FXUS63 KIWX 060518
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1218 AM EST SUN DEC 6 2009
.AVIATION.../06Z TAFS/
VFR CONDITIONS THROUGH THE PERIOD. WAA COUPLED WITH AN APPROACHING
WEAK MID LEVEL DISTURBANCE WILL SUPPORT AN INCREASE IN MID AND
HIGH CLOUDINESS THROUGH THE PERIOD WITH INCREASING SSW WINDS. NO
SIG WX EXPECTED.
&&
.PREV DISCUSSION... /ISSUED 410 PM EST SAT DEC 5 2009/
SHORT TERM...
PESKY LAKE EFFECT IN BERRIEN COUNTY AND STRATOCU CLOUDS CONTINUE TO
BE PROBLEMATIC IN SHORT TERM. AS WE SURMISED ON FRIDAY...AREA OF LOW
CLOUDS THAT WAS ACROSS IL AND INDIANA DRIFTED EAST AND NORTHEAST AND
SATELLITE STILL SHOWS POCKET ACROSS NORTHWEST OHIO. WEAK MID LEVEL
TROUGH OVER THE AREA IS FINALLY MOVING EAST AS SYSTEM ALONG EAST
COAST MOVES OUT. THIS HAS BEEN HELPING TO ERODE SOLID CLOUDS FROM
WEST TO EAST. HOWEVER...DIURNAL CU HAS BEEN FILLING IN WITH CU RULE
IN THE SCT-BKN RANGE. EXPECT MOST OF CU TO DISSIPATE WITH SUNSET BUT
MORE SOLID AREA TO THE EAST WILL AGAIN BE DIFFICULT TO ERODE BUT
SHOULD AT LEAST CONTINUE TO DRIFT EAST WITH PARTIAL CLEARING ACROSS
NW OHIO THIS EVENING. CLEARING SKIES AND LIGHT WINDS ALONG WITH DEW
POINTS STILL IN TEENS SHOULD ALLOW FOR A QUICK TEMP DROP TONIGHT.
HAVE LOWERED MINS A LITTLE INTO MID TEENS JUST ABOUT ALL AREAS WITH
HIGH PRESSURE STILL HOLDING ON.
MID AND HIGH CLOUDS TO INCREASE ON SUNDAY AHEAD OF NEXT SHORT WAVE.
WITH INCREASING CLOUDS AND WEAK WAA SHOULD SEE HIGHS REMAIN IN 30S.
USED NAM12 925MB AS A MIXING HEIGHT FOR MAX TEMPS AND THIS PROVIDED
HIGHS JUST A BIT BELOW GOING GRIDS WHICH SEEMS REASONABLE GIVEN
STRUGGLE TO WARM TODAY AND COLD START SUNDAY MORNING.
THETA E ADVECTION INCREASES LATE SUNDAY NIGHT AHEAD OF APPROACHING
SHORT WAVE THOUGH 12Z MODELS HAVE SLOWED SYSTEM. 09Z SREF
STILL SHOWING MODEST PROBABILITIES FOR LIGHT SNOW LATE SUNDAY NIGHT.
WILL LEAVE HIGHEST POPS IN WEST WITH LOW CHANCE EAST LATE SUNDAY
NIGHT THOUGH BEST FORCING AND MOISTURE ADVECTION LOOK TO BE MONDAY
MORNING. SNOW ACCUMS SHOULD ALSO BE LIGHT AND KEPT AT OR BELOW A
HALF INCH THROUGH 12Z MONDAY.
LONG TERM...
MONDAY THROUGH SATURDAY...A WINTER STORM IS EXPECTED TO IMPACT THE
REGION DURING THE MIDDLE OF THE WEEK WITH A MIX OF RAIN...FREEZING
RAIN...SNOW...SLEET AND BLOWING SNOW POSSIBLE. FOR THIS PACKAGE...
PREFER A TRACK A LITTLE MORE TO THE NORTHWEST OF WHAT WAS EXPECTED
EARLIER GIVEN SUPPORT OF THE CANADIAN AND GFS ENSEMBLES. THE BEST
UPPER AIR SUPPORT MATCHES A FARTHER NW TRACK AND WOULD INDICATE
THE POTENTIAL FOR HEAVY SNOW FROM THE DEFORMATION ZONE WOULD BE
LIMITED TO FAR NW AREAS INCLUDING FAR SW LOWER MICH INTO ADJACENT
AREAS OF NORTHERN INDIANA. HAVE MADE SOME ADJUSTMENTS TO ONGOING
TIMING AND PLACEMENT OF MIXED PRECIPITATION IN THIS REGARD. GFS
ENSEMBLE PLUME DIAGRAMS AND GFS BUFKIT SUPPORT THE POSSIBILITY FOR
HEAVY SNOW FROM TUESDAY EVENING INTO WEDNESDAY MORNING...WITH SNOW
LINGERING LONGER OVER NW AREAS IN THE DEFORMATION ZONE. TEMPS
SHOULD BE CLOSE TO FREEZING TUESDAY NIGHT...WITH A FREEZING
RAIN/SLEET AND SNOW MIX POSSIBLE GIVEN THERMAL PROFILES. BELIEVE
LIMA/AOH AREA WILL LIKELY RISE SEVERAL DEGREES ABOVE FREEZING IN
THE MORNING AHEAD OF THE FRONT SO HAVE GONE WITH A PERIOD OF JUST
RAIN. BELIEVE IDEAL CONDITION EXIST FOR RAPID CYCLOGENESIS OVER
THE AREA AS THE UPPER AIR SUPPORT BECOMES NEGATIVELY TILTED. IF
THE ABOVE SCENARIO IS CORRECT...TEMPS SHOULD FALL SHARPLY OVER THE
ENTIRE AREA WEDNESDAY AFTERNOON WITH A FLASH FREEZE LIKELY. LAKE
EFFECT SNOW SHOULD DEVELOP BY WEDNESDAY EVENING. GIVEN WIND SPEEDS
AND VERY COLD AIR...BLOWING AND DRIFTING OF SNOW IS EXPECTED
CAUSING TRAVEL ISSUES. LAKE EFFECT SNOW MAY PERSIST THROUGH
THURSDAY OVER FAR SW LOWER MICH. HAVE CONTINUED TO TREND TEMPS
DOWN AND EVEN THE WARMER ECMWF OF PREVIOUS RUNS HAS TRENDED TO THE
COLDER GFS. IT LOOKS LIKE VERY COLD TEMPS THURSDAY AND BELIEVE
TEMPS MOST OF THE DAYS OVER NW AREAS WILL STAY BELOW 20 MOST OF
THE DAY.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...LASHLEY
LONG TERM...SKIPPER
AVIATION...JC
