319 AM CDT
MAIN FEATURES OF THE FORECAST THIS MORNING ARE PRECIP POTENTIAL WITH
STORM SYSTEM MOVING THROUGH THE REGION TODAY THROUGH THURSDAY...A
PERIOD OF DRY WEATHER FROM THURSDAY NIGHT INTO SATURDAY...THEN
RELATIVELY MINIMAL RAIN THREAT WITH WINDY STORM WHICH MOVES THROUGH
THE UPPER MIDWEST SUNDAY.
A SURFACE LOW ASSOCIATED WITH A LEAD NORTHERN STREAM SHORT WAVE
TROUGH WAS EAST OF JAMES BAY EARLY THIS MORNING...WITH A SLOW MOVING
COLD FRONT TRAILING THROUGH SOUTHWEST WISCONSIN INTO EASTERN IOWA.
THIS FRONT WILL CONTINUE TO DRIFT TO THE EAST-SOUTHEAST INTO THE
FORECAST AREA THROUGH TONIGHT. NOT MUCH PRECIPITATION NOTED ALONG
THE FRONT AT THIS TIME...THOUGH MODELS CONTINUE TO DEPICT RAIN
BLOSSOMING WITH STRENGTHENING OF THE LOW LEVEL BAROCLINIC ZONE ON
THE COOL SIDE OF THE SURFACE BOUNDARY ACROSS IOWA AND WISCONSIN THIS
AFTERNOON. IN ADDITION...SPLIT FLOW APPEARS MORE PRONOUNCED IN
CURRENT MODEL RUNS THIS AFTERNOON WITH LESS PHASING OF NORTHERN AND
SOUTHERN STREAM SHORT WAVES THAN PREVIOUSLY DEPICTED. THERE ARE
SIGNS OF COUPLED UPPER JET STREAKS AIDING IN ENHANCING UPPER
DIVERGENCE ACROSS THE AREA WEST-NORTHWEST OF THE WFO CHICAGO CWA.
THIS SETS UP THE HEAVIEST PRECIP THROUGH THIS EVENING ACROSS
NORTHEAST IOWA AND SOUTHWEST WISCONSIN...AND WILL THUS RESULT
IN LOWER POPS FARTHER EAST ACROSS THE FA. MEANWHILE THE SOUTHERN
STREAM WAVE CONTINUES TO CLOSE OFF ACROSS THE SOUTHERN PLAINS
TODAY...WITH GUIDANCE IN CLOSER AGREEMENT NOW IN DEVELOPING SURFACE
LOW INTO FAR SOUTHWEST MISSOURI BY THIS EVENING BEFORE OCCLUDING
TONIGHT AS IT TRACKS ACROSS FAR SOUTHERN ILLINOIS AND THE LOWER OHIO
VALLEY. FORCING ALONG THE AFOREMENTIONED FRONTAL ZONE WEAKENS FROM
THE FORECAST AREA AND AREAS TO THE NORTHEAST TONIGHT AS THE NORTHERN
STREAM WAVE MOVES AWAY...WHILE MORE ORGANIZED DEEP ASCENT WITH THE
SOUTHERN STREAM CLOSED LOW SPREADS ACROSS TO LOWER MISSOURI AND OHIO
VALLEYS OVERNIGHT. BEST POTENTIAL FOR STEADIER PRECIP IS THEREFORE
LOOKING TO BE GREATEST OVER THE FAR WESTERN CWA TONIGHT...WITH THE
FAR EAST/SOUTHEAST PARTS OF THE CWA LOOKING LESS LIKELY TO SEE MORE
SIGNIFICANT RAINFALL. PRECIP SHOULD THEN TAPER FROM NORTHWEST TO
SOUTHEAST THROUGH THE DAY THURSDAY AS OLD LOW LEVEL FRONTAL ZONE
CONTINUES TO WEAKEN AND OCCLUDED SYSTEM TO OUR SOUTH TRACKS OFF
THROUGH THE OHIO VALLEY. ANY LINGERING LIGHT RAIN SHOULD MOVE OUT OF
THE FAR SOUTH/SOUTHEAST COUNTIES THURSDAY EVENING...WITH MODEL
FORECAST STORM TOTAL RAINFALL AMOUNTS RANGING FROM 0.25 TO 0.50
INCHES IN THE FAR WESTERN PARTS OF THE CWA TO LESS THAN 0.15 INCHES
IN THE FAR EAST.
TEMPS REMAIN A BIT TRICKY ACROSS THE FORECAST AREA TODAY...WITH
INCREASING THICKER CLOUD COVER AND FRONTAL PASSAGE ACROSS THE
NORTHWEST...AND MILDER PRE-FRONTAL AIR MASS ACROSS THE SOUTHEAST.
WITH TEMPS RELATIVELY MILD TO START WITH THIS MORNING HAVE GENERALLY
GONE WITH WARMER MET GUIDANCE NUMBERS...AND HAVE EVEN ADDED A COUPLE
OF DEGREES TO THIS IN THE SOUTHEAST PARTS OF THE CWA. HAVE FAVORED A
COOLER BLEND OF GUIDANCE THURSDAY IN COOL BLUSTERY NORTHEAST FLOW.
