Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 240007
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
707 PM EST TUE DEC 23 2014

.SYNOPSIS...
ISSUED AT 1038 AM EST TUE DEC 23 2014

A LOW PRESSURE MOVING BY JUST TO THE NORTHWEST IS MOVING LIGHT
RAIN TO DRIZZLE ACROSS THE AREA. HIGH TEMPERATURES TODAY WILL BE
ON THE MILD SIDE RANGING FROM AROUND 50 IN SOUTHERN MICHIGAN TO
THE LOWER 50S NEAR THE OHIO RIVER. TONIGHT RAIN SHOWERS ARE
EXPECTED TO MOVE BACK IN FROM A LOW MOVING NORTHWARD UP FROM THE
GULF OF MEXICO. LOW TEMPERATURES TONIGHT WILL RANGE FROM AROUND 40
IN SOUTHERN MICHIGAN TO AROUND 50 NEAR THE OHIO RIVER. THIS LOW
WILL CONTINUE RAIN CHANCES FOR TOMORROW. THE RAIN IS THEN EXPECTED
TO CHANGE OVER TO SNOW TOMORROW NIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 357 PM EST TUE DEC 23 2014

A DEEPENING SURFACE LOW OF 998 MB HAD MOVED INTO SOUTHERN
MISSISSIPPI THIS AFTERNOON.  A HIGHLY AMPLIFIED UPPER TROF WAS
PROVIDING PLENTY OF UPPER LEVEL SUPPORT WHICH INCLUDED SEVERAL
SHORTWAVE TROFS MOVING THROUGH THE LARGE/LONG WAVE PATTERN. THE
LATEST WATER VAPOR INDICATED ONE OF THESE TROFS ROUNDING THE BASE OF
THE LARGE TROF OVER EAST NM INTO WESTERN TX. NCEP AND OTHER MODEL
VERIFICATION OF THE DEVELOPING LOW WAS MARGINAL TO POOR. FOR NOW...
WENT WITH A GENERAL GFS/GEM/ECMWF TRACK AS THE CANADIAN GEM HAS BEEN
THE MOST CONSISTENT WITH THE TRACK OF THIS SYSTEM THE PAST FEW RUNS.
GIVEN THE THERMAL PROFILES WITH THIS TRACK...EXPECT THE EASTERN EDGE
OF THE HEAVIEST SNOWFALL WITH THIS SYSTEM WILL REMAIN JUST TO THE
WEST OF THE FORECAST AREA. HOWEVER...NOT MUCH COLD IS IS BEHIND THIS
SYSTEM...AND WITH THE INITIAL VERY MILD CONDITIONS EXPECT ONLY LIGHT
SNOWFALL AMOUNTS OVER THE FAR WEST PART OF THE FCST AREA INCLUDING
WESTERN LAPORTE TO WHITE COUNTIES THROUGH LATE WEDNESDAY AFTERNOON.
OTHERWISE...STRONG WINDS WILL DEVELOP LATE WEDNESDAY IN THE
TIGHTENING SURFACE GRADIENT OVER NW OHIO. A WIND ADVISORY MAY BE
NEEDED LATE IN THE DAY FOR THIS AREA DEPENDING ON THE TRACK OF THE
SURFACE LOW.

&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 357 PM EST TUE DEC 23 2014

MAIN CONCERN FOR THE LONG TERM PERIOD IS SNOWFALL AMOUNTS WITH WRAP
AROUND PRECIPITATION AND THE POTENTIAL FOR WIND ADVISORY CRITERIA
TO BE REACHED WEDNESDAY EVENING.

MODELS HAVE COME INTO BETTER AGREEMENT TODAY WITH RESPECT TO THE LOW
POSITION. 12Z GEM/GFS/EURO ALL BRING THE SURFACE LOW BETWEEN FORT
WAYNE AND LIMA NEAR 18Z WEDNESDAY. 12Z NAM IS SLOWER AND THE
FURTHEST WEST SOLUTION WITH A SURFACE LOW TRACK THROUGH COLUMBIA
CITY NEAR 00Z. PREFER THIS WESTWARD TRACK OVER THE OTHERS DESPITE
THE RECENT EASTWARD TREND OF THE MODELS. ACTUALLY WOULD NOT BE
SURPRISED TO SEE THE LOW DEEPEN A BIT MORE THAN MODELED (PERHAPS
985MB) WITH A NEGATIVELY TILTING TROUGH AND A RAPIDLY DEEPENING
SURFACE CYCLONE. IN ADDITION...20Z SURFACE ANALYSIS IS ALREADY
ANALYZING A 998MB CLOSED CONTOUR AT THE SURFACE IN SOUTHEASTERN
LOUISIANA WHICH IS A FEW MB DEEPER THAN ANY 12Z GUIDANCE INDICATED
AT 18Z. HAVE BEEN WATCHING THE LARGE AREA OF CONVECTION BLOW UP
ALONG THE SOUTHERN COAST TODAY TO MONITOR TRENDS FOR ANY INDICATIONS
THAT LATENT HEAT RELEASE NEAR THE SURFACE LOW MAY AID IN
INTENSIFICATION...BUT IT IS STILL A BIT EARLY TO TELL WHAT
EFFECT...IF ANY...IT MAY HAVE. IF THE WESTERN TRACK DOES PROVE TO BE
THE WINNER...A WIND ADVISORY MAY BE NECESSARY FOR THE EASTERN 1/3RD
OF THE FORECAST AREA NEAR 00Z AS THE ISALLOBARIC COMPONENT OF THE
WIND INCREASES WITH THE DEEPENING SURFACE REFLECTION.

