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000
FXUS63 KLOT 092010
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT SAT MAY 9 2009
.DISCUSSION...
310 PM CDT
MAIN FORECAST CONCERNS TODAY INCLUDE ISOLD SHOWER CHANCES THE NEXT
COUPLE DAYS...FOLLOWED BY WARM-UP AND CONVECTIVE CHANCES
ASSOCIATED WITH NEXT SIGNIFICANT SHORTWAVE ARRIVING BY MID-WEEK
SURFACE LOW RESPONSIBLE FOR THIS MORNING`S 40 TO 50 MPH WINDS HAS
RAPIDLY MOVED EASTWARD AND THE REMARKABLE GRADIENT HAS RELAXED
ENOUGH FOR A LAKE BREEZE TO DEVELOP AND PUSH INLAND THIS AFTERNOON
JUST 5 HOURS AFTER NEARLY 50 MPH WNW WINDS. NOW THAT A SURFACE
RIDGE HAS BUILT IN AND IS PROGGED TO FESTER ABOUT THE
REGION...WOULD EXPECT THE TYPICAL SPRINGTIME AFTERNOON LAKE
BREEZES TO FORM THE NEXT COUPLE OF DAYS PROVIDING FOR LAKE
COOLING.
WHILE LOW...THE RAIN CHANCES THE NEXT COUPLE OF DAYS ARE NOT ZERO.
FAIRLY VIGOROUS SHORTWAVE LOCATED OVER THE NORTHERN PLAINS HAS
BEEN PRODUCING SOME SHOWERS THIS AFTERNOON. THIS WAVE IS PROGGED
TO DE-AMPLIFY AS IT TRACKS INTO THE WESTERN GREAT LAKES REGION
SUNDAY...HOWEVER SEVERAL MODELS ARE SPITTING OUT SOME LIGHT QPF.
IT IS QUITE TEMPTING TO INTRODUCE SOME LIGHT SHOWER CHANCES INTO
THE FORECAST FOR SUNDAY...ESPECIALLY GIVEN SREF POPS NEARING 50
PERCENT...BUT WILL HOLD MY BREATHE AND GO WITH CONTINUITY FOR NOW
MAINTAINING A DRY FORECAST. NOTHING ELSE UPSTREAM SHOWING UP ON
WATER VAPOR IMAGERY UPSTREAM OF THIS WAVE...THOUGH NORTHWEST FLOWS
ARE NOTORIOUSLY TROUBLESOME SO RAIN CHANCES CERTAINLY NOT ZERO
HEADING INTO THE START OF THE WORK WEEK.
NEXT MORE SIGNIFICANT SHORTWAVE CURRENTLY OVER THE GULF OF ALASKA
IS PROGGED TO TRACK ALONG THE U.S./CANADIAN BORDER EMERGING TO THE
LEE OF THE ROCKIES TUESDAY NIGHT. STRONG LOW LEVEL JET WILL
DEVELOP IN RESPONSE TO THE HEIGHT FALLS IN ADVANCE OF THIS SYSTEM
AND DRAW INCREASING RICH THETA-E AIRMASS NORTHWARD IN ADVANCE OF
THE SYSTEM. CERTAINLY THERE ARE THE USUAL TRACK/TIMING ISSUES THAT
ARE COMMON THIS FAR OUT...BUT OVERALL LOOKS LIKE A PRETTY GOOD
SHOT AT THUNDERSTORMS WEDNESDAY. GIVEN THE STRENGTH OF THE SYSTEM
IT WILL NEED TO BE WATCHED FOR SEVERE WEATHER POTENTIAL SOMEWHERE
IN THE REGION...BUT THERE`S STILL PLENTY OF TIME TO GET WORKED UP
ABOUT THAT.
DOESN`T APPEAR TO BE ANY SIGNIFICANT SHOT OF COLD AIR TO FOLLOW
BEHIND THE MID-WEEK SYSTEM AS UPPER FLOW QUICKLY GOES ZONAL ONLY
TO POSSIBLY BE FOLLOWED BY ANOTHER SYSTEM TOWARD NEXT WEEKEND.
IZZI
&&
.AVIATION...
