FXUS63 KLOT 290509
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1109 PM CST SAT NOV 28 2009
.DISCUSSION...
255 PM CST
MAIN ISSUES THIS FORECAST PACKAGE REST WITH A COLD FRONT COMING
THROUGH IN THE SHORT TERM AND A POSSIBLE ACCUMULATING SNOWFALL
TOWARD THE MIDDLE OF NEXT WEEK.
RIDICULOUSLY PLEASANT CONDITIONS FOR THE END OF NOVEMBER SHOULD
CONTINUE INTO THE EVENING WITH AN INCREASE IN DEW POINTS UP INTO THE
UPPER 30S TO AROUND 40. A COLD FRONT CURRENTLY STRETCHED ACROSS
CENTRAL WI/IA WILL INCH CLOSER TO THE FORECAST AREA
OVERNIGHT...WHICH WITH WINDS GENERALLY REMAINING OUT OF THE SOUTH TO
SOUTHWEST...SHOULD KEEP LOW TEMPS IN THE UPPER 30S.
CLOUD COVER WILL BE ON THE INCREASE SUNDAY MORNING AS THE VERTICAL
PROFILE MOISTENS UP AND THE COLD FRONT MOVES INTO NORTHERN
ILLINOIS. SHOWERS/LIGHT RAIN IS EXPECTED TO DEVELOP ALONG/BEHIND
THE SFC COLD FRONT YET AHEAD OF THE 850MB FRONT. THE SOUTHERN
STREAM JET STREAK WILL STRENGTHEN INTO SOUTHERN
ILLINOIS...PUTTING THE FORECAST AREA IN THE FAVORABLE LEFT EXIT
REGION FOR LIFT. HAVE BUMPED UP POPS ON SUNDAY WITH THIS ACTIVITY
EXPECTED TO START UP LATER IN THE MORNING AND CLEAR THE CWA BY
EVENING AS HIGH PRESSURE BUILDS IN FROM THE WEST.
THIS HIGH WILL BUILD IN ACROSS MOST OF THE SOUTHERN US...KEEPING ANY
WEAK DISTURBANCES NORTH OF THE REGION EARLY NEXT WEEK. THIS WILL
KEEP OUR CONDITIONS DRY AND SEASONABLE TEMPERATURE-WISE. WILL HAVE
TO KEEP AN EYE ON ONE QUICK MOVING SYSTEM AIMING FOR THE GREAT LAKES
ON MONDAY...BUT FOR NOW IT LOOKS LIKE IT'LL STAY SAFELY ENOUGH
NORTH. TUESDAY IS SHAPING UP TO BE ANOTHER PLEASANT DAY IN A WAA
REGIME WITH HIGHS IN THE UPPER 40S...POSSIBLY TAGGING 50 AGAIN.
MOST OF THE ATTENTION IN THE EXTENDED PORTION OF THIS FORECAST
PACKAGE IS IN REGARDS TO THE PESKY SFC LOW/UPPER LEVEL CLOSED LOW
THAT HAS BEEN ADVERTISED TO TRACK ACROSS THE EASTERN US FOR THE PAST
FEW SETS OF MODEL RUNS. MAIN QUESTION HAS BEEN...WHEN AND
WHERE. THIS QUESTION STILL DOESN'T APPEAR TO BE SETTLED TODAY WITH
THE GFS AND ECMWF HAVING TIMING/TRACK DIFFERENCES. CONFIDENCE
REMAINS LOW WITH THE DETAILS OF WHAT WILL HAPPEN TOWARD THE MIDDLE
OF NEXT WEEK...BUT WITH THE CLOSED UPPER LOW NOW OVER LAND IN
SOUTHERN CALIFORNIA...THE GUIDANCE IS SUGGESTING THAT THIS LOW IS
GOING TO BE PICKED UP BY A NORTHERN STREAM TROF WHICH WILL THEN
TAKE THE SOUTHERN VORT MAX THROUGH TN/KY. WITH COLD AIR WRAPPING
IN BEHIND THIS SYSTEM ACROSS OUR REGION...APPEARS PLAUSIBLE THAT
WE WILL SEE SOME LIGHT SNOW OUT OF THIS SYSTEM WITH THE BEST CHANCES
GOING FROM BENTON COUNTY NORTHWEST. AM CURRENTLY EXPECTING THE
HEAVIEST SNOW BANDS TO STAY WAY SOUTHEAST OF THE FORECAST AREA WITH
THE UPPER/SFC LOW STAYING SOUTHEAST...BUT THIS COULD BE AN
ACCUMULATING SNOWFALL NONE THE LESS. BETTER DETAILS ARE EXPECTED
TO UNFOLD OVER THE NEXT DAY OR SO AS THE NORTHERN KICKER SYSTEM
MAKES IT OVER LAND IN SOUTHWEST CANADA. FOR NOW...HAVE TRENDED
MUCH COLDER THROUGH THE END OF THE EXTENDED PERIOD AND WENT WITH
LIGHT SNOW FOR WEDNESDAY NIGHT INTO EARLY THURSDAY.
