AP-IN--CHI-IN N Area Forecast Discussion, IN

000

FXUS63 KLOT 151533

AFDLOT

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL

1033 AM CDT WED JUL 15 2015

.UPDATE...

1027 AM CDT

NO REAL BIG CHANGES TO GOING FORECAST FOR TODAY. HOWEVER...DID

MAKE SOME MODIFICATIONS TO SKY TRENDS THROUGH THE AFTERNOON.

EARLY MORNING LOW STRATUS IS STILL LINGERING ACROSS COOK COUNTY

AND PORTIONS OF NORTHWEST INDIANA. THESE CLOUDS WILL LIKELY ERODE

OVER THE NEXT COUPLE OF HOURS AS DRIER AIR CONTINUES TO MOVE

THROUGH THE AREA. LOW CLOUDS FURTHER SOUTH IN EAST CENTRAL

ILLINOIS MAY HOLD ON A TAD LONGER AS THEY APPEAR TO HAVE SOME

DIURNAL COMPONENT TO THEM. OTHER LOCATIONS IN MOSTLY SUNNY SKIES

THIS MORNING WILL LIKELY BECOME MORE PARTLY CLOUDY...AS HIGH LEVEL

CIRRUS MAY CONTINUE EASTWARD TOWARD NORTHERN ILLINOIS THROUGH

MIDDAY.

RODRIGUEZ

&&

.SHORT TERM...

328 AM CDT

THROUGH TONIGHT...

QUIET WEATHER IS IN STORE AS HIGH PRESSURE CENTERED OVER THE

NORTHERN GREAT LAKES SLOWLY SHIFTS EAST THROUGH TONIGHT. THERMAL

PROGS SUPPORT HIGHS IN THE UPPER 70S TO AROUND 80 INLAND...WHILE

ONLY AROUND 70 ALONG THE SHORE DUE TO LIGHTER BUT CONTINUED

ONSHORE WINDS. SOME UNCERTAINTY IN CLOUD COVER AS THERE HAVE BEEN

PATCHY LOW CLOUDS OVERNIGHT IN NORTHWEST INDIANA AND SOUTHERN HALF

OF COOK COUNTY. NAM BASED GUIDANCE TRIES TO EXPAND IT EAST THROUGH

MID DAY BEFORE DISSIPATING. WITH NOT MUCH TEMPERATURE ADVECTION

AND STRONG JULY SUN...LOW STRATUS SHOULD MIX OUT THIS MORNING. DO

EXPECT SCATTERED TO BROKEN CUMULUS CLOUDS TO REDEVELOP WITH

HEATING OF DAY...ESPECIALLY IN SOUTHERN THIRD OF CWA WHERE BETTER

MOISTURE WILL EXIST AT TOP OF MIXED LAYER. DESPITE UNIFORM

NORTHEAST FLOW TODAY...THERE WILL BE A LAKE BREEZE PUSH IN THE

AFTERNOON THAT SHOULD CREATE A LAKE SHADOW EFFECT AS IT MOVES

INLAND.

HIGH CLOUD DEBRIS FROM MCS OVER KANSAS AND NEBRASKA THAT IS

ROUNDING STRONG MIDLEVEL RIDGE OVER SOUTHERN PLAINS WILL START TO

MOVE IN DURING THE EVENING HOURS AND THEN INCREASE AND GRADUALLY

LOWER TOWARD DAYBREAK THURSDAY. HAVE MAINTAINED A DRY FORECAST

THROUGH EARLY THURSDAY...THOUGH SOME GUIDANCE/NAMELY ECMWF IS A

BIT QUICKER WITH NEXT SHORT WAVE APPROACHING FROM WEST. BANKING ON

INFLUENCE OF DEPARTING HIGH PRESSURE TO KEEP THINGS DRY. LOWS WILL

BE A BIT BELOW SEASONAL FOR THE WARMEST TIME OF YEAR...IN THE MID

50S TO LOWER 60S.

RC

&&

.LONG TERM...

328 AM CDT

THURSDAY THROUGH TUESDAY...

