328 AM CDT
MAIN FORECAST CHALLENGE IN THE SHORT TERM WILL BE TIMING ARRIVAL OF
RAIN AND ISOLATED THUNDERSTORMS OVER THE NEXT 24 HOURS OR SO.
ADDITIONAL CHALLENGES ARISE BY EARLY NEXT WEEK. EARLY MORNING WATER
VAPOR IMAGERY SHOWS RIDGING OFF THE EASTERN SEABOARD EXTENDING
NORTHWESTWARD TOWARDS NORTHERN QUEBEC. AN UPPER LOW IS OBSERVED
SPINNING NORTHWARD ACROSS THE OHIO VALLEY TOWARDS THE LOWER GREAT
LAKES. A LONGWAVE TROUGH EXTENDS FROM NORTHERN MANITOBA SOUTHWARD
ACROSS WESTERN MN/IA/MO AND INTO ARKANSAS AND IS MOVING EAST. THIS
TROUGH WILL BE OUR MAIN WEATHER MAKER THROUGH THURSDAY. FURTHER
WEST...A BELT OF ZONAL FLOW IS FOUND OVER THE EASTERN PACIFIC AND
U.S. WEST COAST WITH A SERIES OF WEAKER UPPER LOWS SPINNING OFF THE
BRITISH COLUMBIA COAST. AT THE SURFACE...HIGH PRESSURE IS CENTERED
OFF THE COAST OF MAINE WITH LOW PRESSURE TAKING SHAPE ACROSS THE
NORTHERN PLAINS IN RESPONSE TO THE UPPER TROUGH AXIS. THIS LOW
PRESSURE WILL BECOME BETTER ORGANIZED AS IT APPROACHES AND PASSES
THE AREA OVER THE NEXT 36 HOURS OR SO.
TODAY AND THURSDAY...NARROW RIBBON OF CONVERGENCE EXTENDING FROM
EASTERN WISCONSIN SOUTHWARD ACROSS THE ROCKFORD AREA AND THEN
SOUTHWEST FROM THE QUAD CITIES TOWARDS QUINCY CONTINUES TO DRIVE
SCATTERED SHOWER DEVELOPMENT WITH A FEW THUNDERSTORMS ALSO
DEVELOPING IN MORE UNSTABLE AIR CLOSER TO THE MISSISSIPPI
RIVER. THIS ACTIVITY WILL PROBABLY CONTINUE TO FESTER OVER PRETTY
MUCH THE SAME AREAS THROUGH THE MORNING AS HEIGHT FALLS INCREASE AS
THE UPPER TROUGH APPROACHES FROM THE WEST. THE OTHER CONCERN IS FOG
POTENTIAL IN VICINITY OF THE WEAK TROUGH/CONVERGENCE WHERE WINDS
HAVE WEAKENED. DENSE FOG HAS DEVELOPED JUST TO THE WEST OF THE CWA
AS POCKETS OF CLEARING DEVELOP OUTSIDE OF THE SHOWER ACTIVITY. WITH
ADDITIONAL SHOWER ACTIVITY MOVING IN AND EXPECTED TO CONTINUE DENSE
FOG WILL HAVE A TOUGH TIME DEVELOPING ACROSS THE WESTERN CWA. WILL
MENTION FOG WITH CLEARING POCKETS POSSIBLY DEVELOPING DURING LULLS
IN SHOWER ACTIVITY. THE EASTWARD PROGRESSION OF THE UPPER TROUGH AND
THE ASSOCIATED SURFACE LOW WILL BE SLOW AND TIMING HOW QUICKLY THE
ACCOMPANYING RAIN MOVES ACROSS THE CWA CONTINUES TO BE TRICKY. THE
SHORT OF IT IS THAT THIS ISSUANCE WILL SLOW THE PROGRESSION FURTHER.
MODEL GUIDANCE SUPPORTS THIS AND ONE CONTRIBUTING FACTOR TO THE
SLOWER ARRIVAL IS LIKELY SUBSIDENCE ON THE WESTERN PERIPHERY OF THE
UPPER LOW OVER THE OHIO VALLEY. THE BULK OF THE AREA SHOULD REMAIN
DRY OUTSIDE OF THE FESTERING SHOWERS FAR WEST WITH MORE WIDESPREAD
RAIN LOOKING TO HOLD OFF UNTIL MID OR POSSIBLY LATE AFTERNOON ACROSS
WESTERN AREAS ALONG THE INTERSTATE 39 CORRIDOR. WILL BRING LOW
CHANCES INTO THE CHICAGO METRO AREA AND POINTS SOUTH TOWARD KANKAKEE
DURING THE EVENING BUT THIS MAY EVEN BE TOO FAST. RIGHT NOW...PRIME
PRECIP TIME SHOULD BE THIS EVENING AND TONIGHT ACROSS THE WESTERN
CWA AND THURSDAY MORNING INTO EARLY THURSDAY AFTERNOON ACROSS THE
EAST...INCLUDING THE CHICAGO AREA AS THE SURFACE LOW STRENGTHENS AND
MOVES ACROSS CENTRAL OR NORTHERN ILLINOIS. THE SYSTEM WILL THEN
SLOWLY SHIFT EAST GRADUALLY BRINGING AND END TO THE RAIN FROM WEST
TO EAST STARTING THURSDAY AFTERNOON WEST AS A COLD FRONT MOVES
BY.
