240 AM CDT
EXTRAORDINARILY TRICKY FORECAST THE NEXT 24 HOURS WITH RESPECT TO
CLOUD COVER...PRECIP CHANCES...AND TEMPS.
WARM FRONTOGENESIS TAKING PLACE FROM NORTHERN IA EAST INTO SOUTHERN
WISCONSIN EARLY THIS MORNING WITH REGIONAL RADAR MOSAIC SHOWING
TRANSVERSE BANDS OF SHOWERS DEVELOPING ALONG/NORTH OF THE WARM FRONT
AND ON THE NOSE OF THE VERY STRONG 50-60KT LOW LEVEL JET. SOUTHERN
EXTENT OF THESE ELEVATED SHOWERS SHOULD REMAIN NEAR/NORTH OF THE
IL/WI LINE THIS MORNING.
HOWEVER...FORECAST FOR REMAINDER OF TODAY IS ANYTHING BUT STRAIGHT
FORWARD. SOUNDINGS FROM ACROSS THE CENTRAL PLAINS MON EVENING SHOWED
PRESENCE OF A VERY STOUT EML WHICH IS LIKELY TO BE ADVECTED EASTWARD
INTO THE MIDWEST TODAY BY THE DEEP WESTERLY FLOW ALOFT. AS THE STEEP
LAPSE BECOME JUXTAPOSED ABOVE A TONGUE OF MOISTURE (ALBEIT QUITE
MEAGER) BEING ADVECTED NORTHWARD BY THE SCREAMING STRONG LOW LEVEL
JET OUT AHEAD OF SUBTLE SHORTWAVE NOTED OVER KS EARLY THIS MORNING
AM CONCERNED THAT ACCAS FIELD WILL LIGHT UP OVER THE AREA THIS
MORNING. WHILE LOW LEVEL AIRMASS WILL BE SLOW TO MOISTEN
TODAY...PARCELS WITH SOMEWHAT GREATER MOISTURE CONTENT ORIGINATING
OVER THE SOUTHERN PLAINS WILL BE RAPIDLY ADVECTED NORTHWARD AND
ISENTROPICALLY LIFTED BY THE STRONG LOW LEVEL JET. MODELS ARE IN
GOOD AGREEMENT WITH THIS GENERAL SET-UP AND IN SHOWING VERY STRONG
NEARLY SATURATED ASCENT ON THE 305K SURFACE TODAY...WHICH GIVEN THE
STEEP LAPSE RATES COULD VERY WELL BE ENOUGH TO KICK OFF HIGH
ELEVATED SHOWERS (WITH MAYBE A ROGUE LIGHTNING STRIKE OR TWO). HAVE
BUMPED UP SKY COVER A BIT TODAY FROM PREVIOUS FORECAST AND EXPANDED
SLIGHT CHANCE POPS TO ENCOMPASS THE ENTIRE CWA.
SHORTWAVE AND ASSOCIATED MAXIMA IN LIFT SHOULD TRAVERSE THE AREA
RATHER QUICKLY TODAY...SO THAT PRECIP CHANCES SHOULD END THIS
AFTERNOON FROM WEST TO EAST WITH MODE MIXED SUNSHINE EXPECTED IN THE
WAKE OF THE WAVE. HAVE BASICALLY LEFT GOING TEMPS ALONE GIVEN THE
VERY LOW CONFIDENCE IN HOW CLOUD COVER AND POSSIBLE PRECIP WILL PLAY
OUT TODAY. BUST POTENTIAL FOR TEMPS TODAY IS CERTAINLY HIGHER THAN
AVERAGE FOR A 1ST PERIOD FORECAST WITH MORE SUNSHINE LIKELY LEADING
TO HIGHS EVEN WARMER THAN GOING GRIDS AND POSSIBLY EVEN FLIRTING
WITH RECORDS. EVEN IF ABOVE SCENARIO WITH THE CLOUD COVER AND
MID-LEVEL CONVECTION DOES PLAY OUT TODAY WOULD STILL ANTICIPATE
HIGHS TO GET INTO THE UPPER 60S TO MID 70S AS AIR MASS BEING
ADVECTED IN IS VERY WARM (STILL IN THE LOW/MID 60S AT 2 AM IN IOWA).
