000
FXUS63 KIWX 060655
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
155 AM EST FRI DEC 6 2013

.SYNOPSIS...
ISSUED AT 1232 PM EST THU DEC 5 2013

A STALLED COLD FRONT NEAR THE OHIO RIVER WILL GENERATE MODERATE TO
HEAVY SNOW OVER CENTRAL INDIANA AND SOUTHERN OHIO TONIGHT THROUGH
FRIDAY NIGHT. AMOUNTS WILL TAPER OFF THE FURTHER NORTH YOU GO
WITH AREAS NORTH OF ROUTE 24 RECEIVING LESS THAN AN INCH. DRY AND
COLD CONDITIONS EXPECTED FOR THE WEEKEND BEFORE ANOTHER LOW
PRESSURE SYSTEM IMPACTS THE AREA LATE SUNDAY.

&&

.UPDATE...
ISSUED AT 825 PM EST THU DEC 5 2013

00Z RAOBS INDICATE DRY AIR WINNING OUT ALG NRN FRINGE OF FNTL
SCALE CIRC INVOF OF STALLED POLAR FRONT AND GOES ALONG W/LATEST
SHRT RANGE GUIDANCE IN ADVTG LL DRY AIR SWD...UNDERCUTTING BTR MSTR
ALOFT. AS SUCH AND IN LIGHT OF NR TERM GUIDANCE ALIGNMENT OF
MEASURABLE QPF ASSOCD/W CONTRACTED PCPN BAND HAVE CUT OVERNIGHT
POPS SUBSTANTIALLY OUTSIDE SE CORNER OF CWA. BRIEF PD OF SLEET
STILL PSBL ALG A PORTLAND TO LIMA LINE ASSUMING LL WARM NOSE STILL
EXISTS BUT NO DOUBT ERODING ALOFT W/TIME. HWVR OVERALL
CONTRACTION IN PCPN FIELD UPSTREAM CALLS IN DOUBT GRIDDED SNOW
ACCUMS AND WILL DIMINISH AMTS SLIGHTLY YET HOLD W/SPIRIT OF PRIOR
ISSUED ADVISORY. 00Z GUIDANCE MAY OFFER A MORE VERITABLE SOLUTION
TO MAKE ADDNL CHGS.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 411 PM EST THU DEC 5 2013

