FXUS63 KIND 060509
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1209 AM EST SUN DEC 6 2009
.AVIATION...DISCUSSION FOR 06Z.
ONLY THICKENING CIRRUS AND EVENTUALLY ALTOCUMULUS THROUGH THE
TAF PERIOD UNDER SURFACE HIGH PRESSURE. LIGHT TO CALM SOUTH WINDS
TONIGHT APPRCOACHING 10 KNOTS TOMORROW. NEAR SURFACE MOISTURE TOO
SCARCE FOR FOG.
&&
.PREV DISCUSSION... /ISSUED 754 PM EST SAT DEC 5 2009/
UPDATE...NO CHANGES PLANNED TO THE GOING FORECAST.
WITH HIGH PRESSURE IN PLACE OVER THE LOWER MISSISSIPPI AND OHIO
VALLEYS...CLEAR SKIES AND A COLD NIGHT ARE IN ORDER. CURRENT
FORECAST HANDLES THIS WELL BY CUTTING MOS...AS DEWPOINTS ARE RUNNING
SIGNIFICANTLY LOWER THAN GUIDANCE INDICATES...AND RADIATIONAL
COOLING CONDTIIONS SHOULD BE NEARLY IDEAL.
PREV DISCUSSION...RIDGE OF HIGH PRESSURE FROM THE LOWER
MISSISSIPPI RIVER VALLEY EXTENDED NORTH TO CENTRAL INDIANA AND THE
EASTERN GREAT LAKES EARLY THIS AFTERNOON. SKIES WERE MOSTLY CLEAR
AND DEW POINT TEMPERATURES WERE IN THE MIDDLE TEENS.
MAIN FORECAST CHALLENGE TODAY WILL BE SNOW CHANCES ON SUNDAY NIGHT.
FORECAST SOUNDINGS TONIGHT AND SUNDAY REMAIN DRY AS THE HIGH
PRESSURE SYSTEM WILL MAINTAIN CONTROL. WITH ONLY WEAK WARM AIR
ADVECTION AS COLD POOL MOVES EAST...WILL CONTINUE TO CUT MAVMOS LOWS
BY 1-2 DEGREES.
EXPECTING CLOUDS TO INCREASE DURING THE DAY ON SUNDAY AS FORECAST
SOUNDINGS SHOW SATURATION AT THE UPPER LEVELS IN ADVANCE OF THE
APPROACHING SHORT WAVE. THIS SEEMS QUITE REASONABLE AND WILL STICK
AT OR BELOW MAVMOS HIGHS AS PLENTY OF COLD AND DRY AIR WILL REMAIN
IN THE LOWER LEVELS...WHICH WILL BE KEY IN THE NEXT STEP OF THE
FORECAST.
APPROACHING SHORT WAVE WILL PUSH ACROSS THE REGION ON SUNDAY NIGHT
AND MONDAY. 290K GFS ISENTROPIC SURFACE SHOWS GOOD LIFT AFTER 00Z
MONDAY UNTIL 18Z MONDAY. GIVEN THE PREVIOUSLY STATED DRY LOWER
LEVELS...IT MAY TAKE A WHILE FOR THINGS TO MOISTEN UP. SPECIFIC
HUMIDITIES ARE ONLY NEAR 3 G/KG ON THE 290K ISENTROPIC SFC. THUS A
QUICK HITTING...LIGHT PRECIPITATION EVENT IS EXPECTED. FORECAST
SOUNDINGS SHOW MUCH OF THE COLUMN ACROSS THE AREA BELOW FREEZING.
NAM APPEARS A BIT TOO WARM AS COMPARED TO THE GFS AND EVEN SO WHEN
EVAPORATIONAL COOLING IS CONSIDERED...THE WARMER NAM SOUNDINGS COULD
FALL ENTIRELY BELOW ZERO ALSO. HENCE SNOW WILL BE THE WAY TO GO ON
SUNDAY NIGHT AND MONDAY MORNING. THIS COULD MAKE FOR A TRICKY MONDAY
MORNING COMMUTE WITH SNOW ONGOING DURING DRIVE TIME. RECENT COLD
SNAP HAS CERTAINLY COOLED OFF GROUND ENOUGH TO PERMIT
ACCUMULATIONS. ANY ACCUMULATIONS LOOK TO BE ONLY A FEW TENTHS OF AN
INCH...BUT THAT CAN STILL MAKE THINGS TRICKY AT DRIVE TIME
ESPECIALLY WHEN IT COULD BE THE FIRST SNOW OF THE SEASON. WILL
INCLUDE MENTION IN THE HAZARDOUS WEATHER OUTLOOK FOR NOW TO HEIGHTEN
AWARENESS. GIVEN THE EXPECTED CLOUDS AND PRECIPITATION...THE 3
HOURLY MAVMOS TEMPS LOOK MUCH BETTER THAN THE ACTUAL HIGHS ON MONDAY.
