000
FXUS63 KLOT 191521
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1021 AM CDT SAT JUN 19 2010
.DISCUSSION...
348 AM CDT
AFTER QUICK 1-2 PUNCH OF A LATE AFTERNOON AND AN EVENING LINE OF
FAST MOVING...DAMAGING WIND PRODUCING THUNDERSTORMS APPEARS THE
AREA WILL GET A SHORT RESPITE FROM THE FREQUENTLY VISITING
THUNDERSTORMS.
LINEAR THUNDERSTORM COMPLEX...WITH ITS OUTFLOW JUST PROCEEDING
IT...HAS PUSHED WELL SOUTH AND RUNS PRETTY MUCH WEST TO EAST
ACROSS CENTRAL MO...SOUTHERN IL AND CENTRAL IN EARLY THIS
MORNING. BEHIND THE LINE OF STORMS IS A BROAD BAND OF MORE
STRATIFORM RAIN WITH A FEW EMBEDDED THUNDERSTORMS. THIS RAIN IS
LINGERING OVER THE FAR SOUTHEAST PORTION OF THE FORECAST AREA BUT
WILL BE MOVING OUT BY DAYBREAK.
COLD AIR POOL IN WAKE OF THUNDERSTORMS AND RAIN HAS STABILIZED LOW
LEVELS WITH AIRCRAFT DERIVED SOUNDINGS FROM ARRIVALS AND
DEPARTURES AT RFD...ORD...AND MDW ALL SHOWING A SHARP INVERSION
UP TO AROUND 0.8KM AGL. ABOVE THIS STABILIZED LAYER STEEP LAPSE
RATES ARE STILL IN PLACE.
WHILE THE TRUE COLD FRONT WAS BACK ACROSS NW MN AND THE EASTERN
DAKOTAS EARLY THIS MORNING...A LEADING TROUGH MARKED BY A SLIGHT
VEERING OF THE WIND AND MUCH DEFINITIVELY BY A SHARP DROP IN DEW
POINTS OF 10-15 DEG F RUNS FROM CENTRAL LAKE SUPERIOR SOUTHWEST
ACROSS NW WI...SE MN...NW IA...AND ON INTO E CENTRAL NE. PER MODEL
SURFACE DEW POINT PROGS...THIS TROUGH WILL HAVE MOVED ACROSS SE WI
AND NW IL BY 12Z...AND CONTINUING ON TO NW IN...CENTRAL IL AND FAR
NE MO BY 18Z AS THE POSITIVE TILT SHORT WAVE TROUGH OVER WESTERN
ONTARIO AND MN CONTINUES TO MOVE EAST AND OVER THE UPPER GREAT
LAKES REGION.
THOUGH THE CIRRUS SHIELD OVER THE AREA WILL CONTINUE TO THIN THIS
MORNING ALLOWING SURFACE HEATING...THE SURFACE TROUGH AND LOWER
DEW POINTS WILL ARRIVE ACROSS THE AREA RESULTING IN CONVECTIVE
TEMPS WELL ABOVE 100F AND NO THUNDERSTORM DEVELOPMENT EXPECTED
WITH THE SURFACE TROUGH NOR THE TRUE COLD FRONT TODAY.
A STRENGTHENING SOUTHERLY LOW LEVEL FLOW DEVELOPS FROM THE
SOUTHERN TO THE CENTRAL PLAINS TODAY AND SHIFTS EASTWARD TO THE
MID MO VALLEY OVERNIGHT. THIS LOW LEVEL FORCING AND THE DEEP UVV
SUPPORT FROM THE SHORT WAVE CURRENTLY LIFTING NORTHEASTWARD FROM
THE NE CORNER OF CO INTO NEB WILL...IF NOT MAINTAIN THE HIGH
PLAINS CONVECTION...REIGNITE IT WITH AN MCS EXPECTED TO BE MOVING
OVER THE TOP OF THE BROAD...FLAT UPPER RIDGE ACROSS IA OVERNIGHT.
REMNANTS OF THIS COMPLEX MAY CONTINUE ON INTO NORTHERN IL FOR SUN
MORNING AS THE SHORT WAVE AND/OR MCV MOVES OVER THE LOCAL AREA.
THIS RIDGE GRADUALLY SHIFTS EAST SUN AND SUN NIGHT WITH THE AXIS
APPROXIMATELY OVER THE MS RIVER BY 12Z MON. THIS WILL RESULT IN
THE FRONTAL BOUNDARY THAT WILL MOVE THROUGH THE AREA TODAY TO
BEGINNING TO LIFT BACK NORTH AS A WARM FRONT. WITH THIS BOUNDARY
PROGGED TO BE ACROSS NORTHERN IL OR FAR SOUTHERN WI LATE SUN NIGHT
AND MON...ALONG WITH A NEW PARADE OF DISTURBANCES MOVING OVER THE
FLAT RIDGE...CHANCES FOR MORE THUNDERSTORMS RETURN FOR SUNDAY AND
INTO AT LEAST MID WEEK BEFORE THE BOUNDARY MOVES BACK SOUTH ACROSS
THE AREA AND EVENTUALLY TO THE OH RIVER.
SLIGHTLY COOLER AIR WILL BE SPREADING ACROSS THE AREA TODAY. THE
DROP IN DEW POINTS WILL BE NOTICEABLE ACROSS THE NORTHERN PORTION
OF THE FA...AND TO A LESSER DEGREE ACROSS THE FAR SOUTHERN
PORTION AS THEY WILL NOT BE ARRIVING UNTIL DURING THE AFTERNOON.
