Area Forecast Discussion
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000
FXUS63 KLOT 241910
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 PM CDT SUN MAY 24 2015

.SHORT TERM...
209 PM CDT

THROUGH TONIGHT...

VERY SHARP WARM FRONT HAS BEEN GRADUALLY LIFTING NORTHWARD THROUGH
THE AFTERNOON HOURS. TEMPERATURES HAVE SOARED INTO THE 80S BEHIND
THE FRONT...WITH MUGGY MID 60S DEWPOINTS AS WELL. MEANWHILE FAR
NORTHERN ILLINOIS IS HOLDING ONTO THE 70S WITH TEMPS HOLDING AROUND
60 AT THE LAKE WITH ONSHORE WINDS.  ALOFT... A DEEP AND CLOSED UPPER
LOW IS SPINNING OVER NORTHERN COLORADO. A NEGATIVELY TILTED TROUGH
AXIS OUT AHEAD OF THE LOW INTO NORTHERN TEXAS WITH A MODESTLY STRONG
SHORTWAVE ALONG AND AHEAD OF IT. SHOWERS AND THUNDERSTROMS CONTINUE
AHEAD OF THIS FEATURE. CLOSER TO HOME...UPPER LEVEL RIDGING IS IN
PLACE ACROSS THE EASTERN HALF OF THE AREA...AND NO NOTABLE
SHORTWAVES OTHER THAN SOME WEAKER WAVES ARE FOUND IN SW FLOW ALOFT ACROSS
FAR WESTERN ILLINOIS. MORE ORGANIZED SHOWER ACTIVITY FROM I-39
WESTWARD ASSOCIATED WITH THIS...BUT MUCH OF THE AREA REMAINS IN
BROAD AND MOIST SW FLOW. THEREFORE SCATTERED SHOWERS CONTINUE TO
FESTER FARTHER EASTWARD THOUGH THE ARE STRUGGLING A BIT MORE IN
THE LESS FAVORABLE ENVIRONMENT.

EXPECT AS THE AFTERNOON CONTINUES THAT SHOWERS REMAIN LIKELY IN OUR
WESTERN AREAS...WHILE MUCH OF ILLINOIS WILL BE SUSCEPTIBLE TO
SCATTERED SHOWERS THROUGH THE AFTERNOON PERIOD AS WELL. THE SHOWERS
PUT DOWN NEARLY TWO TENTHS OF AN INCH IN AN HOUR AT PEORIA...AND
WITH PW VALUES ON THE RISE...SOME BRIEF DOWNPOURS REMAIN POSSIBLE.
INSTABILITY IS MODEST AND FOCUSED ALONG AND WELL SOUTH OF I-80 WHERE
AN ISOLATED MENTION HAS BEEN HELD...BUT WE DO HAVE SOME STRIKES IN
LASALLE COUNTY AS OF THIS WRITING.

LOOKING FARTHER DOWNSTATE BEHIND THIS BATCH OF SHOWERS CUMULUS FIELD
IS FAIRLY TEMPERED WITH MORE AGITATED CLOUDS IN MISSOURI...AND MORE
SO FARTHER SOUTH IN THE ARKLATEX REGION. HAVE TRIED TO SHOW SOMEWHAT
OF A DOWNWARD TREND IN CHANCES FOR PRECIPITATION ACROSS NE ILLINOIS
TONIGHT IN BETWEEN THE CURRENT ACTIVITY BEFORE THE TROUGH AXIS
BEGINS PIVOTING NORTHWARD. MOIST ISENTROPIC LIFT REMAINS A BIT MORE
ROBUST ALONG AND WEST OF I-39 WHERE OCCASIONAL SHOWERS WILL CONTINUE
EVEN THIS EVENING AND HELD ONTO LIKELY POPS LONGER IN THESE AREAS.