MULTITUDE OF CANADIAN VORTICES TO INTERACT WITHIN NRN CONUS/MIDDLE
CANADIAN LONGWAVE TROF WITH UPSTREAM RIDGELINE REMAINING RATHER
STOIC BTWN 140-150W THROUGH AT LEAST F72. STRONG WSWRLY FLOW WITH
SUBSTANTIAL UPSTREAM SUPPRESSED HEIGHTS ACRS 4 CORNERS REGION TO TAP
MOIST SOUTHERN STREAM WITH NOTABLE WAVE NOW EJECTING THROUGH WRN
NM/TX PANHANDLE. BROAD/LONG DURATION MID LVL HEIGHT FALLS TONIGHT
THROUGH LATE FRIDAY EVENING ON ORDER OF 20-45M/12 HR AIDS IN LARGE
SCALE ASCENT...AND LARGELY ASSOCD WITH SRN PERIPHERAL FLOW DRIVING
ELEVATED FGEN ESPECIALLY NOTABLE THROUGH 600-500 MB LAYER...THAT IS
COINCIDENT WITH PREFERENTIAL DGZ. RETREATING WARM TW LAYER WITH TIME
THIS EVENING SHOULD ALL BUT VANISH BY 03 UTC FRI WITH INIT MIX SN/IP
TO ALL SNOW THEREAFTER. HIGH ELEVATED FGEN/OMEGA RESPONSE WITH
LESSENING RH WITHIN DGZ NOTED ALONG NRN PERIPHERY SHOULD PRODUCE
STRONG DEMARCATION BTWN APPRECIABLE/NEGLIGIBLE TOTALS. HIEST AMOUNTS
ALONG SOUTH OF HARTFORD CITY TO LIMA OHIO LINE IN TANDEM WITH
RELATIVELY CONSTANT I285-295K MIXING RATIOS OF 3.5 TO 4 G/KG.
SLIGHTEST OF HINTS WEAK TROWAL AT 18 UTC FRI ALONG I290K
SFC...DISLOCATED BLO UVM OF INTEREST AND COINCIDENT WITH
ANTICIPATED HIGHEST SNOW ACCUM RATES WITH STRONG/NEAR 45 KNOTS DELTA
V OF I290K WIND VS SYSTEM RELATIVE FLOW IN 18-21 UTC TIMEFRAME.
HOWEVER...HIGH ELEVATION/INIT TW LAYER FOLLOWED BY LESS THAN STELLAR
THICKNESS TO DGZ LRY ALL PROVIDE COUNTERPOINT FOR A RELATIVELY
SUBDUED SLR THROUGH ENTIRE EVENT. NAM/WRFARW/SREF BLEND APPEARS BEST
LINE OF ATTACK WITH SLIGHT NWD SHUNT OF QPF/SNOW FIELDS AND MORE
SUBSTANTIAL CONSTRICTION WRT ISOPLETH OF POP GRIDS. EXTREMELY TIGHT
DIURNAL RANGE GIVEN ONSLAUGHT OF PRECIP SOUTH/THICK CLOUD COVER. ANY
FARTHER NWD SURGE REMAINS SOMEWHAT DOUBTFUL...AS MID TROPOSPHERIC
PATTERN ATYPICAL AS COMMONLY SEEN WITH NEG TILTING SYSTEM WITH TIME.
HOWEVER...SIMILAR RESULTANT EFFECTS MAY BE REALIZED GIVEN
RETROGRESSING 5H PATTERN WITH MULTIPLE EJECTIONS AMID FERVENT
BC/NWRN CANADA SHORTWAVES TO REDIG UPSTREAM WRN NOAM TROF AND THE
MAGNITUDE OF LOW LEVEL ARCTIC SOURCED AIR NOW SPILLING INTO SRN
PLAINS WITH NEARLY 45 DEGREE/24 HRS NET SFC T CHANGES NOTED INTO
NERN TX.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 411 PM EST THU DEC 5 2013

ONE EVENT WILL BE WINDING DOWN AT THE START OF THE PERIOD WITH
ANOTHER TO FOLLOW ON ITS HEELS.

SYNOPTIC PRECIP MAY LINGER A BIT IN FAR SE AREAS INTO FRI EVE BUT
SHOULD QUICKLY PUSH OUT AS DRIER AIR MOVES IN. IN THE NW...LAKE
EFFECT MACHINE WILL KICK IN WITH DELTA T`S AROUND 20 C TO CREATE A
DECENT AMOUNT OF INSTABILITY AND SOME SNOW SHOWER ACTIVITY. SEVERAL
LIMITING FACTORS TO SIG ACCUMULATIONS INCLUDE 1) INVERSION HGTS AT
OR BELOW 7000 FT 2) NARROW COLUMN OF HIGHER MSTR 3) HIGHEST MSTR AND
LIFT NOT CO LOCATED WITH DGZ. HAVE KEPT WITH GENERAL IDEA OF PREV
SHIFT BUT NUDGED UP HIGHER WITH AT LEAST SOME MEASURABLE EXPECTED
FRIDAY NIGHT.

