964
FXUS63 KIWX 091720
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1220 PM EST MON NOV 9 2009
AVIATION
SW WINDS IN ADVANCE OF APPROACHING COLD FRONT STREAMING MOISTURE
NORTHEAST INTO THE FORECAST AREA. CIGS WILL LOWER TO BORDERLINE
MVFR BUT BASED ON UPSTREAM OBS HAVE RETAINED BKN VFR CIGS. WINDS
WILL VEER NORTH TO NORTHEAST THROUGH THE PD AS WEAK FRONTAL ZONE PASSES
TERMINALS. PRECIP ASSOC WITH THIS SYSTEM IS EXPECTED TO BE SPARSE
WITH THE WINDOW OF IMPACT BEING PUSHED BACK TO MIDDAY THROUGH
AFTERNOON TUESDAY AS UPSTREAM FLOW BOGS DOWN WITH TROPICAL SYSTEM
MOVING ONSHORE IN THE GULF. WITH LOW CHC FOR PRECIP CONFINED TO
LAST FEW TAF PD HOURS AND MODEL SOLNS CONTINUING TO DOWNPLAY
POTENTIAL...HAVE LEFT ANY PRECIP WORDING OUT OF THE 18Z TAF
ISSUANCE.
PREV DISCUSSION... /ISSUED 356 AM EST MON NOV 9 2009/
SHORT TERM...
STRONG UPR LEVEL RIDGE REMAINS OVER ERN U.S. THIS MORNING. A WK
SHRTWV WAS LIFTING NE OVER THE TOP OF RIDGE THROUGH THE UPR GRTLKS.
SFC CDFNT ASSOCIATED WITH THIS SHRTWV WILL MOVE SE ACROSS THE AREA
THIS AFTN/EVE. MOISTURE LIKELY LACKING ALONG FRONT FOR ANY PRECIP
WITH FROPA THIS AFTN/EVE, HWVR, ANOTHER SHRTWV IS STILL EXPECTED
TO MOVE EAST FROM THE NRN ROCKIES THIS MORNING TO THE UPR GRTLKS
TONIGHT AND THEN DIG SE ACROSS THE REGION TUE. MODELS HAVE TRENDED
WEAKER/DRIER WITH THIS SYSTEM AS IT MOVES ACROSS OUR AREA SINCE
THIS TIME YDAY, BUT STILL APPEARS IT MAY PROVIDE SUFFICIENT LIFT
FOR A FEW SHOWERS. LOWERED POPS/QPF IN LINE WITH MODEL TRENDS BUT
KEPT A CHC IN THE FCST DURING THIS PD. AS THIS SHRTWV MOVES EAST
OF THE AREA TUE NIGHT...SUBSIDENCE AND RIDGE BUILDING INTO THE
AREA SHOULD RESULT IN CLEARING SKIES.
AS FOR TEMPS...MOS HAD A COOL BIAS ON HIGHS YDAY, HWVR, THERE IS
CONSIDERABLE CIRRUS STREAMING NORTHWARD FROM GULF HURRICANE ATTM
WHICH SHOULD LIMIT DIURNAL HEATING TODAY, SO BELIEVE MAV HIGHS FOR
TODAY ARE CLOSE. THIS HIGH CLOUDINESS SHOULD CONT OVER THE AREA
TONIGHT, SO GENERALLY WENT AOA WARMEST MOS FOR MINS. CAA ON TUE
WITH LIKELY LINGERING CLOUDS ESPECIALLY SE PORTION OF CWA... ALONG
WITH NE FLOW OFF LH/LE WHERE WATER TEMPS AROUND 50F...SUGGEST MOS
HIGHS ARE TOO WARM... STAYED CLOSE TO PREVIOUS FCST IN M50S. WITH
HIGH BUILDING INTO THE AREA TUE NGT...CLEARING SKIES, DIMINISHING
WINDS, AND DRY AIR MASS SHOULD RESULT IN GOOD RADIATIONAL COOLING
CONDITIONS...FCST MINS AOB COOLEST MOS TEMPS.
LONG TERM...
