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 200824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
324 AM CDT SUN APR 20 2014

.DISCUSSION...
319 AM CDT

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH MAX TEMPS TODAY WITH A
POSSIBILITY OF LAKE COOLING...AND THEN WITH INCREASING CHANCES FOR
SHOWERS AND THUNDERSTORMS ON MONDAY.

QUIET CONDITIONS CONTINUE THIS MORNING AS HIGH PRESSURE REMAINS
SITUATED ACROSS THE REGION...WHILE SURFACE TROUGH/BOUNDARY ARE
SITUATED WELL NORTHWEST OF THE CWA. MID/UPPER LEVEL PATTERN IS
FAIRLY ACTIVE ACROSS THE CONUS THIS MORNING WITH EXITING VORT MAX
TO THE NORTH AND APPROACHING WEAKER/LOW AMPLITUDE UPPER LEVEL
TROUGH LIFTING NORTHEAST TO THE SOUTHERN PLAINS...AND WITH ANOTHER
VORTICITY MAXIMA SHIFTING EAST THROUGH THE NORTHWEST CONUS. THESE
FEATURES HAVE PROVIDED A FAIR AMOUNT OF MID AND HIGH LEVEL
MOISTURE OVER THE CENTRAL CONUS...BUT WITH THE MAJORITY OF THIS
MOISTURE STAYING WEST OF THE CWA. WITH THE FRONTAL BOUNDARY HELD
UP TO THE NORTHWEST TODAY...EXPECT DRY CONDITIONS ONCE AGAIN TODAY
AND FOR MOST OF TONIGHT BUT WITH A SLOW INCREASE IN CLOUD COVER
THROUGHOUT THE DAY. LATEST SATELLITE IMAGERY DEPICTING MID/HIGH
LEVEL CLOUD COVER TRYING TO INCH ITS WAY CLOSER TO THE WEST AND
NORTHWEST CWA AND ALTHOUGH I DO ANTICIPATE A PORTION OF THIS CLOUD
COVER TO CLIP THE FAR NORTHWEST AND NORTHERN CWA...BULK OF THIS
CLOUD COVER SHOULD REMAIN OUTSIDE OF THE CWA THROUGH EARLY
AFTERNOON. COULD SEE SOME OF THIS CLOUD COVER SPILL FURTHER EAST
FOR SOME PERIODS TODAY...BUT STILL THINK IT WONT BE ENOUGH TO
PROVIDE ANYTHING MORE THAN PARTLY CLOUDY SKIES. EVEN WITH
POTENTIAL FOR CLOUDS TO PUSH ACROSS A PORTION OF THE CWA...FEEL
THAT TODAY WILL BE A RATHER WARM DAY WITH WELL ABOVE NORMAL TEMPS
IN THE MID TO UPPER 70S ACROSS THE CWA. AS WAA STEERS THERMAL AXIS
OVERHEAD TODAY...DID RAISE TEMPS A COUPLE OF DEGREES WITH MOST
LOCATIONS OBSERVING THESE MID/UPPER 70 DEGREE TEMPS WITH LOCATIONS
ACROSS THE EASTERN CWA LIKELY MORE IN THE LOW 70 RANGE. LAKE
COOLING COULD BECOME AN ISSUE LATER THIS AFTERNOON AS SURFACE
PATTERN RELAXES AND LOW LEVEL FLOW WEAKENS. THIS COULD RELAX THE
SURFACE WINDS ENOUGH TO ALLOW FOR SOME ONSHORE TURNING OF THE
WINDS MAINLY FOR CHICAGO NORTHWARD INTO LAKE COUNTY...WITH A
SLIGHT POSSIBILITY FOR THIS TO OCCUR OVER NORTHWEST INDIANA.
ALTHOUGH DID ACCOUNT FOR THIS IN THE MAX T GRID...FEEL THAT MOST
OF THE WARMING WILL OCCUR PRIOR TO THIS TURNING OF THE WINDS AND
RESULTANT COOLING. SO LOCATIONS NEAR THE LAKE WILL LIKELY OBSERVE
UPPER 60S OR LOWER 70S BEFORE THIS POSSIBLE COOLING OCCURS LATER
THIS AFTERNOON.

