FXUS63 KLOT 240516
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1116 PM CST WED DEC 23 2009
.DISCUSSION...
.NEAR TERM...THIS EVENING THROUGH THURSDAY EVENING...
CHALLENGING AND GENERALLY COLD AND RAW FORECAST FOR THE NEXT 24 OR
SO HOURS...
UPPER AIR ANALYSIS INDICATES DEEP UPPER TROUGH OVER NORTHERN TEXAS
AND SOUTHERN OKLAHOMA...AND ASSOCIATED SURFACE LOW OVER THE SOUTHERN
OZARKS. LOW PRESSURE IS EXPECTED TO CONTINUE TO MOVE NORTH UP THE
MISSISSIPPI VALLEY...EVENTUALLY MAKING ITS WAY TO EASTERN IOWA BY
FRIDAY MORNING.
A LITTLE CLOSER TO HOME...PRECIPITATION HAS BEEN ONGOING SINCE THIS
MORNING ACROSS THE AREA...WITH A GRADUAL INCREASE IN INTENSITY FROM
SOUTH TO NORTH DURING THE DAY TODAY. EXPECT THAT PRECIPITATION WILL
CONTINUE IN A STEADY FASHION THROUGH THE EVENING...OVERNIGHT...AND
DAY ON THURSDAY. PRECIPITATION PROBABILITIES NOT MUCH OF A
CHALLENGE IN THIS EVENT...WITH ALL LOCATIONS VIRTUALLY ASSURED OF
SEEING SOME SORT OF HYDROMETER FALLING FROM THE SKY AT SOME POINT.
PRECIP TYPE...HOWEVER...IS A DIFFERENT STORY...WITH MANY LOCATIONS
HOVERING WITHIN A DEGREE OR TWO OF FREEZING TODAY.
FREEZING LINE THIS MORNING STARTED OUT FROM SOUTHERN LA SALLE TO
SOUTHERN LIVINGSTON...FORD..IROQUOIS...AND BENTON COUNTIES. AT THIS
HOUR...32 DEGREE LINE HAS MADE ITS WAY NORTH TO SOUTHERN LEE COUNTY
SOUTHEAST TO KANKAKEE COUNTY...TO CENTRAL NEWTON AND JASPER COUNTIES
IN INDIANA. BASED ON NAM12 AND SREF OUTPUT...REALLY DON'T EXPECT TO
SEE FREEZING LINE MAKE IT ANY FARTHER NORTH TONIGHT. AS A RESULT OF
LOCATIONS NORTH OF AFOREMENTIONED FREEZING LINE BEING A DEGREE OR
TWO BELOW FREEZING...MIX OF FREEZING RAIN AND SLEET WILL BE THE
DOMINANT PRECIP TYPE THIS EVENING AND OVERNIGHT. AS THE PARENT
UPPER AND SURFACE LOWS MAKE IT A LITTLE CLOSER TO THE AREA THURSDAY
MORNING...EXPECT TO SEE A SURGE OF WARM AIR AT THE SURFACE DURING
THE MORNING HOURS...RESULTING IN SURFACE TEMPS RISING ABOVE FREEZING
ACROSS THE ENTIRE FORECAST AREA BY NOON....WITH PRECIPITATION
TRANSITIONING TO JUST PLAIN RAIN.
WITH A RATHER LENGTHY TIME OF FREEZING RAIN EXPECTED THIS EVENING
AND OVERNIGHT...AND HEALTHY QPF...REALLY SPENT QUITE A BIT OF TIME
CONSIDERING IMPACTS OF THIS FREEZING RAIN EVENT...AND AT
LEAST CONSIDERED THE IDEA OF A WINTER STORM OR ICE STORM WARNING.
WITH TEMPERATURES SO MARGINAL FOR FREEZING RAIN ACCUMULATIONS (MANY
LOCATIONS SOMEWHERE BETWEEN 31 AND 32 DEGREES)...I'M NOT CONVINCED
THAT ICE ACCUMULATION WILL BE ALL THAT EFFICIENT ON MANY SURFACES.
ADDITIONALLY...CAN'T TOTALLY RULE OUT A FEW SPOTS IN THE ADVISORY
BRIEFLY BOUNCING ABOVE FREEZING FOR AN HOUR OR TWO TONIGHT...WHICH
WOULD OBVIOUSLY RESULT IN LOWER ICE ACCUMULATIONS. THAT BEING
SAID...BEST ICE ACCUMULATIONS WILL LIKELY BE ON ELEVATED
SURFACES...VEHICLES...AND ANY UNTREATED ROADWAYS OR
SIDEWALKS...WHICH COULD GET TREACHEROUS FOR A TIME THIS EVENING AND
OVERNIGHT.
