Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 210544
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1244 AM CDT MON APR 21 2014

.DISCUSSION...
259 PM CDT

THIS AFTERNOON THROUGH TONIGHT...
SKIES HAVE REMAINED MOSTLY SUNNY THIS AFTERNOON...AND WITH
SOUTHERLY FLOW HAS ALLOWED SFC TEMPS TO QUICKLY PUSH WELL INTO THE
70S ACROSS THE BULK OF THE FORECAST AREA WITH A HANDFUL OF POINTS
AT 80 DEGREES. DEW POINTS WERE ABLE TO RISE TO ARND 40...HOWEVER
WITH FULL SUNSHINE THE MIXING HAS BEEN EFFECTIVE AT PRODUCING SOME
SUBSIDENCE AND PUSHED DEW POINTS BACK INTO THE UPR 30S. WHILE THE
ANTI-CYCLONIC FEATURE HAS BECOME CENTERED WELL EAST OF THE
REGION...ENOUGH OF AN INFLUENCE REMAINS ACROSS THE WESTERN OHIO
VALLEY AND THE FORECAST AREA THAT DRY WEATHER WILL PREVAIL THROUGH
THE EVENING AND LIKELY THRU THE OVERNIGHT.

THERE IS SOME CONCERN THAT THE ISOLATED SHOWERS/THUNDERSTORMS THAT
DEVELOPED THIS AFTERNOON ACROSS NORTHERN IOWA MAY CREEP
EAST...HOWEVER FEEL THAT WITH THE SOUTHERLY FLOW THIS AREA OF PRECIP
SHUD BE ABLE TO LIFT NORTHEAST AND REMAIN WEST/NORTHWEST OF THE CWFA
THIS EVENING/OVERNIGHT. TONIGHT WILL REMAIN MILD WITH TEMPS HOLDING
IN THE LOW/MID 50S. THE COOLEST LOCATIONS WILL LIKELY BE FOCUSED
NEAR LAKE MICHIGAN.

CONFIDENCE IN DRY WEATHER THRU OVERNIGHT...MEDIUM/HIGH.
CONFIDENCE IN TEMPS...HIGH.

MONDAY THROUGH TUESDAY...
MID-LVL HEIGHTS BEGIN TO LOWER EARLY MON...HOWEVER LOW/MID LEVELS
REMAIN MOISTURE STARVED. THE MID-LVL WEAK VORT IS PROGGED TO SLIDE
EAST INTO THE OZARKS EARLY MON MORNING...AND WITH THE SOUTHERLY FLOW
OUT AHEAD OF THIS FEATURE...LLVLS SHOULD SLOWLY MOISTEN. GUIDANCE
HAS BEEN STEADILY BACKING OFF ON PRECIP CHANCES ARRIVING ACROSS THE
FORECAST AREA...AND HAVE TRIMMED BACK POPS ACCORDINGLY. INSTABILITY
DOES BUMP UP CLOSER TO MIDDAY MON...HOWEVER THE PEAK INSTABILITY
TIMEFRAME APPEARS TO BE FOCUSED BETWEEN 21-00Z.

NORTHERN STREAM MID-LVL VORT PIVOTS EAST ACROSS NORTHERN WISC MON
AFTN...WHICH MAY PROVIDE SOME ADDED FORCING AS THE FRONTAL BOUNDARY
NEARS THE CWFA. EXPECT PRECIP COVERAGE TO REMAIN LOW. GIVEN THE
INSTABILITY PROGGED TO BE NEARING 400-600J/KG BASED OFF OF LOCAL
WRF...THIS CONTINUES TO SUPPORT THINKING OF CHC THUNDER. SPC
CONTINUES TO HAVE THE AREA HIGHLIGHTED FOR GENERAL THUNDER. TEMPS
WILL ONCE AGAIN STEADILY WARM INTO THE MID/UPR 70S. COULD SEE A FEW
POINTS STILL TOUCH 80 DEGREES...ALTHOUGH WITH SLIGHTLY HIGHER LLVL
MOISTURE THE RATE OF CLIMB MAY BE DIMINISHED AND TEMPS COULD HOLD
GENERALLY IN THE MID 70S.

THE FRONTAL BOUNDARY SHUD NEAR THE NORTHWEST CWFA ARND 00Z...AND
WILL STEADILY BRING DRIER AIR IN AND SHUT-OFF PRECIP FROM NORTHWEST
TO SOUTHEAST. HAVE PUSHED UP THE ENDING TIME OF POPS CLOSER TO 6Z
TUE...AS WINDS TURN NORTHWEST.

MID-LVL TROUGH PIVOTS OVERHEAD MIDDAY TUE. THE SFC RIDGE CENTER WILL
BE CENTERED NORTHWEST OF THE CWFA TUE...THIS WILL KEEP TEMPS HELD
DOWN IN THE MID/UPR 50S AND LIKELY UPR 40S FOR LOCATIONS ADJACENT TO
LAKE MICHIGAN. THE FAR SOUTH/SOUTHWEST CWFA SHOULD BE ABLE TO WARM
BACK TO ARND 60.

CONFIDENCE IN PRECIP MON...MEDIUM/HIGH.
CONFIDENCE IN TEMPS...HIGH.

WEDNESDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW WILL SETUP SHOP ACROSS THE REGION WED. WITH LIGHT
EAST/NORTHEAST FLOW OFF OF LAKE MICHIGAN...TEMPS WILL STRUGGLE TO
WARM BEYOND THE UPR 40S/LOW 50S FOR AREAS ADJACENT TO THE LAKE.
INLAND AREAS WILL WARM INTO THE UPR 50S TO LOW 60S WED.

THEN THE FOCUS TURNS TOWARDS THE NEXT WEATHER SYSTEM POISED TO TAKE
SHAPE ACROSS THE CENTRAL PLAINS WED NGT. GUIDANCE HAS BEEN RATHER
CONSISTENT WITH THE SFC RIDGE SLIDING EAST OF THE FORECAST AREA LATE
WED NGT...WITH A WARM FRONTAL BOUNDARY LIFTING NORTH FROM THE SFC
LOW AND BRINGING PRECIP CHCS BACK TO THE AREA. GUIDANCE PROGS THE
TRACK OF THE SFC LOW TO BE LIFTING NORTHEAST INTO THE UPPER MIDWEST
THUR MORNING. INSTABILITY DOES APPEAR LIKELY TO DEVELOP AND INCREASE
FOR THUR...THUS HAVE HELD ONTO THE MENTION OF THUNDER. FRONTAL
BOUNDARY SHUD ARRIVE OVER THE AREA FRI...WHICH WILL BRING AN END TO
THE CONVECTIVE CHANCES. GUIDANCE INDICATES A DRY WEDGE LIFTING
NORTHEAST INTO THE FORECAST AREA FRI.

DEPENDING ON CLOUD COVER FRI...TEMPS MAY BE ABLE TO WARM BACK INTO
THE MID/UPR 60S OR POSSIBLY LOW 70S ACROSS THE SOUTHERN CWFA. THEN
FOR THE UPCOMING WEEKEND TEMPS ARE BACK INTO THE MID/UPR 50S.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* SCATTERED SHOWERS/THUNDERSTORMS DEVELOPING MONDAY AFTERNOON.

RODRIGUEZ

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

QUIET CONDITIONS TONIGHT/EARLY MONDAY MORNING...WITH MID/HIGH
LEVEL CLOUD COVER CONTINUING TO STREAM OVERHEAD AND SOUTH TO
SOUTHWEST WINDS REMAINING IN PLACE. EXPECT WINDS TO BECOME MORE
SOUTHWEST BY MID MORNING MONDAY WHILE SPEEDS INCREASE THROUGH MID
DAY AND THE AFTERNOON. EXPECT CLOUD COVER TO INCREASE WITH VFR
CEILINGS LIKELY BY MID DAY...AS SCATTERED SHOWERS BEGIN MOVING
ACROSS THE TERMINALS. THIS SCATTERED DEVELOPMENT WILL LIKELY
PERSIST IN THE AFTERNOON UNTIL BETTER DEVELOPMENT ARRIVES OUT
AHEAD OF APPROACHING FRONT LATE IN THE AFTERNOON AND EARLY
EVENING. ITS DURING THIS TIME THAT BEST THUNDER POTENTIAL WILL BE
BEFORE PRECIP QUICKLY EXITS TO THE EAST WITH FROPA...AND WITH
SOUTHWEST TO WEST WINDS TURNING TO THE NORTHWEST.

RODRIGUEZ


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

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH SHOWER/THUNDERSTORM POTENTIAL...WITH
  MEDIUM CONFIDENCE OF TIMING/DURATION.

RODRIGUEZ

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

TUESDAY AND WEDNESDAY...VFR.

THURSDAY...VFR EARLY...THEN A PERIOD OF SHRA/TSRA LIKELY LATE.

FRIDAY AND SATURDAY...MVFR CIGS POSSIBLE.

IZZI

&&

.MARINE...
125 PM CDT

LOW PRESSURE TRACKING ACROSS NORTHERN ONTARIO...WILL PUSH A
FRONTAL BOUNDARY ACROSS THE NORTHERN PORTION OF THE LAKE TONIGHT
INTO MONDAY. THIS WILL SET UP A PERIOD OF LIGHT AND VARIABLE
WINDS THERE THROUGH MONDAY. A SECOND AREA OF LOW PRESSURE WILL
MOVE ALONG THIS FRONT LATE MONDAY...AND ONCE THIS LOW MOVES EAST
OF THE LAKE...A PERIOD OF STRONGER NORTHERLY WINDS WILL SET UP
ACROSS THE LAKE MONDAY NIGHT INTO TUESDAY...BEFORE HIGH PRESSURE
BUILDS OVER THE LAKE WEDNESDAY NIGHT. THESE STRONGER NORTHERLY
WINDS COULD RESULT IN SMALL CRAFT ADVISORY CONDITIONS WITH HIGH
WAVES INTO THE NEAR SHORE WATERS FOR TUESDAY.

THE LATER PORTION OF THE WEEK APPEARS TO REMAIN ACTIVE
ACROSS THE GREAT LAKES REGION. IT APPEARS THAT ANOTHER SIGNIFICANT
AREA OF LOW PRESSURE WILL IMPACT THE UPPER MIDWEST AND THE GREAT
LAKES REGION LATE IN THE WEEK AND INTO EARLY NEXT WEEKEND. THIS
SYSTEM COULD PRODUCE PERIODS OF THUNDERSTORMS ACROSS THE LAKE AND
ALSO ADDITIONAL PERIODS OF SIGNIFICANT WINDS.

KJB

&&

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

$$

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