MADE ONLY MINOR CHANGES TO ONGOING FORECAST SNOWFALL AMOUNTS. FELT
GEM HAD THE BEST HANDLE ON THE THERMODYNAMIC ENVIRONMENT AND THUS
MADE ONLY MINOR EDITS TO THESE TOP DOWN VARIABLES BEFORE CREATING
HOURLY WEATHER GRIDS. BIG QUESTION WHICH IS STILL YET TO BE ANSWERED
IS HOW FAR EAST THE DEFORMATION ZONE WILL TRANSLATE ON WEDNESDAY
EVENING IN THE WAKE OF THIS SURFACE LOW. THERE IS GENERAL AGREEMENT
FOR AT LEAST A FEW HOURS OF MODERATE INTENSITY PRECIPITATION TO
REMAIN IN THE FAR NW AREAS AFTER THE BOUNDARY LAYER SUFFICIENTLY
COOLS TO CHANGE PRECIPITATION TO ALL SNOW...ALTHOUGH THE DEFORMATION
BAND QUICKLY BEGINS TO DISSIPATE AND LIFT NORTH. THE OUTLIER TO THIS
SOLUTION IS THE 12Z ECMWF WHICH DRAGS A MODERATE INTENSITY
DEFORMATION BAND ACROSS A MAJORITY OF OUR FORECAST AREA. WITH HOW
QUICKLY THIS SYSTEM IS LIFTING NORTHWARD...DO NOT ANTICIPATE THIS
SOLUTION VERIFYING. FINALLY...CONCERNED THAT WITH GROUND
TEMPERATURES IN THE LOW 40S AND SURFACE TEMPS REMAINING ABOVE
FREEZING UNTIL AFTER 00Z WILL INHIBIT THE CHANCES FOR ACCUMULATING
SNOWFALL. IF PORTIONS OF THE NORTHWEST CWA SEE A FEW HOURS OF
MODERATE SNOWFALL SHORTLY AFTER THE CHANGEOVER OCCURS...THIS SHOULD
LAY A BASE FOR ADDITIONAL SNOWFALL ACCUMULATION...BUT FOR AREAS
WHICH DO NOT SEE THESE MODERATE SNOWFALL RATES...ACCUMULATION MAY BE
QUITE DIFFICULT EXCEPT FOR ELEVATED SURFACES.

THE LACK OF COLD AIR BEHIND THIS STORM SYSTEM WILL MEAN HIGH
TEMPERATURES IN THE MID 30S ON THURSDAY AND RISING INTO THE MID 40S
BY FRIDAY. SEVERAL WEAK WAVES WILL MOVE THROUGH THE FLOW IN THE
WEEKEND TIMEFRAME...BUT THE MODELS ARE REALLY STRUGGLING TO HANDLE
THESE WAVES UNTIL WE GET THE CHRISTMAS EVE SYSTEM OUT OF HERE. FOR
THIS REASON COULD NOT JUSTIFY MAKING ANY CHANGES TO SUPERBLEND
BEYOND DAY 3.

&&

.AVIATION/UPDATE...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 707 PM EST TUE DEC 23 2014

MID LVL ECHOES DVLPG ALG A KMCX TO KEKM LINK THIS EVENING A LIKELY
PROXY FOR POSITIONING OF MID LVL BAROCLINIC ZONE AND SHLD SERVE AS A
PATHWAY FOR H85 LOW TRACK ON WED. THUS VFR CONDS THIS EVENING WILL
RAPIDLY COLLAPSE OVERNIGHT AS FORCING FOR ASCENT BLOSSOMS ESP TWD
DAYBREAK. UNTIL THEN NWD MSTR FLUX CONTS TO GET STRANGLED FM
WIDESPREAD LWR MS VALLEY CONVN AND SUSPECT ANY SFC BASED RAINFALL
WILL BE SPOTTY ACRS BOTH NWRN AND SERN ZONES.

ON WED IFR TO LIFR CONDS AT TIMES XPCD TO PERSIST WELL INTO WED
EVENING AS SUBSTANTIAL SFC LOW DVLPS NEWD INTO THE GREAT LAKES.
SOLID HIGHRES CONSENSUS PORTENDS CHGOVR TO -SN AT KSBN ARND 20Z W/A
PD OF ACCUMULATING SNOW LIKELY INTO MID WED EVENING. OTRWS FWA
TERMINAL RESIDES FIRMLY IN WARM SECTOR OF APCHG CYCLONE W/ONLY RAIN
XPCD AS ASSOCD DEFORMATION ZONE TIED TO CLOSING CYCLONE ALOFT WILL
TEND TO HOLD WEST AS DRY SLOT PIVOTS UP ACRS WRN OH. STG FALL/RISE
COUPLET ASSOCD/W PASSING SFC CYCLONE WILL YIELD A PD OF STG SFC
BASED GUSTS LT PD AT KFWA. 00Z TAF ISSUANCE MAY LIKELY BE UNDERDONE
GIVEN AVAILABLE 18Z GUIDANCE DEPICTION OF MID 980`S INTENSITY SFC
CYCLONE INVOF OF THE TRI-STATE. WILL REACCESS FOR 06Z ISSUANCE.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 1 PM WEDNESDAY TO 4 PM EST THURSDAY
     FOR LMZ043-046.

&&

$$

SYNOPSIS...LOTHAMER
SHORT TERM...SKIPPER
LONG TERM...BENTLEY
AVIATION...T


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