18Z TAFS...MAIN CONCERN THIS PERIOD ARE WINDS INTO THIS EVENING
AND CIGS. LOW PRESSURE RESPONSIBLE FOR STRONG WINDS EARLIER THIS
MORNING HAS RAPIDLY MOVED EAST AND IS NOW LOCATED NEAR LAKE
ONTARIO. PRESSURE GRADIENT ACROSS THE AREA HAS WEAKENED QUITE A
BIT...SO MUCH SO THAT A LAKE BREEZE FORMED A FEW HRS AGO AND HAS
SINCE PUSHED WEST THRU ORD/MDW AS WELL AS GYY. WIND DIRECTION HAS
TURNED NORTHEAST WITH SPEEDS GENERALLY 10KTS OR LESS. THE NAM
MODEL SEEMS TO BE HANDLING THIS LAKE BREEZE AND ASSOCIATED
DIRECTIONS THE BEST BUT INDICATES THE LAKE BREEZE MAY SLOW OR EVEN
STALL. STILL SEEMS TO HAVE A STEADY SPEED AS IT MOVES INTO DU PAGE
AND WILL COUNTIES SO HAVE GONE WITH A PREVAILING NORTHEASTERLY
WIND AT ORD/MDW/GYY BUT HELD SHORT OF DPA AND WILL NEED TO MONITOR
ITS MOVEMENT OVER THE NEXT FEW HRS. AS SUNSET APPROACHES THE LAKE
BREEZE WILL WASH OUT...WHERE EVER IT ENDS UP...AND AT SOME POINT
DURING THE EARLY/MID EVENING...EXPECT WINDS TO TURN BACK WEST OR
NORTHWESTERLY BUT UNDER 10KTS. AS HIGH PRESSURE BUILDS ACROSS THE
REGION TONIGHT...WINDS WILL LIKELY GO LIGHT WESTERLY OR LIGHT AND
VRB BY MORNING. WEST/NORTHWEST WINDS INCREASE TO 10 TO 15 KTS
SUNDAY MORNING BUT EXPECT ANOTHER LAKE BREEZE TO MOVE THRU THE
TERMINALS EARLY/MID AFTERNOON.
CIGS HAVE GENERALLY GONE VFR AT MOST OF THE TAFS. LOWER CLOUDS IN
THE 1-2KFT RANGE ACROSS SOUTHERN WI ARE SLOWLY LIFTING...
ESPECIALLY AS THEY MOVE SOUTH INTO NORTHERN IL WHERE SFC TEMPS ARE
FEW DEGREES WARMER. OVERALL...EXPECT PREVAILING 3-4KFT CIGS BUT
CAN/T COMPLETELY RULE OUT SOME HIGH MVFR...MAINLY THRU MID
AFTERNOON.
12Z MODELS ALSO HINT AT SOME SHOWERS DEVELOPING OVER NORTHEAST IL
LATER THIS AFTERNOON...20Z-23Z...THEN QUICKLY SHIFTING SOUTHEAST.
INSTABILITY RATHER LIMITED ALONG WITH AN INVERSION IN THE 700-800
MB LEVEL OFF MODEL SOUNDINGS. LAKE BREEZE MIGHT PROVIDE ENOUGH SFC
CONVERGENCE FOR SOME ISOLATED ACTIVITY. THOUGH CONFIDENCE TOO LOW
TO INCLUDE IN THIS FORECAST. CMS
&&
.MARINE...
224 PM...LOW PRESSURE OVER NEW YORK WILL CONTINUE TO QUICKLY LIFT
ACROSS NEW ENGLAND TONIGHT. BROAD BUT WEAK HIGH PRESSURE OVER THE
NORTHERN AND CENTRAL PLAINS WILL MOVE EAST ACROSS THE LAKES AND
THE OHIO VALLEY SUNDAY INTO MONDAY AS IT STRENGTHENS. BY TUESDAY...
THIS HIGH WILL EXTEND FROM NEW ENGLAND TO THE SOUTHEAST U.S. AS IT
CONTINUES TO SLOWLY MOVE EAST. THIS HIGH WILL ALLOW A LAKE BREEZE
TO FORM ACROSS THE IL/IN NEARSHORE SUNDAY AND MONDAY AFTERNOONS. A
TROUGH OF LOW PRESSURE WILL DEVELOP OVER THE PLAINS TUESDAY NIGHT
INTO WEDNESDAY WITH DEEP LOW PRESSURE MOVING NORTHEAST ACROSS
ONTARIO WEDNESDAY INTO WEDNESDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 1 AM SUNDAY.
&&
$$
