FXUS63 KLOT 042359
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
559 PM CST THU DEC 4 2008
.DISCUSSION...
315 PM CST
FLURRIES AND ISOLATED SNOW SHOWERS LATE THIS AFTERNOON INTO THIS
EVENING...VERY COLD TONIGHT...
SHEAR AXIS EXISTS ALONG THE UPPER TROUGH STRETCHING FROM EASTERN
CANADA ACROSS THE GREAT LAKES TO THE CENTRAL ROCKIES. A MINOR SHORT
WAVE EMBEDDED IN THIS FLOW IS MOVING EAST ACROSS IOWA AND SOUTHERN
MINNESOTA. CLOUDS AND ACCOMPANYING SNOW FLURRIES AND A FEW SNOW
SHOWERS ARE MOVING ACROSS SOUTHERN WISCONSIN...AND NORTHWEST AND
NORTH CENTRAL ILLINOIS AT MID AFTERNOON AND WILL CONTINUE TO
SPREAD EAST. SKIES CLEAR LATER TONIGHT AS THE UPPER TROUGH AXIS
SINKS FURTHER SOUTHEAST. THIS...ALONG WITH A REINFORCEMENT OF COLD
AIR AND THIN SNOW COVER WILL ALLOW TEMPERATURES TO FALL TO SINGLE
DIGITS ACROSS THE NORTHERN AND WESTERN PORTIONS OF THE FORECAST
AREA GIVEN THAT CURRENT READINGS ARE ONLY IN THE TEENS AND LOWER 20S.
MINOR ACCUMULATING SNOW LIKELY LATE FRIDAY NIGHT INTO SATURDAY
MORNING WITH SOME MODERATION IN TEMPERATURES...BUT STILL BELOW
NORMAL...
NEXT PRECIPITATION MAKER IS THE STRONG SHORT WAVE CURRENTLY MOVING
ACROSS SOUTHERN YUKON...TOPPING THE UPPER RIDGE OVER THE WESTERN
NORTH AMERICAN COAST. CLIPPER SYSTEM TO DROP SOUTHEAST ACROSS THE
CANADIAN ROCKIES OVERNIGHT AND REACH SOUTHERN MANITOBA BY FRIDAY
EVENING. AS THE SYSTEM APPROACHES THE UPPER GREAT LAKES THE LOW
LEVEL FLOW BACKS TO SOUTHWESTERLY. THESE SOUTHWEST WINDS AND
INCREASING CLOUD COVER DURING FRIDAY NIGHT SHOULD KEEP
TEMPERATURES FROM FALLING TOO FAR OVERNIGHT.
WHILE THE SURFACE LOW TRACKS ACROSS SOUTHERN LAKE SUPERIOR...THE
UPPER PENINSULA OF MICHIGAN AND NORTHERN LAKE HURON LATE FRIDAY
NIGHT AND SATURDAY...STRONG WARM AIR ADVECTION AND RESULTING
ISENTROPIC LIFT IS INDICATED SOUTH ACROSS NORTHERN AND CENTRAL
ILLINOIS AND EXPECT GENERALLY 1 TO 3 INCHES TOTAL.
COLD AGAIN SATURDAY NIGHT...SUNDAY AND SUNDAY NIGHT...
THE UPPER TROUGH MOVES EAST TO OVER THE CENTRAL GREAT LAKES AND
THE LOWER OHIO VALLEY BY SATURDAY EVENING WITH THE COLD FRONT
TRAILING FROM THE CLIPPER CROSSING THE NORTHERN LAKES PUSHING
ACROSS THE FORECAST AREA. THE RETURN TO DEEP NORTHWEST FLOW
QUICKLY BRINGS THE COLD AIR BACK TO REGION. TEMPERATURES WILL RUN
WELL BELOW NORMAL SATURDAY NIGHT THROUGH SUNDAY NIGHT.
CHANCE OF MORE LIGHT SNOW ACCUMULATION MONDAY THROUGH MONDAY
NIGHT...
UPPER LOW CURRENTLY SOUTH OF THE ALEUTIANS IS PROGGED BY THE
LONGER RANGE MODELS TO DIG INTO THE CENTRAL ROCKIES DURING THE DAY
MONDAY WITH THE ASSOCIATED SURFACE LOW IN THE SOUTHERN PLAINS.
THE LOW IS FORECAST TO REMAIN WELL SOUTH OF THE REGION BUT A SETUP
SIMILAR TO WEDNESDAY DEPICTED WITH ANOTHER COLD FRONTAL PASSAGE
AND GOOD MID AND UPPER LEVEL FORCING.
