Area Forecast Discussion
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000
FXUS63 KLOT 260308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT OVERNIGHT.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.


//DISCUSSION...UPDATED 00Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE ALREADY BEGUN TO EASE AND SHOULD
CONTINUE TO EARLY THIS EVENING. A LOW-LEVEL JET WILL DEVELOP
OVERHEAD WITH SOME 40 KT AND POSSIBLY 45 KT FLOW AT 1500-2000 FT
FROM 05Z-12Z. STORMS ARE EXPECTED TO DEVELOP THROUGH THE EVE AHEAD
OF A FRONT FROM NORTHERN MO THROUGH IA AND INTO WI. WHILE THESE
WILL INCH EASTWARD SOME...THEY ARE GENERALLY EXPECTED TO REMAIN
NORTH AND NORTHWEST OF AREA TAF SITES...POSSIBLY CLOSING IN ON
RFD VERY LATE TONIGHT.

AS AN UPPER DISTURBANCE...PARTLY CONVECTIVELY ENHANCED...MOVES
FROM THE SOUTHERN PLAINS THIS EVENING TO NORTHERN IL BY LATE DAY
TUESDAY...SHOWERS AND SOME STORMS ARE EXPECTED TO EVOLVE INTO THE
REGION. GIVEN THE SUPPORT FOR LIFT ACROSS THE AREA THROUGHOUT THE
DAY THANKS TO BEING IN A FAVORABLE UPPER JET REGION...THE
LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA LASTS BASICALLY FROM
15Z THROUGH 02Z. THIS MAKES IT DIFFICULT TO TARGET A SPECIFIC
WINDOW FOR THUNDER. HAVE MADE OUR BEST FORECAST FOR EARLY TO MID
AFTERNOON...BUT COULD VERY WELL BE SHIFTED OR EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY AND AT TIMES MAY BE SHIFTING
SOME FROM SOUTHEAST TO SOUTHWEST DEPENDING ON CONVECTIVE ACTIVITY
COVERAGE. GUSTS ARE POSSIBLE THROUGH THE ENTIRE DAY AND APPEAR TO
BE EVEN MORE LIKELY IN THE EVENING AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH IN 40 KT SSW FLOW AROUND 1000-1500 FT OVERNIGHT...BUT LOW
  IN TRUE LLWS OCCURRING.

* HIGH IN WINDS TONIGHT AND TUESDAY MORNING. MEDIUM ON SPECIFICS
  AFTER.

* MEDIUM ON MVFR CIGS TUESDAY MORNING AND LOW-MEDIUM ON START TIME
  AND HOW LOW CIGS WILL DROP.

* HIGH ON SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW ON SPECIFIC
  TSRA TIMING WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.


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

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

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

$$

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