.
WINTER STORM WARNING FROM 4 AM TO 7 PM EST SATURDAY FOR OHZ001-
002-004-005-015.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EST SUNDAY
FOR LMZ043-046.
SYNOPSIS...LASHLEY
SHORT TERM...MARSILI
LONG TERM...MARSILI
AVIATION...LASHLEY
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