UPPER RIDGE THEN DEVELOPS EAST ACROSS THE MISSISSIPPI VALLEY AND
WESTERN LAKES THURSDAY NIGHT AND FRIDAY IN THE WAKE OF THE DEPARTING
UPPER LOW. FRIDAY MORNING MAY BE A CHILLY ONE ESPECIALLY ACROSS FAR
NORTH/NORTH CENTRAL IL GIVEN PROXIMITY TO SURFACE RIDGE AND THE
POTENTIAL FOR STRONG RADIATIONAL COOLING. LIGHT EAST FLOW AROUND THE
SURFACE HIGH WILL MAKE FOR DRY AND SLIGHTLY MILDER CONDITIONS
FRIDAY...THOUGH WARM ADVECTION AND STRONG RETURN FLOW DOESNT REALLY
SET UP UNTIL LATER FRIDAY NIGHT AND SATURDAY.
EYES THEN TURN TOWARD DEEP UPPER TROUGH OVER WESTERN CONUS HEADING
INTO THE WEEKEND. LONGER RANGE GUIDANCE CONTINUES TO BE CONSISTENT
IN DEPICTING A STRONG NEGATIVELY TILTED SHORT WAVE LIFTING FROM THE
PLAINS INTO THE UPPER MIDWEST BY EARLY SUNDAY. BOTH 00Z GFS AND 12Z
ECMWF INDICATE A 990 MB SURFACE LOW NEAR THE NORTH DAKOTA/MINNESOTA
BORDER BY SUNDAY MORNING. GFS/GEM/ECMWF ALL DEPICT BEST LOW LEVEL
MOISTURE ADVECTION REMAINS WEST OF THE MISSISSIPPI RIVER DURING THE
DAY SATURDAY...WITH THE LOW LEVEL MOISTURE EVENTUALLY SPREADING EAST
INTO THE FORECAST AREA BY SUNDAY AS THE OCCLUDED FRONT PUSHES ACROSS
THE AREA. MODELS ARE PRETTY STINGY WITH THE PRECIP DEVELOPMENT THIS
FAR SOUTH/EAST OF THE LOW...WITH MOST OF THE QPF DEVELOPING ALONG
THE FRONT AS IT SLOWS/STALLS ACROSS OUR FAR EASTERN COUNTIES IN
INDIANA AND EAST CENTRAL IL LATE SUNDAY. FORECAST SOUNDINGS AND
TIME/HEIGHT DEPICTIONS INDICATE MOISTURE IS RATHER SHALLOW HOWEVER
SUGGESTING ONLY LOWER CHANCE POPS. BY 12 MONDAY...GUIDANCE DIFFERS
ON HOW FAR EAST THE FRONT MAKES IT. THE 00Z GEM CLEARS THE
CWA...WHILE THE 00Z GFS/12Z ECMWF APPEAR TO HANG UP THE FRONT OVER
OUR FAR SOUTHEAST AS IT BECOMES MORE PARALLEL TO THE UPPER FLOW.
HAVE HELD ON TO SOME LOW CHANCE POPS SOUTH/SOUTHEAST HERE PER
GFS/ECMWF. DURING THE WEEKEND...TEMPS SHOULD AGAIN RISE INTO THE 60S
SATURDAY ESPECIALLY OVER THE SOUTHERN CWA...THOUGH IT APPEARS LOW
LEVEL THERMAL RIDGE ACTUALLY MOVES THROUGH SATURDAY NIGHT. LOW LEVEL
MIXING IS DEEPER BEHIND THE FRONT SUNDAY...SUGGESTING FAIRLY WINDY
CONDITIONS DURING THE DAY.
ANOTHER SHORT WAVE IS PROGGED TO APPROACH THE REGION IN SOUTHWEST
FLOW ALOFT MONDAY NIGHT OR TUESDAY...INCREASING PRECIP THREAT AGAIN
TOWARD THE VERY END OF THE EXTENDED FORECAST.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* SOUTHERLY WINDS WITH SPORADIC GUSTS THROUGH THE AFTERNOON BEFORE
FROPA LATE IN THE AFTERNOON WITH WINDS SHIFTING TO THE
NORTH...AND GUSTS INCREASING INTO THE OVERNIGHT HOURS.
* CHANCES FOR SHOWERS INCREASING BY LATE THIS EVENING.
* CEILINGS ON THE DOWNWARD TREND LATE THIS EVENING WITH MVFR
CEILINGS AND EVEN IFR CEILINGS A DEFINITE POSSIBILITY.
RODRIGUEZ
//DISCUSSION...UPDATED 12Z...
