Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 230812
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

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

KMD

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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