FRIDAY THROUGH SUNDAY...COOLER AND DRIER AIR WILL MOVE IN THURSDAY
NIGHT AND FRIDAY MORNING ON BRISK WESTERLY WINDS WHILE H85 TEMPS
COOL TO BETWEEN 1 AND 3 C. THIS SHOULD HOLD HIGHS TO THE UPPER 50S
NORTH AND THE LOWER 60S SOUTH BUT THERE SHOULD BE A FAIR AMOUNT OF
SUNSHINE INTO EARLY AFTERNOON. A SECOND SURGE OF COOLER MID LEVEL
AIR DROPS SOUTHWARD DOWN THE WESTERN FLANK OF THE UPPER LOW. THIS
MAY BRING SCATTERED SHOWERS BACK TO THE AREA FRIDAY AFTERNOON AND
EARLY FRIDAY EVENING. THE UPPER LOW WILL THEN LIFT INTO EASTERN
CANADA SATURDAY MORNING AS DE-AMPLIFYING UPPER RIDGING APPROACHES
FROM THE WEST BRINGING WARM ADVECTION BACK TO THE REGION. THIS
SHOULD RESULT IN TEMPS A FEW DEGREES WARMER THAN FRIDAY. THE MID
LEVEL BAROCLINIC ZONE TIGHTENS UP SATURDAY NIGHT AS A FAST MOVING
SHORTWAVE MOVES SOUTHEASTWARD TOWARDS THE MID AND UPPER MISSISSIPPI
RIVER VALLEY. A SURFACE LOW WILL ALSO DEVELOP AND PASS OVER OR JUST
SOUTH OF THE AREA SUNDAY MORNING BRINGING A COLD FRONT WITH IT. IF
THE TIMING HOLDS THEN ANY PRECIP ASSOCIATED WITH THE SYSTEM WILL BE
CLEAR OF THE AREA SUNDAY AFTERNOON.
MONDAY THROUGH WEDNESDAY...MODEL AGREEMENT IS DECENT IN TERMS OF THE
GENERAL EVOLUTION OF THE UPPER FLOW PATTERN EARLY NEXT WEEK BUT
TIMING AGREEMENT IS LOW. A DEEP UPPER LOW IS EXPECTED TO DIG INTO
THE CENTRAL U.S. AND SPAWN STRONG CYCLOGENSIS SOMEWHERE ALONG THE
MISSISSIPPI RIVER VALLEY THEN DEEPEN AS IT PASSES THE AREA. BOTH THE
ECMWF AND GFS BRING IN WHAT COULD BE THE COLDEST AIR OF THE SEASON
TO DATE FOR THE MIDDLE PART OF THE WEEK.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 10Z...
* PRECIP CHANCES WEDNESDAY
* LAKE BREEZE POTENTIAL IN THE AFTERNOON
SHEA
//DISCUSSION...UPDATED 10Z...
TWO NOTED CHANGES FOR THE 10Z AMD CYCLE...FIRST WAS THE INCLUSION
OF CB GROUPING AT RFD FOR THIS MORNING. THERE HAVE BEEN A FEW
STRIKES TO THE SW OF JVL. BEST ELEVATED INSTABILITY POCKETS EXIST
OUT THERE AND COULD SEE THE OFF AND ON SHOWERS CONTINUE FOR THE
NEXT FEW HOURS. THE SECOND AND LARGER CHANGE IS PUSHING BACK THE
ONSET OF PRECIP...AGAIN. GUIDANCE HAS SLOWED DOWN THE TIMING IT
WILL IMPACT THE EASTERN TERMINALS CONSIDERABLY...AND RELFECTED
THAT IN THE LATEST TAFOR.
//DISCUSSION...UPDATED 06Z...