AFTER NOON ON THURSDAY...PRECIP CHANGE TO ALL RAIN WILL RESULT IN
MORE OF A HYDROLOGIC THREAT THAN WINTER WEATHER...AND SHOULD WASH
AWAY MUCH OF THE ICE THAT ACCUMULATES OVERNIGHT.
BOXELL
LONGER TERM...THU NIGHT THRU DAY 7...
FCST CONCERNS ARE CONTINUED THREAT OF MODERATE TO HEAVY RAINFALL
AND POTENTIAL FOR FLOODING PROBLEMS AS LARGE CENTRAL CONUS STORM
SYSTEM ALREADY SLOWED BY LATE THU IN ITS LIFTING OUT OF THE PLAINS
WITH CORE OF JET MAX FCST TO BE STILL JUST APPROACHING BASE OF UPR
TROF WITH ANOTHER DIGGING SWRD OVR THE NRN RCKYS. MODELS SIMILAR IN
EVENTUALLY CONSOLIDATING SRN PLAINS UPR LOW AND UPR LOW DROPPING S
OVR THE NRN HI PLAINS IN ASSOCIATION WITH THE UP STREAM DIGGING JET
MAX SOMEWHERE OVR/NEAR THE MID MS VALLEY BY MIDDAY FRI. ASSOCIATED
SFC LOW EXPECTED TO BE IN NRN MO FAR SRN IA THU NIGHT-FRI MORNING.
WITH ENTIRE FA TO BE IN MILD AIR BY THU EVE PCPN WILL BE ALL RA.
VERY STRONG LOW AND MID LVL 50-60KT FEED OF 0.9 TO 1.0 IN
PRECIPITABLE WATER FROM LATE THU AFTERNOON THRU LATE THU NIGHT
COMBINED WITH VERY STRONG DEEP ISENTROPIC LIFT CENTERED RIGHT OVER
THE FA CERTAINLY KEEPS ONE ON NOTICE FOR HEAVY RAINFALL POTENTIAL
DURING THIS TIME WITH WIDESPREAD 1.5-2.5 INCH TOTALS AND LOCAL 3 IN
AMOUNTS EXPECTED. THIS ALONE ENUF TO CAUSE HYDRO PROBLEMS WITH
SNOWMELT JUST THAT MUCH MORE RUNOFF. THUS...FLOOD WATCH FOR THU
AFTERNOON THRU THU NIGHT REMAINS.
CLOSE...CONSOLIDATED UPPER LOW TO ONLY VERY SLOWLY DRIFT OVER THE
UPR MIDWEST FRI THRU SAT NIGHT BEFORE STARTING TO ACCELERATE TO THE
ENE ACROSS THE GRTLKS SUN. SLOW MOVEMENT ALLOWS LOW LVL COLD AIR TO
WRAP WELL INTO THE SYSTEM SO EXPECT RA TO CHANGE TO SN DURING THE
DAY FRI WITH TEMPS FALLING FROM MORNING HIGHS IN MID AND UPR 30S TO
LWR 30S AND UPR 20S DURING THE AFTERNOON.
SLOW PROGRESS WILL KEEP THREAT OF SN GOING RIGHT THRU THE WEEKEND
THO WITH SYSTEM BECOMING VERTICALLY STACKED THERMAL FORCING LOST SO
INTENSITY OF SN WILL BE LIGHT. COLD MID WINTER TEMPS FOR LATE
WEEKEND INTO NEXT WEEK AS NW FLOW AND SFC RIDGE BUILDING OUT OF
CENTRAL CANADA KEEPS REGION IN COLD AIR THO CORE OF COLDEST AIR
LOOKS TO PUSH ACROSS THE CENTRAL AND EASTERN LAKES TO THE
NORTHEASTERN U.S.
TRS
&&
.AVIATION...
0600 UTC TAFS...A VERY CHALLENGING FORECAST SITUATION FOR THE
TERMINALS OVERNIGHT.