WITH THE RETURN OF THE FRONT ON MONDAY COMES THE HIGH DEW POINTS
SO HUMID/MUGGY CONDITIONS WILL PREVAIL UNTIL THE NEXT FROPA
MIDWEEK.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 15Z...
ONLY MINOR CONCERN TODAY IS FOR GUSTY WEST WINDS WHICH WILL
DEVELOP BY MIDDAY.
IZZI
//DISCUSSION...UPDATED 12Z...
LAST NIGHTS THUNDERSTORM COMPLEX HAS SHIFTED WELL SOUTH OF
TERMINALS INTO SOUTHERN MO/OHIO VALLEY THIS MORNING.AND SFC WIND
FIELD HAS FINALLY RETURNED TO SYNOPTIC WEST/SOUTHWEST. BROAD
TROUGH OVER UPPER MIDWEST/GREAT LAKES WILL MOVE EAST TODAY...WITH
WIND SHIFT TO THE WEST EXPECTED AS BOUNDARY LAYER MIXING DEEPENS
OVER THE NEXT COUPLE OF HOURS. FORECAST SOUNDINGS FROM 00Z/06Z
MODEL FORECASTS CONTINUE TO INDICATE BREEZY CONDITIONS WITH GUSTS
AROUND 20 KTS DURG THE DAY. BROAD SFC HIGH PRESSURE CURRENTLY OVER
THE NORTHERN PLAINS WILL BUILD SOUTHEAST TONIGHT AND EARLY SUNDAY
WITH WEAKENING PRESSURE GRADIENT WHICH WILL ALLOW LIGHT NORTHWEST
WINDS THIS EVENING...EVENTUALLY VEERING AROUND TO NORTHEAST SUNDAY
MORNING.
VFR CONDITIONS EXPECTED TODAY WITH DEBRIS CIRRUS DISSIPATING AND
LITTLE IN WAY OF CU ACCOUNT DRIER LOW LEVEL AIR FILTERING IN. MID
LEVEL SHORT WAVE LIFTING OUT OF THE SOUTHWESTERN STATES WILL BRING
RETURN OF MID/HIGH CLOUDS TONIGHT HOWEVER AS WARM/MOIST ADVECTION
BECOMES RE-ESTABLISHED ACROSS CENTRAL PLAINS...WITH TSTMS
EXPECTED TO DVLP TO OUR WEST ACROSS NEB/IA OVRNGT ON NOSE OF LOW
LEVEL JET. MID LEVEL WAVE PROGGED INTO SRN WI/NRN IL BY SUNDAY
MIDDAY...AND WHILE LLVLS XPCTD TO BE STABLE WITH NORTHEAST/EAST
SFC FLOW MAY SEE SOME DECAYING RW/TRW MOVE EAST TOWARD/ACROSS
TERMINALS AFTER SUNRISE. AT THIS TIME THIS ONLY AFFECTS ORD 30
HOUR TAF...AND HAVE INDICATED PROB30 FOR SHRA WITH CB VFR CLOUD
DECK.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 15Z...
* HIGH CONFIDENCE IN WINDS AND VFR TODAY AND TONIGHT
* LOW/MEDIUM CONFIDENCE IN SHRA/TSRA CHANCES SUN AM
IZZI
//OUTLOOK FOR ORD/MDW FOR 18Z SUNDAY-12Z THURSDAY...UPDATED 06Z...
SUNDAY...CHC TSRA. MAINLY VFR.
MONDAY...CHC TSRA. MAINLY VFR.
TUESDAY...CHC TSRA. MAINLY VFR.
WEDNESDAY...CHC TSRA. MAINLY VFR.
THURSDAY...VFR.
BEACHLER
&&
.MARINE...
201 AM CDT
MAIN MARINE FORECAST COMPLEXITIES LAY IN NEAR TERM...WITH GUSTY
SOUTH TO SOUTHWEST WINDS ACROSS LAKE MICHIGAN THIS MORNING.
THESE GUSTY WINDS ARE IN RESPONSE TO TIGHTENING OF PRESSURE GRADIENT
BETWEEN AREA OF LOW PRESSURE AND TRAILING COLD FRONT ACROSS ONTARIO
AND THE UPPER MIDWEST...AND SMALL BUBBLE HIGH OVER NORTHERN IL LEFT
OVER FROM PAIR OF STRONG THUNDERSTORM COMPLEXES LATE FRIDAY. THESE
WINDS EXPECTED TO GRADUALLY DECREASE THIS MORNING AS LOW PULLS AWAY
TO THE NORTHEAST...AND HIGH RAPIDLY WEAKENS OFF TO THE SOUTH. WINDS
EXPECTED TO REMAIN SOUTHWESTERLY THROUGH MUCH OF DAY AS WEAK COLD
FRONT TRAILS CANADIAN LOW...THEN SHIFT WEST/NORTHWEST LATER THIS
AFTERNOON/TONIGHT AS FRONT SAGS SOUTHEAST OF THE LAKE AND HIGH
PRESSURE RIDGE BUILDS IN FROM THE NORTHERN PLAINS AND UPPER MIDWEST.
THIS HIGH TO SLIDE ACROSS THE LAKE SUNDAY...DRIFTING TO THE UPPER
OHIO VALLEY SUNDAY NIGHT AND MONDAY AS ANOTHER AREA OF LOW PRESSURE
BEGINS TO DEVELOP ACROSS THE HIGH PLAINS.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
