Area Forecast Discussion
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619
FXUS63 KLOT 200744
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 AM CDT WED MAY 20 2015

.SHORT TERM...
301 PM CDT

THROUGH WEDNESDAY...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH INCREASING CHANCES FOR
SHOWERS WEDNESDAY...AND BELOW NORMAL TEMPS.

PERSISTENT STRATUS IS FINALLY ERODING AS IT SLOWLY DRIFTS
SOUTHEAST THROUGH THE CWA. EXPECT CLEARING TO OCCUR FROM NORTHWEST
TO SOUTHEAST OVER THE NEXT SEVERAL HOURS...WITH FAR NORTHEAST
ILLINOIS AND NORTHWEST INDIANA OBSERVING THIS CLOUD COVER THE
LONGEST. CLEARER SKIES WILL BE IN PLACE BY EARLY THIS EVENING
WHILE QUIET/DRY CONDITIONS WILL BE OBSERVED. MADE MINOR
ADJUSTMENTS TO LOW TEMPS TONIGHT WITH UPPER 30S TO LOW 40S
EXPECTED ACROSS THE CWA.

CLOUD COVER WILL INCREASE LATER TONIGHT INTO WEDNESDAY MORNING
WITH MID/HIGH CLOUDS SPREADING NORTHEAST ACROSS THE REGION. THIS
WILL OCCUR OUT AHEAD OF UPPER LEVEL SYSTEM OVER THE PLAINS
SHIFTING EAST/NORTHEAST TOWARDS THE AREA. CURRENT PRECIP OVER THE
PLAINS WILL LIFT ACROSS THE REGION WEDNESDAY MORNING...BUT WITH
GUIDANCE STILL VARYING TO THE EXTENT OF THE NORTHWARD PUSH. DID
INCREASE POPS TO LIKELYS FOR THE SOUTHERN CWA LATE WEDNESDAY
MORNING INTO THE EARLY AFTERNOON BUT DID LIMIT POPS ACROSS THE
NORTHERN THIRD OF THE CWA. ALTHOUGH BEST CHANCES FOR SHOWERS WILL
BE ALONG AND SOUTH OF INTERSTATE 80...DID BRING AT LEAST SLIGHT
CHANCE POPS TO AREAS FURTHER NORTH WITH THE POSSIBILITY FOR A MORE
NORTHWARD MOVEMENT. HOWEVER...IF THIS WERE TO OCCUR ACROSS THE
NORTHERN CWA...IT WOULD LIKELY ONLY BE IN THE FORM OF AN ISOLATED
SHOWER OR TWO. LITTLE TO NO INSTABILITY WILL LIMIT ANY POTENTIAL
FOR THUNDERSTORMS...AND HAVE CONTINUED MENTION OF ONLY RAIN. WITH
SOME UNCERTAINTY AS TO THE EXTENT OF THE PRECIP ON
WEDNESDAY...MADE ONLY SLIGHT CHANGES TO GOING MAX TEMPS. CURRENT
FORECAST MAX TEMPS IN THE LOW TO MID 50S COULD BE ON THE HIGH SIDE
IF MORE EXPANSIVE PRECIP SHIELD PRESENTS ITSELF...WITH THE
POSSIBILITY FOR SOME AREAS TO NOT RISE OUT OF THE 40S.

RODRIGUEZ

&&

.LONG TERM...
310 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

SKIES WILL CLEAR WEDNESDAY NIGHT BEHIND THE DEPARTING
WAVE...YIELDING CHILLY CONDITIONS TO START THURSDAY. THIS WILL
QUICKLY CHANGE THURSDAY...WITH NORTHWESTERLY WAA...WEST NORTHWEST
WINDS AND DEEP MIXING IN THE DRY AIRMASS ALLOWING TEMPERATURES TO
WARM TO AROUND 70. SOME HIGH-BASED CU MAY DEVELOP AT THE TOP OF THE
MIXED LAYER...WHICH MAY REACH 750 MB. A BACKDOOR COLD FRONT WILL
DROP SOUTH THURSDAY NIGHT...TURNING WINDS ONSHORE BY DAYBREAK
FRIDAY. AIRMASS FRIDAY WILL BE SUPPORTIVE OF HIGHS IN THE LOW 70S
INLAND UNDER PLENTY OF SUN...BUT LAKESHORE SHOULD BE KEPT IN THE 50S
BY ONSHORE FLOW.

MID/UPPER PATTERN WILL SHIFT TO SOUTHWESTERN TROUGHING AND EASTERN
RIDGING OVER THE HOLIDAY WEEKEND AS DEEP UPPER LOW NEAR HUDSON BAY
GETS SHUNTED EAST. EXPECTING A QUIET DAY ON SATURDAY...WITH EC
SEEMING TO BE OUTLIER IN BREAKING OUT PRECIP DURING THE AFTERNOON.
THERMAL FIELDS SUPPORT HIGHS IN THE 70S...EXCEPT EAST-SOUTHEAST
ONSHORE FLOW IS LIKELY TO LIMIT THE IL SHORE TO THE 60S. MULTIPLE
DISTURBANCES IN SOUTHWEST FLOW ALOFT WILL MOVE ACROSS THE AREA
SUNDAY THROUGH TUESDAY. IN ADDITION...LOW PRESSURE OVER THE
CENTRAL PLAINS SHOULD PASS NORTH OF THE AREA ON MEMORIAL DAY. GOOD
MOISTURE RETURN WILL SEND DEWPOINTS BACK INTO THE 60S SUNDAY
NIGHT...ALONG WITH PWAT VALUES CLIMBING TO ~1.5 TO 1.75 INCHES.

