Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 031136
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
636 AM CDT WED JUN 3 2015

.SHORT TERM...
330 AM CDT

THROUGH THURSDAY...

.SHORT TERM...THROUGH THURSDAY...

ANOTHER REPEAT MORNING ON TAP TODAY WITH HIGH CLOUDS DRIFTING
THROUGH THE AREA OUT AHEAD OF CONVECTION IN THE PLAINS AND UPPER
MIDWEST. SEVERAL SMALL SCALE DISTURBANCES CONTINUE TO RIDE ENE ON
THE PERIPHERY OF AN UPPER RIDGE AXIS WHICH EXTENDS FROM SOUTHERN NEW
MEXICO NE INTO IOWA/CENTRAL ILLINOIS. THESE MAKE LITTLE HEADWAY
AGAIN TODAY AS THE RIDGE CONTINUES TO HOLD/SLOWLY STRENGTHEN.
SURFACE HIGH PRESSURE WILL DRIFT TO THE ATLANTIC SEABOARD TODAY WITH
SYNOPTIC WINDS TURNING SOUTHEASTERLY. THIS WILL ALLOW THE LOW LEVEL
AIRMASS WARMS SOME 3 DEGREES C PER 850/25 TEMP ANALYSIS. LOCAL CLIMO
WHICH PERFORMED WELL TODAY...WOULD SUGGEST READINGS IN THE UPPER 70S
TO LOW 80S. MODELS STILL SUGGEST A LAKE BREEZE TODAY...THE WARMING
WILL CONTINUE TO TRANSLATE TO LAKE SHORE AREAS WHICH SHOULD AT LEAST
PUSH THE MID TO UPPER 60S.

MOST GUIDANCE NOW...INCLUDING THE ECMWF...HAS BACKED OFF ON THE
EASTWARD PROGRESSION OF SHOWERS AND STORMS FOR THURSDAY...AT LEAST
FOR THE DAYTIME HOURS. CONVECTIVELY DRIVEN VORT MAX WILL BE PUSHING
INTO A STILL STRENGTHENING RIDGE WHICH SHOULD KEEP MOST IF NOT ALL
AREAS DRY. THE WARMING TREND CONTINUES WITH ANOTHER 2-3C AT 850/925.
THUS LOW TO MID 80S SEEM REASONABLE. LOW LEVEL WINDS ARE NOT STRONG
ENOUGH TO COMBAT A LAKE BREEZE...BUT IT SHOULD BE LATER IN THE DAY
SO MID 70S LOOK TO MAKE AN APPEARANCE EVEN ALONG THE LAKE.

KMD

&&

.LONG TERM...
330 AM CDT

THURSDAY NIGHT THROUGH TUESDAY...

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...

DISTURBANCES GET A BIT CLOSER TO THE AREA SUCH THAT EVENING
CONVECTION COULD BE A CONCERN LATER THURSDAY NIGHT. ISENTROPIC
LEVELS INCREASES AND THE HIGH PWAT AIR IN THE PLAINS GETS DRAPED
OUR AREA. A COLD FRONT WILL BE WORKING ITS WAY SOUTHWARD THROUGH
THE DAY AS WELL. SO CHANCES FOR SHOWERS AND STORMS BOTH IN THE
MORNING AND THE AFTERNOON TIME FRAMES...WITH BEST CHANCES IN OUR
WESTERN SET OF COUNTIES.

THE LONGER TERM FEATURES NUMEROUS IMPULSES EJECTING FROM A TROUGH IN
THE WEST THAT WILL DAMPEN WITH TIME...WITH THESE IMPULSES RIDING
ALONG AND FLATTENING A STRONG UPPER RIDGE THAT HOLDS FIRM OVER THE
SOUTHERN PLAINS. WITH THIS RIDGE IN PLACE...THIS SETS THE STAGE FOR
THESE SHORTWAVES TO TAKE AIM AT THE REGION. MEANWHILE AT THE SURFACE
A COLD FRONT SINKS THROUGH THE AREA FRIDAY NIGHT...BUT A MID LEVEL
BAROCLINIC ZONE REMAINS DRAPED SOMEWHERE ACROSS THE REGION DURING
THE REMAINDER OF THE EXTENDED PERIOD.  HAD TO CONTINUE TO TEMPER
PRECIPITATION CHANCES OVER THE WEEKEND AND BEYOND DUE TO THE FACT
THAT TIMING INDIVIDUAL WAVES IN THIS PATTERN WILL BE EXTREMELY
CHALLENGING...AND THAT IS CERTAINLY PLAYING OUT IN THE SPREAD
AMONGST MID AND LONGER RANGE MODEL GUIDANCE. HAVE CARRIED HIGHEST
CHANCES FRIDAY AND AGAIN SUNDAY. THERE WILL LIKELY BE PERIODS OF
SHOWERS AND THUNDERSTORMS...AND THE CHALLENGE IN THE COMING DAYS
WILL BE TO HONE IN ON SOME OF THOSE DETAILS WITH REGARDS TO WHERE
AND WHEN. THE AIRMASS REMAINS RATHER JUICY ALL ALONG...MEANING
HEAVY RAINFALL CAN BECOME A CONCERN AT ANY TIME...AND MORE SO IF
SEVERAL WAVES OCCUR.

