Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLOT 240558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT SUN MAY 24 2015

.SHORT TERM...
236 PM CDT

TONIGHT AND SUNDAY...
PRECIPITATION TIMING AND COVERAGE WILL BE THE MAIN FOCUS THROUGH THE
DAY SUNDAY. AFTERNOON WATER VAPOR IMAGERY SHOWS A LARGE UPPER LOW
SPINNING OVER UTAH/COLORADO WITH AN UPPER RIDGE AMPLIFYING OVER THE
EASTERN PLAINS AND TRANSLATING NORTHEAST. THIS CREATES A SOUTH TO
SOUTHWESTERLY UPPER FLOW FROM WEST TEXAS/NEW MEXICO INTO THE MIDWEST
WITH AN EMBEDDED UPPER WAVE MOVING NORTHEAST FROM EASTERN
KANSAS/OKLAHOMA. AT THE SURFACE...LOW PRESSURE IS OVER WEST
TEXAS/NEW MEXICO WITH A WARM FRONT DEVELOPING EASTWARD INTO
OKLAHOMA. THE LOW WILL LIFT NORTHEAST INTO THE CENTRAL HIGH PLAINS
TONIGHT AND SUNDAY MORNING. MID LEVEL WARM ADVECTION WILL INCREASE
LATE TONIGHT AS THE SYSTEM ADVANCES NORTHEAST WITH THE LOW LEVEL JET
DEVELOPING ACROSS THE MID/UPPER MISSISSIPPI RIVER VALLEY. THUS THE
BULK OF THE OVERNIGHT PRECIPITATION/CONVECTION WILL LIKELY STAY TO
THE WEST OF THE FORECAST AREA BUT SOME SCATTERED ACTIVITY WILL BE
POSSIBLE LOCALLY OVERNIGHT...MAINLY OVER WESTERN AREAS...THANKS TO
THE INCREASED WARM ADVECTION AND MOISTURE FLUX. THE THREAT REMAINS
MINIMAL SO WILL ONLY MENTION SLIGHT POPS WEST LATE TONIGHT THROUGH
DAYBREAK SUNDAY.

WARM ADVECTION STRENGTHENS ACROSS THE AREA SUNDAY...ESPECIALLY FROM
LATE MORNING THROUGH THE AFTERNOON. THE WARM FRONTAL BOUNDARY WILL
BE FOCUSED ACROSS IOWA AND LOSE DEFINITION TO THE EAST. HIGH RES
GUIDANCE RANGES FROM VERY LITTLE PRECIP ACTIVITY THROUGH THE DAY TO
WELL ORGANIZED ACTIVITY...MAINLY IN THE AFTERNOON. AM THINKING THAT
THERE MAY BE SOME LINGERING SPOTTY ACTIVITY AFTER DAYBREAK...MAINLY
NORTH/WEST...WITH A WINDOW FOR MINIMAL COVERAGE MID/LATE MORNING.
CHANCES/COVERAGE THEN INCREASE DURING THE AFTERNOON AS BETTER
FORCING SPREADS IN. STILL TOUGH TO PIN DOWN THE BEST WINDOWS FOR
PRECIP BUT PREFER THE AFTERNOON HOURS OVERALL...BUT WILL START TO
RAMP UP POPS DURING THE EARLY AFTERNOON. NORTHWEST INDIANA WILL
LIKELY HAVE THE LOWEST PRECIP CHANCE OF ANYWHERE IN THE CWA.
MORNING ACTIVITY WOULD PRIMARILY BE SHOWERS WITH THUNDER POTENTIAL
SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. THE
MOST ABUNDANT CLOUD COVER WILL BE WEST AS WILL THE OVERALL BEST
CHANCE OF RAIN SO TEMPS WILL LIKELY BE LIMITED TO THE MID 70S THERE
...WHILE THE REST OF THE INLAND CWA SEES UPPER 70S/AROUND 80. A
SOUTHEAST WIND WILL ONCE AGAIN KEEP ILLINOIS LAKESHORE AREAS COOL
WITH COOLING EXTENDING FURTHER INLAND ACROSS EASTERN LAKE COUNTY IL.

MDB

&&

.LONG TERM...
236 PM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE EXTENDED LOOKS UNSETTLED WITH NUMEROUS CHANCES OF RAIN AND
THUNDERSTORMS. AN UPPER LEVEL RIDGE REMAINS OVER THE REGION SUNDAY
NIGHT WITH A CLOSED LOW OVER THE ROCKIES.  AS THE LOW PUSHES OVER
THE DAKOTAS MONDAY MORNING...A SERIES OF SHORTWAVE TROUGHS BEGINS TO
MARCH OVER THE REGION. EXPECTING THE SHORTWAVE TROUGH TRAIN TO
CONTINUE THROUGH THURSDAY UNTIL THE UPPER LEVEL TROUGH PUSHES EAST
OF THE REGION.

HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE CONUS SUNDAY
NIGHT WITH A SURFACE LOW FORMING OVER THE CENTRAL PLAINS EARLY
MONDAY MORNING.  THE LOWS WARM FRONT LIFTS NORTH THROUGH THE REGION
EARLY MONDAY MORNING AS WELL. A LOW LEVEL JET SHIFTS EAST THROUGH
THE CWA SUNDAY NIGHT AND EXPECTING TO SEE SHOWERS AND PERHAPS A FEW
THUNDERSTORMS FIRE AND THEN FESTER NORTH OF THE JET/S NOSE.
FORECASTED CAPE IS NOT OVERLY IMPRESSIVE WITH ONLY A COUPLE OF
HUNDRED OF J/KG TO WORK WITH.  WINDS WILL BE IN EXCESS OF 40 KT JUST
A COUPLE THOUSAND FEET OFF OF THE GROUND SO MY MAIN CONCERN FOR ANY
SEVERE WEATHER WOULD BE HIGHER WINDS MIXING DOWN TO THE SFC.

EXPECTING A LULL IN ACTIVITY MONDAY AFTN AS THE MAIN VORTICITY
STREAMER AND LOW LEVEL JET SHIFT EAST OF THE CWA.  SOUTHWEST WINDS
WILL BE GUSTING TO ARND 30 MPH MONDAY AFTN. HAVE LOW CONFIDENCE IN
SKY COVER AND SKY COVER WILL PLAY A BIG PART IN HOW WARM WE GET
MONDAY. DECIDED TO GO A COUPLE OF DEGREES WARMER SO ALL AREAS ARE
AROUND 80. HOWEVER LOCAL CLIMATE STUDIES SUGGEST IF WE ARE
SUNNY...WE COULD SEE MID 80S.  IN ADDITION TO WARMER TEMPS...THE
AMPLE SUNSHINE COULD KICK OFF MORE THUNDERSTORMS...BUT THINKING WE
WILL HAVE ENOUGH CLOUD COVERAGE TO KEEP CONVECTION AND TEMPS IN
CHECK.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE MONDAY NIGHT BUT
THINKING THE MAJORITY OF ACTIVITY WILL BE OVER CENTRAL IL CLOSER TO
THE UPPER LEVEL VORTICITY. DID RAISE POPS SOUTH OF I-80 TO AROUND 30
PERCENT IN CASE ANY OF THE ACTIVITY TO OUR SOUTH BLEEDS INTO THE
CWA. WE REMAIN IN THE WARM SECTOR SO KEPT MIN TEMPS MILD IN THE MID
60S.

TUESDAY WILL BE ANOTHER DAY SPENT IN THE WARM SECTOR WITH
THUNDERSTORM CHANCES INCREASING THROUGH THE AFTERNOON. SOUTHWEST
WINDS WILL STILL BE GUSTY...BUT ONLY BTWN 25 AND 30 MPH. THINKING
CLOUD COVER WILL BE MORE PROMINENT TUESDAY SO LOWERED HIGHS INTO THE
UPPER 70S.  PWAT VALUES INCREASE TO OVER 1.5 INCHES TUESDAY SO COULD
SEE SOME HEAVY DOWNPOURS.

SHOWERS AND STORMS SHIFT EAST AS THE COLD FRONT SWINGS THROUGH LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING.  ADDITIONAL SHOWERS AND STORMS
ARE PSBL WEDNESDAY AS THE UPPER LEVEL TROUGH FINALLY MOVES
THROUGH...BUT HAVE LOW CONFIDENCE IN OCCURRENCE AND COVERAGE SINCE WE
MAY BE STABLE.  TEMPS WILL NOT FALL MUCH BEHIND THE COLD FRONT WITH
HIGHS IN THE UPPER 70S AWAY FROM THE LAKE. SOME GUIDANCE MEMBERS
SUGGEST WINDS WILL TURN OFF OF THE LAKE SO HAVE HIGHS IN THE LOW 70S
ALONG THE LAKE SHORE. HAVE LOW CONFIDENCE IN WIND DIRECTION ALONG
THE LAKE FRONT WEDNESDAY.

LATE NEXT WEEK LOOKS WARM WITH HIGH TEMPS IN THE 80S.  COULD SEE
ISOLATED SHOWERS AND STORMS THURSDAY BUT THE BETTER CHANCE FOR
PRECIP IS FRIDAY WHEN A BOUNDARY APPROACHES FROM THE NORTHWEST.
GUIDANCE DIFFERS IN HOW QUICKLY THE BOUNDARY WILL SHIFT EAST SO
CAPPED POPS IN THE CHANCE RANGE.

JEE

&&

.AVIATION...

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

* WINDS BECOMING SOUTHEAST TO 10 KT+ BY LATE MORNING SUNDAY...WITH
  GUSTS UP TO 20KT THROUGH THE AFTERNOON AND EVENING.

* SLIGHT CHANCE OF -SHRA SUNDAY MORNING THEN SLOWLY INCREASING
  CHANCES SHRA WITH POSSIBLE INCLUDING TSRA EARLY EVENING THROUGH
  THE NIGHT.