LIGHT SOUTHERLY WINDS AND VFR CONDITIONS ARE EXPECTED OVERNIGHT
FOR ALL OF THE EASTERN TERMINALS. ACROSS RFD THIS EVENING ARE THE
TAIL END OF SHOWERS THAT MOVED THROUGH EARLIER THIS EVENING. OF
CONCERN FOR RFD IS THE POTENTIAL FOR CIGS AND VIS TO TANK. WITH
THE LIGHT SHOWERS...BL MOISTURE HAS INCREASED AND IF SKIES CLEAR
OUT...WE WILL RADIATE OUT QUICKLY...AS IS SEEN AT FEP. WILL NEED
TO MONITOR FOR THOSE TRENDS...BUT AM LEANING IN THAT DIRECTION
INTO THE PREDAWN HOURS. WITH THE DRY CONDITIONS AND NO PRECIP
EAST...NO CONCERNS FOR ALL OTHER TERMINALS.
ANOTHER LAKE BREEZE IS EXPECTED THIS AFTERNOON...IN SIMILAR
FASHION TO PREVIOUS DAYS. SYNOPTIC FLOW WILL ALREADY BE OUT OF THE
SOUTH TO SOUTHEAST...AND WINDS WILL BEGIN TO PULL OUT OF THE 120
TO 130 RANGE WHEN IT PICKS UP/MOVES THROUGH. CONDITIONS ARE
EXPECTED TO DETERIORATE TOMORROW EVENING FOR ALL TERMINALS AS A
COLD FRONT BEGINS TO WORK THROUGH. CURRENT FORECAST PACKAGE IS
INTRODUCING VCSH INTO THE EVENING HOURS WITH SHOWERS OVERNIGHT.
TRENDS HAVE BEEN CONTINUALLY BRINGING THE FRONT THROUGH
SLOWER...AND MAY NEED TO TWEAK THE ONSET BY A FEW HOURS. STILL A
CONSISTENT SIGNAL THAT THE HEAVIEST OF SHOWERS /AND POTENTIALLY A
CLAP OF THUNDER/ WILL LIKELY OCCUR BEYOND 12Z ON THE 13TH. WITH
THE HEAVIEST OF ACTIVITY...EXPECT CIGS TO FALL WITH VISBY DOING
SIMILAR IN THE HEAVIEST OF SHOWERS. IFR CONDITIONS ARE
ANTICIPATED...WITH LIFR BEING A POSSIBILITY AS WELL.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 10Z...
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY
* MEDIUM TO HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP ONSET...HIGH ON INCREASING COVERAGE LATE
SHEA
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...SHOWERS AND ISOLATED THUNDERSTORMS. MVFR AND IFR
POSSIBLE.
* FRIDAY...SLIGHT CHANCE SHRA...OTHERWISE VFR.
* SATURDAY...VFR.
* SUNDAY AND MONDAY...SLIGHT CHANCE SHRA...OTHERWISE VFR.
BMD
&&
.MARINE...
256 AM CDT
BROAD AREA OF HIGH PRESSURE CONTINUES TO DRIFT EAST ACROSS NEW
ENGLAND STRETCHING NORTH THROUGH EASTERN QUEBEC...MEANWHILE AN
AREA OF LOW PRESSURE CONTINUES TO DEVELOP ACROSS SOUTHERN
MANITOBA. THIS LOW PRESSURE IS EXPECTED TO LIFT NORTHEAST.
ASSOCIATED WITH THIS LOW PRESSURE SYSTEM WILL BE YET ANOTHER WEAK
LOW PRESSURE SYSTEM...THAT IS EXPECTED TO RAPIDLY DEEPEN AS IT
APPROACHES THE GREAT LAKES REGION THURSDAY INTO FRIDAY. GUIDANCE
CONTINUES TO SUGGEST THAT THE PRESSURE GRADIENT WILL TIGHTEN
SUBSTANTIALLY...AND CREATE GALE FORCE WINDS. AT THIS POINT HAVE
HELD OFF ON ANY HEADLINES...HOWEVER CONFIDENCE CONTINUES TO GROW
THAT GALE CRITERIA WILL PROBABLY BEGIN TO OCCUR SOMETIME EARLY
FRIDAY MORNING. IT APPEARS A FEW GUSTS MAY APPROACH 40KT WITH THIS
SYSTEM.
THEN AFTER THIS POTENT LOW PRESSURE SYSTEM LIFTS NORTHEAST AWAY
FROM THE GREAT LAKES REGION...MODEL GUIDANCE IS BEGINNING TO HINT
AT YET ANOTHER POTENT LOW PRESSURE WILL APPROACH THE GREAT LAKES
REGION TUE. THIS SECOND SYSTEM TAKES ON A CLASSIC FALL LIKE
SETUP.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
