🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1216 PM CST SUN FEB 24 2013

DISCUSSION...
1023 AM CST

GOING FORECAST FOR TODAY LARGELY ON TRACK. DID FURTHER REDUCE
CLOUD COVER IN THE GRIDS TODAY ANTICIPATING A SUNNY AFTERNOON. THE
LATE FEB SUN ALREADY HAS AND SHOULD CONTINUE TO DO ITS THING
WARMING US UP AND COMMENCING THE MELTING PROCESS. HAVE NUDGED HIGH
TEMPS UP A BIT TO ACCOUNT FOR THIS...OTHERWISE GOING FORECAST HAS
THINGS WELL IN HAND.

AFTER TAKING A PRELIMINARY PERUSAL OF 12Z GUIDANCE HAVENT SEEN
ANY BIG SURPRISES REGARDING THE TUESDAY SYSTEM...STILL LOOKS LIKE
A HIGH IMPACT EVENT WITH POTENTIAL FOR SNOWFALL AMOUNTS
APPROACHING AND POSSIBLY EVEN EXCEEDING WARNING CRITERIA OVER
PORTIONS OF THE CWA. WOULD LIKE TO GET A LOOK AT THE 12Z ECMWF AND
FURTHER ACCESS REMAINDER OF GUIDANCE BEFORE MAKING ANY
DECISION...BUT MAY NEED TO AT LEAST CONSIDER A WINTER STORM WATCH
FOR PORTIONS OF THE CWA WITH THE AFTERNOON FORECAST PACKAGE.

IZZI

//PREV DISCUSSION...
307 AM CST

MAIN FOCUS THIS MORNING WILL BE DEALING WITH THE NEXT WINTER SYSTEM
TO IMPACT THE REGION ON TUESDAY BRINGING SNOWFALL AND A WINTRY MIX
TO PORTIONS OF THE OUTLOOK AREA.

TODAY AND MONDAY...
THIS MORNING...HIGH PRESSURE SPANS THE LOWER TO UPPER MISSISSIPPI
VALLEY AND SHOULD PROVIDE QUIET WEATHER TODAY AND MONDAY. LOWER
STRATUS DECK HAS MOSTLY BEEN ERODED THIS MORNING AND THROUGH THE
REMAINDER OF TODAY EXPECT PLENTY OF SUNSHINE WITH ONLY SOME THIN
CIRRUS. OVERNIGHT...SLOWER PROGRESSION OF THE RIDGE MEANS WE SHOULD
STILL BE SOLIDLY UNDER THE RIDGE AXIS...THUS FELT THERE WAS
POTENTIAL FOR STRONG RADIATIONAL COOLING AND DROPPED LOW
TEMPERATURES SEVERAL DEGREES. WILDCARD WILL BE INCREASING CLOUDS AS
THE NEXT AREA OF LOW PRESSURE APPROACHES FROM THE SOUTHWEST.

TUESDAY...
UPPER LOW IS SEEN DIGGING SOUTHEAST ACROSS THE INTERMOUNTAIN WEST
EARLY THIS MORNING...AND WILL CONTINUE TO DIG SOUTHEAST INTO TEXAS
BY LATE TONIGHT. MEANWHILE...SURFACE LOW OVER THE COLORADO
FRONTRANGE WILL DO THE PANHANDLE DIP TODAY..THEN BEGIN TO LIFT
NORTHEAST AND DEEPEN MONDAY AS THE NEGATIVELY TILTED H5 TROUGH/LOW
BEGINS TO LIFT NORTHEAST. SURFACE LOW PEAKS AROUND 990MB EARLY
TUESDAY MORNING OVER SOUTHERN MISSOURI...THEN BEGINS TO SLOWLY FILL
AS THE LOW OCCLUDES AND SHIFTS NORTH. GUIDANCE IN DECENT AGREEMENT
THROUGH TUESDAY AFTERNOON WITH THE LOW CENTER NEAR ST LOUIS BUT
CONTINUES TO STRUGGLE ON HOW QUICKLY THE LOW WILL FILL AND MOVE
NORTHWARD THEREAFTER. THIS SYSTEM DOES TAP INTO ABUNDANT GULF
MOISTURE WITH STRONG MOISTURE TRANSPORT INTO THE MID MISSISSIPPI
VALLEY...AND MODERATE TRANSPORT INTO NE IL/NW IN.