EXPECT TONIGHT TO REMAIN ON THE DRY SIDE BUT WITH SOME POSSIBILITY
FOR A STRAY SHOWER OR TWO MORE TO MOVE ACROSS THE FAR NORTHWEST
CWA MORE TOWARDS EARLY MONDAY MORNING. AS SEVERAL WAVES OF ENERGY
LIFT NORTHEAST OUT AHEAD OF APPROACHING TROUGH TO THE SOUTHWEST
AND THE STRONGER AND MORE DEFINED MID LEVEL TROUGH DROPS SOUTHEAST
THROUGH THE NORTHERN PLAINS AND UPPER MIDWEST MONDAY...EXPECT
SURFACE TROUGH TO BECOME MORE ORGANIZED AND THEN DEEPEN AS IT
BEGINS WORKING EAST TOWARDS THE CWA BY MID DAY MONDAY.
ALTHOUGH...IT DOES APPEAR AS IF A SLOWER TREND IS SHOWING UP
WITHIN MODEL GUIDANCE AND HAVE REFLECTED THIS TREND IN THE GRIDS
KEEPING ONLY CHANCE POPS MAINLY FOR THE NORTHWEST HALF OF THE CWA
THROUGH MID DAY MONDAY. LARGE SCALE SUPPORT INCREASES AS WELL AS
LOW/MID LEVEL CONVERGENCE STRENGTHENING THROUGH THE AFTERNOON. AS
THIS OCCURS...IT DOES APPEAR THAT SOME BETTER MOISTURE RETURN DOES
FINALLY OCCUR OUT AHEAD OF THIS TROUGH/FRONTAL BOUNDARY. EXPECT
SCATTERED SHOWER DEVELOPMENT TO PERSIST THROUGH THE AFTERNOON WITH
THE BEST CHANCES FOR PRECIP ACROSS THE ENTIRE CWA EXPECTED DURING
THIS TIME FRAME. GUIDANCE HAS CONTINUED THE INCREASING INSTABILITY
TREND...WITH INSTABILITY AXIS NOW ANTICIPATED WELL INTO WISCONSIN
AND OUT OVER THE LAKE. DID INCREASE MENTION OF THUNDER...WITH
CHANCE THUNDER FOR THE ENTIRE CWA ON MONDAY. WITH FLOW ALOFT
RATHER WEAK AS WELL AS THE INSTABILITY TO BE ON THE WEAKER
SIDE...AT THIS TIME EXPECT ANY THUNDERSTORM DEVELOPMENT TO BE
WEAK/UNORGANIZED. TROUGH/FRONT WILL PUSH THROUGH MONDAY EVENING
WITH CONFIDENCE STILL LOW WITH REGARDS TO CONTINUED CHANCES FOR
THUNDER...ESPECIALLY WITH GUIDANCE SHOWING THIS WEAK INSTABILITY
QUICKLY BEING SHUNTED TO THE SOUTH OF THE CWA. SO HAVE LEFT OUT
ANY MENTION OF THUNDER FOR MONDAY EVENING OVER THE SOUTHEAST THIRD
OF THE CWA...BUT COULD POSSIBLY BE INCLUDED WITH LATER FORECASTS.

RODRIGUEZ

&&

.AVIATION...

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

* NONE.

RATZER

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

SOUTHEAST WINDS NEAR 10 KT WILL VEER SOUTH SUNDAY MORNING AND
INCREASE SLIGHTLY...WITH A FEW OCCASIONAL GUSTS 15-20 KT POSSIBLE
DURING THE AFTERNOON HOURS. DRY VFR CONDITIONS WILL CONTINUE...
WITH SCT MID/HIGH CLOUDS INCREASING AND EVENTUALLY FORMING A MORE
SOLID MID-LEVEL DECK SUNDAY NIGHT.

RATZER

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

* HIGH CONFIDENCE ALL FORECAST ELEMENTS.

RATZER

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

MONDAY...AFTERNOON SHRA LIKELY. BRIEF MVFR POSSIBLE.

TUESDAY AND WEDNESDAY...VFR.

THURSDAY...CHANCE SHRA/TSRA...MAINLY AT NIGHT.

FRIDAY...VFR PROBABLE.

IZZI

&&

.MARINE...
217 AM CDT

HIGH PRESSURE RIDGE AXIS HAS MOVED EAST OF THE LAKE THIS MORNING...
WHILE LOW PRESSURE WELL TO THE NORTH WAS MOVING FROM MANITOBA INTO
ONTARIO. THIS LOW WILL CONTINUE EAST TO NEAR JAMES BAY BY THIS
EVENING...WITH A COLD FRONTAL TROUGH TRAILING SOUTHWEST ACROSS THE
UPPER MIDWEST AND CENTRAL PLAINS TO ANOTHER LOW DEVELOPING OVER THE
SOUTHERN HIGH PLAINS. THIS FRONT WILL BEGIN TO SAG ACROSS NORTHERN
LAKE MICHIGAN LATER TONIGHT...AS A WEAK LOW PRESSURE WAVE LIFTS
NORTHEAST INTO THE GREAT LAKES REGION ALONG THE TRAILING COLD FRONT.
LOW PRESSURE WILL CONSOLIDATE AND DEEPEN ACROSS THE CENTRAL AND
EASTERN LAKES REGION BY LATE MONDAY AS AN UPPER DISTURBANCE DIGS
INTO THE REGION...WITH THE COLD FRONT MOVING TO THE EAST AND
SOUTHEAST OF SOUTHERN LAKE MICHIGAN MONDAY EVENING. WITH THE LOW
DEEPENING OFF TO THE EAST...AND A BROAD AREA OF HIGH PRESSURE
BUILDING ACROSS THE UPPER MIDWEST...NORTHERLY WINDS WILL BRIEFLY
INCREASE INTO THE 20-25 KT RANGE ACROSS LAKE MICHIGAN MONDAY
NIGHT AND TUESDAY. THE SURFACE HIGH PRESSURE RIDGE WILL THEN
SPREAD EAST ACROSS THE WESTERN LAKES REGION TUESDAY NIGHT INTO
WEDNESDAY. ANOTHER FAIRLY DEEP LOW PRESSURE SYSTEM WILL THEN MOVE
ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST WEDNESDAY NIGHT INTO
THURSDAY...WITH INCREASING SOUTH WINDS IN THE 25-30 KT RANGE
DEVELOPING ACROSS LAKE MICHIGAN. THE LOW WILL MOVE ACROSS THE
NORTHERN LAKES THURSDAY WITH A COLD FRONT MOVING EAST ACROSS THE
LAKE BY THURSDAY NIGHT.

RATZER

&&

.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.