Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 170245
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
945 PM CDT WED APR 16 2014

.DISCUSSION...
331 PM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP AND TEMP TRENDS
THURSDAY INTO FRIDAY...AND THEN WITH A DEFINITE WARMING TREND THIS
WEEKEND INTO NEXT WEEK.

WITH VORT MAX SHIFTING EAST/NORTHEAST ACROSS THE CENTRAL CONUS
THIS AFTERNOON...ATTENDANT SURFACE LOW CONTINUES TO SLOWLY SHIFT
EAST THROUGH EASTERN NEBRASKA AND IOWA THIS AFTERNOON AS A FAIRLY
TIGHT PRESSURE GRADIENT HAS ESTABLISHED ITSELF ACROSS THE CWA.
SOUTH TO SOUTHEAST HAVE PICKED UP THIS AFTERNOON WITH SOME
LOCATIONS ACROSS NORTHERN ILLINOIS GUSTING UP TO 30 TO 35 MPH. AS
THIS SURFACE LOW PUSHES NORTHEAST THROUGH IOWA AND INTO SOUTHERN
WISCONSIN TONIGHT...EXPECT WINDS TO TURN MORE SOUTH/SOUTHWEST
WHILE DIMINISHING BUT STILL GUSTING TO AROUND 25 TO 30 MPH FOR A
TIME THIS EVENING. BEST FORCING REMAINS WELL NORTH OF THE CWA AS
THIS VORT MAX AND LOW MOVE ACROSS THE REGION...WITH THE CWA
REMAINING DRY TONIGHT. MOST GUIDANCE IN AGREEMENT WITH A DRY
FORECAST TONIGHT...BUT STILL THINK THERE COULD BE A BRIEF LIGHT
SHOWER OR AT LEAST SOME SPRINKLES RIGHT ALONG THE
ILLINOIS/WISCONSIN BORDER WITH THE WAA PUSH OVERNIGHT. HAVE NOT
MADE MENTION OF THIS WITH LOWER CONFIDENCE AT THIS POSSIBILITY AND
DUE TO THE FACT THAT IF IT WERE TO OCCUR...ANTICIPATE ANYTHING
THAT FALLS TO ONCE AGAIN BE ON THE LIGHTER SIDE AND BRIEF. EXPECT
CURRENT CLEAR OR PARTLY CLOUDY SKIES IN PLACE TO SEE SOME INCREASE
IN CLOUD COVER TONIGHT...WITH A PERIOD OF CLOUDY SKIES LATER
TONIGHT ESPECIALLY OVER THE NORTHERN HALF OF THE CWA WITH OTHER
LOCATIONS SOUTH TO BE MORE PARTLY CLOUDY.

SURFACE LOW WILL CONTINUE NORTHEAST ON THURSDAY WEAKENING
SIGNIFICANTLY BY MID DAY AS UPPER SUPPORT IS QUICKLY LOST.
PERSISTENT WAA AND SOUTH/SOUTHWEST FLOW SHOULD ALLOW FOR SURFACE
TEMPS TO RISE INTO THE UPPER 50S AND LOWERS 60S THURSDAY...EVEN
WITH PARTLY CLOUDY/PARTLY SUNNY SKIES IN PLACE. INITIAL DRY
CONDITIONS AS SURFACE TROUGH/FRONT PUSH THROUGH THURSDAY WILL BE
REPLACE WITH AN INCREASE IN RAIN CHANCES LATER IN THE DAY AS
MID/UPPER LEVEL TROUGH SWING ACROSS THE REGION. IT DOES APPEAR AS
THIS RAIN WILL ONCE AGAIN BE ON THE LIGHTER SIDE AND STAY CONFINED
TO THE SOUTHEAST TWO THIRDS OF THE CWA...AND HAVE MAINTAINED HIGH
CHANCE POPS THURSDAY NIGHT. EXPECT ANY LINGERING RAIN TO QUICKLY
EXIT FRIDAY MORNING AS DRIER/COOLER AIR MOVES ACROSS THE
CWA...WITH SLIGHTLY COOLER TEMPS ESPECIALLY NEAR THE LAKE.
ALTHOUGH...IT DOES APPEAR THAT AN OVERALL WARMING TREND WILL START
THIS WEEKEND AND LIKELY CONTINUE INTO NEXT WEEK. HAVE CONTINUED
THIS WARMING TREND BY MAKING SLIGHT UPWARD ADJUSTMENTS ABOVE
GUIDANCE. WITH THIS WARMING TREND A LIKELY INCREASE IN MOISTURE
WILL OCCUR AS WELL AND AS PRECIP CHANCES ARRIVE EARLY NEXT
WEEK...THERE WILL ALSO BE POSSIBILITIES FOR THUNDER. CONFIDENCE IS
LOW WITH THIS POSSIBILITY AND SO HAVE LEFT OUT ANY MENTION OF
THUNDER AT THIS TIME...BUT COULD SEE A TREND TOWARDS THIS SOLUTION
POSSIBLE OVER THE NEXT COUPLE OF DAYS.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LLWS CONDITIONS DEVELOPING OVERNIGHT WHEN GUSTS SUBSIDE IN MORE
  STABLE CONDITIONS.

