Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 300000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
700 PM CDT MON JUN 29 2015

.SHORT TERM...
224 PM CDT

THROUGH TUESDAY...

TONIGHT...SHOWER/THUNDER TRENDS WILL BE THE MAIN FOCUS TONIGHT AS
ANOTHER IN A SERIES OF UPPER WAVES TRAVERSES THE AREA. LATE
AFTERNOON SHOWER/THUNDER ACTIVITY WILL FADE AS THE PRIMARY WAVE
DRIVING THE ACTIVITY SHIFTS TO THE EAST AND DAYLIGHT BEGINS TO WANE.
WATER VAPOR IMAGERY SHOWS ADDITIONAL WAVES MOVING SOUTHEAST ACROSS
MINNESOTA WITH THE MOST PRONOUNCED WAVE APPROACHING NORTHWEST
WISCONSIN. SHOWERS AND STORMS CONTINUE TO MARCH SOUTHEASTWARD WITH
THIS SECOND WAVE WHILE NEW SCATTERED ACTIVITY IS DEVELOPING TO THE
SOUTH ACROSS EXTREME SOUTHEAST MN AND SOUTHWEST WI IN CONJUNCTION
WITH THE SE MN WAVE. GUIDANCE IS MIXED ON HOW LONG ALL OF THIS
ACTIVITY WILL CONTINUE INTO THE NIGHT AND THEREFORE HOW MUCH IMPACT
THE CWA WILL SEE. BASED ON LATEST TRENDS AND NEAR TERM
GUIDANCE...SHOWERS AND STORMS COULD REACH THE NORTHWEST CWA BY MID
EVENING THEN CONTINUE ACROSS THE AREA OVERNIGHT IF THEY HOLD
TOGETHER. SOME OF THE ACTIVITY WITH THE SE MN WAVE MAY BE MORE
DIURNALLY DRIVEN SO IT MAY FADE AS IT MOVES CLOSER TO THE AREA EARLY
THIS EVENING. EXPECT THE MORE ORGANIZED NORTHERN ACTIVITY TO MAKE
BETTER PROGRESS AND HOLD TOGETHER LONGER SO WILL WORK A BAND OF LOW
LIKELY/HIGH CHANCE POPS ACROSS THE AREA FROM MID EVENING THROUGH THE
OVERNIGHT HOURS THEN EXIT THEM TO THE EAST EARLY TOMORROW MORNING.
AM A BIT CONCERNED THAT THE ARRIVAL OF POPS MAY BE JUST A BIT SLOW
SO MAY NEED TO SPEED THE PROGRESSION UP BY AN HOUR OR TWO GOING INTO
EARLY EVENING SO STAY TUNED. WOULD EXPECT ANY WIND THREAT WITH THIS
ACTIVITY TO BE DIMINISHING AS IT APPROACHES LEAVING HEAVY
DOWNPOURS/ISOLATED FLOODING AS THE PRIMARY CONCERN.

TUESDAY...ANY LEFTOVER OVERNIGHT PRECIP WILL EXIT TO THE EAST BY MID
TUESDAY MORNING AS AN UPPER TROUGH AXIS CLEARS TO THE EAST. THE MAIN
SURFACE LOW WILL LAG BEHIND THE UPPER WAVE BUT WILL DRAG A COOL
FRONTAL BOUNDARY ACROSS THE AREA THROUGH THE MORNING. THERE DOES NOT
APPEAR TO BE MUCH OF A COHERENT FOCUS FOR ADDITIONAL ORGANIZED
DEVELOPMENT THROUGH THE MORNING BUT WITH BROADER ASCENT IN PLACE
ISOLATED ACTIVITY IS POSSIBLE. HIGH PRESSURE WILL BE BUILDING ACROSS
WESTERN LAKE SUPERIOR WHILE BRINGING A STRONGER PRESSURE GRADIENT TO
NORTHERN SECTIONS OF LAKE MICHIGAN AHEAD OF IT. A SECONDARY COOL
FRONTAL BOUNDARY LOOKS TO DEVELOP AND DROP DOWN LAKE MICHIGAN
TUESDAY AFTERNOON WHICH MAY SERVE TO TRIGGER ISOLATED/SCATTERED
SHRA/TSRA DEVELOPMENT DURING THE AFTERNOON...ESPECIALLY LATER...
GIVEN THAT THE AIRMASS BEHIND THE INITIAL FRONT WILL STILL BE MOIST
AND UNSTABLE. WILL CARRY CHANCE POPS DURING THE MID/LATE AFTERNOON
INTO THE EARLY EVENING HOURS ACROSS NORTHEAST IL AND FAR NORTHWEST
IN. HIGH TEMPS WILL BE IN THE UPPER 70S TO AROUND 80 WITH LAKEFRONT
AREAS COOLING LATE IN THE DAY AS WINDS SHIFT NORTHEAST WITH THE
SECONDARY FRONTAL PASSAGE.

