Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 231946
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
246 PM 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 20Z...

* SW WINDS GUSTING TO ARND 17KT THIS AFTN.

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE

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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA...MEDIUM-
  HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW CONFIDENCE IN
  HOW LOW THE CIGS WILL BE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

.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/NWSCHICAGO
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.