BRIEF DRY PERIOD SAT INTO SAT NIGHT AS HIGH PRESSURE BUILDS
OVERHEAD. HOWEVER...AS SUNDAY APPROACHES THE NEXT WAVE CURRENTLY
MOVING THROUGH THE EASTERN PACIFIC WILL DROP INTO THE PLAINS AND
ALLOW FOR RAPID CYCLOGENESIS THAT WILL MOVE TOWARD THE REGION SUNDAY
INTO MONDAY. MODELS REMAIN CONSISTENT ON A SPLIT PATTERN WITH
HIGHEST QPF ASSOCIATED ALONG AND NORTHWEST OF THE DEVELOPING LOW
FROM IOWA INTO CENTRAL MICHIGAN MUCH FURTHER SOUTHEAST ALONG THE
BAROCLINIC ZONE OVER THE OHIO VALLEY. IN BETWEEN ISENTROPIC
LIFT/OVERRUNNING SETUP STILL LOOKS TO OCCUR ACROSS THE FORECAST AREA
TO BRING A GOOD CHANCE FOR LIGHT MEASURABLE PRECIP. LIGHT SNOW
CHANCES WILL BEGIN TO INCREASE SUNDAY AFTERNOON AND PEAK SUNDAY
NIGHT. SEVERAL COMPLICATIONS ARRIVE SUNDAY NIGHT IN TERMS OF PTYPE
AND FULL QPF POTENTIAL. TONGUE OF LL WARM AIR WILL MOVE INTO AT
LEAST THE SE QUARTER TO THIRD OF THE AREA IN THE 6 TO 12Z SUN
WINDOW. AROUND THIS SAME TIME...ICE CRYSTAL FORMATION WILL DIMINISH
OR CEASE ENDING ANY HEAVIER PRECIP BUT POSSIBLY SETTING THE STAGE
FOR A PERIOD OF FREEZING DRIZZLE BEFORE EVERYTHING SHIFTS OUT
SUNDAY. GIVEN THE EVENT IS STILL A FEW DAYS OUT HAVE OPTED TO JUST
RUN WITH A MENTION OF FREEZING DRIZZLE IN THE GRIDS AND STICK WITH
LIKELY LIGHT SNOW WITH CHANCE FOR MAYBE AN INCH OR 2. LAKE EFFECT
WILL GET STIRRED UP ONCE AGAIN IN THE WAKE OF THE SYSTEM WITH SOME
ACCUMULATION POTENTIAL IN FAVORED NW FLOW AREAS.

SERIES OF REINFORCING SHOTS OF COLD AIR WILL KEEP TEMPS WELL BELOW
NORMAL THROUGH THE PERIOD WITH COLDEST AIR AT THIS POINT IN THE WAKE
OF THE WEEKEND SYSTEM WHEN SOME AREAS WON`T CLIMB ABOVE 20 FOR
HIGHS AND LOWS COULD VERY WELL PLUMMET THROUGH THE SINGLE DIGITS
WITH SNOW COVER FURTHER COMPLICATING THINGS IF WINDS CALM ENOUGH.
SOME MODERATION IN TEMPS WILL OCCUR TOWARDS THE END OF THE
PERIOD...BUT STILL A GOOD 10 DEGREES BELOW NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 155 AM EST FRI DEC 6 2013

A RELATIVELY NARROW AREA OF FRONTAL LIFT WAS SOUTHEAST OF THE FWA
TERMINAL. CONCERNS FOR THE NW EXTENT OF SNOW INCLUDE THE PRESENCE
OF A VERY DRY LAYER GIVEN DETROIT AND LINCOLN SOUNDINGS. A WAVE ALONG
THE FRONT WILL MOVE NORTHEAST TODAY...AND SHOULD ALLOW THE SNOW AREA
TO SHIFT NORTHWEST ACROSS THE FWA AREA MAINLY THIS AFTERNOON. BEST
LIFT WITH WITH THIS SYSTEM WILL REMAIN SOUTHEAST OF FT WAYNE. SO FOR
THIS CYCLE...HAVE KEPT MVFR CONDITIONS WITH SNOW BASICALLY 18-24Z.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR INZ026-
     027-032>034.

MI...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 8 PM EST THIS EVENING FOR OHZ016-
     024-025.

LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST SATURDAY FOR LMZ043-046.

&&

$$

UPDATE...T
SYNOPSIS...BENTLEY
SHORT TERM...MURPHY
LONG TERM...FISHER
AVIATION...SKIPPER


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