FXUS63 KLOT 090528
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1128 PM CST TUE DEC 8 2009
.DISCUSSION...
903 PM CST
NO CHANGES TO GOING HEADLINES...WITH 5+ INCHES OF SNOW ALREADY
REPORTED THIS EVENING IN WARNING AREA. MINOR ADJUSTMENTS TO NEAR
TERM FORECAST BASED ON LATEST SATELLITE AND RADAR TRENDS.
EVENING RAOB/WATER IMAGERY DEPICTS COMPLEX WINTER STORM ACROSS
MIDWEST. MAIN UPPER TROUGH OVER NORTHEAST KS...WHILE LEAD SHORT WAVE
LIFTING ACROSS NORTHERN IL. SFC LOW SOMEWHAT ELONGATED ACROSS
CENTRAL MO INTO SRN IL THANKS TO TWO PRONGED MID LEVEL FORCING
FOCUS. 00Z WRF REMAINS IN LINE WITH EARLIER GUIDANCE...WITH MAIN
UPPER TROUGH BECOMING NEGATIVELY TILTED AND LIFTING NORTHEAST ACROSS
NORTHERN IL THROUGH 12Z WED...WITH SFC LOW TIGHTENING UP AS IT
DEEPENS RAPIDLY AND MOVES ACROSS NRN IL TOWARD SUNRISE.
HAVE SEEN A PERIOD OF MIXED PRECIP ACROSS EASTERN HALF OR SO OF CWA
THIS EVENING...THOUGH DRY SLOT ASSOCIATED WITH LEAD SHORT WAVE
APPEARS TO BE WORKING INTO THIS AREA PER RECENT SATELLITE/RADAR
TRENDS. WITH LOSS OF MID LEVEL MOISTURE AND ICE NUCLEATION EXPECT TO
TRANSITION TO LIGHT RAIN/DRIZZLE ACROSS AREAS EAST OF INTERSTATE 55
FOR THE NEXT SEVERAL HOURS. FARTHER WEST...MID LEVEL CIRCULATION AND
MOISTURE WITH MAIN WAVE TO AFFECT EASTERN IA/NORTHWEST IL AND THUS
FAVORS KEEPING THREAT OF SNOW ACROSS NORTH CENTRAL IL...WITH PERHAPS
SOME MIX OF LIGHT RAIN/DRIZZLE FOR A FEW HOURS. HAVE ALREADY
RECEIVED REPORTS OF 5-6 INCHES OF NEW SNOW ACCUMULATION DURING THE
EVENING FROM ROCKFORD AREA...THUS SEE NO REASON TO CHANGE GOING
WINTER STORM WARNING. HAVE RECEIVED NUMEROUS REPORTS OF 1-3 INCHES
OF WET SNOW AND SLEET FROM ADVISORY AREA AND ALSO PLAN NO CHANGES TO
THAT HEADLINE.
OTHER CONCERN AT THIS TIME IS POTENTIAL FOR WIND ADVISORY/WARNING
WEDNESDAY. SFC LOW OVER NORTHERN IL/LAKE MICHIGAN EARLY IN THE DAY
PLACES WEAKEST GRADIENT CONDITIONS ACROSS LOT CWA DURING THE
MORNING. CONCERN FOR NOW IS THAT LIGHT SNOW ACCUMULATION IN HIGHER
SNOW/LIQUID RATIO SNOW SHOWERS DURING THE DAY MAY SUPPORT MORE OF A
WINTER WEATHER ADVISORY FOR BLOWING SNOW. WANT TO AVOID SHUFFLING
HEADLINES AROUND...THOUGH FEEL A NEED TO ADDRESS ESPECIALLY SOUTHERN
COUNTIES WHERE TIGHTER GRADIENT AND CURRENT GUIDANCE INDICATE WINDS
INTO WARNING RANGE. WILL LOOK AT THIS MORE CLOSELY OVER NEXT COUPLE
OF HOURS FOR POTENTIAL WIND HEADLINE ACROSS SOUTHERN CWA.
RATZER/BOXELL
&&
.AVIATION...
1130 PM CST
0600 UTC TAFS...THE ONGOING WINTER STORM WILL CONTINUE BRING A
PLETHORA OF PROBLEMS FOR AVIATION WEATHER CONCERNS.
