584
FXUS63 KIWX 220849
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
349 AM EST SUN NOV 22 2009
SHORT TERM
..TODAY THROUGH MONDAY NIGHT
RELATIVELY QUIET SHORT TERM PERIOD BEFORE MORE ACTIVE PATTERN BEGINS
TO AFFECT THE AREA. BIGGEST CONCERN WILL BE AMOUNT OF FOG THIS
MORNING AND AMOUNT OF CLOUD COVER AND POPS FOR MONDAY AND MONDAY NIGHT.
SURFACE HIGH PRESSURE OVER EASTERN GREAT LAKES PROVIDING CLEAR SKIES
AND LIGHT WINDS FOR OUR AREA THIS MORNING. FOG WAS FINALLY BEGINNING
TO FORM AROUND 07Z AND SHOULD CONTINUE AND BECOME LOCALLY DENSE BY
DAYBREAK. NO HEADLINES PLANNED AT THIS TIME AS NO SIGNS OF
WIDESPREAD DENSE FOG BUT WILL MONITOR FURTHER DEVELOPMENT.
FOG SHOULD BURN OFF THIS MORNING WITH MOSTLY SUNNY CONDITIONS
EXPECTED ONCE AGAIN. A NEARLY CARBON COPY OF SATURDAY WITH MORE SUN
IN THE SOUTHEAST. TEMPS MAY BE JUST A FEW DEGREES WARMER WITH MIXING
FROM 900MB INDICATED BY NAM12 SOUNDINGS. THIS MATCHES LATEST MOS AND
INHERITED GRIDS SO ONLY SOME MINOR TWEAKS MADE.
SHORT WAVE EXITING THE INTERMOUNTAIN WEST THIS MORNING WILL HELP
PICK UP WAVE SITTING IN DEEP SOUTH AND LIFT IT NORTHEAST. MODELS
HAVE BEEN HINTING AT INCREASING MOISTURE ACROSS OUR
AREA...ESPECIALLY IN THE EAST...LATE TONIGHT INTO MONDAY. 2100 UTC
SREF 12HR PROBABILITIES FOR MEASURABLE PCPN HAVE INCREASED TO OVER
70 PERCENT IN OUR EAST FOR MONDAY AND MONDAY MONDAY NIGHT. EXPECT
MODELS ARE OVERDOING WESTERN PERIPHERY OF MOISTURE BUT SOME LIGHT
SHOWERS ARE POSSIBLE IN FAR SOUTHEAST AND HAVE ADDED A LOW CHANCE TO
ACCOUNT FOR THIS AND FOR BETTER COLLABORATION. AMOUNTS SHOULD BE
TENTH OF AN INCH OR LESS AND THIS IS ALSO SUPPORTED BY VERY LOW SREF
PROBABILITIES FOR MORE THAN A TENTH OF AN INCH. CLOUD COVER ALSO
EXPECTED TO INCREASE SUNDAY NIGHT AND MONDAY ACROSS ENTIRE AREA AS
THESE WAVES PHASE AND MOVE ACROSS THE REGION. TEMPERATURES ON MONDAY
WILL BE A LITTLE COOLER BUT STILL ABOVE NORMAL WITH INCREASED CLOUD
COVER. SIMILAR STORY MONDAY NIGHT AHEAD OF MORE POTENT WAVE THAT
WILL BRING SIGNIFICANTLY COOLER AIR FOR LATER IN THE WEEK.
LONG TERM /TUESDAY THROUGH SATURDAY/
GFS/ECMWF BEGINNING TO COME INTO AGREEMENT IN...AT LEAST IN TERMS OF
SLOWER ARRIVAL OF PRECIP WITH INTENSIFYING LOW PRESSURE TO THE WEST.
THE RESULT IS A SLOW DOWN IN THE ONSET OF CHC POPS FOR TUESDAY FROM
WEST TO EAST. BEST CHANCE LOOKS TO ARRIVE LATE AFTERNOON TUES AND
MORE SO TUES NGT INTO WEDS. HAVE INCREASED POPS TO 50 PERCENT TUES
NGT BUT HOLD OFF ON LIKELY AS EXACT TRACK OF LOW REMAINS A BIT
PROBLEMATIC RANGING FROM TRACKING ACROSS THE CWA TO ACROSS PORTIONS
OF WISCONSIN. ENSEMBLE GUIDANCE SHOWS THE LARGE DISPARITY IN
CONFIDENCE WITH POPS RANGING FROM 20 TO AS HIGH AS 80. ALSO WITH THE
FURTHER WEST TRACK...THERMAL PROFILES WAY TOO WARM TO SUPPORT
CONTINUED MENTION OF MIX PRECIP TUES NGT SO THIS HAS BEEN REMOVED.
PRECIP CHANCES WILL LINGER INTO WEDS NGT WHEN QUESTIONS CONTINUE AS
TO THE SPEED AND DEGREE OF THE COLD AIR IN THE WAKE OF THE SYSTEM.
GFS CONTINUES TO BE THE FASTER OF THE MEDIUM RANGE MODELS IN THE
ARRIVAL OF THE COLD AIR BY WEDS NGT VS THE ECMWF DURING THE DAY
THURS. WILL GENERALLY FOLLOW THE MEAN 850 MB TEMPS DEPICTED BY THE
GFS ENSEMBLE WHICH BRINGS READINGS INTO THE -4 TO -6 C RANGE BY
FRIDAY. DEPENDING ON AMOUNT OF CLOUD COVER...GUIDANCE MAY BE A BIT
TOO WARM WITH READING NOT FAR FROM CLIMO IN THE LOWER 40S. FOR NOW
WILL LEAVE TEMPS AND MIX PRECIP MENTION ALONE GIVEN ENOUGH TIMING
ISSUES IN EARLIER PERIODS TO RAISE A BIT OF DOUBT ON EXACT TIMING IN
LATER PERIODS. BOTH MODELS LINGER THE COOLER AIR AROUND INTO LATE
FRIDAY WHEN SOME MODERATION BEGINS...WITH THE GFS OF COURSE BEING
THE MORE EXTREME OF THE TWO MODELS.
AVIATION
HIGH PRESSURE OVER THE AREA WITH CLEAR SKIES AND LIGHT WINDS
TONIGHT. EXPECT MVFR BR TO DEVELOP WITH IFR POSSIBLE TOWARD
DAYBREAK. SHOULD SEE THIS BURN OFF QUICKLY AFTER SUNRISE WITH RETURN
TO VFR CONDITIONS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
SHORT TERM...LASHLEY
LONG TERM...FISHER
AVIATION...LASHLEY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page