Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 190810
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 AM CDT SUN APR 19 2015

.SHORT TERM...
302 PM CDT

THROUGH SUNDAY NIGHT...

SCATTERED SHOWERS AND STORMS WILL CONTINUE TO FIRE ALONG A
BRADFORD IL TO RENSSELAER INDIANA LINE THIS AFTERNOON. THE STORMS
FORMED ALONG A BACK DOOR COLD FRONT SINKING SOUTH THROUGH THE
REGION. WHILE CURRENT CONDITIONS SUPPORT ISOLATED TO SCATTERED
THUNDERSTORM DEVELOPMENT...THEY DO NOT SUPPORT SEVERE STORMS. THE
STORMS QUICKLY DISSIPATE LATE THIS AFTERNOON AS THE LITTLE
INSTABILITY OUT THERE WEAKENS AND THE FRONT CONTINUES SOUTH.

LOOKING HIGHER UP IN THE ATMOSPHERE...A CLOSED LOW IS OVER THE
CENTRAL PLAINS AND IT OPENS TO A WAVE SUNDAY AFTERNOON AS ANOTHER
CLOSED LOW SINKS SOUTH OVER SOUTHERN MANITOBA.  A SURFACE LOW FORMS
OVER THE SOUTHERN MS RIVER VALLEY THIS EVENING AND PUSHES NORTH
THROUGH NORTHERN INDIANA BY SUNDAY EVENING BEFORE CONTINUING OVER
THE SOUTHERN MICHIGAN PENINSULA SUNDAY NIGHT.

FOR THE FORECAST TONIGHT...CONDITIONS ARE RATHER DRY WITH DEW POINT
DEPRESSIONS AROUND 30 DEGREES.  THINKING IT WILL TAKE LONGER THAN
THE MODELS SUGGEST FOR PRECIP TO DEVELOP OVER THE REGION.  AS SUCH
HAVE A DRY FORECAST GOING THROUGH TONIGHT.  FOR SUNDAY...THINKING
PRECIP CHANCES WILL INCREASE FROM SOUTH TO NORTH THROUGHOUT THE
MORNING WITH RAIN LIKELY ALONG AND SOUTH OF I-80 BY NOON. SOME OF
THE LATEST GUIDANCE SUGGESTS THE LOW MAY BE SLOWER WHICH WOULD LEAD
TO A SLOWER PROGRESSION OF RAIN. I AM EXPECTING WIDESPREAD
WIDESPREAD RAIN COVERAGE SUNDAY AFTERNOON AND EVENING WITH ISOLATED
EMBEDDED THUNDER AND POCKETS OF HEAVY RAIN.

FOR THE THUNDER...CONDITIONS ARE NOT OVERLY RIPE FOR THUNDERSTORMS.
FORECAST SOUNDINGS FEATURE ONLY A COUPLE OF HUNDRED J/KG OF ELEVATED
CAPE THROUGHOUT THE AFTERNOON. THINKING THE LOW WILL PROVIDE ENOUGH
LIFT TO FORCE A FEW EMBEDDED THUNDERSTORMS AND EXPECTING THE STORMS
TO FORM CLOSE TO THE LOW.  NOT EXPECTING THUNDER AFTER 00Z AS THE
LOW PULLS AWAY OVER MICHIGAN.

FOR RAINFALL...PWAT VALUES WILL BE AROUND AN INCH WITH UP TO 1.5
INCHES OVER EASTERN IL AND INDIANA. 1 INCH IS ABOVE AVERAGE WHILE
1.5 INCHES IS IN THE 99TH PERCENTILE...AKA VERY VERY ABOVE NORMAL.
THEREFORE POCKETS OF HEAVIER RAIN ARE POSSIBLE TOMORROW AFTERNOON
ESPECIALLY EAST OF I-55. EXPECTING 0.5-0.75 INCHES OF RAIN WEST OF I-
55 SUNDAY AND SUNDAY EVENING...AND 0.75-1.00 ALONG AND EAST OF I-55.
0.5-0.75 INCHES OF RAIN COULD FALL IN A 6 HOUR PERIOD ALONG AND EAST
OF I-55 SUNDAY AFTERNOON WHICH COULD LEAD TO PONDING ON ROADS AND
RISES ON LOCAL CREEKS AND RIVERS.

