Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 030522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1222 AM CDT TUE MAY 3 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 NORTH
CENTRAL 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 06Z TAFS...

RIDGE OF HIGH PRESSURE OVER THE REGION WILL BRING LIGHT WINDS AND
VFR CONDITIONS TO THE NORTHERN ILLINOIS AND NORTHWEST TERMINALS
OVERNIGHT. THE RIDGE AXIS WILL SHIFT TO OUR SOUTH AS A COLD FRONT
DROPS INTO WISCONSIN DURING THE DAY TUESDAY. WEST-SOUTHWEST WINDS
WILL OVERSPREAD THE TERMINALS AS THIS HAPPENS...BECOMING GUSTY
DURING THE MID TO LATE AFTERNOON. BY AROUND 06Z TUESDAY EVENING
THE FRONT SHOULD BE NEAR THE IL/WI STATE LINE...THOUGH THERE IS
STILL A 2-3 HOUR WINDOW OF UNCERTAINTY DUE TO VARIOUS TIMING
SOLUTIONS FROM THE MODELS. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED OUT AHEAD OF THE FRONT WHICH WILL CROSS
THE TERMINALS SOMETIME DURING THE EARLY OVERNIGHT HOURS. BEHIND
THE FRONT...WINDS WILL TURN NORTHERLY AND BECOME GUSTY ONCE
AGAIN...WITH GUSTS INTO THE LOW TO MID 20 KT RANGE POSSIBLE
TUESDAY NIGHT. LOW CIGS ARE EXPECTED TO OVERSPREAD THE REGION
BEHIND THE FRONT AS WELL...WITH LOW END MVFR CONDITIONS CURRENTLY
ANTICIPATED.

BMD

&&

.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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