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000 FXUS63 KLOT 160351 AFDLOT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1024 PM CDT SUN MAR 15 2009 .DISCUSSION... 920 PM CDT AN UPPER LEVEL SHORT WAVE CONTINUES TO SLOWLY APPROACH THE MID MS RIVER VALLEY THIS EVENING. UPPER LEVEL CIRCULATION AT 02Z APPEARS TO BE CENTERED ACROSS NORTHWEST MISSOURI...WITH RATHER EXTENSIVE MID LEVEL CLOUDINESS ACROSS MOST OF NORTHERN ILLINOIS/NORTHWEST INDIANA AHEAD OF THIS FEATURE. LATEST SEVERAL WATER VAPOR FRAMES SUGGEST THE UPPER LEVEL CIRCULATION ASSOCIATED WITH THIS SHORT WAVE IS BEGINNING TO FEEL UPSTREAM SHORT WAVE MOVING ACROSS THE DAKOTAS WHICH SHOULD ALLOW FOR A MORE EAST SOUTHEAST TRACK OF THE NORTHERN MISSOURI SHORT WAVE OVERNIGHT. EVENING RAOB FROM DVN STILL DEPICTING A VERY DRY LOW/MID LEVEL PROFILE WHILE ILX RAOB HAS MOISTENED UP SOME WITH WEAK LOW LEVEL MOISTURE ADVECTION OUT AHEAD OF APPROACHING SHORT WAVE. SURFACE OBSERVATIONS FROM NORTHEAST MISSOURI/SOUTHEAST IOWA HAVE BEEN INDICATING SOME -RA FROM TIME TO TIME AND STILL NOT OUT OF THE QUESTION FOR SOME SPRINKLES OR VERY LIGHT RAIN SHOWERS TO AFFECT MAINLY SOUTHERN PORTIONS OF THE FORECAST AREA OVERNIGHT GIVEN EXPECTED SOUTHEAST TRACK OF THE UPPER LEVEL VORT MAX. MINS OVERNIGHT WILL BE DEPENDENT ON POSSIBILITY OF ANY BREAKS IN MID LEVEL CLOUDS...AND OVERALL IDEA OF MID 30S NORTH TO LOWER 40S SOUTH STILL APPEARS TO BE REASONABLE. UPDATED ZONES WILL BE SENT SHORTLY MAINLY JUST TO SLIGHTLY INCREASE SKY COVER AND GO WITH MORE OF MOSTLY CLOUDY WORDING FOR REMAINDER OF THE NIGHT. MARSILI && .PREV DISCUSSION... 317 PM CDT FEW CHANGES OVERALL TO GOING FORECAST...MAINLY FOCUSED ON MINIMAL LIGHT PRECIP THREAT TONIGHT/EARLY MONDAY...WARM TEMPS INTO MID WEEK THEN FROPA/PRECIP AND COOLER TREND IN LATER PERIODS OF FORECAST. INITIALLY...BEAUTIFUL SPRINGLIKE AFTERNOON IN PROGRESS ACROSS THE CWA WITH LIGHT WINDS AND PLENTY OF SUN ALLOWING CONTINUED MODERATION IN TEMPS. OF COURSE...AREAS ALONG THE LAKE MICHIGAN SHORE ONLY IN THE 40S...BUT TEMPS 55-60 FARTHER INLAND. TAKING A LOOK UPSTREAM HOWEVER...WATER VAPOR LOOPS SHOWS OLD MID LEVEL CIRCULATION STILL SPINNING ACROSS MISSOURI VALLEY OF EASTERN NEB/WESTERN IA THIS AFTERNOON. WHILE LOW LEVELS FAIRLY DRY ACROSS OUR AREA...SURFACE ANALYSIS AND 12Z RAOB FROM KSGF INDICATES SOME MOISTURE BEING PULLED NORTHWARD WITH WEAK SURFACE WAVE/TROUGH NOTED ACROSS WEST CENTRAL MO. REGIONAL RADAR MOSAIC DOES SHOW SOME SCATTERED LIGHT RAIN SHOWERS HAVE DEVELOPED AHEAD OF MID LEVEL TROUGH AND 12Z RUNS OF WRF/GFS BOTH TRY TO SQUEEZE OUT A HUNDREDTH OR SO INTO MAINLY SOUTHERN PORTIONS OF WFO CWA LATER TONIGHT/EARLY MONDAY MORNING AS CIRCULATION DRIFTS NORTHEAST ACROSS THE AREA. WITH THIS IN MIND...HAVE ADDED LOW CHANCE POP FOR A FEW SPRINKLES FROM AFTER MIDNIGHT TONIGHT INTO EARLY MONDAY MAINLY SOUTH OF I-80. MID LEVEL TROUGH