OVERNIGHT IS WHEN THINGS WILL RAMP UP ACROSS OUR LOCAL AREA. THE NEGATIVELY
TILTED TROUGH AXIS GETS SHUNTED NORTHEASTWARD ON A POTENT
MID/UPPER LEVEL JET. LOW LEVEL MOISTURE ADVECTION INCREASES WHICH
WILL BRING THE MOST ORGANIZED PERIOD OF SHOWERS AND
ISOLATED/SCATTERED THUNDERSTORMS ACROSS THE AREA...AFTER MIDNIGHT
AND INTO THE MORNING OF MEMORIAL DAY. WITH A VERY STRONG LOW LEVEL
WIND FIELD AND AND CLOSED SURFACE LOW PASSING ACROSS EASTERN
IOWA...SOUTHERLY WINDS WILL BE RAMPING UP CONSIDERABLY LATE
TONIGHT INTO MEMORIAL DAY MORNING.

MORE ON THE WINDS TOMORROW AND THE LONG TERM DISCUSSION SOON...

KMD

&&

.LONG TERM...
229 AM CDT

MONDAY THROUGH SATURDAY...

FOR MEMORIAL DAY...LARGEST CONCERN FOR THE DAY WILL BE ON PRECIP
TIMING/COVERAGE. GUIDANCE HAS BEEN RELATIVELY CONSISTENT THAT A
LOBE OF VORTICITY WILL BE LIFTING NORTH ACROSS THE MID-MISSOURI
VALLEY EARLY MON...WITH A SFC WAVE PROGGED TO BE OVER CENTRAL IOWA
BY DAYBREAK MON. THE CHANNEL OF NEARLY 2.00 INCHES OF PWAT AND
ANOMALOUSLY STRONG 850MB V-WIND OR MOISTURE TRANSPORT...WILL BE
STEADILY SHIFTING EAST/NORTHEAST ACROSS THE FORECAST AREA SHORTLY
AFT DAYBREAK. BY MID-MORNING THE MOIST PLUME WILL BE DEPARTING THE
WESTERN CWFA AND BY MIDDAY OR SHORTLY BEFORE...THE REMAINDER OF
THE FORECAST AREA COULD BE DRY. IN ADDITION TO THE PRECIP ENDING
BY MIDDAY...CLOUD COVER SHOULD QUICKLY ERODE WITH ONLY A FEW
CLOUDS LINGERING IN THE AFTERNOON HOURS. UNFORTUNATELY THE TRADE
OFF FOR A DRY HOLIDAY AFTERNOON WILL BE THE BREEZY CONDITIONS.
MIXING WILL BE MAXIMIZED GIVEN THE LACK OF CLOUD COVER...SO EXPECT
GUSTS TO NEAR 35 MPH AND POSSIBLY FLIRT WITH 40MPH FOR A FEW
HOURS. HAVE ALSO NUDGED TEMPS UP A DEGREE...WITH GENERALLY 80 TO
84 DEG EXPECTED.

THE WARM/MOIST AIR WILL CONTINUE TO ADVECT ACROSS THE REGION MON NGT
INTO TUE...WITH YET ANOTHER VERY MILD OVERNIGHT. HAVE TEMPS MAINLY
IN THE MID 60S BUT COULD SEE THIS NOT BEING WARM ENOUGH. THE
WILDCARD WILL BE CLOUD COVER...WHICH IS CLOUDS HOLD OFF
LONGER...TEMPS COULD STILL DIP INTO THE LOW/MID 60S. THE DEW POINTS
HOLDING IN THE 60S WOULD LIKELY SLOW THE RATE OF FALL OVERNIGHT.

TUESDAY THROUGH SATURDAY... 500MB TROUGH AXIS WILL REMAIN IN A
SLIGHTLY NEGATIVE ORIENTATION ACROSS THE CENTRAL CONUS...WITH A WEAK
SFC FEATURE LIFTING NORTH ACROSS THE MID-MISSOURI VALLEY TUE
MORNING. BROAD MID-LVL RIDGING WILL REMAIN OVER THE SOUTHEAST
CONUS...MEANWHILE HIGH-AMPLITUDE RIDGING CONTINUES ACROSS WESTERN
CANADA/ALASKA. THIS WILL MAINTAIN A RELATIVELY ACTIVE SOUTHWEST FLOW
PATTERN FOR THE CENTRAL CONUS/GREAT LAKES REGION THROUGH THUR/FRI.

