Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 021952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
252 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

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

$$

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