COLD AGAIN TUESDAY NIGHT THROUGH THURSDAY...
HIGH AMPLITUDE UPPER TROUGH MOVES EAST WITH AXIS FROM HUDSON BAY
SOUTH TO THE CENTRAL GULF OF MEXICO AT 12Z WEDNESDAY. THIS KEEPS
THE FRIDGE DOOR WIDE OPEN ALLOWING COLD AIR TO CONTINUE TO DRAIN
ACROSS CENTRAL CANADA AND THE MIDWEST.
TRS
&&
.AVIATION...
0000 UTC TAFS...MAIN CONCERN FOR THE FIRST FEW HOURS OF THE 00Z
TAF UPDATE CONCERNS PATCHES OF LIGHT SNOW AND OCNL MVFR CEILINGS.
LATEST SATELLITE IMAGERY SHOWS A MID LEVEL IMPULSE CROSSING THE
UPPER MIDWEST. THIS FEATURE HAS BROUGHT LIGHT SNOW TO THE REGION.
VISIBILITY HAS LARGELY REMAINED VFR WITH OCNL BURSTS OF MVFR AND
IFR. LATEST RADAR TRENDS INDICATE THAT THE SNOW RATES ARE
WEAKENING...SO HAVE ONLY INCLUDED TEMPO GROUPS FOR MVFR VISIBILITY
AND CEILINGS...THOUGH AN OCCASIONAL BURST OF IFR VIS IN AN
ISOLATED HEAVIER SNOW SHOWER IS NOT OUT OF THE QUESTION. RADAR
IMAGERY SHOWS 2 DISTINCT PATCHES OF SNOW...WHICH SHOULD MOVE
THROUGH THE AREA BY AROUND MIDNIGHT. THE REMAINDER OF THE NIGHT
SHOULD BE QUIET WITH VFR CIGS AND DECREASING WINDS GRADUALLY
BACKING FROM NWLY TO SWLY.
THE MAIN CONCERN FOR TOMORROW WILL BE WINDS. WITH THE HIGH
PRESSURE SLIDING DOWN TO THE LOWER MISSISSIPPI VALLEY AND A
STRENGTHENING LOW DROPPING OUT OF CANADA AND ACROSS THE UPPER
MISSISSIPPI VALLEY...WINDS WILL CONTINUE TO BACK
SOUTHWESTERLY...STRENGTHEN AND BECOME QUITE GUSTY BY LATE MORNING.
FREQUENT GUSTS TO AROUND 25KT ARE EXPECTED. ANOTHER ROUND OF SNOW
WILL IMPACT THE TERMINALS TOMORROW NIGHT...BUT WILL NOT OCCUR
UNTIL AFTER THE END OF THE 00Z TAF PERIOD.
KREIN
&&
.MARINE...
1147 AM CST
WITH HIGH PRESSURE CENTERED TO THE SOUTH OF THE LAKES...WINDS SHUD
REMAIN RATHER BRISK OVER THE UPR MIDWEST THRU THE LAKES REGION FOR
QUITE SOME TIME. THE PRESSURE GRADIENT IS FURTHER TIGHTENED BY A
SHORT WAVE DROPPING SOUTHEAST INTO THE UPPER MS VLY ON FRIDAY.
THIS SFC TROF DEEPENS AS IT DROPS OVER THE LAKES FRI NGT AND
SATURDAY. HIGH WINDS NEAR 30 KTS CROSS THE THRESHOLD INTO GALES BY
THAT TIME. THESE SUBDUE A BIT IN THE OPEN LOW PRESSURE CENTER BUT
PICK UP AGAIN TO GALES FROM THE NW BY SAT NGT. AS HIGH PRESSURE
BUILDS OVER THE LAKES ON SUNDAY...IT IS PSBL FOR GALES TO DIMINISH
CONSIDERABLY SUN NGT WHILE HIGH PRESSURE SWITCHES WINDS TO THE
SOUTH AGAIN. WITH ANOTHER LOW PRESSURE SYSTEM SWINGING ACROSS
CANADA AND THE PLAINS SUN NIGHT...PRESSURE GRADIENT FORCES CUD
INTENSIFY AGAIN TO SUPPORT SOUTH GALES AHEAD OF THIS NEXT SYSTEM.
RLB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 5 PM SATURDAY.
GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM FRIDAY TO 3 AM
SUNDAY.
&&
$$
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