000
FXUS63 KIWX 300855
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
355 AM EST SAT NOV 30 2013

.SYNOPSIS...
ISSUED AT 355 AM EST SAT NOV 30 2013

HIGH PRESSURE OVER THE EAST COAST WILL MAINTAIN DRY WEATHER TODAY
WITH SOUTHERLY WINDS BRINGING SLIGHTLY WARMER CONDITIONS. A WEAK
LOW PRESSURE SYSTEM WILL PASS THROUGH THE GREAT LAKES TONIGHT INTO
SUNDAY BUT PRECIPITATION WILL BE CONFINED TO NORTHERN LOWER
MICHIGAN.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM EST SAT NOV 30 2013

BENIGN WEATHER CONTINUES TODAY. PAIR OF SHORTWAVES SEEN ON LATEST
WATER VAPOR IMAGERY WILL BE THE MAIN FEATURES OF INTEREST FOR
SENSIBLE WEATHER IMPACTS INTO TONIGHT. THE FIRST...HIGHLY
SHEARED...PV ANOMALY IS CURRENTLY ENTERING THE OHIO VALLEY. WITH THE
AID OF SOME ELEVATED WAA...THIS WAVE IS RESPONSIBLE FOR THE CURRENT
BLANKET OF MID/UPPER LEVEL CLOUDS. THIS SHORTWAVE WILL EXIT THE AREA
BY LATER TODAY THOUGH AND WEAK SUBSIDENCE...OR SIMPLY A LACK OF ANY
FORCED ASCENT WITH A VERY DRY AIRMASS...IN ITS WAKE SHOULD SUPPORT
AT LEAST PARTIAL CLEARING BY THE AFTERNOON. STOUT SUBSIDENCE
INVERSION AND LOW SUN ANGLE WILL MAKE MIXING TO EVEN 925MB DIFFICULT
TODAY BUT CONTINUED SSW FLOW/WAA SHOULD ALLOW AFTERNOON TEMPS TO
CLIMB INTO THE LOW 40S...EVEN MID 40S IN OUR SOUTHWEST COUNTIES.
SECOND...SLIGHTLY MORE ROBUST...WAVE IS CURRENTLY ENTERING THE
NORTHERN GREAT LAKES AND WILL SEND A WEAK COLD FRONT THROUGH THE
REGION LATE TONIGHT AND INTO TOMORROW. MOISTURE WILL BE AT A
SIGNIFICANT PREMIUM AND UPPER LEVEL SUPPORT IS VERY LIMITED THIS FAR
SOUTH. BROAD CONVERGENCE AND DECENT MOISTURE POOLING BELOW 850MB MAY
SUPPORT SOME FOG/STRATUS/DRIZZLE FORMATION SUNDAY MORNING BUT NAM
BUFR SOUNDINGS FOR OUR AREA ARE STILL AWFULLY DRY THROUGH 12Z AND
EXPECT ACTUAL PRECIP WILL BE HARD TO COME BY. HAVE THEREFORE KEPT
OUT ANY MENTION OF FOG OR DRIZZLE WITH MAINLY JUST AN OVERCAST
STRATUS DECK EXPECTED AT THIS TIME. WILL HAVE TO KEEP A CLOSE EYE ON
THIS THOUGH AS SURFACE TEMPS NEAR 32F COULD SUPPORT SOME PATCHY
FREEZING DRIZZLE IF MOISTURE DEPTH IS A LITTLE BETTER THAN WHAT
CURRENT MODELS INDICATE.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 355 AM EST SAT NOV 30 2013

TRANSITION TO AN AMPLIFIED PATTERN WITH ANOTHER ARCTIC SURGE
EXPECTED BY END OF THE LONG TERM PERIOD. FEW CHANGES IN OVERALL
THINKING WITH THIS PACKAGE AS MODELS CONTINUE TO AGREE ON LARGE
SCALE CHANGES AND OVERALL PATTERN BUT POOR CONTINUITY WITH
IMPORTANT DETAILS. MODEL PREFERENCE CONTINUES TO BE A BLEND OF
MEDIUM RANGE MODELS AND ENSEMBLES.

WEAK FRONT WILL BE SAGGING INTO THE AREA TO START THE PERIOD ON
SUNDAY. NAM12 REMAINS CONSISTENT IN SHOWING A SATURATED NEAR SURFACE
LAYER ALONG BOUNDARY...ESPECIALLY ACROSS NORTHERN HALF OF CWA. WITH
MELTING SNOWPACK AND SHALLOW COLD AIR ALONG WITH LIGHT WIND FIELD
SUNDAY MORNING COULD CERTAINLY SEE A STRATUS DECK INVADE WITH LOW
PROBABILITY OF SOME FOG AND DRIZZLE DEVELOPING. CONFIDENCE REMAINS
HIGHER IN THE CLOUD DEVELOPMENT AND ANY PCPN WOULD BE RATHER LIGHT
GIVEN THE SHALLOW NATURE OF MOISTURE DEPICTED IN SOUNDINGS. THUS
HAVE CONTINUED WITH INCREASING CLOUDS AND NO MENTION OF PCPN FOR
NOW.

