328 AM CDT
THE LONG STRETCH OF DRY WEATHER WILL BE ENDING FOR AT LEAST SOME OF
THE WESTERN THIRD TO HALF OF THE AREA TODAY AND TONIGHT. THE REST OF
THE AREA SHOULD SEE ANOTHER DAY AND POSSIBLY TWO OF DRY WEATHER
BEFORE MORE WIDESPREAD SHOWER ACTIVITY ARRIVES WEDNESDAY
AFTERNOON/EVENING. EARLY MORNING WATER VAPOR IMAGERY SHOWS THE UPPER
RIDGE THAT WAS SO PERSISTENT ACROSS THE AREA NOW EXTENDING FROM THE
NEW ENGLAND COAST NORTHWESTWARD TO HUDSON BAY. THE TROUGH THAT HAS
BEEN TO THE WEST HAS NOW MOVED EASTWARD AND DE-AMPLIFIED OVER THE
ROCKIES AND HIGH PLAINS WITH MORE OF A ZONAL FLOW NOW ACROSS THE
WEST COAST AND EASTERN PACIFIC. THE INITIAL FEATURE OF CONCERN IS A
CIRCULATION MOVING NORTHWARD ACROSS MANITOBA WITH A TROUGH AXIS
EXTENDING SOUTHWARD INTO THE MISSISSIPPI RIVER VALLEY. THIS TROUGH
ALONG WITH A WEAK SURFACE BOUNDARY WILL BRING THE SHOWER CHANCES TO
WESTERN PARTS OF THE AREA TODAY. THE OTHER FEATURE OF NOTE IS A LOW
AMPLITUDE LONGWAVE TROUGH MOVING ACROSS THE ROCKIES AT THE EASTERN
EXTENT OF THE ZONAL FLOW NOW OVER THE WEST COAST. THIS TROUGH WILL
PROMOTE SURFACE CYCLOGENESIS ACROSS THE CENTRAL AND NORTHERN PLAINS
WITH THIS SYSTEM REACHING THE LOCAL AREA LATER WEDNESDAY.
TODAY THROUGH FRIDAY...THE MANITOBA UPPER LOW WILL CONTINUE
NORTHWARD WITH THE ASSOCIATED TROUGH AXIS SLOWLY MOVING EASTWARD AND
LOSING DEFINITION. THERE IS ALSO A HINT OF A WEAK SURFACE
FRONT/CONVERGENCE BOUNDARY THAT WILL MOVE INTO THE WESTERN CWA AS
WELL. RADAR MOSAIC SHOWS CLUSTERS OF SHOWERS MOVING NORTHWARD ACROSS
NORTHEAST MISSOURI AND EASTERN IOWA AS A RESULT OF THIS SYSTEM AND
THESE WILL SLOWLY SHIFT EASTWARD TODAY. WILL CONTINUE WITH SLIGHT
AND LOW CHANCE POPS FROM ROUGHLY CENTRAL MCHENRY COUNTY SOUTHWEST
TOWARDS WESTERN LASALLE COUNTY WITH THE BEST CHANCE THIS AFTERNOON
AND THIS EVENING. EXPECT THAT COVERAGE OF SHOWERS WILL PROBABLY
DECREASE WITH TIME AS THE FORCING STARTS TO FALL APART DURING THE
EVENING. SLIGHT CHANCES WILL DRIFT INTO THE WESTERN CHICAGO METRO
DOWN TO THE PONTIAC AREA THIS EVENING. EXPECT THAT AREAS TO THE EAST
WILL REMAIN DRY THROUGH TONIGHT. WARM WEATHER WILL CONTINUE WITH
HIGHS IN THE MID TO UPPER 70S WITH WARMEST READINGS ALONG AND SOUTH
OF INTERSTATE 80. LAKESHORE AREAS WILL LIKELY BE HELD TO THE LOWER
70S. THE TROUGH OVER THE ROCKIES WILL TREK EASTWARD WITH SURFACE LOW
PRESSURE DEVELOPING FROM SOUTHERN MANITOBA TO IOWA BY WEDNESDAY
AFTERNOON. AN UPPER WAVE WILL MOVE ACROSS THE SOUTHERN EXTENT OF THE
UPPER TROUGH HELPING TO FOCUS SURFACE LOW DEVELOPMENT OVER CENTRAL
