FXUS63 KLOT 280446
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1046 PM CST FRI NOV 27 2009

.DISCUSSION...
311 PM CST

HIGHLIGHT OF THE FORECAST PERIOD IS ON SATURDAY WHEN WARMER AIR IS
PROGGED TO ADVECT INTO THE REGION ON THE BACKSIDE OF THE RIDGE
AXIS OF HIGH PRESSURE CURRENTLY MOVING THROUGH NORTHWEST INDIANA.
A WEAK AREA OF LOW PRESSURE AND A WARM FRONT WILL TRACK NORTHEAST
TONIGHT ALONG A COLD FRONT THAT CURRENTLY LIES ACROSS THE DAKOTAS
AND CENTRAL PLAINS. WITH SUNNY SKIES AND LIGHT WINDS OUT OF THE
SOUTH TO SOUTHWEST...TEMPERATURES ARE FORECAST TO REACH THE MID
50S ON SATURDAY ALTHOUGH THE DAY WILL START OUT ON THE COOL SIDE
WITH SUB-FREEZING TEMPS SATURDAY MORNING.

THE AFOREMENTIONED COLD FRONT IS THEN FORECAST TO COME THROUGH
THE REGION ON SUNDAY ALONG WITH A WEAK UPPER LEVEL SHORT WAVE
TROF...BRINGING A SLIGHT CHANCE FOR SOME LIGHT RAIN ALONG WITH IT.
ANY RAIN THAT DOES OCCUR WILL BE VERY BRIEF AND NOT AMOUNT TO MUCH
AND BY NO MEANS WILL LEAD TO AN ALL DAY WASHOUT. TEMPERATURES WILL
NOT DROP OFF SUBSTANTIALLY BEHIND THIS FRONT...BUT IT WILL MARK A
GRADUAL DROP OFF BACK TO WHAT IS CONSIDERED NORMAL FOR THIS TIME
OF YEAR. THIS LIGHT RAIN IS EXPECTED TO CLEAR THE SOUTHEASTERN
PORTION OF THE FORECAST AREA ON SUNDAY EVENING. PRECIP WILL LIGHT
UP MORE ALONG THIS FRONT AS IT MOVES INTO CENTRAL INDIANA AS A
MORE POTENT UPPER LEVEL TROF COMES THROUGH AND INTERACTS WITH THIS
SFC FEATURE.

FAIRLY QUIET AND SEASONABLE CONDITIONS ARE EXPECTED THROUGH THE
EXTENDED PERIOD AS THE COLD FRONT MOVES OFF TOWARD THE EAST COAST
AND A BROAD RIDGE OF HIGH PRESSURE WILL BE SHIFTING FROM THE
ROCKIES EAST TOWARD THE OHIO RIVER VALLEY. ANOTHER WEAK LOW IS
EXPECTED TO STAY NORTH OF THE FORECAST AREA TUESDAY INTO
WEDNESDAY. WARMER AIR IS STILL EXPECTED TO MOVE INTO THE MIDWEST
AHEAD OF IT AND BRING OUR HIGH TEMPS UP INTO THE UPPER 40S ON
WEDNESDAY.

MAIN QUESTION/UNCERTAINTY LINGERS WITH A POTENT LOW PRESSURE
SYSTEM THAT HAS BEEN FORECAST TO DEVELOP ACROSS THE SOUTHERN US
AND LIFT NORTHEAST TOWARD THE END OF NEXT WEEK. GUIDANCE HAS BEEN
BOUNCING BACK AND FORTH WITH WHERE TO TAKE THIS LOW. THE LATEST
TREND APPEARS TO BE TAKING THE LOW OFF TOWARD THE ATLANTIC COAST
WITH JUST A BROADER UPPER LEVEL TROF AFFECTING OUR WEATHER. HAVE
KEPT SOME LOW CHANCE POPS IN THERE FOR THURSDAY WITH THE UPPER
VORT MAX OVER THE GREAT LAKES PER THE 12Z GFS/ECMWF WITH THE
EXPECTATION OF COLDER AIR MOVING IN ACROSS THE REGION GOING INTO
NEXT WEEKEND.

HALBACH

&&

.AVIATION...
1045 PM CST

0600 UTC TAFS...WX NIL TIL VERY LATE IN VALID PD OF TAFORS AND
ONLY ITEM OF INTEREST IS EXACT TIMING OF WSHFT OF LIGHT SFC WINDS FM
SW TO NW.

SFC RIDGE AXIS CURRENTLY EXTENDS ACROSS THE OH VALLEY NNW OVER
NORTHERN LAKE MI AND EASTERN LK SUPERIOR. WITH RIDGE TO E...WEAK
RATHER ILL DEFINED LO TO THE W AND A WARM FRONT ACROSS SW IA...NE MO
AND FAR SOUTHERN IL PREVAILING SFC FLO AT TERMINALS TO BE FM THE
SSE OVERNIGHT INTO SAT MORNING. LIGHT WIND TO BECOME SOUTHERLY DURING
THE MORNING AND THEN FROM THE SW IN THE AFTERNOON AS RIDGE DRIFTS
TO THE CENTRAL LAKES AND UPPER OH VALLEY AND THE LO PRES TROF
APPROACHES EVER SO SLOWLY FM THE NW.

FOR OVERNIGHT SAT NIGHT...SOME TIMING DIFFERENCES AS TO WHEN
TROF/COLD FRONT MOVES ACROSS N CENTRAL AND NE IL. WILL GO WILL SLOWER
PACE AS CONSENSUS OF MODELS AND TREND OF LIGHTLY SLOWER MOVEMENT
BY LATEST ETA RUN...EXCELLENT CONTINUITY IN GFS BETWEEN CURRENT AND
PREVIOUS RUNS...AS WELL AS SUPPORT FROM 12Z GFS ENSEMBLE MEAN AND
12Z ECMWF. 21Z SREF DID LEAN MORE TOWARD A BIT EARLIER PASSAGE ALA
LATEST ETA. 

TRS

&&

.MARINE...
127 PM CST

A LARGE HIGH EXTENDS FROM SOUTHERN MISSISSIPPI TO ONTARIO CANADA
THIS AFTERNOON. THE HIGH LIES OVER LAKE MICHIGAN. THIS RIDGE WILL 
MOVE EAST TO THE EASTERN UNITED STATES BY SATURDAY NIGHT. A LOW
WILL MOVE INTO SOUTHERN WISCONSIN. THE WIND OVER LAKE MICHIGAN
 WILL BE NORTHWEST THIS EVENING AND WILL SWITCH TO SOUTHWEST LATE
TONIGHT. DURING SATURDAY NIGHT THE WIND WILL BECOME WEST. DURING
THE DAY SUNDAY WE EXPECT A NORTHWEST WIND WITH SPEED OF 15 TO 25
KNOTS. WE EXPECT A CHANCE OF RAIN SHOWERS ON SUNDAY.

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$