LATER IN THE WEEK ENSEMBLES BEGIN TO NUDGE A 500MB VORT SOUTH FROM
CENTRAL CANADA WITH A SFC FEATURE PROGGED TO DEVELOP ALONG THE LEE-
SIDE OR THE NORTHERN PLAINS. CLOSER TO FRI/SAT...OPER SOLUTIONS
DEVELOP THIS SFC FEATURE WITH A FRONTAL BOUNDARY SLIDING SOUTH FROM
CANADA. CONFIDENCE REMAINS LOW ON HOW THINGS WILL EVOLVE LATER IN
THE WEEK...ALTHOUGH ENSEMBLES ARE DEMONSTRATING MINIMAL SPREAD THAT
THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN WITH A SEMI-ZONAL
ORIENTATION DEVELOPING.

WILL CONTINUE TO CARRY PERIODIC CHANCES FOR SHOWERS/STORMS...AND
TEMPS GENERALLY SEASONAL TO SLIGHTLY ABOVE SEASONAL THROUGH THE BULK
OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS TURNING SOUTH AND BECOMING BREEZY LATE THIS
  AFTERNOON.

* ISOLD-SCT SHRA POSSIBLE THROUGH THE AFTERNOON WITH A LESSER
  CHANCE THIS EVENING. PERIOD OF SHRA/TSRA EXPECTED LATE TONIGHT.

* SOUTH WINDS INCREASE EARLY MONDAY MORNING WITH 30 KT GUSTS
  LIKELY AND 35+KT GUSTS POSSIBLE. DIRECTION TURNS SOUTHWEST
  TOWARD MID MORNING. SPEEDS EASE MID-LATE MONDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 18Z...

SHRA COVERAGE CONTINUES TO SLOWLY INCREASE ACROSS CENTRAL AND
WESTERN IL AND LIFT NNE. EXPECT ISOLD-SCT COVERAGE THROUGH THE
AFTERNOON WITH MOST FREQUENT SHRA OCCURRENCE AT RFD AND LEAST AT
GYY. WARM FRONTAL BOUNDARY IS STILL SOUTH OF THE TERMINALS AND
HAVE SEEN A SHARPER EAST COMPONENT TO THE WINDS OVER THE LAST FEW
HOURS NORTH OF THE FRONT. DO EXPECT A SHIFT TO SOUTH OR SSE WINDS
LATER THIS AFTERNOON AND TIMING IN TAF MAY NEED TWEAKING. ONCE
WINDS TURN SOUTH SHOULD SEE SOME INCREASE IN SPEED AS WELL AS
MORE FREQUENT GUSTS TOWARDS 20 KT. SHRA COVERAGE LOOKS TO WANE A
BIT THIS EVENING THOUGH THERE MAY BE A SLIGHTLY BETTER CHANCE FOR
SOME TS TO OCCUR WITH ANY SHRA. COVERAGE WILL LIKELY INCREASE FROM
WEST TO EAST OVERNIGHT WITH A BAND OF SHRA/TSRA EXPECTED TO MOVE
ACROSS THE TERMINALS LATE TONIGHT INTO FIRST THING MONDAY MORNING.
HAVE INCLUDED TEMPO TSRA FOR THE MOST LIKELY PERIOD OF OCCURRENCE.
A PERIOD OF MVFR CIGS IS ALSO EXPECTED LATE TONIGHT AND EARLY
MONDAY MORNING.