OVERALL HAVE HIGH CONFIDENCE IN WIDESPREAD RAIN SUNDAY AND ISOLATED
THUNDERSTORMS.  HAVE HIGH CONFIDENCE IN HEAVY RAINFALL...BUT ONLY
MEDIUM-HIGH CONFIDENCE IN THE EXACT LOCATION AS THE HEAVIER RAINFALL
WILL BE TIED CLOSE TO THE LOW.

TEMPS ON SUNDAY WILL ONLY BE IN THE 60S WITH 50S EXPECTED ALONG THE
LAKE.  THERE IS A CHANCE THE LOW MAY SHIFT EAST AND WE GET IN THE
WARM SECTOR WHICH WOULD LEAD TO WARMER HIGHS. HOWEVER GUIDANCE SEEMS
VERY CONSISTENT ON THE LOW TRAVELING TO OUR EAST SO KEPT A COOLER
FORECAST GOING. RAIN CONTINUES SUNDAY NIGHT WITH LOWS AROUND 50.

JEE

&&

.LONG TERM...
302 PM CDT

MONDAY THROUGH SATURDAY...

THE UPPER LEVEL TROUGH REMAINS OVER THE UPPER MIDWEST THROUGH MID
NEXT WEEK BEFORE SLOWLY SHIFTING EAST LATE NEXT WEEK. COOLER AIR
ASSOCIATED WITH THE LOW MOVES IN MONDAY WITH HIGHS IN THE UPPER 50S.
 MONDAY BEGINS WITH RAIN OVER THE MAJORITY OF THE REGION AND THE
AREA OF RAIN PUSHES EAST OVER EASTERN INDIANA MONDAY NIGHT.

FOR EARLY NEXT WEEK LOOKING AT BELOW NORMAL TEMPERATURES FOR MOST OF
NEXT WEEK WITH HIGHS RANGING FROM THE UPPER 50S SOUTH OF I-80 TO THE
LOW TO MID 50S NORTH OF I-80. HIGHS ALONG THE LAKE WILL BE AROUND 50
WITH FLOW OFF THE LAKE MID AND LATE NEXT WEEK.  THE REALLY
UNFORTUNATE PART IS OVERNIGHT LOWS.  LOOKING AT LOWS IN THE MID 30S
TO AROUND 40 MONDAY NIGHT AND TUESDAY NIGHT WITH LOWS DROPPING
FURTHER INTO THE LOW TO MID 30S MID TO LATE NEXT WEEK.  ITS TOO FAR
OUT TO PUT FROST INTO THE GRIDS BUT WILL KEEP AN EYE ON CONDITIONS
SINCE THE GROWING SEASON HAS BEGUN.

HAVE LOW CONFIDENCE IN PRECIP CHANCES IN THE LONG TERM. COULD SEE
SHOWERS TUESDAY AND WEDNESDAY AS VORTICITY STREAMERS CREATE FORCING
OVER THE REGION. HOWEVER WITH LIMITED CONFIDENCE WENT WITH A SLIGHT
CHANCE TUESDAY AND KEPT WEDNESDAY DRY.  THE REST OF THE WEEK LOOKS
DRY AS WELL WITH SURFACE HIGH PRESSURE. A SURFACE LOW PASSES OVER
THE GULF REGION LATE NEXT WEEK AND THINKING THE PRECIP WITH THAT
WILL STAY OVER SOUTHERN IL AND INDIANA.

JEE

&&

.AVIATION...

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

* EAST WINDS ARND 6 TO 10 KT...OCCASIONAL GUSTS TO 17KT.

* WINDS TURN NORTH LATE TONIGHT...THEN NORTHWEST EARLY MON.

* RAIN OVERSPREAD TAF SITES LATE THIS AFTN THRU TONIGHT.

* POSSIBLE LOW END MVFR CIGS OR PATCHY IFR CIGS DEVELOPING.