HALBACH
&&
.AVIATION...
0600 UTC TAFS...WEAK FRONT CONTINUES TO SLOWLY MOVE ACROSS THE
AREA WITH BROAD REGION OF WEAK PRESSURE GRADIENT ALLOWING WINDS TO
GO NEARLY CALM. CALM WINDS...LONG LATE NOV NIGHT...AND ONLY SCT
CIRRUS DECK IS ALLOWING FOR VERY EFFICIENT RADIATIONAL COOLING AND
MAY ALLOW FOR SOME LIGHT FOG TO DEVELOP TONIGHT...MAINLY AT
DPA/RFD AWAY FROM THE MORE URBANIZED AREAS. HAVE RECENTLY BEGUN TO
SEE SOME LIFR STRATUS DEVELOP IN SPOTS OVER NORTHERN IOWA...WHICH
IS WHAT MODELS SUGGEST WILL BE THE BEGINNINGS OF OUR STRATUS DECK
SUNDAY. HAVE INTRODUCED LOWER CIGS EARLIER IN THE DAY BUT STILL
GOING TO ERR ON THE OPTIMISTIC SIDE WITH LOW END MVFR CIGS WHICH
IS WHAT MOS PROBABILITY TABLES SUGGEST HAVE THE HIGHEST CHANCE OF
VERIFYING DESPITE RAW MOS OUTPUT OF IFR CIGS. OVERNIGHT SHIFT WILL
BE ABLE TO MONITOR STRATUS DEVELOPMENT AND HAVE A BETTER HANDLE ON
IFR POTENTIAL WITH SUBSEQUENT TAF ISSUANCES. STILL APPEARS AS
THOUGH SOME LIGHT RAIN COULD DEVELOP AS THE WEAK SFC LOW MOVES UP
THE FRONT SUNDAY...THOUGH NOT ANTICIPATING A SIGNIFICANT PRECIP
EVENT AT THIS TIME. CIGS SHOULD CLIMB DURING THE AFTERNOON AS COLD
AIR MASS AND BOUNDARY LAYER DEEPEN CAUSING STRATUS DECK TO LIFT.
AS SFC LOW MOVES OUT LOOK FOR NW WINDS TO PICK UP DURING THE
AFTERNOON SUNDAY WITH A BIT OF GUSTINESS EXPECTED IN STRENGTHENING
COLD AIR ADVECTION REGIME.
IZZI
&&
.MARINE...
232 PM CST
A FRONT WILL MOVE THROUGH LAKE MICHIGAN TONIGHT. A LOW WILL MOVE
ACROSS WISCONSIN AND ANOTHER MAY MOVE ACROSS NORTHERN ILLINOIS.
THIS WILL BRING A WIND SHIFT FROM THE SOUTH AROUND 10 KNOTS TO THE
NORTH AND INCREASING TO 15 TO 25 KNOTS BY SUNDAY AFTERNOON. THERE
WILL BE AREAS OF RAIN. THE WAVES WILL BE 1 TO 3 FEET. A NORTH WIND
WILL BECOME SOUTHWEST DURING THE DAY MONDAY. WE EXPECT AN INCREASE
IN SPEED TO 15 TO 25 KNOTS FROM THE SOUTHWEST BY MONDAY AFTERNOON.
THIS IS IN RESPONSE TO A HIGH BUILDING OVER OKLAHOMA BY MONDAY
AFTERNOON.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
