Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 020518
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1218 AM CDT THU JUL 2 2015

.UPDATE...

934 PM CDT

FOR MID-EVENING UPDATE...

NARROW CORRIDOR OF SCATTERED LIGHT RAIN CONTINUES TO MAKE ITS WAY
EAST-SOUTHEAST ACROSS A CORRIDOR ROUGHLY FROM DIXON TO JOLIET AT 9
PM...AND WHILE LIGHT RAIN IS FALLING FROM A 10-12 THOUSAND FOOT
MID-DECK AND SHOWING SOME EROSION IN INTENSITY AND COVERAGE...HAVE
NO REASON NOT TO TAKE LOW-CHANCE POPS ALL THE WAY INTO NORTHWEST
INDIANA INTO THE OVERNIGHT HOURS. OTHERWISE...SATELLITE IMAGERY
DOES SHOW SOME DECREASE IN SKY COVER ACROSS THE IL/WI BORDER AREA
AND EXPECT SKIES TO BECOME PARTLY CLOUDY ACROSS THE NORTHERN PARTS
OF THE CWA AFTER MIDNIGHT.

HAVE UPDATED HOURLY POP/WX/SKY GRIDS AND TWEAKED TEMPS ESPECIALLY
NEAR LAKE MICHIGAN WHERE READINGS HAVE FALLEN TO THE MID-50S.

RATZER

&&

.SHORT TERM...
327 PM CDT

THROUGH SATURDAY...

GENERALLY QUIET CONDITIONS EXPECTED THROUGH THE PERIOD AS
STEERING FLOW WILL TEND TO KEEP BEST FORCING TO THE SOUTH OF THE
CWA. IN THE NEAR TERM...HAVE MAINTAINED A DRY FORECAST FOR MOST
AREAS THIS EVENING THROUGH MIDNIGHT OUTSIDE OF LOW CHANCE POPS FOR
THE FAR SOUTHERN CWA OWING TO POTENTIAL SLIGHT EXPANSION OF
SHOWERS CURRENTLY TO THE WEST/SOUTHWEST. ALSO MONITORING SMALL
AREA OF PRECIP DROPPING SOUTHEAST THROUGH EASTERN IOWA.
EXTRAPOLATING THIS ALONG SOUTHEASTWARD MEAN FLOW ALOFT...IT WOULD
CLIP AREAS ACROSS NORTH CENTRAL ILLINOIS. HOWEVER...AT THIS
TIME...LITTLE PRECIP IS ACTUALLY MAKING IT TO THE GROUND. WITH
RATHER DRY CONDITIONS IN PLACE OVER THE CWA...WOULD EXPECT FURTHER
EROSION OF THIS PRECIP WITH EVEN LESS OF IT MAKING IT TO THE
GROUND. SO...IF ANYTHING WERE TO OCCUR...IT WOULD BE A BRIEF
SPRINKLE. CLOUD COVER TONIGHT MAY BE A LITTLE CHALLENGING...BUT
WENT MORE AGGRESSIVE WITH CLOUD COVER IN THE NEAR TERM AND LATER
TONIGHT. MID/HIGH CLOUDS APPROACHING WILL PROVIDE CONTINUED CLOUDY
CONDITIONS THIS EVENING...AND THEN LOW STRATUS OVER THE SOUTHERN
HALF OF THE LAKE AND SOUTHWEST MICHIGAN LOOKS TO WORK ITS WAY BACK
SOUTHWEST MORE TOWARDS EARLY THURSDAY MORNING.

A CONTINUED SOUTHERLY TREND WITH APPROACHING SYSTEMS THURSDAY
THROUGH SATURDAY HAS OCCURRED...AND HAVE LOWERED POPS THROUGH THE
PERIOD WITH DRY CONDITIONS EXPECTED FOR THE CWA. ALTHOUGH TEMPS
WILL CONTINUE TO BE BELOW NORMAL THROUGH THE END OF THE
WORK...TEMPS WILL BEGIN TO REBOUND BY SATURDAY WITH HIGHS AROUND
80 FORECAST. HOWEVER...PERSISTENT ONSHORE FLOW WILL KEEP TEMPS
LOWER NEAR THE LAKE.

RODRIGUEZ

&&

.LONG TERM...
327 PM CDT

SATURDAY NIGHT THROUGH WEDNESDAY...