ILLINOIS WEDNESDAY NIGHT. IN ADDITION THE LOCAL AREA WILL BE
POSITIONED IN THE LEFT EXIT REGION OF AN APPROACHING UPPER JET. ALL
OF THIS FORCING WILL LEAD TO RAIN AND POSSIBLE THUNDER DEVELOPMENT
AS EARLY AS WEDNESDAY MORNING ACROSS NORTH CENTRAL ILLINOIS WITH
PRECIP SPREADING EASTWARD INTO NORTHEAST ILLINOIS AND NORTHWEST
INDIANA WEDNESDAY AFTERNOON AND EVENING. OVERALL HAVE SLOWED THE
EASTWARD PROGRESSION OF THE RAIN BASED ON LATEST SATELLITE AND MODEL
TRENDS. THE UPPER TROUGH AXIS WILL PIVOT NORTHEASTWARD THURSDAY
ALLOWING COOLER AND DRIER AIR TO MOVE IN FROM THE WEST. THIS WILL
BRING AN END TO RAIN SHOWERS FROM WEST TO EAST LATER THURSDAY INTO
THURSDAY EVENING AS WELL. H85 TEMPS WILL FALL TO BETWEEN 6 AND 8 C
THURSDAY WHICH COMBINED RAIN AND CLOUD COVER...THOUGH SUNSHINE MAY
APPEAR BY LATE AFTERNOON FOR FAR WEST AND SOUTHWEST AREAS...WILL
KEEP TEMPS IN THE 60S.
A SHORTWAVE WILL MOVE DOWN THE WESTERN FLANK OF THE LONG WAVE UPPER
TROUGH WHICH WILL BE TO THE NORTH AND EAST THURSDAY NIGHT. THIS WILL
BRING A SECOND PUSH OF COOLER MID LEVEL AIR PUSHING H85 TEMPS INTO
THE 2 TO 4 C RANGE BY FRIDAY MORNING. MOST AREAS WILL REMAIN DRY BUT
CANNOT RULE OUT SOME INSTABILITY SHOWERS...ESPECIALLY DOWNWIND OF
LAKE MICHIGAN ACROSS NORTHWEST INDIANA. HIGH WILL PROBABLY STRUGGLE
TO REACH 60 NORTH BUT MAKE THE LOWER 60S SOUTH.
SATURDAY THROUGH MONDAY...MODEL AGREEMENT QUICKLY DIMINISHES FOR THE
WEEKEND AND EARLY NEXT WEEK...WITH INTERNAL MODEL CONSISTENCY ALSO
LACKING TO AN EXTENT. THE ECMWF REMAINS MUCH MORE AMPLIFIED WITH THE
UPPER FLOW PATTERN THAN THE GFS. THERE CONTINUES TO BE SUPPORT FOR A
DRY SATURDAY WITH CYCLONIC UPPER FLOW MOVING EAST OF THE AREA IN
FAVOR OF ANTICYCLONIC FLOW ASSOCIATED WITH RIDGING TO THE WEST.
TEMPS WILL BE TOUGH BECAUSE THE MAGNITUDE AND TIMING OF WARM
ADVECTION WILL BE DICTATED BY THE AMPLITUDE OF THE PATTERN. A WEAKER
AND MORE PROGRESSIVE PATTERN WOULD RESULT IN A MUCH QUICKER ARRIVAL
OF WARM AIR ASSOCIATED WITH THE RIDGE. WILL REMAIN CONSERVATIVE WITH
TEMPS SATURDAY FOR NOW WITH THE EXPECTATION THAT MODEL CONTINUITY
WILL BE LOW FOR THE NEXT SEVERAL RUNS. CONFIDENCE IS LOWER FROM
SUNDAY ONWARD WITH THE PATTERN DIFFERENCES. STRONGER RIDGING WOULD
YIELD A DRY FORECAST INTO MONDAY WITH THE WEAKER RIDGING POSSIBLY
ALLOWING A COOL FRONT TO DROP INTO THE AREA SUNDAY. GENERALLY MILD
TEMPS WILL CONTINUE IN EITHER SCENARIO AT THIS POINT.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 10Z...
* NO CONCERNS OVERNIGHT
* WEAK LAKE BREEZE POTENTIAL THIS EVENING
SHEA
//DISCUSSION...UPDATED 06Z...