FREEZING RAIN CONTINUES ACROSS NRN IL. TEMPERATURES HAVE CHANGED
VERY LITTLE OVER THE PAST SEVERAL HOURS AND REMAIN RIGHT AT THE
FREEZING MARK. THUS...WITH SUBSTANTIAL SNOW STILL ON THE GROUND...NO
WARM ADVECTION AND WINDS REMAINING ELE/ESELY...EXPECT THAT
TEMPERATURES WILL REMAIN CONSTANT THROUGH THE NIGHT. THUS HAVE
MAINTAINED FREEZING PCPN IN THE FORECAST AND DELAYED THE CHANGE
OVER FROM FREEZING PCPN TO LIQUID PCPN UNTIL AROUND NOON. MODEL RH
PROFILES SHOW SOME DRIER AIR ADVECTING IN ABOVE 18KFT LATER
TONIGHT...AND TIMING LATEST RADAR TRENDS SHOW THE BACK EDGE OF THE
HEAVIER PCPN MOVING INTO NRN IL BY ARND 08Z...SO HAVE TRANSITIONED
THE PCPN OVER TO FZDZ. DEEP LAYER MOISTURE MOVES BACK OVER THE
AREA BY EARLY AFTERNOON AND SFC TEMPERATURES SHOULD FINALLY RISE
ABOVE FREEZING...SO PCPN CHANGE OVER TO ALL LIQUID. RAIN WILL
CONTINUE FOR THE REMAINDER OF THE DAY...BECOMING HEAVIER DURG THE
EVENING HOURS.
WINDS WILL REMAIN GENERALLY ELE-ESELY THROUGH THE PERIOD AS THE
SFC LOW TRACKS NEWD FROM ERN TEXAS THROUGH THE OZARKS...INTO THE
MIDDLE MISSISSIPPI VALLEY. WITH HIGH PRESSURE REMAIN NRLY STNRY
OVER ERN CANADA AND AND A STRONG SFC LOW APPROACHING FROM THE
SOUTHWEST...WINDS WILL CONTINUE TO STRENGTHEN THROUGH THE NIGHT
AND THROUGH THE DAY TOMORROW. BY TOMORROW AFTERNOON...SUSTAINED
WINDS OF 20-25KT AND GUSTS TO 30KT ARE LIKELY.
KREIN
&&
.MARINE...
340 PM CST
A RIDGE OF HIGH PRESSURE ACROSS THE CENTRAL GREAT LAKES REGION WILL
CONTINUE TO SLOWLY SHIFT TO THE EAST BY THURSDAY. MEANWHILE...AN
AREA OF LOW PRESSURE WILL MOVE OUT OF THE SOUTHERN PLAINS TONIGHT
AND INTO THE MID MISSISSIPPI VALLEY REGION BY THURSDAY. WITH THE
APPROACH OF THIS SYSTEM...WINDS WILL CONTINUE TO INCREASE FROM THE
SOUTH UP THROUGH THE NORTHERN HALF. EAST GALES WILL BE POSSIBLE
ACROSS THE SOUTHERN HALF LATE TONIGHT INTO THURSDAY MORNING AND
CONTINUE TO INCREASE AS THIS LOW DRAWS NEAR. WITH THE NORTHWARD
PROGRESSION OF THIS LOW...WINDS WILL ALSO INCREASE ON THE NORTH HALF
WITH GALES POSSIBLE BY THURSDAY AFTERNOON. GALES WILL CONTINUE
ACROSS THE ENTIRE LAKE INTO FRIDAY BEFORE THEY DIMINISH BELOW GALE
FORCE FRIDAY AFTERNOON. THE AREA OF LOW PRESSURE RESPONSIBLE FOR
THIS INCREASE IN WINDS OVER THE NEXT COUPLE OF DAYS WILL BE SLOW TO
EXIT THE REGION...FINALLY EXITING OFF TO THE EAST LATE IN THE
WEEKEND. ALTHOUGH...AS IT BEGINS TO EXIT...IT WILL CONTINUE TO
WEAKEN WITH WINDS DOING THE SAME.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...ICE STORM WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023 UNTIL 8 AM
THURSDAY.
FLOOD WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-ILZ023-
ILZ032-ILZ033-ILZ039...NOON THURSDAY TO 6 AM FRIDAY.
WINTER WEATHER ADVISORY...ILZ014 UNTIL 8 AM THURSDAY.
IN...FLOOD WATCH...INZ001-INZ002-INZ010-INZ011-INZ019...NOON THURSDAY
TO 6 AM FRIDAY.
ICE STORM WARNING...INZ001-INZ002-INZ010-INZ011 UNTIL 8 AM
THURSDAY.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
LMZ874-LMZ876-LMZ878...4 AM THURSDAY TO NOON FRIDAY.
GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...4 PM THURSDAY TO NOON FRIDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 4 AM THURSDAY.
&&
$$