MDB

&&

.LONG TERM...
319 PM CDT

TUESDAY NIGHT THROUGH MONDAY...

THE BEGINNING OF THE PERIOD TUESDAY EVENING MAY BEGIN WITH
ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS STILL ACROSS THE
CWA...BUT EXPECT WHATEVER LINGERING DEVELOPMENT TO DIMINISH.
DEPARTING LARGE SCALE ASCENT AND A GOOD PUSH OF COOLER/DRIER AIR
ACROSS THE CWA TUESDAY NIGHT...WILL ALLOW FOR ANY FURTHER PRECIP
DEVELOPMENT ACROSS THE REGION TO REMAIN SOUTH OF THE CWA. WITH
THIS COOLER/DRIER AIRMASS IN PLACE AND WITH DIMINISHING
WINDS/CLEARING SKIES...DID LOWER LOW TEMPS TUESDAY NIGHT WITH
TEMPS DROPPING INTO THE 50S FOR MOST AREAS. ALTHOUGH NORTHWEST
FLOW ALOFT WILL PREVAIL ON WEDNESDAY...IT IS BECOMING MORE LIKELY
THAT THE BEST DEVELOPMENT FOR FURTHER PRECIP WILL BE TO THE
SOUTHWEST/SOUTH OF THE CWA. SO DID REMOVE POPS FOR MOST LOCATIONS
DURING THIS TIME BUT DID LEAVE SLIGHT CHANCE WORDING FOR THE FAR
SOUTHWEST CWA OWING TO SOME SLIGHT VARIABILITY AMONG MODEL
GUIDANCE. HOWEVER...COULD SEE THESE SLIGHT CHANCE POPS BEING
REMOVED WITH DRIER CONDITIONS THE MORE LIKELY TREND. ALSO LOWERED
SKY COVER TUESDAY NIGHT INTO WEDNESDAY WITH CLEARER SKIES BECOMING
MORE LIKELY BUT WITH SEVERAL MID LEVEL IMPULSES TRAVERSING THE
FLOW...COULD SEE SOME PERIODIC MID/HIGH LEVEL CLOUD COVER.

THE DRIER TREND WITH A MORE SOUTHWARD PLACEMENT OF BEST PRECIP
DEVELOPMENT WILL LIKELY CONTINUE WEDNESDAY NIGHT INTO
THURSDAY...WITH HIGH PRESSURE EXPANDING ACROSS MUCH OF THE REGION.
BELOW NORMAL TEMPS LOOK TO CONTINUE DURING THIS PERIOD AS WELL
WITH TEMPS FALLING TO THE 50S AGAIN. LOWERED TEMPS DURING THIS
PERIOD AND MAY NOT HAVE LOWERED ENOUGH ESPECIALLY ACROSS FAR
NORTHERN ILLINOIS WHERE TEMPS COULD FALL INTO THE 40S. WITH
STEERING FLOW KEEPING GENERAL MOVEMENT OF APPROACHING MID LEVEL
IMPULSES TO THE SOUTH AND WITH DOMINATING HIGH PRESSURE IN
PLACE...SUNNY SKIES WILL BE IN PLACE THURSDAY. HOWEVER...COOLER
AIRMASS AND ONSHORE FLOW WILL HELP KEEP TEMPS BELOW NORMAL...IN
THE 70S AND THE UPPER 60S NEAR THE LAKE. DRY CONDITIONS SHOULD
CONTINUE THURSDAY NIGHT BUT WITH CONFIDENCE LOWERING INTO
FRIDAY...AS GUIDANCE VARIES WITH A POSSIBLE SYSTEM PUSHING ACROSS
THE CWA. HAVE MAINTAINED CHANCE POPS FOR SHOWERS/THUNDERSTORMS ON
FRIDAY...BUT WILL NEED TO MONITOR THIS PERIOD FOR ANOTHER POSSIBLE
DRY DAY. GOING INTO THE WEEKEND...GUIDANCE DOES VARY BUT AT THIS
TIME...SATURDAY IS APPEARING TO BE ANOTHER DRY PERIOD FOR MOST
AREAS.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SCATTERED SHRA LATE THIS EVENING/EARLY MORNING.
* CHANCE OF SHRA TUESDAY AFTERNOON.
* POSSIBLE MVFR CIGS OVERNIGHT/TUESDAY MORNING.
* LAKE BREEZE/SHIFT TO NORTHEAST LATE TUESDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 00Z...

