000
FXUS63 KLOT 050005
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
605 PM CST SAT FEB 4 2012

.DISCUSSION...
259 PM CST

FAIRLY BORING WEATHER THE NEXT WEEK WITH THE FORECAST CHALLENGES
TODAY REVOLVING AROUND LITTLE DETAILS LIKE TEMPS...SKY COVER...AND
MAYBE EVEN SOME FOG.

THE LOT CWA IS LIVING ON THE EDGE TODAY...THE EDGE OF THE
DEFORMATION ZONE OF THE WEAKENING UPPER LOW THAT IS WITH SCATTERED
SHOWERS OVER SOUTHERN 1/3RD OF THE AREA AND MOSTLY SUNNY SKIES FAR
NORTH. SHOWERS AND ASSOCIATED CLOUD COVER SHOULD BOTH MIGRATE
SOUTHWARD LATE THIS AFTERNOON EXITING SOUTHERN CWA BY 00Z OR SHORTLY
AFTER. GIVEN TODAY`S RAINFALL AND ANTICIPATED CLEARING SKIES AND
LIGHT WINDS THE POTENTIAL EXISTS FOR FOG TO DEVELOP LATER TONIGHT
OVER SOUTHERN CWA. HAVENT HIT ESPECIALLY HARD IN THE GRIDS YET BUT
WOULDNT BE THAT HARD TO ENVISION SOME AREAS GETTING SOCKED IN.

ASSUMING ANY FOG/STRATUS THAT FORMS DOESN`T BECOME TOO THICK AND
SLOW TO MIX OUT SUNDAY...THEN MOST AREAS SHOULD SEE A GREAT DEAL OF
SUNSHINE AND YET ANOTHER UNSEASONABLY MILD AFTERNOON. LOW LEVEL
TRAJECTORIES FOR TOMORROW AFTERNOON ORIGINATE OVER LOW MICHIGAN
WHERE TEMPS CLIMBED INTO THE LOW TO MID 40S TODAY...SO A COUPLE
DEGREES WARMER THAN THAT LOOKS LIKE A REASONABLE TARGET FOR OUR
HIGHS TOMORROW ASSUMING CLOUDS BEHAVE.

TRANSIENT SHORTWAVE RIDGING WILL TRAVERSE THE AREA MONDAY AS H8
TEMPS MODERATE TO NEARLY +5C WITH FORECAST SOUNDINGS SHOWING LITTLE
OR NO CLOUDINESS. SUSPECT THAT GUIDANCE IS UP TO ITS TYPICAL 2011-12
WINTER COOL BIAS AND HAVE BUMPED UP TEMPS 1 TO 2 CATEGORIES ABOVE
GUIDANCE AND THINK THAT TEMPS HAVE A GOOD SHOT AT FLIRTING WITH IF
NOT EXCEEDING 50F FOR HIGHS ACROSS MUCH OF THE CWA.

COLD FRONT MOVES THROUGH LATE MONDAY NIGHT INTO TUESDAY MORNING WITH
MODERATE SHOT OF MODIFYING ARCTIC AIR PUSHING IN TUESDAY INTO TUES
NIGHT. MOISTURE LIKELY TO BECOME TRAPPED BENEATH FRONTAL INVERSION
WITH SKIES BECOMING CLOUDY. FORECAST SOUNDINGS SUGGEST THAT
INVERSION HEIGHTS COULD BE HIGH ENOUGH FOR SOME LAKE EFFECT SNOW
SHOWERS INTO NE IL TUESDAY AS LAKE-850MB DELTA T`S GET INTO THE
12-14C RANGE. NOT LOOKING LIKE ANY BIG DEAL HOWEVER WITH TEMPS BELOW
INVERSION TOO WARM FOR ANY APPRECIABLE SNOW GROWTH AND
THERMODYNAMICS ALSO BEING QUITE MARGINAL.

WILL NEED TO KEEP AN EYE ON LOW AMPLITUDE NORTHERN STREAM WAVE
PROGGED TO RIPPLE THROUGH THE REGION TUESDAY NIGHT INTO WEDNESDAY.
MODEL QPF LOOKS PRETTY UNIMPRESSIVE SO ONLY HAVE SLIGHT CHANGE POPS
FOR LIGHT SNOW TUES NIGHT INTO WEDNESDAY...THOUGH NW FLOW SYSTEMS
LIKE THIS ONE CAN OCCASIONALLY BECOME OVERACHIEVERS AND PRODUCE
SOME ACCUMS.

TEMPS LOOK TO MODERATE SOMEWHAT WED NIGHT INTO THURSDAY AHEAD OF THE
NEXT CLIPPER AND ASSOCIATED ARCTIC FRONT WHICH LOOKS LIKE IT COULD
BRING A MORE HEALTHY SHOT OF COLD AIR BY THE END OF THE WEEK. ON THE
LARGE SCALE...MEDIUM RANGE GUIDANCE IS IN BETTER AGREEMENT THAN
YESTERDAY IN DEVELOPING TROUGHINESS OVER EASTERN NOAM ALLOWING FOR A
SHOT OF MODIFIED ARCTIC AIR FRIDAY INTO SAT WITH TEMPS POSSIBLY EVEN
DROPPING A BIT BELOW AVERAGE FOR THE FIRST TIME IN WEEKS!