AXIS MOVES OFF TO THE EAST MONDAY MORNING...WITH SOUTH LOW LEVEL FLOW DEVELOPING IN RESPONSE TO SIGNIFICANTLY STRONGER AREA OF LOW PRESSURE MOVING ACROSS CENTRAL CANADA. LITTLE CHANGE TO THIS PORTION OF THE FORECAST AS CLOUDS MOVE OFF...AND TEMPS WARM INTO THE 60S MONDAY...AND INTO THE UPPER 60S/LOWER 70S WEDNESDAY WITH EXCEPTION OF AREAS ALONG ILLINOIS LAKE MICHIGAN SHORE WHERE ANOTHER WEAK SOUTHEAST LAKE BREEZE EXPECTED MONDAY AS SFC GRADIENT REMAINS SLIGHTLY SOUTHEAST. STRONGER SOUTH GRADIENT WINDS TUESDAY SHOULD LIMIT/PREVENT LAKE BREEZE DEVELOPMENT. SURFACE RIDGE AXIS REMAINS ACROSS GULF/SOUTHEASTERN STATES LIMITING MOISTURE RETURN AND CLOUD COVER BOTH DAYS. SURFACE COLD FRONT TRAILING CANADIAN LOW THEN PUSHES SOUTHEAST INTO NORTHERN IL/NORTHWEST INDIANA TUESDAY NIGHT...SETTLING ACROSS CWA ON WEDNESDAY. MODELS REMAIN CONSISTENT IN DEVELOPING PRECIPITATION ALONG/BEHIND THE FRONT TUESDAY NIGHT/WEDNESDAY BEFORE SAGGING FRONT AND PRECIP SOUTH OF THE AREA WEDNESDAY NIGHT. LONGER RANGE GUIDANCE IN BETTER AGREEMENT IN BUILDING SURFACE HIGH PRESSURE ACROSS THE AREA THURSDAY AND SLIDING IT OFF TO THE SOUTHEAST BY LATE FRIDAY. GUIDANCE THEN DIVERGES LATE IN THE DAY 6-7 PERIOD...MAINLY WITH HOW FAST SURFACE HIGH DEPARTS STAGE RIGHT...AND TIMING OF DEVELOPMENT OF LOW PRESSURE ACROSS THE PLAINS LATE NEXT WEEKEND. AS MENTIONED ABOVE...LITTLE CHANGE MADE DURING THIS PERIOD WITH COOLER THAN AVERAGE TEMPS ESPECIALLY THURSDAY/FRIDAY AS COOL SURFACE HIGH BUILDS ACROSS REGION. RATZER && .AVIATION... 0600 UTC TAFS...HAD A BIT OF A LAKE BREEZE MOVE INTO ORD MDW AND GYY WHILE SOUTH WINDS PREVAIL AT DPA AND RFD. ALL WINDS BLO 10 KTS AND SHUD WEAKEN UNDER WEAK HIGH PRESS FIELD TO LIGHT AND VRBL. SOME MVFR HAZE THIS MRNG LIKELY TO REPEAT AROUND SUNRISE BUT OTRW NO IMPACT TO AVIATION CONCERNS. WARM AIR ADVECTIONS AC AND CI FROM A MID LVL TROF SLIPPING ACROSS ILLINOIS OVERNIGHT WITH UPR RIDGING RETURNING OVER ILLINOIS BY AFTN MONDAY. MAY AGAIN SEE AN AFTN LAKE BREEZE VECTORING WINDS FROM THE SOUTH TO THE SE ON MONDAY BUT STILL FORESEE NO AVIATION IMPACTS THRU THE NEXT 36 HOURS. RLB && .MARINE... 120 PM...A WEAKENING RIDGE OF HIGH PRESSURE EXTENDS FROM THE TEXAS GULF COAST...THROUGH THE OHIO VALLEY TO THE MID ATLANTIC REGION. THIS RIDGE...COMBINED WITH STRONGER HIGH PRESSURE OVER SERN CANADA WILL CONTINUE TO INFLUENCE LAKE MICHIGAN BY KEEPING WINDS RELATIVELY LIGHT AND GENERALLY SOUTHERLY THROUGH MONDAY. BY TUESDAY...A DEVELOPING TROUGH OF LOW PRESSURE WILL HELP STRENGTHEN THE PRESSURE OVER THE LAKE...INCREASING THE SOUTHERLY WINDS TO 20-30KT. A WEAK COLD FRONT ASSOCIATED WITH THE TROUGH IS EXPECTED TO SWEEP ACROSS LAKE MICHIGAN LATE TUESDAY NIGHT. HIGH PRESSURE WILL THEN BUILD ACROSS THE NORTHERN PLAINS WEDNESDAY AND WEDNESDAY NIGHT AND AND THE WESTERN GREAT LAKES THURSDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
