065
FXUS63 KLOT 240758
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
158 AM CST TUE NOV 24 2009
DISCUSSION
1035 PM CST
QUICK LATE EVENING UPDATE TO ACCOUNT FOR DENSE FOG THAT HAS
ALREADY STARED TO FORM ACROSS MUCH OF THE AREA. SATELLITE REVEALS
THAT LOW STRATUS THAT COVERED MUCH OF THE REGION THIS MORNING HAS
ERODED TO THE NORTH...ALLOWING SKIES TO CLEAR. HIGH AND MID LEVEL
CLOUD COVER MAY BEGIN TO INCREASE NEAR DAYBREAK AS WARM AIR
ADVECTION DEVELOPS AHEAD OF STORM SYSTEM CURRENTLY OVER FAR
NORTHEASTERN KANSAS...BUT FOG SHOULD ALREADY BE WELL ESTABLISHED
AT THAT POINT. UPDATED GRIDS AND TEXT PRODUCTS ALREADY SENT.
BOXELL
AVIATION
0600 UTC TAFS...THE LOW CEILINGS SEEM TO BE ERODING TOWARDS THE
NORTH. THERE WILL BE SOME SCATTERED LOW CLOUDS LEFT THIS MORNING.
A WARM FRONT MAY BE DEVELOPING OVER CENTRAL ILLINOIS. THIS WARM
AIR LIFTING NORTHWARD ALONG THE FRONTAL SLOPE MAY BE ERODING THE
LOW CLOUDS. THE INVERSION SEEN ON ACARS SOUNDINGS WILL TRAP THE
MOISTURE NEAR THE GROUND. THE AIR WILL COOL BY RADIATION AND FOG
IS EXPECTED TO DEVELOP. WE WILL ADJUST THE TAFS FOR FOG. THE
VISIBILITY MAY FALL TO 1 TO 2 MILES OR LESS IN THE FOG. ROCKFORD
AND CHICAGO MAY NOT HAVE CLEAR SKIES UNTIL EARLY MORNING. THE FOG
MAY NOT BECOME THICKER AT THOSE LOCATIONS UNTIL EARLY MORNING.
THERE WILL BE IFR CONDITIONS EITHER BY THE CLOUDS OR THE FOG AT
MOST OF THE AIRPORTS THIS MORNING. THE LOW WILL MOVE INTO IOWA
WITH AN OCCLUDED FRONT BY TUESDAY EVENING. WE WILL FORECAST RAIN
FOR TUESDAY AFTERNOON AND TUESDAY NIGHT.
MARINE
158 AM CST
MAIN CONCERN FOR MARINE FORECAST IS PERIOD OF STRONG NORTHWEST WINDS
LATE THURSDAY INTO EARLY FRIDAY BEHIND LOW PRESSURE SYSTEM AND
ASSOCIATED PUSH OF COLD AIR ACROSS THE WESTERN LAKES.
LOW PRESSURE CURRENTLY ANALYZED OVER NORTHEASTERN KANSAS TO MOVE
NORTHEAST ACROSS WISCONSIN AND NORTHERN/CENTRAL LAKE MICHIGAN THOUGH
WEDNESDAY EVENING. WITH LOW MOVING ACROSS CENTRAL/NORTHERN LAKE
MICHIGAN...MAY SEE A BRIEF PERIOD OF GUSTY 20-25 KNOT
SOUTHWEST/WEST WINDS ON FAR SOUTH END LATE WEDNESDAY/WEDNESDAY
NIGHT. MORE IMPORTANTLY...SECOND UPPER DISTURBANCE DIGGING INTO
TROUGH ALOFT WILL MAINTAIN SLIGHT DEEPENING OF TRAILING
TROUGH/COLD FRONT WEDNESDAY NIGHT INTO THURSDAY. THIS TRAILING
TROUGH WILL MOVE ACROSS THE LAKE THURSDAY...WITH TIGHTENING OF
PRESSURE GRADIENT AND SURGE OF LOW LEVEL COLD AIR EXPECTED TO
PRODUCE NORTHWEST WINDS AROUND 30 KNOTS LATE THURSDAY/THURSDAY
NIGHT. MODEL FORECAST SOUNDINGS OVER THE LAKE DURING THIS PERIOD
INDICATE GUSTS JUST BELOW GALE FORCE...THOUGH A FEW GALE FORCE
GUSTS ARE POSSIBLE. PRESSURE GRADIENT AND ASSOCIATED NORTHWEST
WINDS WILL THEN GRADUALLY DECREASE FRIDAY...AS LOW CONTINUES TO
PULL AWAY TO THE NORTHEAST AND WEAK HIGH PRESSURE RIDGE SPREADS
ACROSS THE MISSISSIPPI VALLEY AND WESTERN LAKES FRIDAY NIGHT.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...DENSE FOG ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 10 AM TUESDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 10
AM TUESDAY.
LM...NONE.
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