THE LOW QUICKLY PULLS NORTHEAST ON MONDAY NIGHT INTO TUESDAY AS A
RIDGE OF HIGH PRESSURE QUICKLY BUILDS IN FROM THE SOUTHEASTERN
STATES. THIS WILL ALSO HELP PREVENT MUCH IN THE WAY OF COLD AIR
ADVECTION. HOWEVER THE DEVELOPING LOW OVER THE PLAINS STATES BEGINS
TO ADVECT DEEPER MOISTURE ACROSS INDIANA ON TUESDAY. GIVEN THE
UNCERTAINTY AT THIS TIME WILL THUS WILL STICK CLOSE TO GUIDANCE FOR
POPS AND LOWS MONDAY NIGHT AND HIGHS ON TUESDAY.
AS FOR THE EXTENDED...AN ACTIVE WEATHER WEEK IS IN STORE. HIGH
PRESSURE OVER THE EASTERN PARTS OF THE COUNTRY WILL MOVE EAST BY
WEDNESDAY AS A STRONG...DEVELOPING AND DEEPENING LOW PRESSURE SYSTEM
APPROACHES FROM OKLAHOMA. ECMWF AND GFS ARE IN PRETTY GOOD AGREEMENT
WITH THE OVERALL SYSTEM...BUT HAVE SLIGHT DIFFERENCES WITH THE
DETAILS. HENCE WILL USE BLEND FOR NOW. AT THIS TIME IT APPEARS THERE
SHOULD BE ENOUGH WARM AIR ADVECTION AHEAD OF THE SYSTEM THAT MUCH OF
THE PRECIPITATION SHOULD BE RAIN. FORECAST SOUNDINGS THAT FAR OUT
SHOW TEMPERATURES BELOW 750MB ABOVE FREEZING THROUGH 12Z WEDNESDAY.
COLD FRONT WILL PASS ON WEDNESDAY...BUT DEEP MOISTURE ALSO DEPARTS
WITH IT AS THE LOW SPEEDS TO THE NORTHEAST. HENCE EXPECT ANY RAIN TO
SHUT OFF AS THE COLD AIR ADVECTION BEGINS ON WEDNESDAY...HOWEVER
CANNOT RULE OUT SOME STRAY SNOW SHOWERS. GIVEN THE DEEPENING LOW
PRESSURE SYSTEM HAVE INCLUDED SOME GUSTY WINDS OVER 30 MPH IN THE
GRIDS AND WILL CONTINUE TO WATCH THIS CLOSES. WILL MENTION THE
STRONG WINDS IN THE HAZARDOUS WEATHER OUTLOOK LATER TODAY.
IN THE WAKE OF THE MID WEEK SYSTEM...COLD AIR AND CYCLONIC FLOW WILL
KEEP CLOUDS...FLURRIES AND BELOW NORMAL TEMPERATURES ACROSS THE AREA
ON THURSDAY. WARM AIR ADVECTION BEGINS ON FRIDAY AS A WARM FRONT
APPROACHES AND THE COLD POOL MOVES NORTHEAST...BUT LIMITED MOISTURE
AT THIS TIME SHOULD JUST RESULT IN AN INCREASE IN CLOUD COVER.
ECMWF AND GFS DISAGREE WITH THE APPROACH OF ANOTHER SYSTEM ON
SATURDAY. AT THIS TIME...GIVEN ALL THE ACTIVE WEATHER YET TO COME
THROUGH WILL KEEP THE FORECAST DRY UNTIL A BETTER CONSENSUS IS
ACHIEVED.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...PUMA
AVIATION...MK
UPDATE...NIELD