SATURDAY EVENING IS LOOKING LIKE IT WILL REMAIN DRY FOR 4TH OF
JULY FIREWORKS IN THE ABSENCE OF ANY REAL FORCING OR INSTABILITY.
THIS PATTERN LOOKS TO CONTINUE INTO SUNDAY AND SUNDAY
EVENING...THOUGH A FEW STRAY SHOWERS/POP-UP TSTORMS CANNOT BE
RULED OUT ACROSS THE SOUTHERN PORTION OF THE CWA. ATTENTION THEN
TURNS TO MONDAY AS MODEL GUIDANCE CONTINUES TO ADVERTISE THE
SOUTHWARD MOVEMENT OF A LOW AMPLITUDE TROUGH WELL TO THE NORTHWEST
WITH A CORRESPONDING COLD FRONT. WAA LOOKS TO RAMP UP DURING THE
DAY ON MONDAY...THOUGH MOST OF THE DAY WILL LIKELY REMAIN DRY AS
THE BEST FORCING STAYS NORTH OF THE AREA. MODEL GUIDANCE HAS
STARTED TO AGREE THAT THE COLD FRONT WILL PASS THROUGH THE CWA
LATE MONDAY NIGHT INTO EARLY TUESDAY MORNING. HOWEVER...RUN-TO-RUN
INCONSISTENCY HAS LED TO LOW CONFIDENCE ON THE EXACT TIMING OF THE
FROPA...AS WELL AS THE STRENGTH OR COVERAGE OF ANY ASSOCIATED
CONVECTION. AREA-WIDE SLIGHT POPS MAY HAVE TO BE ADJUSTED IN
FUTURE FORECASTS AS MODEL GUIDANCE CONSISTENCY INCREASES. THERE
ARE ALSO QUESTIONS ON WHETHER THE FRONT WILL PASS RIGHT ALONG OR
STALL INTO THE TUESDAY AND WEDNESDAY TIMEFRAME...WHICH WOULD HAVE
IMPLICATIONS ON AREAWIDE POPS...CLOUD COVER...AND TEMPS.

BATZEK/BORCHARDT/NIXON

&&

.AVIATION...

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

* POTENTIAL FOR IFR CIGS EARLY THURSDAY MORNING.

BMD

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

HIGH PRESSURE STRETCHES FROM MINNESOTA EAST ACROSS MICHIGAN
LEAVING NORTHERN ILLINOIS UNDER A MODERATE NORTHEASTERLY GRADIENT
MUCH OF THE PERIOD. SOME PATCHY LOW CIGS ARE ONCE AGAIN IN PLACE
OVER THE AREA THIS MORNING WITH SOME MODELS SUGGESTING IT WILL
MOVE OVER THE TERMINALS LATE TONIGHT/EARLY THURSDAY MORNING. WITH
THE ONSET OF MIXING EXPECT ANY LOW CIGS THAT MAY BE IN PLACE TO
MIX OUT AND FOR WINDS TO INCREASE ABOVE 10 KT THROUGH THE
AFTERNOON INTO THE EVENING. WINDS SHOULD DROP OFF AGAIN DURING
THE EVENING. OUTSIDE OF THE POSSIBILITY FOR LOW CIGS EARLY
THURSDAY...EXPECT PRIMARILY VFR CONDITIONS..NORTHWEST WINDS...AND
DRY WEATHER THROUGH THE TAF PERIOD.

BMD

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

* LOW IN IFR.
* HIGH IN REMAINING FORECAST ELEMENTS.

BMD

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

FRIDAY THROUGH SUNDAY...VFR.

MONDAY AND TUESDAY...CHANCE FOR SHRA/TSRA AND ASSOCIATED VSBY
IMPACTS.

RC

&&

.MARINE...
356 PM CDT

ON THE EDGE OF HIGH PRESSURE TO THE NORTH/NORTHWEST...NORTHERLY
FLOW IS PERSISTING OVER THE LAKE. SPEEDS HAVE GENERALLY STAYED IN
THE 10 TO 20 KT RANGE OVER THE OPEN WATERS...WHILE 10 TO 15 KT HAS
BEEN OBSERVED ALONG THE NEARSHORE IN ILLINOIS/INDIANA.
HOWEVER...VEERING FLOW HAS ALLOWED FOR THE HIGHER WAVES TO REACH
PORTIONS OF THE INDIANA SHORE WITH WAVES OF 3 TO 6 FT BEING
REPORTED THIS AFTERNOON. THESE HIGHER WAVES SHOULD DIMINISH THIS
EVENING AND OVERNIGHT...WITH THE SMALL CRAFT ADVISORY GOING
THROUGH THIS EVENING. NORTHERLY FLOW WILL ONCE AGAIN BE OBSERVED
ON THURSDAY AND AS THE SURFACE PATTERN TIGHTENS UP...SPEEDS WILL
LIKELY RETURN BACK TO THE 10 TO 20 KT RANGE FOR BOTH THE OPEN
WATERS AND NEARSHORE.

RODRIGUEZ

&&

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

$$

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