STAYED GENERALLY CLOSE TO CONSENSUS BLEND FOR POPS SUNDAY THROUGH
TUESDAY...WITH SUNDAY NIGHT AND MEMORIAL DAY CURRENTLY FAVORED FOR
POTENTIALLY MORE WIDESPREAD CONVECTION. WOULD NOT EXPECT THE WHOLE
PERIOD TO BE A WASHOUT...BUT WILL NEED TO WATCH FOR HEAVY
DOWNPOURS IN SEASONABLY MOIST AIRMASS. COLD FRONT LOOKS TO MOVE
ACROSS THE AREA ON TUESDAY...BUT SIGNS POINT TO THE PATTERN
REMAINING ACTIVE BEYOND DAY 7. REGARDING TEMPERATURES...LOCAL
CLIMO FOR 850 MB AND 925 MB TEMPS IN THE TEENS CELSIUS SUPPORTS AT
LEAST WELL INTO THE 70S INLAND ON SUNDAY AND UPPER 70S-LOWER 80S
MONDAY AND TUESDAY. READINGS COULD END UP WARMER IF WE GET MORE
SUN THAN CURRENTLY FORECAST. WITH INCREASING DEWPOINTS...THE
SECOND HALF OF MEMORIAL DAY WEEKEND WILL TURN RATHER MUGGY.
ONSHORE FLOW LOOKS LIKELY INTO NORTHEAST ILLINOIS ON SUNDAY...BUT
THEN OFFSHORE FLOW EXPECTED THE REST OF THE PERIOD.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCE FOR RAIN WEDNESDAY AFTERNOON.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE STRETCHES FROM THE NORTHERN PLAINS ACROSS THE UPPER
MISSISSIPPI VALLEY TONIGHT WITH LIGHT NORTH/NORTHEAST FLOW IN
PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA. CONDITIONS
SHOULD REMAIN FAIRLY UNCHANGED OVERNIGHT...OTHER THAN SLOWLY
LOWERING HIGH/MID LEVEL CLOUD COVER. THIS IS IN ADVANCE OF AN AREA
OF LOW PRESSURE MOVING EAST ACROSS THE PLAINS WITH WIDESPREAD RAIN
MOVING INTO PORTIONS OF IOWA AND MISSOURI. PRECIP SHOULD ADVANCE
INTO ILLINOIS BY LATE MORNING EARLY AFTERNOON TOMORROW. THE
NORTHERN EXTENT OF THE PRECIP SHIELD WILL BE IN THE VICINITY OF
THE TERMINALS...AND IT REMAINS UNCERTAIN AT THIS TIME WHICH SIDE
OF THE LINE THE TERMINALS WILL BE ON...SO FOR NOW WILL MAINTAIN
PROB30 FOR PRECIP TOMORROW AFTERNOON. IF PRECIP DOES FALL...CLOUD
BASES WILL BE FAIRLY HIGH SO EXPECT SOME EVAPORATION AND LITTLE IF
ANY IMPACTS ON VSBY.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN PRECIP AT TERMINALS.
* MEDIUM-HIGH IN VFR CONDITIONS THROUGH PERIOD.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. WEST WINDS.

FRIDAY...VFR. NORTHEAST WINDS.

SATURDAY NIGHT THROUGH SUNDAY...PERIODIC CHANCES FOR TSRA.
SOUTHEAST WINDS.

MONDAY...CHANCES FOR TSRA. SOUTHWEST WINDS.

MDB

&&

.MARINE...
244 AM CDT

HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY ALLOWING LIGHT
FLOW AND AFTERNOON LAKE BREEZES ACROSS THE SOUTH END OF THE
LAKE...WHILE SOUTHWEST WINDS OF 15 TO 20 KT ARE IN PLACE ACROSS
THE NORTH. WEST WINDS WILL BE IN PLACE ACROSS THE LAKE ON THURSDAY
AS A SLOW MOVING TROUGH GRADUALLY SLIDES SOUTH ACROSS THE LAKE.
WINDS TURN NORTH/NORTHEAST BEHIND THE TROUGH WHICH SHOULD CLEAR
THE SOUTH END OF THE LAKE BY EARLY ON FRIDAY. HIGH PRESSURE BUILDS
BACK OVERHEAD ON FRIDAY...THEN SOUTH FLOW RETURNS ACROSS THE LAKE
FOR THE WEEKEND.

BMD

&&

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

$$

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