SURFACE WIND FEATURES SET UP AND WILL ALLOW LIGHT SOUTHERLY FLOW
THROUGH THE OVERNIGHT PERIOD. DENSER CIRRUS THIS EVENING SHOULD
PRECLUDE ANY BR/VISBY RESTRICTIONS AS SEEN YESTERDAY
MORNING...OTHERWISE OVERALL WEATHER PICTURE FOR THE DAY IS
SIMILAR TO YESTERDAY. EXPECT ANOTHER WEAK LAKE BREEZE TO DEVELOP
AND POTENTIALLY MOVE ACROSS THE TERMINALS LATE IN THE EVENING
AGAIN. WOULDNT EXPECT ANYTHING OVERLY STRONG AGAIN...AND HEDGED IN
THAT DIRECTION WITH WINDS JUST TO THE SOUTH OF EAST AROUND 22Z.
WEAK FRONTAL BOUNDARY WILL CONTINUE TO SLOWLY ENCROACH FROM THE
WEST AND PRECIP POTENTIAL WILL BEGIN TO INCREASE. AT THIS
POINT...ALL EASTERN TERMINALS ARE STILL LOOKING DRY FOR THE 24/30
HOUR TAFOR. RFD ON THE OTHER HAND IS SHOWING THE BETTER CHANCES
INTO THE OVERNIGHT HOURS. CONFIDENCE IS STILL LOW WITH TIMING AND
OVERALL IMPACT AND WILL CONTINUE WITH A PROB30 AT THIS
POINT...UNTIL BETTER SPECIFICS CAN BE ZEROED IN ON. THUNDER
POTENTIAL STILL LOOKS LOW WITH ONLY WEAK ELEVATED INSTABILITY
NOTED ON FORECAST SOUNDINGS...WITH MINIMAL FORCING/MOISTURE
AVAILABLE. OTHERWISE CIGS WILL SLOWLY BEGIN TO TREND DOWNWARD AND
EVEN WITH THE RAINFALL POTENTIAL...FORECAST SOUNDINGS CONTINUE TO
INDICATE THAT BASES WILL STILL REMAIN VFR.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 10Z...
* MEDIUM-HIGH CONFIDENCE IN THE WIND FORECAST
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS
SHEA
//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...
* WEDNESDAY AND THURSDAY...OCCASIONAL SHRA WITH MVFR OR EVEN
BRIEF IFR POSSIBLE ESPECIALLY WED NGT/THURS MORNING.
* FRIDAY AND SATURDAY...SLGT CHC SHRA FRI...OTHERWISE VFR.
* SUNDAY...SLGT CHC SHRA WITH MVFR CIGS.
RATZER
&&
.MARINE...
231 AM CDT
BROAD RIDGE OF HIGH PRESSURE CONTINUES TO PROVIDE AN INFLUENCE ON
THE WEATHER FOR THE WESTERN GREAT LAKES REGION. THIS RIDGE OF HIGH
PRESSURE IS EXPECTED TO STEADILY SLIDE EAST/NORTHEAST...AS AN AREA
OF LOW PRESSURE LIFTS NORTHEAST FROM MANITOBA INTO WESTERN
ONTARIO LATER TODAY. THEN A SECOND AND STRONGER AREA OF LOW
PRESSURE IS EXPECTED TO DEVELOP LATE IN THE WEEK ACROSS AND
PROVIDE A SIGNIFICANT INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN
FRIDAY THROUGH EARLY SATURDAY...WITH A VERY TIGHT PRESSURE
GRADIENT. IN ADDITION WINDS ARE EXPECTED TO APPROACH GALE CRITERIA
FRIDAY THROUGH EARLY SATURDAY. AT THIS TIME HAVE OPTED TO HOLD OFF
ON ANY HEADLINES...HOWEVER IF MODEL SOLUTIONS CONTINUE TO
STRENGTHEN THIS SYSTEM...A GALE WATCH MAY BE ISSUED.
MUCH COOLER AIR WILL ARRIVE...ALLOWING WAVES TO STEADILY BUILD
LATE IN THE WEEK INTO EARLY THIS WEEKEND BEFORE THE PRESSURE
GRADIENT SLACKENS.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