WINDS JUST ABOVE THE SURFACE WILL INCREASE OVERNIGHT WITH SPEEDS
NEAR 50 KT BY 2000 FT. SURFACE WINDS WILL PICK UP THROUGH THE
OVERNIGHT WHICH MAY NEGATE LOW LEVEL WIND SHEAR SO WILL NOT
INCLUDE A MENTION FOR NOW...BUT WILL CONTINUE TO MONITOR. SURFACE
WINDS WILL MARKEDLY INCREASE AFTER DAYBREAK MONDAY MORNING AS A
SURFACE LOW PASSES WEST OF THE TERMINALS. SOUTH WINDS JUST EITHER
SIDE OF 180 DEGREES WILL RAMP UP AND GUST 30-35 KT THEN TURN
SOUTHWEST TOWARD 230 DEGREES OR SO BY MID MORNING. THERE IS SOME
SUGGESTION THAT THERE COULD BE A SHORT 1-2 HR WINDOW WHERE GUSTS
COULD BE HIGHER EARLY IN THE MORNING BUT THE LIKELIHOOD OF THAT IS
NOT CLEAR AT THIS POINT SO WILL CAP GUSTS AT 35 KT OR LESS FOR
NOW. WINDS LOOK TO REMAIN SOUTHWEST INTO THE AFTERNOON...THOUGH
RFD MAY TURN MORE WESTERLY...AND SPEEDS SHOULD GRADUALLY EASE MID/LATE
AFTERNOON.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE EVENING. MEDIUM
  CONFIDENCE IN TIMING OF A SHIFT TO SOUTHERLY WINDS.

* MEDIUM CONFIDENCE THAT SHRA COVERAGE WILL BE ISOLD-SCT THROUGH
  THE AFTERNOON WITH LESSER COVERAGE THIS EVENING. MEDIUM-HIGH
  CONFIDENCE IN SHRA-TSRA OCCURRING LATE TONIGHT.

* HIGH CONFIDENCE IN WIND GUSTS REACHING 30KT AND MEDIUM-HIGH
  CONFIDENCE IN 35KT MONDAY MORNING. MEDIUM-HIGH CONFIDENCE IN
  SOUTH DIRECTION TURNING SOUTHWEST MID MORNING WHILE SPEEDS
  REMAIN STRONG. MEDIUM CONFIDENCE IN SPEEDS EASING MID-LATE
  MONDAY AFTERNOON.

MDB

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

MONDAY NIGHT...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY
SOUTHWEST WINDS.

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

KREIN

&&

.MARINE...
244 AM CDT

WARM/MOIST AIR WILL BE STEADILY LIFTING NORTH OVER THE
LAKE LATER TODAY AND CONTINUE THROUGH EARLY NEXT WEEK. THIS WILL
LIKELY ALLOW AREAS OF FOG TO DEVELOP...AND COULD BECOME DENSE AT
TIMES.

THE GRADIENT QUICKLY INCREASES LATE TONIGHT FROM THE
SOUTHWEST/SOUTH...WITH GUSTS NEARING 25-30KT FOR THE NEARSHORE
WATERS OF IL/IN THROUGH MON NIGHT. AS A RESULT HAVE HOISTED A SMALL
CRAFT ADVISORY FOR MON/MON NIGHT. WITH GUIDANCE TRENDING UP ON
GUSTS...IT IS POSSIBLE WE MAY SEE A GALE FORCE GUSTS OR TWO OCCUR
MON AFTERNOON IN THE IL/IN NEARSHORE WATERS. THEN ANOTHER WAVE WILL
LIFT NORTH TUE AND COULD BRING GUSTY WINDS YET AGAIN TO THE
NEARSHORE WATERS. EXPECT THE GUSTS NOT TO PUSH OUT FAR OVER THE OPEN
WATERS AS THE WATER REMAINS MUCH COLDER...WHICH WILL LIKELY ALLOW A
STABLE MARINE LAYER TO DEVELOP AND LIMIT HOW MUCH MIXING CAN OCCUR
FROM THE WINDS ALOFT TO THE SFC. IN ADDITION THIS WILL LIKELY LIMIT
HOW LARGE THE WATERS WILL BUILD.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM MONDAY TO 4 AM TUESDAY.

&&

$$

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