Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | 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 141956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT SUN SEP 14 2014

.DISCUSSION...
240 PM CDT

MAIN FOCUS IS ON OUR NEXT RAIN CHANCE WHICH COMES VERY LATE TONIGHT
THROUGH MUCH OF MONDAY...AND A CONTINUATION OF COOL/BELOW AVERAGE
TEMPS FOR MID-SEPTEMBER.

IN THE NEAR TERM...A PLEASANT BUT STILL COOL WEATHER WAS IN PLACE
ACROSS THE REGION THIS AFTERNOON. SURFACE HIGH PRESSURE WAS CENTERED
OVER THE EASTERN GREAT LAKES...WITH RIDGING EXTENDING SOUTHWEST
ACROSS INDIANA AND ILLINOIS. THE RESULT IS MOSTLY SUNNY AND SLIGHTLY
MILDER CONDITIONS WITH TEMPS REACHING THE MID 60S IN MOST SPOTS AND
UPPER 60S IN A COUPLE IN THE WEST/SOUTH PARTS OF THE CWA. LIGHT
WINDS AND CLEAR SKIES THIS EVENING WILL ALLOW TEMPS TO FALL OFF
FAIRLY QUICKLY HOWEVER...WITH READINGS DROPPING THROUGH THE 50S THIS
EVENING AND INTO THE MID-UPPER 40S LATER TONIGHT BEFORE CLOUDS BEGIN
TO INCREASE AFTER MIDNIGHT.

THIS INCREASE IN CLOUD COVER LATE TONIGHT WILL BE IN ASSOCIATION
WITH A MID-LEVEL SHORT WAVE TROUGH CURRENTLY DIGGING SOUTHEAST FROM
SASKATCHEWAN INTO MONTANA PER AFTERNOON GOES VAPOR IMAGERY.
INCREASING SOUTHERLY LOW LEVEL FLOW WILL DEVELOP AS THIS WAVE DIGS
SOUTHEAST...WITH 925-850 MB LAYER MOISTURE TRANSPORT INCREASING ON
THE NOSE OF A 30-35 KT LOW LEVEL JET WHICH DEVELOPS FROM THE TX/OK
PANHANDLE REGION. THIS AXIS OF MOISTURE TRANSPORT EVENTUALLY WORKS
INTO NORTHERN MISSOURI AND WEST CENTRAL IL MONDAY MORNING AS THE JET
VEERS MORE WEST-SOUTHWESTERLY. WHILE A FEW SHOWERS MAY DEVELOP
ACROSS FAR NORTH CENTRAL IL PRIOR TO SUNRISE...IT APPEARS THAT THE
BEST FORCING WILL ARRIVE SHORTLY AFTER...AS MID-LEVEL VORT
APPROACHES. A COMBINATION OF 40-50 METER HEIGHT FALLS...UPPER
DIVERGENCE BENEATH THE RIGHT REAR ENTRANCE REGION OF A 100+ KT UPPER
JET STREAK OVER THE GREAT LAKES...AND DEVELOPING FRONTOGENETIC
FORCING WITHIN THE LOW-MID LEVELS SHOULD PROVIDE SUFFICIENT FORCING
FOR PRODUCING RAIN/SHOWERS ACROSS THE AREA DURING THE DAY MONDAY.
WITH VARIOUS MODEL QPF AMOUNTS IN THE 0.25 TO 0.35 RANGE...RAIN IS
EXPECTED TO TAPER OFF FROM THE WEST/NORTHWEST LATE MONDAY AFTERNOON
AND EARLY MONDAY EVENING AS THE RELATIVELY PROGRESSIVE DISTURBANCE
MOVES EAST OF THE FORECAST AREA. STRONG HEIGHT RISES THEN ACCOMPANY
DEVELOPMENT OF SURFACE HIGH PRESSURE ACROSS THE MID-MISSISSIPPI
VALLEY MONDAY NIGHT AND TUESDAY.

SURFACE HIGH PRESSURE IS EXPECTED TO LINGER ACROSS THE ACROSS THE
MIDWEST FOR MUCH OF THE REMAINDER OF THE WEEK...SETTING THE STAGE
FOR DRY WEATHER WITH COOL NIGHTS AND COOLER THAN AVERAGE BUT SLOWLY
MODERATING TEMPS THROUGH NEXT WEEKEND. AFTER CLOUD/PRECIP INFLUENCED
TEMPS ONLY IN THE UPPER 50S/LOWER 60S OVER MUCH OF THE AREA
MONDAY...DAYTIME HIGHS SHOULD MODERATE THROUGH THE 60S THROUGH
WEDNESDAY AND THEN FINALLY INTO THE 70S FOR THE END OF THE
WEEK/WEEKEND. COLDEST OVERNIGHT MINS LOOK TO BE LATE MONDAY NIGHT AS
HIGH PRESSURE BUILDS IN  WITH LOW 40/A FEW UPPER 30S...WITH LOWS
GRADUALLY MODERATING INTO THE 50S BY THE END OF THE WEEK.