CATEGORICALLY...EXPECT IFR...AND OCNL LIFR...CONDITIONS TO PERSIST
THROUGH THE LATE MORNING HOURS AS CIGS OF 700-800FT HAVE SETTLED
OVER THE AREA. EXPECT LITTLE CHANGE IN CIGS THROUGH THE
NIGHT...EXCEPT THAT CIGS MAY DROP TO LIFR AS THE MAIN CORE OF COLD
AIR ASSOCIATED WITH THE UPPER LOW MOVES OVERHEAD DURG THE EARLY
MORNING HOURS. VSBY HAS GENERALLY IMPROVED TO 2-4SM AS THE
PREDOMINANT PCPN TYPE HAS CHANGED OVER TO RAIN...EXCEPT FOR RFD
WHERE PCPN CONTINUES TO BOUNCE AROUND BETWEEN LIQUID...FROZEN AND
A MIX. AS THE SFC LOW MOVES THROUGH NERN MO AND INTO NWRN IL...THE
ASSOCIATED PCPN SHIELD OVER NERN IL HAS MOVED TO THE NORTH...BUT
NWRN IL REMAINS UNDER A PIVOT POINT IN THE WARM ADVECTION PATTERN.
THUS...PCPN WILL BECOME RATHER SPARSE...EVEN CHANGING TO DZ DURG
THE EARLY MORNING HOURS AT ORD/MDW/DPA. RFD MAY SEE A BRIEF PERIOD
OF DZ OR DZSN...BUT PCPN THERE WILL LIKELY MORE QUICKLY CHANGE
BACK OVER TO SNOW.
CONDITIONS WILL DETERIORATE RAPIDLY AS THE SFC LOW PULLS AWAY FROM
THE AREA BY AROUND SUNRISE...WITH WINDS STRENGTHENING
DRAMATICALLY. AT THIS POINT...COLD ADVECTION WILL INCREASE AND
WINDS WILL QUICKLY INCREASE TO 25-30KT WITH FREQUENT GUSTS TO
40KT. AS THE WINDS INCREASE AND THE PCPN TURNS BACK OVER TO
SNOW...BLOWING SNOW WILL BECOME A CONCERN. HAVE MAINTAINED MVFR
VIS AS THE SNOW DECREASES ON THE TAIL END OF THE SYSTEM...BUT IF
THE SNOW BECOMES DRY ENOUGH AND WINDS REMAIN STRONG ENOUGH...MAY
HAVE TO ADJUST VIS LOWER WITH THE BLOWING SNOW.
FINALLY...BY ARND 00Z...ANY RESIDUAL SNOW WILL END AND WINDS WILL
BEGIN TO WEAKEN. HOWEVER...SINCE WINDS WILL STILL BE QUITE
BRISK...EXECT SOME VIS REDUCTION WITH BLOWING SNOW...BUT EVEN THAT
WILL FINALLY SUBSIDE TOWARD THE END OF THE PERIOD.
KREIN
&&
.MARINE...
143 PM CST
A RIDGE OF HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE
EAST TO NEW ENGLAND TONIGHT. LOW PRESSURE OVER THE TEXAS PANHANDLE
WILL INTENSIFY RAPIDLY AS IT MOVES NORTHEAST TO CHICAGO BY
WEDNESDAY MORNING. THE LOW WILL MOVE TO LAKE HURON BY WEDNESDAY
EVENING...AND INTO QUEBEC THURSDAY. GALE FORCE EASTERLY WINDS WILL
DEVELOP THIS EVENING. AS THE STRENGTHENING LOW APPROACHES SOUTHERN
LAKE MICHIGAN LATE TONIGHT...STORM FORCE WIND GUSTS ARE
LIKELY...MAINLY OVER THE NORTH HALF OF THE LAKE. IN THE WAKE OF
THE DEEPENING LOW...STORM FORCE WIND GUSTS ARE LIKELY MAINLY
OVER SOUTH AND CENTRAL PART OF THE LAKE WEDNESDAY INTO WEDNESDAY
EVENING. HIGH PRESSURE WILL MOVE INTO THE SOUTHERN PLAINS AND
LOWER MISSISSIPPI VALLEY THURSDAY AND FRIDAY. THIS RIDGE OF HIGH
PRESSURE WILL MOVE ACROSS THE WESTERN GREAT LAKES FRIDAY NIGHT AND
SATURDAY...ALLOWING WINDS AND WAVES TO CALM DOWN.
ALLSOPP
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011 UNTIL 6 PM WEDNESDAY.
WINTER WEATHER ADVISORY...ILZ012-ILZ013-ILZ014-ILZ019-ILZ020
UNTIL 6 PM WEDNESDAY.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 AM WEDNESDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...9 PM WEDNESDAY TO 4 AM
FRIDAY.
STORM WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 AM WEDNESDAY TO 9 PM
WEDNESDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...9 PM WEDNESDAY TO NOON FRIDAY.
GALE WARNING...NEARSHORE WATERS UNTIL 4
AM FRIDAY.
&&
$$