KREIN

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

STRONG...GUSTY SSELY WINDS WILL REMAIN A CONCERN UNTIL SHORTLY
AFTER SUNSET...AND THEN LLWS WILL BECOME THE MAIN FORECAST
CONCERN. A STRONG PRESSURE GRADIENT REMAINS IN PLACE ACROSS THE
REGION BETWEEN LOW PRESSURE MOVING THROUGH IOWA AND HIGH PRESSURE
OVER NEW ENGLAND. AS THE LOW LIFTS NEWD THROUGH WISCONSIN
TONIGHT...THE PRESSURE GRADIENT WILL RELAX...LEADING TO DECREASING
SUSTAINED WINDS. DEEP LAYER MIXING WILL ALSO SUBSIDE AS A SURFACE
BASED INVERSION DEVELOPS AFTER SUNSET WITH THE DRY AIRMASS AT THE
SFC COOLING RAPIDLY. WITH WINDS AT THE TOP OF THE INVERSION
EXPECTED TO REMAIN SWLY AT ARND 40 KT...ABOVE SSELY WINDS ARND 10
KT AT THE SFC...LLWS WILL BE A DISTINCT POSSIBILITY...SO HAVE ADDED
LLWS GROUPS TO ALL SITES. WIND DIRECTION WILL GRADUALLY VEER MORE
LY OVERNIGHT AS A COLD FRONT APPROACHES THE REGION. WITH THE SFC
LOW EXPECTED TO BECOME NRLY STNRY OVER CNTRL WI BY TOMORROW
MORNING...THE ASSOCIATED COLD FRONT WILL BE SLOW TO PUSH THROUGH
THE REGION...BUT ANTICIPATE THAT WINDS WILL EVENTUALLY VEER SWLY
TO WLY THROUGH THE DAY TOMORROW. THERE MAY BE SOME GUSTINESS IN
THE COLD ADVECTION BEHIND THE FRONT...BUT WINDS ALOFT ARE EXPECTED
TO BE MUCH LIGHTER TOMORROW WITH GUSTS ONLY REACHING ARND 18-20 KT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE IN LLWS POTENTIAL.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

FRIDAY...VFR. WX NIL.

SATURDAY...VFR. WX NIL.

SUNDAY...CHC RAIN. MVFR POSSIBLE.

MONDAY...CHC RAIN EARLY. OTRW...VFR/WX NIL.

TUESDAY...VFR. WX NIL.

WEDNESDAY...SLIGHT CHC RAIN. MVFR POSSIBLE.

KREIN

&&

.MARINE...
203 PM CDT

LOW PRESSURE...CURRENTLY ACROSS FAR WESTERN IOWA...WILL SHIFT
NORTHEASTWARD ACROSS THE UPPER LAKES REGION BY LATE
THURSDAY...WHILE WEAKENING. THIS WILL RESULT IN A CONTINUATION OF
THE SOUTH-SOUTHEASTERLY WINDS ACROSS THE LAKE TONIGHT AROUND 30 KT
RANGE. HOWEVER...AS A WEAK FRONTAL BOUNDARY MOVES ACROSS THE LAKE ON
THURSDAY...THE WINDS ABATE AND BECOME WEST-NORTHWESTERLY BY THURSDAY
EVENING. GENERALLY LIGHT NORTHERLY FLOW IS EXPECTED FRIDAY AND INTO
EARLY SATURDAY AS A WEAK SURFACE RIDGE OF HIGH PRESSURE BUILDS OVER
THE LAKE. THE WINDS LOOK TO INCREASE AGAIN OUT OF THE
SOUTH-SOUTHEAST LATER SATURDAY/SATURDAY EVENING AS THIS SURFACE
RIDGE SHIFTS EAST OF THE LAKES AND ANOTHER LOW TAKES SHAPE ACROSS
THE PLAINS.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 AM THURSDAY.

&&

$$

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