MID AND HIGH LEVEL MOISTURE SLOWLY INCREASING THIS MORNING AS
SYSTEM TO THE WEST CONTINUES TO TAKE SHAPE. AS THIS SYSTEM SLOWLY
SHIFTS EAST WITH TIME TODAY...EXPECT MID LEVEL MOISTURE TO BE ON
THE INCREASE. THE OVERALL TREND WITH CHANCES FOR SHOWERS AND LOW
LEVEL CLOUD COVER OVER THE LAST COUPLE OF DAYS HAS BEEN TO FURTHER
DELAY THE ONSET. THIS TREND HAS CONTINUED WITH THIS MORNINGS
FORECAST AS ONCE AGAIN THE ONSET OF PRECIP AND THIS LOW LEVEL
CLOUD COVER HAS BEEN PUSHED FURTHER BACK INTO THE EVENING. ALL
GUIDANCE THIS MORNING MAINTAINS THE IDEA OF THIS TREND...AND HAVE
THE TAFS REFLECTING THIS. DO STILL THINK THAT A DOWNWARD TREND IN
CEILINGS WILL OCCUR THIS EVENING WITH VFR CEILINGS BECOMING LOW
END MVFR. THE POSSIBILITY OF IFR CEILINGS IS ALSO LOOKING LIKE A
POSSIBILITY...SO HAVE BEGUN THIS TREND WITH THIS FORECAST PACKAGE.
SOUTHERLY WINDS WILL PERSIST OUT AHEAD OF THE TROUGH OF LOW
PRESSURE AND ASSOCIATED COLD FRONT...BUT SHOULD SEE A DIMINISHING
TRENDS IN GUSTS INTO THE AFTERNOON. GUIDANCE WAS ALSO WANTING TO
PUSH BACK TIMING OF FROPA...BUT HAVE STRAYED AGAINST THIS AT THIS
TIME. THINKING THAT THIS FRONT MIGHT BE ABLE TO SLIDE DOWN A
COOLER LAKE...AND SO HAVE CONTINUED THE TREND OF SHIFTING WINDS TO
THE NORTH LATE THIS AFTERNOON AND EARLY EVENING. THEN WITH A GOOD
PUSH OF COLDER AIR AND STRONGER WINDS ALOFT...NORTHERLY GUSTS WILL
ONLY INCREASE INTO THURSDAY MORNING.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION...WITH MEDIUM
CONFIDENCE OF TIMING FROPA LATER THIS AFTERNOON.
* HIGH CONFIDENCE OF SHOWERS...WITH MEDIUM CONFIDENCE OF
TIMING/TRENDS.
* MEDIUM CONFIDENCE OF TIMING/TRENDS FOR MVFR CEILINGS...WITH LOW
CONFIDENCE OF IFR CEILINGS.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT...VFR.
FRIDAY...VFR.
SATURDAY...VFR.
SUNDAY...VFR.
MONDAY...CHANCE OF SHRA LATE...OTHERWISE VFR.
TUESDAY...SHRA LIKELY...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
327 AM CDT
STRONGER LOWER LEVEL WINDS ARE WORKING THEIR WAY TO THE
SURFACE...COINCIDENT WITH A WEAK SURFACE TROUGH LIFTING ACROSS THE
SOUTHERN LAKE THIS MORNING. WITH THIS...WINDS HAVE BEEN ON THE
INCREASE FOR THE ILLINOIS NEARSHORE WATERS AND DID HOIST A SMALL
CRAFT ADVISORY THROUGH 10AM THIS MORNING...THOUGH MAGNITUDES SHOULD
BEGIN TO BE ON THE WANE AND BELOW ADVISORY LEVEL BEFORE THAT. THE
SOUTH TO SOUTHWESTERLY WINDS WILL CONTINUE THROUGH THE MORNING
BEFORE BECOMING NORTHERLY AS A COLD FRONT SLIDES ACROSS THE LAKE
INTO THE AFTERNOON AND EVENING HOURS. BEHIND THE FRONT...WINDS
WILL BE ON THE INCREASE...AS WILL WAVES. THE NEED FOR A SMALL
CRAFT ADVISORY WILL BE NECESSARY FOR THE OVERNIGHT PERIOD AND
LIKELY THROUGH EARLY FRIDAY MORNING /WITH A GENERAL THINKING OF 06
TONIGHT TO 09Z FRIDAY MORNING/ AS WINDS ARE FORECAST TO INCREASE
TO 30 KTS OUT OF THE NORTH TO NORTHWEST...AND WAVES WILL INCREASE
TO THE 6 TO 9 FT RANGE. DUE TO THE FACT THAT A SMALL CRAFT
ADVISORY IS CURRENTLY OUT FOR THE ILLINOIS SHORES THIS
MORNING...DECIDED TO HOLD OFF ON THE EVENING ADVISORY FOR THE
INDIANA SHORES /AND ILLINOIS SHORES/ UNTIL THE PRESENT ADVISORY IS
CANCELLED. DO EXPECT WINDS TO DIMINISH LATER THIS MORNING AND INTO
THE AFTERNOON/EVENING HOURS BEFORE PICKING UP INTO THE OVERNIGHT
HOURS...AND DIDNT ISSUE THE ADVISORY THROUGH FRIDAY MORNING FOR
THAT REASON. WINDS MAY ALSO FLIRT WITH GALE CRITERIA FOR THE
SOUTHERN OPEN WATERS...BUT OMITTED ANY WORDING AT THIS POINT.
SHEA
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 AM
WEDNESDAY.
&&
$$