CONCERN WITH REGARDS TO SEVERE WEATHER BEGIN TO ENTER THE PICTURE
ONCE A DEEPER UPPER LOW SINKS SOUTH OUT OF CANADA. SEVERAL GUIDANCE
MEMBERS INDICATE THIS OCCURS AS EARLY AS SUNDAY...WITH OTHERS
PUSHING THINGS OFF INTO NEXT WEEK. BUT WITH THAT UNCERTAINTY IN
MIND...A STRONGER WIND FIELD ALOFT DURING THIS LATTER TIME FRAME
WOULD POSE A GREATER SEVERE WEATHER THREAT.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* LAKE BREEZE WITH EASTERLY WINDS NEAR 10 KTS THIS AFTERNOON. CMS

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE OVER THE EASTERN LAKES AND OHIO VALLEY WILL SLOWLY
MOVE EAST TODAY AND TONIGHT. LIGHT SOUTHEASTERLY WINDS WILL SHIFT
EASTERLY AT ORD/MDW THIS AFTERNOON AS A LAKE BREEZE DEVELOPS AND
MOVES INLAND. EXPECT PREVAILING SPEEDS GENERALLY UNDER 10KTS...
BUT SPEEDS MAY INCREASE TO 10KTS OR SO FOR AN HR OR TWO BEHIND THE
LAKE BREEZE. CONFIDENCE REMAINS LOW ENOUGH TO MAINTAIN CURRENT 8
KTS FOR NOW. CMS

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH FOR A LAKE BREEZE...MEDIUM FOR TIMING AND ASSOCIATED WIND
  SPEEDS. CMS

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

* THURSDAY NIGHT...CHANCE OF SHRA/TSRA. LIGHT EASTERLY WINDS.
* FRIDAY...CHANCE OF SHRA/TSRA. MVFR LIKELY. NORTHEAST WINDS.
* SATURDAY...SLIGHT CHANCE OF SHRA/TSRA. MVFR POSSIBLE. NORTHEAST
  WINDS.
* SUNDAY...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. SOUTHWEST WINDS.
* MONDAY...CHANCE OF SHRA/TSRA. WEST WINDS.
* TUESDAY...SLIGHT CHANCE OF SHRA/TSRA. NORTHWEST WINDS.

&&

.MARINE...

257 AM...A RIDGE OF HIGH PRESSURE FROM QUEBEC TO THE OHIO VALLEY
WILL SLOWLY SHIFT EAST TODAY. STRONGER HIGH PRESSURE WILL BUILD
ACROSS ONTARIO THURSDAY NIGHT AND FRIDAY...PUSHING A COLD FRONT
SOUTH ACROSS LAKE MICHIGAN LATE THURSDAY NIGHT INTO FRIDAY
MORNING. THERE REMAINS UNCERTAINTY REGARDING HOW STRONG THE
GRADIENT WILL BECOME BEHIND THIS FRONT. CURRENTLY MAINTAINING
10-20 KTS FROM THE NORTH/NORTHEAST BUT ITS POSSIBLE THAT SPEEDS
COULD BE STRONGER. AS THE HIGH MOVES EAST OVER THE WEEKEND...
WINDS WILL TURN SOUTHEASTERLY SATURDAY NIGHT AND THEN SHIFT
WESTERLY SUNDAY NIGHT AS LOW PRESSURE MOVES ACROSS THE NORTHERN
LAKES...DRAGGING A COLD FRONT ACROSS THE LAKE. CMS

&&

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

$$

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