THURSDAY WILL SEE A SHORT WAVE TROUGH ADVANCING EASTWARD ON THE

NORTH SIDE OF THE WELL-ESTABLISHED UPPER HIGH/RIDGE ACROSS THE

SOUTHERN PLAINS. THERE IS A FAIR AMOUNT OF NWP DISCREPANCY IN

LATITUDE ON HOW THIS TRANSLATES AND CORRESPONDING DETAILS. THE

GENERAL TREND THE PAST SIX ACTIVE AND WET WEEKS HAS BEEN FOR

GUIDANCE TO BE TOO FAR NORTH IN THE DAY 2-3 PERIOD WITH AREAS OF

CONVECTION/MCS ACTIVITY. THIS PLAYS INTO THURSDAY BECAUSE AT LEAST

A COUPLE AREAS OF REGIONAL CONVECTION ARE EXPECTED TO BE ONGOING

EARLY IN THE MORNING WITHIN WARM ADVECTION AND FORCING AHEAD OF

THE AFOREMENTIONED TROUGH. THERE ARE SOME INDICATIONS THAT SOME OF

THE ACTIVITY BY 12Z COULD BE AS FAR SOUTH AS MISSOURI AND AS FAR

EAST AS NORTHWEST/NORTH CENTRAL ILLINOIS...AND THOSE MESOSCALE

DETAILS WILL LIKELY PLAY INTO FORECAST ON THURSDAY. SO HAVE LEANED

TOWARD A MORE SOUTHERN NWP SOLUTION FOR THURSDAY AND THURSDAY

NIGHT...SUCH AS THE 00Z EC AND SOMEWHAT THE 00Z GFS. ALSO HAVE

CONTINUED TO SUPPORT THE CHANCE OF SOME SHOWERS AND POSSIBLY A FEW

STORMS MOVING INTO AND POSSIBLY WELL INTO THE CWA THURSDAY MORNING

WITHIN WARM ADVECTION...WITH POPS FURTHER EAST THAN MOST NWP

SOLUTIONS INDICATE.

THURSDAY SHOULD SEE PLENTY OF HIGH AND PROBABLY MID CLOUD COVER TO

KEEP TEMPERATURES FROM CONSIDERABLY WARMING DESPITE A SURFACE WARM

ADVANCING/EVOLVING NORTHWARD IN RESPONSE TO A SURFACE LOW ACROSS

NORTHERN OR CENTRAL IA AT MIDDAY. WITH ASCENT AND FORCING ALOFT

IMPROVING THROUGH THE DAY AND CONTINUED MOIST ASCENT ON 25-35 KT

850MB FLOW...STORM CHANCES WILL GRADUALLY INCREASE. THERE IS

EXPECTED TO REMAIN A CAP ON SURFACE-BASED CONVECTION FOR MUCH OF THE

DAY...HOWEVER THAT MAY WEAKEN LATE IN THE DAY AND INTO EARLY-MID

EVENING IF STRONG ENOUGH RETURN FLOW OR SOME CLEARING OCCURS.

DEPENDING ON INSTABILITY...WHICH RIGHT NOW LOOKS LIMITED...A

SCATTERED SEVERE STORM POSSIBILITY CENTERED A LITTLE NORTHWEST OF

THE AREA COULD EXIST FURTHER EAST INTO EVENING ESPECIALLY

CONSIDERING THE DYNAMICS...BUT AGAIN INSTABILITY MAY LIMIT

CONVECTION COVERAGE AND POTENCY.

GRADUAL HEIGHT RISES ARE FORECAST TO SLOWLY ADVANCE NORTHWARD FRIDAY

AND FRIDAY NIGHT WITH A LOW-LEVEL THERMAL RIDGE AND INCREASING DEW

POINTS INTO THE 70S PUSHING INTO THE REGION AS WELL. THIS WILL

BEGIN A WARM AND HUMID PERIOD INTO THE WEEKEND. NWP SOLUTIONS HOLD

ONTO SCATTERED STORM PRECIP CHANCES ON FRIDAY BUT ANY FORCING

LOOKS PARTICULARLY LOW AMPLITUDE AND A FOCUS LOOKS WEAK...SO NOT

PARTICULARLY CONFIDENT ON THAT OCCURRING AND EVEN LESS CONFIDENT

ON SATURDAY...WITH ONLY THE EC REALLY INDICATING A SUBTLE SHORT

WAVE INDUCING SOME PRECIP. THE 850MB TEMPERATURES FORECAST BY THE

00Z GFS AND EC ARE AT 22C ON SATURDAY INTO EARLY SUNDAY WHILE THE

EC IS MORE AROUND 19C-20C. THE FORMER SUPPORTS CORRELATING

SURFACE HIGHS IN THE MID 90S AS AN AVERAGE OF REANALYSIS DATA FOR

THIS TIME OF YEAR...BUT WITH UNCERTAINTIES THAT COME ALONG WITH

BEING ON THE NORTH EDGE OF A RIDGE AND NOT PARTICULARLY STRONG

CAPPING FORECAST...ALONG WITH THE TRENDS THIS SUMMER...HAVE

CONTINUED TO BE CONSERVATIVE WITH FORECAST HIGHS THIS WEEKEND AND

INDICATE AROUND 90. THE HIGH DEW POINT AIR LOOKS MORE CONFIDENT

GIVEN GUIDANCE SOLUTIONS AND WET GROUND OVER UPSTREAM AREAS WITHIN

THE LOW-LEVEL FLOW. FORECAST APPARENT TEMPERATURES...WHILE

DETERMINISTIC AND SEVERAL DAYS OUT YET...DO INDICATE HEAT

ADVISORY CRITERIA FOR A PORTION OF THE AREA ON SATURDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NORTHEAST WINDS TODAY.