THIS PACKAGE...FELT THE NAM REPRESENTED FAIRLY MIDDLE OF THE PACK
TRACK OF THE LOW WHICH TAKES THE LOW NEAR KLAF. MAIN CONCERN FOR A
WINTRY MIX IS MAINLY SOUTH OF INTERSTATE 80 WHERE TEMPERATURES ARE
NEAR THE FREEZING MARK BELOW ROUGHLY 8KFT. NAM LAYER MAX WET BULB
TEMPS SHOW THE BEST POTENTIAL FOR FULLY MELTING FALLING PRECIP
TUESDAY MID TO LATE MORNING SOUTH OF A PONTIAC TO RENSSELAER LINE.
MORNING LOWS ARE EXPECTED TO BE JUST BELOW FREEZING...SO WONT TAKE
MUCH WARMING UNTIL WE PUSH TEMPS ABOVE ENDING THE FREEZING RAIN
THREAT...BUT THE POTENTIAL REMAINS. FARTHER NORTH UP THROUGH ROUGHLY
AN OTTAWA TO VALPARAISO LINE...MARGINALLY ABOVE FREEZING WET BULB
TEMPS WOULD SUPPORT ONLY PARTIAL MELTING AND POTENTIAL FOR
SLEET/SNOW MIX. NORTH OF THAT LINE...APPEARS MAINLY SNOW FOR THE
ENTIRETY OF THE EVENT. NAM GUIDANCE IS SUPPORTED BY SREF/GEFS
FREEZING RAIN PROBABILITIES WHICH ALSO HINT AT THE BEST CHANCES
ACROSS OUR FAR SOUTHERN COUNTIES. BY LATE TUESDAY AFTERNOON OR
EVENING...EXPECT THE COLUMN TO COOL FOR PRECIP TO CHANGE TO SNOW
ACROSS THE CWA. GIVEN THE RELATIVELY WARM SOUNDINGS AND A NOT SO
DEEP DGZ...DONT EXPECT VERY HIGH SNOW TO LIQUID RATIOS...BUT
ABUNDANT MOISTURE AS PREVIOUSLY MENTIONED WILL HELP OFFSET THIS AS
FAR AS SNOW TOTALS ARE CONCERNED.

MEANWHILE TUESDAY AFTERNOON/EVENING...THE BEST FORCING SHIFTS NORTH
ACROSS NORTHERN ILLINOIS AS NOTED BY MID LEVEL FGEN AND STRONG Q
CONVERGENCE. THIS COUPLED WITH STEEP LAPSE RATES/NEGATIVE EPV ALOFT
MAY LEAD TO DEEP VERTICAL RESPONSE ENHANCING THE MESOSCALE BANDING
POTENTIAL AND CAUSING LOCALIZED HIGHER SNOWFALL AMOUNTS.

ALL SAID WILL CALL FOR SOME PRELIMINARY SNOW TOTALS THROUGH LATE
TUESDAY EVENING. NORTH OF ROUGHLY PONTIAC TO VALPARAISO...THERE IS
POTENTIAL FOR 3 TO 6 INCHES OF SNOW...WITH AMOUNTS QUICKLY TAPERING
TO LESS THAN AN INCH SOUTH OF THAT LINE WHERE MUCH OF THE PRECIP
WILL FALL AS A WINTRY MIX OR RAIN. THE GARCIA METHOD WOULD SUPPORT
SLIGHTLY HIGHER TOTALS...AND GIVEN THE CURRENT EXPECTED TRACK OF THE
LOW...THE AXIS OF HEAVIEST SNOWFALL WOULD BE EXPECTED ROUGHLY FROM
MENDOTA THROUGH THE NORTHERN SUBURBS OF CHICAGO. KEEP IN MIND THAT
ADDITIONAL SNOWFALL WILL OCCUR BEHIND THIS SYSTEM TUESDAY NIGHT
THROUGH THE REMAINDER OF THE WEEK...AND THESE SNOWFALL AMOUNTS DO
NOT YET INCLUDE THOSE PERIODS.