KREIN

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

A WEAK WARM FRONT LIFTING THROUGH THE REGION WILL BRING A CHANCE
FOR SOME SCT SHRA THROUGH THE LATE NIGHT AND MORNING HOURS.
HOWEVER...AT THIS TIME...IT APPEARS ACTIVITY SHOULD BE TOO SPARSE
TO INCLUDE IN THE TAFS RIGHT NOW. WHILE THE WARM FRONT REMAINS TO
THE SOUTH OF THE TERMINALS...WINDS SHOULD BECOME SELY OVERNIGHT
AND THEN VEER TO SLY TO SSWLY AS THE WARM FRONT PUSHES TO THE
NORTH INTO WISCONSIN. ALSO...BY EARLY EVENING AS THE WARM FRONT
PUSHES TO THE NORTH...LOW LEVEL MOISTURE WILL BE ON THE INCREASE
AS A STRENGTHENING LOW LEVEL JET TRANSPORTS COPIOUS AMOUNTS OF
MOSTURE INTO THE REGION. THE ONE FACTOR LOWERING CONFIDENCE IN TS
COVERAGE INVOF THE TERMINALS IS THAT THE MAIN UPPER LEVEL FORCING
WILL STILL BE TO THE WEST IN THE EVENING...SO...WILL WILL ONLY GO
WITH VCTS AND PROB30 TS MENTIONS AT THIS TIME.

CONFIDENCE IS HIGHER WITH THE WIND FORECAST. AS THE WARM FRONT
PUSHES TO THE NORTH OF THE TERMINALS AND WINDS BECOME SLY...WINDS
SPEEDS WILL ALSO INCREASE AS THE SFC PRESSURE GRADIENT STRENGTHENS
AND SOME MIXING OF THE STRONG LOW LEVEL JET BRINGS GUSTIER WINDS
AT THE SFC. WILL CARRY GUSTS TO 20KT THROUGH THE EVENING...BUT IT
IS POSSIBLE THAT GUSTS COULD BE CLOSER TO 25 KT OR SLIGHTLY HIGHER
TOMORROW NIGHT.

KREIN

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

* MEDIUM CONFIDENCE WIND DIRECTION TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN WIND SPEED TRENDS.

* MEDIUM CONFIDENCE IN SHRA/TSRA TRENDS. STARTING TIME COULD BE
  LATER THAN CURRENTLY INDICATED.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY...TSRA AND MVFR LIKELY IN THE MORNING. IFR POSSIBLE. GUSTY
         SOUTHWEST WINDS.
TUESDAY... TSRA LIKELY. GUSTY SOUTHWEST WINDS.
WEDNESDAY...CHANCE OF TSRA. WEST WINDS TURNING EAST.
THURSDAY...SLIGHT CHANCE OF TSRA. EAST WINDS.
FRIDAY...CHANCE OF TSRA. WEST WINDS.

MTF

&&

.MARINE...
236 PM CDT

HIGH PRESSURE OVER THE LOWER GREAT LAKES AND APPALACHIANS
WILL SHIFT OFF THE EAST COAST TONIGHT WHILE A SURFACE RIDGE AXIS
LINGERS ACROSS THE WESTERN LAKES. LOW PRESSURE WILL MOVE
NORTHEASTWARD FROM THE SOUTHERN HIGH PLAINS AND EVENTUALLY TO
WESTERN LAKE SUPERIOR BY MONDAY EVENING. A TROUGH OF LOW PRESSURE
MOVING ACROSS EASTERN ONTARIO THIS AFTERNOON HAS HELPED TO TIGHTEN
THE PRESSURE GRADIENT ACROSS NORTHERN LAKE MICHIGAN WHICH HAS
ALLOWED STEADY/BREEZY SOUTHWEST WINDS WHILE A WEAKER GRADIENT TO
THE SOUTH HAS ALLOWED FOR AN ONSHORE FLOW. WINDS WILL DIMINISH
TONIGHT AS THE GRADIENT WEAKENS BUT THE GRADIENT WILL TIGHTEN LATER
SUNDAY ALLOWING WINDS TO COME UP A BIT. DIRECTION WILL REMAIN
SOUTHERLY...FAVORING SOUTHWEST WINDS NORTH AND SOUTHEAST WINDS
SOUTH. WITH THE LOW PASSING WEST OF THE LAKE MONDAY SPEEDS WILL
FURTHER INCREASE AND MAY REACH SMALL CRAFT ADVISORY LEVELS FROM THE
SOUTH AND SOUTHWEST. A WARM AND MOIST AIRMASS WILL ADVECT IN WITH A
SHALLOW STABLE LAYER HOLDING IN PLACE OVER THE LAKE WHICH WILL
LIKELY RESULT IN FOG DEVELOPING...PERHAPS AS EARLY AS SUNDAY
AFTERNOON...BUT MORE SO SUNDAY NIGHT THROUGH MONDAY. ANOTHER LOW IS
FORECAST TO CROSS THE REGION TOWARD WEDNESDAY RESULTING IN NORTHERLY
WINDS TO THE NORTH OF THE TRACK AND SOUTHERLY WINDS TO THE SOUTH.
HIGH PRESSURE QUICKLY CROSSES BEHIND THE LOW LATER IN THE WEEK
BRINGING A RETURN TO SOUTHERLY WINDS AS IT MOVES OFF TO THE EAST.

MDB

&&

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

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.