WEDNESDAY THROUGH SUNDAY
MEAN RIDGING IS IN STORE FOR THE REGION DURING THE PERIOD...AS
UPSTREAM WESTERN CONUS TROUGHING AND THE REMNANTS OF IDA IMPACT A
MODIFYING INFLUENCE ON THE UPPER FLOW. UPPER VORTEX NOW ENTERING THE
PAC NW IS EXPECTED TO SPLIT WITH DIGGING INTO THE WESTERN
CONUS...WITH THE NORTHERN STREAM COMPLIMENT TRACKING INTO THE
CANADIAN PRAIRIE PROVINCES. STAUNCH WAA AHEAD OF THIS SYSTEM WILL
HELP SUPPORT RIDGING INTO THE EASTERN CONUS WITH INFERRED BLOCKING
AS THE GOMEX TROPICAL WAVE GETS SANDWICHED BETWEEN THE BUILDING
CONUS UPPER HIGH AND THE MASSIVE ATLANTIC RIDGE. THE OVERALL
SYNOPTIC EVOLUTION WILL FEATURE A PROLONGED PERIOD OF
RIDGING...SUPPORTING ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS.
FORECAST MODELS AND ENSEMBLES HAVE OPTED FOR A MORE PROGRESSIVE
APPROACH NEARING THE END OF THE PERIOD...BUT GIVEN THE SETUP...ONE
WOULD TEND TO LEAN TOWARD A SOLUTION THAT OFFERS A TREND TO BLOCKING
AS IN THE 00Z ECMWF. THE FORECAST STILL CONTAINS MUCH UNCERTAINTY BY
DAY 7 GIVEN MODEL DISAGREEMENT AND AN ANOMALOUSLY WARM/DEEP RIDGE IN
PLACE. HOWEVER...DO FEEL A TREND TO ABOVE NORMAL IS WARRANTED GIVEN
SIGNALS FOR BLOCKING.
WED-FRIDAY...DEPARTING UPPER TROUGH WILL SUPPORT WEAK CAA INTO THE
REGION WITH SFC HIGH PRESSURE DOMINATING THE WEATHER. HAVE OPTED TO
KEEP THINGS COOL ON WED IN THE WAKE OF THE DEPARTING MID LEVEL
IMPULSE...WITH A TREND TO MUCH DRIER LL FIELDS. THIS WILL SUPPORT
COOLER OVERNIGHT LOWS THU MORNING. DID RAISE HIGH TEMPS THU AND FRI
IN LINE WITH CONTINUED VERY WARM H85 PROGS IN FORECAST MODEL SUITES
AND AFOREMENTIONED CONCERNS. GIVEN CURRENT PROGS /MOSTLY SUNNY
CONDITIONS...WAA REGIME...AND INCREASINGLY DEEPER MIXING/ FEEL THAT
HIGHS WELL INTO THE 60S ARE LOOKING MORE LIKELY THU AND ESPECIALLY
FRI...WITH TEMPS POSSIBLY RUNNING SOME 15 TO 20 DEGREES ABOVE
NORMAL. CONCERNS ON PERIOD NUMBER AND THE POTENTIAL FOR A RIDGE
TOPPING DISTURBANCE PRECLUDE RAISING TEMPS ANY HIGHER AT THIS POINT.
OTHERWISE...DRY WEATHER IS EXPECTED.
SAT-SUN...FORECAST MODELS CONTINUE TO PROGRESS THE WESTERN TROUGH
INTO THE GREAT LAKES WITH AN ASSOCIATED SFC LOW/COLD FRONT. AS
STATED ABOVE...THE PREFERENCE IS TOWARD A SLOWER HEIGHT EVOLUTION
WHICH WOULD SUPPORT AN EXTENDED PERIOD OF UPPER RIDGING AND WARM DRY
WEATHER. HAVE RETAINED POPS SAT NIGHT INTO SUN FOR UPPER TROUGH AND
SFC CYCLONE APPROACH GIVEN UNCERTAINTY AND PREFERENCE TOWARD
CONSISTENCY...BUT A WARM DRY START TO THE WEEKEND IS LOOKING MORE
LIKELY. HAVE OPTED FOR ABOVE NORMAL TEMPS BUT WITH A TREND TO CLIMO
UNTIL BETTER CONFIDENCE IN THERMAL AND MOMENTUM FIELDS IS
ESTABLISHED.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
SHORT TERM...JT
LONG TERM...JC
AVIATION...LUD
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