SHOWER ACTIVITY CONTINUES TO DECREASE IN COVERAGE ACROSS THE
CHICAGO AREA TERMINALS WHILE SHOWERS AND A FEW THUNDERSTORMS
CONTINUE FURTHER WEST AND SOUTH OF THE TERMINALS. THIS ACTIVITY
WILL SLOWLY DIMINISH OVER THE NEXT FEW HOURS WITH LOSS OF DAYTIME
HEATING. ADDITIONAL SHOWERS/THUNDERSTORMS ACROSS SOUTH/CENTRAL WI
WILL MOVE SOUTH LATER THIS EVENING. SHORT TERM/HI RES GUIDANCE
SHOWS THIS ACTIVITY SLOWLY WEAKENING BUT STILL ARRIVING INTO
NORTHERN IL. HOW MUCH CONTINUES ACROSS THE TERMINALS INTO THE
EARLY MORNING HOURS REMAINS SOMEWHAT UNCERTAIN...BUT MAINTAINED
CURRENT SHOWER MENTION AND WILL NEED TO MONITOR TRENDS THRU THE
EVENING.

A WEAK GRADIENT HAS ALLOWED WINDS TO BECOME LIGHT AND VARIABLE
WHICH WILL TEND TO FAVOR CALM THIS EVENING. EVENTUALLY WINDS WILL
SHIFT MORE LIGHT WESTERLY OR NORTHWESTERLY OVERNIGHT...THEN
INCREASE IN SPEED LATER TUESDAY MORNING. WINDS WILL SHIFT MORE
NORTHERLY IN THE AFTERNOON AND LIKELY TURN NORTHEAST OFF THE LAKE
BY LATE TUESDAY AFTERNOON/EARLY EVENING.

PREVAILING VFR CIGS...OUTSIDE ANY PRECIP AREAS...SHOULD CONTINUE
THIS EVENING...WITH MVFR CIGS POSSIBLE OVERNIGHT INTO TUESDAY
MORNING. CONFIDENCE IS PRETTY LOW REGARDING SPECIFIC HEIGHTS SO
DIDN/T MAKE ANY SIGNIFICANT CHANGES. FOG WILL ALSO BE POSSIBLE
OVERNIGHT DEPENDING ON EXTENT OF CLOUD COVER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW FOR SHRA LATE THIS EVENING/OVERNIGHT.
* MEDIUM FOR MVFR CIGS OVERNIGHT/TUESDAY MORNING.
* LOW FOR SHRA TUESDAY AFTERNOON.
* MEDIUM FOR WINDS THRU THE PERIOD...MEDIUM FOR SHIFT TO NORTHEAST
  TUESDAY AFTERNOON...LOW FOR TIMING. CMS

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

* WEDNESDAY AND THURSDAY...DRY/VFR. NORTHEAST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA/TSRA. NORTHEAST WINDS.
* SATURDAY...SLIGHT CHANCE OF SHRA. EAST WINDS.
* SUNDAY...SLIGHT SHRA/TSRA. SOUTHEAST WINDS.

&&

.MARINE...
301 AM CDT

EXPECT A WEAK GRADIENT MUCH OF THE UPCOMING WEEK WITH THE
EXCEPTION OF TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. EXPECT
GENERALLY LIGHT WINDS TODAY AND TONIGHT AS LAKE MICHIGAN LIES
BETWEEN TWO AREAS OF LOW PRESSURE WHICH WILL EVENTUALLY MERGE OVER
THE EASTERN GREAT LAKES LATER ON TUESDAY. WINDS BRIEFLY PICK UP
MAINLY IN THE 15 TO 20 KT OCCASIONALLY 25 KT RANGE OUT OF THE
NORTH BEHIND THE DEPARTING LOW AND AHEAD OF A RIDGE BUILDING SOUTH
INTO THE REGION. EXPECT LIGHT WINDS TO RETURN TO CLOSE OUT THE
WEEK AND CONTINUE INTO THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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