BEACHLER

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

WITH THE DEPARTING HIGH PRESSURE TO THE EAST...MID-LVL MOISTURE
WAS SLOWLY LIFTING NORTH ACROSS THE NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS HAS ALLOWED A CIRRUS CLOUD DECK TO THICKEN...AND
ADDITIONAL MOISTURE IS EXPECTED TO LIFT NORTHEAST AS A LOW
PRESSURE SYSTEM NEARS THE REGION LATER TONIGHT INTO EARLY MON.
GUIDANCE HAS BEEN SLOWLY TRENDING LATER WITH THE ARRIVAL OF PRECIP
UNTIL AFT 18Z...AND MAY NOT BE CLOSER TO 23Z. WILL CONTINUE TO
MENTION VCSH BUT PUSH IT TO 20Z...THEN EXPECT THE COVERAGE TO
INCREASE IN PRECIP CLOSER TO 23Z. WITH THE STEADILY THICKEN AND
LOWER CLOUDS...THE CHALLENGE IS ALSO ON WIND SPEEDS. IT IS STILL
POSSIBLE GUSTS WILL NEED TO BE PUT BACK INTO THE TAF...ALTHOUGH
WITH THE ABUNDANT CLOUD COVER...IT IS QUESTIONABLE HOW FREQUENT
GUSTS WILL OCCUR AT THE TAF SITES. SO HAVE REMOVED THE MENTION AT
THIS TIME AND JUST INCREASED THE SUSTAINED WINDS. THEN AT SOME
POINT LATE THIS EVENING CIGS ARE EXPECTED TO QUICKLY DIP TO MVFR
AND POSSIBLY TO IFR CONDS. PRECIP COVERAGE WILL BEGIN TO DIMINISH
EARLY MON...AND MAY TREND TOWARDS PATCHY DRIZZLE WHICH MAY ALSO
FURTHER LOWER CIGS AND VSBYS EARLY MON MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL ELEMENTS THROUGH 18Z...MEDIUM CONFIDENCE
  IN WIND DIR/SPEED AFT 18Z.

* MEDIUM CONFIDENCE IN PRECIP TIMING/COVERAGE.

* HIGH CONFIDENCE IN CIGS DIMINISHING TO AT LEAST MVFR CONDS AFT
  21Z...AND MEDIUM CONFIDENCE IN CIGS BECOMING IFR AFT 3Z MON.

BEACHLER

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

MONDAY...CHANCE OF SHRA/MVFR. GUSTY WEST-NORTHWESTERLY WINDS.

TUESDAY...SLGT CHANCE PM SHRA...BUT MAINLY VFR. GUSTY WEST WINDS.

WEDNESDAY...SLGT CHANCE SHRA. MAINLY VFR. WEST-NORTHWEST WINDS.

THURSDAY...VFR. NORTH-NORTHEAST WINDS.

FRIDAY...MAINLY VFR. CHC PM SHRA.

KJB

&&

.MARINE...
257 AM CDT

LOW PRESSURE OVER THE CENTRAL PLAINS WILL SLOWLY LIFT NORTHEAST
TOWARDS THE LOWER GREAT LAKES REGION TONIGHT/EARLY MON. GUIDANCE
CONTINUES TO INDICATE THE GRADIENT WILL TIGHTEN ACROSS THE
LAKE...HOWEVER THIS APPEARS TO BE MORE FOCUSED ALONG THE SOUTHERN
TIP OF THE LAKE. WITH THE CONTINUED EASTERLY WINDS...IT IS
POSSIBLE MARGINAL SMALL CRAFT CONDITIONS MAY DEVELOP FOR THE
ILLINOIS SHORELINE LATER TODAY INTO TONIGHT. THE LOW PRESSURE WILL
THEN APPROACH THE LAKE AND BRIEFLY WEAKEN THE GRADIENT EARLY MON.
THEN AS THE LOW LIFTS NORTHEAST LATER IN THE DAY MON...IT WILL
DEEPEN AND MERGE WITH ANOTHER LOW...WHICH WILL CREATE A TIGHT
GRADIENT OVER THE LAKE AND INCREASING WEST/NORTHWEST TUE. AFTER
TUE THE DOMINANT WIND DIRECTION WILL BE NORTHWEST THROUGH MID-
WEEK...BEFORE RELAXING TO THE WEST. THIS WILL ALLOW HIGHER WAVES
TO BE FOCUSED IN THE SOUTHERN HALF OF LAKE MICHIGAN THROUGH MID-
WEEK.

BEACHLER

&&

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

$$

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