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* NO REAL CONCERNS IN THE NEAR TERM.

* LIGHT NORTH/NORTHEAST WINDS TONIGHT AND SUNDAY.

* OUTSIDE POSSIBILITY FOR FOG DEVELOPMENT OVERNIGHT.

RODRIGUEZ

//DISCUSSION...UPDATED 00Z...

SOLID AREA OF LOW AND MID LEVEL MOISTURE CONTINUES TO LINGER
ACROSS THE AREA AS THE CURRENT SYSTEM IN PLACE SLOWLY MOVES
THROUGH THE REGION. ALTHOUGH...WITH THE SYSTEMS SLOW SOUTHERLY
TRACK...MANY SITES HAVE OBSERVED THIS LOW LEVEL STRATUS SCATTERING
OUT OVER THE LAST COUPLE OF HOURS. EXPECT THIS TREND TO CONTINUE
INTO THE EVENING AS THIS SYSTEM SLOWLY PULLS AWAY. ANY LINGERING
MID/HIGH LEVEL MOISTURE WILL ALSO SHIFT SOUTHWARD WITH SKIES
BECOMING CLEAR OVERNIGHT. WITH THESE CLEAR SKIES IN PLACE AND
DIMINISHING WINDS...FOG/LOW STRATUS DEVELOPMENT REMAINS A
POSSIBILITY TONIGHT. ALTHOUGH LATEST TRENDS/GUIDANCE WOULD SUGGEST
THAT BETTER FOG DEVELOPMENT WOULD BE JUST SOUTH OF THE TERMINALS
WHERE HIGHER MOISTURE CONTENT AIR RESIDES...SO HAVE LEFT OUT OF
THE FORECAST AT THIS TIME. WILL CONTINUE TO MONITOR TRENDS/LATEST
GUIDANCE AND ADJUST ACCORDINGLY. OUTSIDE OF THE SLIGHT POSSIBILITY
FOR FOG/STRATUS...NOT EXPECTING MUCH IN TERMS OF CLOUD COVER
THROUGH THE REMAINDER OF THE FORECAST PERIOD.

LIGHT WINDS WILL REMAIN OUT OF THE NORTH/NORTHEAST TONIGHT INTO
SUNDAY. ALTHOUGH WITH HIGH PRESSURE SHIFTING SOUTHEAST...WINDS
SHOULD SHIFT MORE NORTHWEST SUNDAY AFTERNOON BUT STILL REMAIN ON
THE LIGHT SIDE.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE IN WIND SPEED AND DIRECTION.

* LOW/MEDIUM CONFIDENCE FOR FOG DEVELOPMENT OVERNIGHT.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE SNOW SHOWERS...OTHERWISE VFR.

WEDNESDAY...VFR.

THURSDAY...VFR.

FRIDAY...VFR.

RODRIGUEZ

&&

.MARINE...
233 PM CST

LARGE RIDGE OF HIGH PRESSURE CONTINUES TO BE STRETCHED ACROSS THE
NORTHERN GREAT LAKES REGION...WEST THROUGH THE HIGH PLAINS. OVER THE
PAST SEVERAL HOURS IT HAS BEGUN TO SHOW SIGNS OF WEAKENING...AND
GUIDANCE WOULD SUPPORT THIS AS WELL. THE RIDGE WILL THEN CONSOLIDATE
INTO A CENTRAL/SOUTHERN PLAINS HIGH PRESSURE...ALLOWING THE WINDS
ACROSS THE WESTERN GREAT LAKES AND LAKE MICHIGAN TO BE FROM THE
NORTH SUNDAY. A WEAK FRONTAL BOUNDARY SAGS SOUTH ACROSS THE NORTHERN
PORTION OF LAKE MICHIGAN MONDAY...THEN THE RIDGE BEGINS TO PUSH
EAST. AN INCREASED GRADIENT DOES OCCUR OVER THE NORTHERN PORTION OF
THE LAKE MONDAY...HOWEVER WINDS GENERALLY WILL BE FROM THE
WEST/SOUTHWEST ARND 15 TO 25 KT. WEATHER PATTERN REMAINS RELATIVELY
BENIGN THROUGH MID-WEEK. WINDS MAY BUMP BACK UP TO 15 TO 25 KT
TUE/WED...HOWEVER ANOTHER LARGE RIDGE OF HIGH PRESSURE IS POISED TO
PUSH INTO THE UPPER MIDWEST WED INTO THUR. PRIOR TO THIS ARRIVAL
COLD AIR ADVECTION MAY ALLOW WAVES TO INCREASE FOR A PERIOD OF TIME.

BEACHLER

&&

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

$$

NWS LOT Office Area Forecast Discussion