NUMERICAL GUIDANCE...PARTICULARLY THE HI-RES MODELS...ARE DEPICTING
STRONGER FORCING THIS EVENING WITH APPROACHING SHORTWAVE AND SFC
LOW. WHILE CAPE VALUES WILL BE WEAK DUE TO LESS THAN STELLAR
MOISTURE RETURN...THE VERY STEEP MID LEVEL LAPSE RATES COULD BE
ENOUGH TO SUPPORT SCATTERED THUNDERSTORMS BREAKING OUT THIS EVENING.
MANY OF THE HI-RES CONVECTIVE ALLOWING MODELS ARE BREAKING OUT
THUNDERSTORMS OVER NORTHERN ILLINOIS THIS EVENING...ENOUGH SO THAT I
FELT COMFORTABLE HITTING POPS A BIT HARDER IN THE GRIDS THOUGH STILL
TOO GUN SHY TO GO WITH LIKELYS.
ANY SHOWERS/STORMS WILL END FROM NW TO SE ACROSS THE AREA WED NIGHT
AS FRONT SETTLES SOUTH OF THE AREA...BEFORE SLOWING DOWN OR EVEN
STALLING OUT DOWNSTATE AS IT BECOMES MORE ALIGNED WITH THE UPPER
FLOW. MID-LEVEL FLOW IS THEN FORECAST TO BACK SOMEWHAT IN ADVANCE OF
DIGGING/AMPLIFYING NORTHERN STREAM SHORTWAVE AND COULD RESULT IN
SOME RAIN SPREADING BACK NORTH INTO MAINLY OUR SOUTHERN CWA
WEDNESDAY AFTERNOON AND EVENING. MEANWHILE...FAIRLY EXTENSIVE
STRATUS AND STRENGTHENING NORTHERLY FLOW/COLD AIR ADVECTION SHOULD
RESULT IN VERY LITTLE RECOVERY IN TEMPS FROM MORNING LOW WEDNESDAY.
SEASONABLY STRONG HUDSON BAY VORTEX PROGGED TO DEVELOP LATER THIS
WEEK LEAVING US IN A NORTHWEST FLOW ALOFT. SERIES OF SHORTWAVES
PIVOTING AROUND THE POLAR VORTEX COULD RESULT IN SOME INCREASE IN
CLOUD COVER AND MAYBE EVEN A SHOWER OR TWO...BUT OVERALL LOOKS TO BE
A FAIRLY DRY PATTERN WITH BELOW AVERAGE TEMPS INTO THE WEEKEND.
WHILE THE DETAILS ARE FUZZY...THERE ARE SIGNS IN THE MEDIUM RANGE
GUIDANCE THAT THE NORTHWEST FLOW WILL BREAK DOWN LATE IN THE WEEKEND
INTO EARLY NEXT WEEK WITH A RETURN TO NEAR IF NOT SLIGHTLY ABOVE
AVERAGE TEMPS.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* LLWS LINGERING THRU DAYBREAK WITH WINDS AT 2KFT AGL TOUCHING
50KT.
* -SHRA TO SHRA WILL PASS THROUGH TERMINALS BETWEEN 16 AND 18Z.
* GUSTY CONDS TUES WITH WINDS TURNING SOUTH WITH GUST TOUCHING
25KT BY MIDDAY. GUSTS DIMINISH AFTER SUNSET TUES.
* SHRA AFT 01Z WED.
* PSBL LOW END MVFR TO HIGH END IFR CIGS LATE TUES NIGHT/EARLY
WED MORNING BEHIND COLD FROPA.
* GUSTY NORTH WINDS WED WITH GUSTS 15-20KT.
JEE
//DISCUSSION...UPDATED 12Z...
WARM FRONT CURRENTLY ON THE WI/IL BORDER THIS MORNING. A BROAD
AREA OF SHOWERS HAS DEVELOPED TO OUR NORTH AND WEST THIS MORNING.
IN ADDITION...WINDS 2KFT AGL ARE REACHING 50KT RESULTING IN A
GOOD BIT OF LLWS. LLWS WILL DIMINISH AS SURFACE WINDS PICK UP
LATER THIS MORNING. THE LINE OF SHRA TO OUR WEST WILL REACH THE
RFD TERMINAL BY 15Z AND ORD/MDW BY 16Z. THE RAIN SHOULD BE
LIGHT...BUT LOOKING AT RADAR NOW...MODERATE SHRA IS A POSSIBILITY.
SOUTHERLY WINDS WILL PICK UP THIS AFTERNOON WITH GUSTS UP TO 25KT.