UPPER PATTERN EVOLVES INTO A LONG WAVE TROUGH OVER THE EAST COAST
WITH AN UPPER RIDGE ACROSS THE ROCKIES BY FRIDAY. SLIGHT EASTWARD
PROGRESSION AND FLATTENING OF THE PATTERN ALLOWS RETURN OF
WARMER/HIGHER MOISTURE CONTENT AIR INTO THE REGION INTO THE WEEKEND.
THIS YIELDS AN INCREASING CHANCE OF SHOWERS/THUNDERSTORMS AS A
MID-LEVEL DISTURBANCE PROPAGATES THROUGH THE FLOW AND A SURFACE
TROUGH APPROACHES AND MOVES ACROSS THE AREA FRIDAY NIGHT THROUGH
SUNDAY.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* NONE IN THE NEAR TERM.

* VFR CEILINGS AND RAIN ARRIVING MID MORNING ON
  MONDAY...CONTINUING THROUGH MID/LATE AFTERNOON.

* MVFR CEILINGS BY MIDDAY MONDAY...POSSIBLY IFR FOR A TIME.

* SOUTHWEST WINDS BECOMING WEST AND THEN NORTHWEST MONDAY
  MORNING...BECOMING MORE NORTHERLY LATE IN THE FORECAST PERIOD.

RODRIGUEZ

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

HIGH PRESSURE REMAINING IN PLACE EARLY THIS AFTERNOON ALLOWING FOR
QUIET CONDITIONS ACROSS THE TERMINALS...WHILE A LIGHT SOUTHWEST
WIND PERSISTS. VFR CONDITIONS WILL CONTINUE THIS AFTERNOON INTO
TONIGHT...WHILE MID/HIGH LEVEL CLOUD COVER SLOWLY INCREASE
TONIGHT. WINDS VARYING FROM WEST SOUTHWEST TO SOUTH SOUTHWEST WILL
LIKELY CONTINUE THIS AFTERNOON...BUT WITH THE PREVAILING DIRECTION
STAYING IN THIS SOUTHWEST DIRECTION. CURRENT SURFACE TROUGH TO THE
WEST WILL APPROACH THE TERMINALS ON MONDAY AND AS THIS
OCCURS...EXPECT RAIN TO OVERSPREAD THE TERMINALS THROUGH MONDAY
MORNING AND LIKELY INCREASE IN INTENSITY THROUGH MID DAY. DONT
ANTICIPATE VIS TO FALL TOO LOW IN THIS LIGHT RAIN...FALLING TO AT
MOST 3-5SM AT TIMES. PRECIP SHIELD WILL LIKELY BE FAIRLY
PROGRESSIVE EXITING THE TERMINALS BY MID/LATE AFTERNOON.
CONFIDENCE IS HIGH WITH CEILINGS LOWERING TO MVFR DURING THIS TIME
BUT LOW WITH THE POSSIBILITY OF IFR CEILINGS. IFR CEILINGS WILL
LIKELY BE PRESENT AROUND THE TERMINALS BUT LIKELY BE
PATCHY...UNDER THE BETTER PRECIP DEVELOPMENT.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF RAIN...MEDIUM HIGH CONFIDENCE OF TIMING AND
  DURATION.

* MEDIUM HIGH CONFIDENCE OF MVFR CEILINGS AND TIMING...LOW
  CONFIDENCE OF IFR.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...CHANCE OF SHOWERS IN THE AFTERNOON/EVENING WITH MVFR PSBL.
TUESDAY THROUGH FRIDAY...PRIMARILY VFR.
SATURDAY...CHANCE OF THUNDERSTORMS.

BMD

&&

.MARINE...
144 PM CDT

HIGH PRESSURE CENTERED OVER THE OHIO VALLEY WILL CONTINUE TO
SLOWLY LIFT NORTHEAST...BECOMING CENTERED OVER NEW ENGLAND MONDAY
MORNING. ALONG THE WESTERN END OF THIS HIGH PRESSURE CENTER IS A
TIGHTER GRADIENT...WHICH HAS BECOME EVIDENT ALONG THE NORTHERN
PORTIONS OF LAKE MICHIGAN WITH WINDS GUSTING AT TIMES TO 30KT FROM
THE SOUTHWEST. A FRONTAL BOUNDARY WILL SWEEP ACROSS LAKE MICHIGAN ON
MONDAY TURNING WINDS WEST/NORTHWEST. THEN ANOTHER RIDGE OF HIGH
PRESSURE WILL BRING ANOTHER PERIOD OF LIGHTER WINDS TO THE LAKE
MONDAY NGT THRU TUE.

HIGH PRESSURE WILL THEN REMAIN IN PLACE THROUGH EARLY
THURSDAY...THEN LIFT NORTHEAST WITH FLOW TURNING SOUTHERLY AND A
TIGHTENING GRADIENT THURSDAY NGT THROUGH FRIDAY. AT THIS TIME IT
IS POSSIBLE WIND COULD GUST TO 30KT FRIDAY NIGHT INTO
SATURDAY...MAINLY FOR THE NORTHERN HALF OF THE LAKE.

BEACHLER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
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.