Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 222010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT WED OCT 22 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE

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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

RATZER

&&

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

$$

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