CURRENTLY THINKING THAT THE MIXING FROM THE STRONG WINDS WILL HELP
SKIES SCT OUT BRIEFLY THIS AFTERNOON BEFORE THE MAIN AREA OF RAIN
MOVES IN. SHRA AND SCATTERED TSRA WILL DEVELOP ALONG THE COLD
FRONT AND MOVE THROUGH THE TERMINALS AFTER 02Z WEDNESDAY. ANY TS
MAY PRODUCE BRIEF STRONG WINDS. THE MAJORITY OF SHRA WILL BE
THROUGH THE TERMINALS BY 07Z...BUT LINGERING NUISANCE SPRINKLES
WILL REMAIN THROUGH THE NIGHT. WINDS WILL BECOME WESTERLY AND
GUSTS WILL DIMINISH AFTER SUNSET.
BEHIND THE FROPA...WINDS WILL BE OUT OF THE NORTH AND GUSTS UP TO
20KT ARE POSSIBLE. CIGS WILL FALL TO AT LEAST LOW MVFR. NOT
CONFIDENT ENOUGH TO PUT PREVAILING HIGH END IFR INTO THE TAFS
ATTM. CIGS WILL BEGIN TO IMPROVE WEDNESDAY AFTERNOON.
JEE
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* MEDIUM CONFIDENCE IN TIMING OF SFC WIND GUSTS AND VFR CONDS LINGERING
THRU MUCH OF TUE.
* MEDIUM CONFIDENCE WITH VCSH EARLY THIS AFTERNOON AS SOME SHOWERS
MAY BE STRONGER WITH A BOLT OR TWO OF LIGHTNING.
* LOW CONFIDENCE IN FORECAST AFT 00Z WED.
JEE
//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...
WEDNESDAY NIGHT...VFR WITH SLT CHC SHRA.
THURSDAY THROUGH FRIDAY...VFR. PATCHY MVFR WITH CHC SHRA.
SATURDAY THROUGH MONDAY...VFR.
JEE
&&
.MARINE...
155 AM CDT
LOW PRESSURE ACROSS THE MID MISSOURI VALLEY THIS MORNING IS
LIFTING A WARM FRONT NORTHWARD ACROSS THE SOUTHERN PORTION OF LAKE
MICHIGAN. THIS FRONT WILL BE THE TRANSITION ZONE BETWEEN GUSTY
SOUTHERLY WINDS SOUTH OF THE FRONT...AND GUSTY EAST NORTHEASTERLY
WINDS TO THE NORTH. WITH GUSTY OFFSHORE SOUTHERLY WINDS EXPECTED
ACROSS MY NEAR SHORE WATERS...I HAVE ISSUED A SMALL CRAFT ADVISORY
FOR SOUTHERLY WINDS UP TO 30 KT. THIS IS FOR ALL OF MY INDIANA
NEAR SHORE ZONES. HOWEVER...IN ILLINOIS I LEFT THE NEAR SHORE
WATERS NORTH OF CHICAGO OUT OF THE ADVISORY...AS SLIGHTLY WEAKER
WINDS ARE EXPECTED THERE.
THE LOW WILL SHIFT EASTWARD ACROSS THE SOUTHERN FRINGE OF LAKE
MICHIGAN LATER THIS EVENING. THIS WILL ALLOW THE WINDS TO BECOME
NORTHERLY ACROSS THE ENTIRE LAKE AS THE LOW CONTINUES TO THE EAST
ACROSS THE OHIO VALLEY. DUE TO THE GOOD COLD AIR ADVECTING OVER THE
LAKE AND RAPIDLY RISING PRESSURES ALONG THE BACK SIDE OF THE LOW...I
EXPECT 25 TO 30 KT NORTHERLY WINDS LATE TUESDAY NIGHT INTO
WEDNESDAY. I WOULD NOT BE SURPRISED TO SEE A FEW GALE FORCE GUSTS
WEDNESDAY MORNING. HOWEVER...OVERALL IT APPEARS THAT THE WINDS WILL
REMAIN SUB GALE FORCE.
THE MAIN ISSUES WITH THESE NORTHERLY WINDS WILL BE FOR THE NEAR
SHORE WATERS. IT APPEARS THAT ANOTHER SMALL CRAFT ADVISORY WILL BE
NEEDED FOR EARLY WEDNESDAY INTO THURSDAY MORNING...MAINLY FOR WAVES
ABOVE 4 FEET. THE NORTH TO SOUTH FETCH WILL ALLOW WAVES ALONG THE
SOUTHERN HALF OF THE LAKE TO BUILD INTO THE 4 TO 8 FT RANGE.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
10 PM TUESDAY.
&&
$$