MODELS SHOW A WEAK SHORT WAVE MOVING THROUGH THE AREA ON MONDAY.
WHILE FORCING REMAINS WEAK MOISTURE DEPTH DOES INCREASE WITH WEAK
FGEN FORCING AHEAD OF THIS FEATURE. SEVERAL MODELS NOW SHOWING SOME
LIGHT QPF WITH MOS POPS IN THE LOW CHANCE RANGE. HAVE OPTED TO
INCLUDE A LOW POP WITH THIS PACKAGE. PCPN TYPE WOULD BE MAINLY LIGHT
SNOW NORTH AND RAIN SOUTH AS CRITICAL LOW LEVEL THICKNESS 1300M LINE
BISECTS THE CWA WHILE 850MB TEMPS RANGE FROM AROUND 0C SOUTH TO -4C
NORTH. NAM12 SHOWS A DECENT AREA OF LIFT AND FGEN FORCING MOVING
THROUGH EASTERN AREAS MONDAY EVENING SO ADDED A LOW CHANCE FAR EAST.

WHILE THESE WEAK SHORT WAVES TRAVERSE THE AREA...DEEPER MEAN TROUGH
WILL BE SETTING UP IN THE WEST AS COLD UPPER LOW DROPS SOUTHWARD AS
MONSTER RIDGE BUILDS NORTHWARD THROUGH THE EASTERN PACIFIC REGION.
DOWNSTREAM HEIGHTS OVER GREAT LAKES WILL RISE WITH WARM AIR
ADVECTION DEVELOPING. THIS WILL LEAD TO A BRIEF WARM UP WITH TEMPS
CLIMBING ABOVE NORMAL ON WED AND THU.

VERY COLD AIR TO SPILL SOUTH ACROSS WESTERN CONUS WHILE SLOWLY
BLEEDING EASTWARD AS ARCTIC FRONT SLOWLY MOVES EAST. JET ENERGY
ROUNDING BASE OF UPPER LOW WILL HELP GENERATE A STRONG SURFACE LOW
ALONG BAROCLINIC ZONE OVER THE PLAINS MID WEEK. AS THIS LOW LIFTS
NORTH...TRAILING ARCTIC FRONT WILL SLIDE EAST ACROSS OUR AREA
THURSDAY WITH GRADUALLY DEEPENING COLD AIR WEDGE INTO FRIDAY. DEEP
MOISTURE TAP EXPECTED AHEAD AND ALONG FRONT AS COMBINATION OF GULF
AND PACIFIC MOISTURE COME TOGETHER. MODELS DEPICTING HEAVY RAINFALL
POSSIBILITY ACROSS THE OH AND TN VALLEY REGIONS WITH DECENT RAINFALL
OVER OUR AREA. HAVE KEPT POPS IN HIGH CHANCE RANGE THU AND THU NIGHT
WITH TIMING ISSUES LIMITING HIGHER POPS AT THIS TIME.

MAIN LONG WAVE TROUGH AXIS REMAINS ACROSS THE PLAINS FRIDAY INTO
SATURDAY WHICH ALLOWS COLD AIR TO SPREAD ACROSS A LARGE PART OF THE
CENTRAL CONUS. OF CONCERN IS THE SUBSTANTIAL JET ENERGY ASSOCIATED
WITH THIS TROUGH AND POTENTIAL FOR A STRONGER SECONDARY LOW TO EJECT
OUT OF SOUTHERN PLAINS ALONG MAIN POLAR FRONT FRIDAY.
CLIMATOLOGICALLY THIS SETUP FAVORS A PAN HANDLE HOOK AND A DECENT
SYNOPTIC SNOW IN THE OH VALLEY REGION BUT DEPENDENT ON SECONDARY LOW
DEVELOPMENT. MODELS CURRENTLY SHOWING SEVERAL WEAKER LOWS RIDING
BOUNDARY WHICH COULD BE A REFLECTION OF MODEL RESOLUTION AND POORLY
SAMPLED JET ENERGY STILL WELL OUT OVER THE PACIFIC. THIS WILL BE
INTERESTING TO WATCH AND SEE IF MODELS BEGIN TO RESOLVE A STRONGER
AND MORE COMPACT SECONDARY WAVE IN LATER RUNS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1224 AM EST SAT NOV 30 2013

VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. SHEARED OUT
MIDLEVEL WAVE IS CURRENTLY GENERATING SOME HIGH BASED CLOUD COVER
OVER THE REGION BUT VERY DRY LOW LEVEL AIR WILL KEEP CEILINGS WELL
ABOVE 5 KFT. SOUTHEASTERLY WINDS WILL INCREASE AND VEER THROUGHOUT
THE DAY AS THE NEXT COLD FRONT APPROACHES. THIS FRONT MAY BRING
SOME REDUCTION IN FLIGHT CATEGORY BY SUNDAY MORNING BUT NOT UNTIL
AFTER 06Z.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...LASHLEY
AVIATION...AGD


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