WEDNESDAY THROUGH SATURDAY...
GUIDANCE CONTINUES TO SHOW BLOCKING HIGH DEVELOPING OVER THE NORTH
ATLANTIC ENHANCING THE NEGATIVE PHASE OF THE NORTH ATLANTIC
OSCILLATION. FOR US...THIS MEANS THAT TROUGHING IS EXPECTED TO
PERSIST ACROSS THE EASTERN CONUS WITH THE SURFACE LOW EXPECTED TO
SLOW/MEANDER AND GRADUALLY FILL OVER THE EASTERN GREAT LAKES REGION.
THIS LEAVES N IL/NW IN UNDER CYCLONIC FLOW WHICH SHOULD KEEP US
CLOUDY THROUGH MUCH OF THE WEEK WITH PERIODIC CHANCES OF LIGHT
SNOW/FLURRIES. COLD ADVECTION INTO THE AREA WILL INCREASE THE
INSTABILITY OVER LAKE MICHIGAN AND BY THURSDAY MAY SEE AN INCREASE
IN LAKE EFFECT SNOW ACTIVITY OVER FAR NE IL AND NW IN AND LASTING
THROUGH THE WEEKEND.

DEUBELBEISS

&&

AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* NONE.

JEE

//DISCUSSION...UPDATED 18Z...

A HIGH PRESSURE RIDGE STRETCHES FROM SOUTHERN IL TO MINNESOTA TO
CENTRAL ONTARIO. THE RIDGE AXIS WILL DRIFT OVER NORTHERN IL THIS
EVENING WITH WESTERLY WINDS BECOMING EITHER LIGHT AND VARIABLE OR
CALM. CLOUDS WILL SLOWLY INCREASE OVERNIGHT AHEAD OF THE NEXT
SYSTEM...BUT THINKING THEY WILL BE CLEAR LONG ENOUGH FOR IFR FOG
TO DEVELOP AT THE USUAL PLACES. USUAL PLACES BEING RFD...DPA AND
RFD. CONFIDENCE IS MEDIUM ON THE FOG BECAUSE IF CLOUDS MOVE IN
QUICKER...FOG IS LESS LIKELY TO DEVELOP. HOWEVER IF CLOUD COVER IS
SLOWER...COULD SEE DENSER FOG.

THE HIGH PUSHES EAST BY MONDAY MORNING WITH EAST WINDS LESS THAN
10 KT EXPECTED. BTWN THE INCREASING CLOUD COVER AND MIXING
INCREASING IN THE MORNING...THINKING FOG SHOULD DISSIPATE
RELATIVELY QUICKLY WITH VFR CONDITIONS BY MID MORNING.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...VFR. INCREASING EAST WINDS LATE.

TUESDAY...SNOW...POSSIBLY HEAVY. SOME SLEET OR RAIN POSSIBLE. IFR
TO LIFR CONDITIONS LIKELY. WINDY WITH BLOWING SNOW.

WEDNESDAY THROUGH SATURDAY...MVFR CIGS. PERIODIC SNOW SHOWERS OR
FLURRIES.

RATZER

&&

MARINE...
1215 PM CST

WINDS WILL BE LIGHT ACROSS LAKE MI THE REST OF TODAY TIL LATE MON
AS A HIGH PRESSURE RIDGE MOVES OVER THE WESTERN AND CENTRAL GREAT
LAKES. EAST WINDS WILL FRESHEN MONDAY NIGHT ON SOUTHERN LAKE
MICHIGAN AS A DEEPENING LOW TURNS NORTHEASTWARD FROM THE SOUTHERN
PLAINS. EAST TO NORTHEAST WINDS CONTINUE TO INCREASE...LIKELY TO
REACH GALE FORCE...ON ALL OF THE LAKE TUESDAY AND TUESDAY NIGHT
AS THE LOW CROSSES SOUTHWEST AND EAST CENTRAL ILLINOIS AS WELL AS
WEST CENTRAL AND NORTHEASTERN INDIANA. DURING WEDNESDAY THE LOW
MOVES NORTH NORTHEASTWARD TO NEAR THE SOUTH END OF LAKE SUPERIOR.
THIS WILL MAINTAIN NORTH GALES ON LAKE MICHIGAN THROUGH THE DAY
WEDNESDAY AND INTO THURSDAY NIGHT. SMALL CRAFT ADVISORY
CONDITIONS WILL LIKELY OCCUR FOR A FEW HOURS OVERNIGHT MONDAY BUT
NO ADVISORY WILL BE ISSUED AS IT WOULD ONLY BE A RAMP-UP TO THE
GALES EXPECTED BY TUESDAY MORNING.

TRS

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
     LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 AM TUESDAY TO
     MIDNIGHT FRIDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...6 PM TUESDAY TO MIDNIGHT FRIDAY.

&&

$$