* SMALL CHANCE FOR SHRA THURSDAY PRIOR TO 18Z.

RC/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

GENERALLY QUIET AVIATION CONDITIONS TODAY AND TONIGHT WITH HIGH

PRESSURE SPREADING SOUTHEASTWARD FROM THE NORTHERN GREAT LAKES.

AREA OF MVFR CIGS CURRENTLY AT MDW AND GYY HAS BEEN DEVELOPING

HOLES AND STRONG JULY SUN SHOULD ERODE THE CLOUD DECK THIS

MORNING..BUT CANNOT RULE OUT A BRIEF PERIOD OF MVFR AT ORD.

FURTHER INLAND...EXPECTING A FEW TO SCT CU CLOUDS.

MAIN QUESTION TODAY IS WHETHER NORTHEAST WINDS WILL REACH 10 KT

AT ORD. FORECAST SOUNDINGS SUGGEST PREVAILING SPEEDS WILL BE CLOSE

TO BUT GENERALLY LESS THAN 10 KT. A LAKE BREEZE IS EXPECTED TO

PUSH INLAND THIS AFTERNOON...AND WHILE IT MAY HAVE BRIEF 7/810 KT

SPEEDS WITH IT...NOT EXPECTING MUCH MORE THAN THAT. WINDS WILL

DIMINISH THIS EVENING AS AREA WILL REMAIN UNDER INFLUENCE OF HIGH

PRESSURE...THEN PICK UP OUT OF THE SOUTH-SOUTHEAST ON THURSDAY AS

THE HIGH SLIDES EAST AND LOW PRESSURE APPROACHES FROM THE WEST.

THERE IS A SMALL CHANCE FOR SHRA THURSDAY MORNING...BUT TOO LOW TO

MENTION IN THE ORD 30 HR TAF. BETTER CHANCE FOR SHRA/TSRA WILL BE

NEAR RFD AND POSSIBLY NOT UNTIL LATE IN THE DAY OR THE EVENING FOR

THE EASTERN TERMINALS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN GENERAL WITH WIND TRENDS...MEDIUM IN PREVAILING SPEEDS

REMAINING AT GENERALLY LESS THAN 10 KT.

* LOW IN ANY SHRA ON THURSDAY PRIOR TO 18Z.

RC/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...DECENT CHANCE FOR SHRA/TSRA AND ASSOCIATED VSBY

IMPACTS.

FRIDAY THROUGH MONDAY...PERIODIC CHANCES FOR SHRA/TSRA AND

ASSOCIATED VSBY IMPACTS...OTHERWISE VFR OUTSIDE OF ANY PRECIP.

TUESDAY...VFR.

RC

&&

.MARINE...

435 AM CDT

NORTHERLY WINDS HAVE BEEN A BIT SLOW TO SUBSIDE ON THE SOUTHERN

TIP OF THE LAKE...KEEPING WAVES ELEVATED. SHOULD STILL BE ABLE TO

EXPIRE SMALL CRAFT ADVISORY AT 10 AM AS PLANNED WITH WINDS

CONTINUING TO DIMINISH DUE TO HIGH PRESSURE SPREADING SOUTHEAST.

THERE COULD BE A BRIEF INCREASE IN NORTHERLY GUSTS TO CLOSE TO 20

KT ALONG THE EASTERN SHORE OF THE LAKE THIS AFTERNOON. HIGH

PRESSURE WILL SLIDE EAST TONIGHT AND LOW PRESSURE WILL APPROACH

FROM THE PLAINS...TURNING WINDS SOUTHEAST. INCREASING PRESSURE

GRADIENT WILL STRENGTHEN SOUTHEAST WINDS TO 10 TO 20 KT ON

THURSDAY AND THEN 15 TO 25 KT ON THURSDAY NIGHT. GENERALLY LIGHTER

SOUTH AND SOUTHWEST WINDS ARE IN STORE THROUGH THE WEEKEND AFTER

THE LOW PRESSURE CROSSES THE LAKE THURSDAY NIGHT INTO

FRIDAY...WITH WEAK HIGH PRESSURE CENTERED OVER THE EASTERN LAKES

AND A LOW PRESSURE TROUGH SLOWLY APPROACHING FROM THE PLAINS.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...

IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 1 PM WEDNESDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 1 PM WEDNESDAY.

LM...NONE.

&&

$$

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Delivered by Weather Underground Inc. Wed Jul 15 2015 11:33AM EDT