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Weather Story NWS Chicago, IL |
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The year without a winter will continue for the next few days at least. Clearing skies and light winds overnight may lead to some patchy fog development, especially along and south of I-80 where most of the precipitation occurred over the last 48 hours. On Sunday, we'll be on the eastern periphery of a large area of high pressure, likely allowing for plenty of sun and yet another day of above normal temperatures across the area. Full sunshine and west southwest winds out ahead of a cold front will make for an even milder day on Monday. Colder air will arrive on Tuesday, but temperatures will still end up at or above average due to the lack of snow cover over the region. Some lake effect snow showers may develop and affect far northeastern Illinois.
000 FXUS63 KLOT 050506 AFDLOT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1106 PM CST SAT FEB 4 2012 .DISCUSSION... 819 PM CST THE LOW TO OUR SOUTHEAST CONTINUES TO SLOWLY MOVE EASTWARD ACROSS THE KENTUCKY/TENNESSEE BORDER. CLOUD COVER IS SLOWLY MOVING SOUTHWARD...A BIT SLOWER THAN PREVIOUSLY THOUGHT. ADJUSTED SKY COVER GRIDS TO REFLECT THE SLOWER TREND. ALSO MADE A COUPLE MINOR ADJUSTMENTS TO THE TEMPS. ADJUSTED PLACES WHERE CLOUD COVER LINGERED UP...WHILE SOME LOCATIONS ARE RADIATING A BIT BETTER THAN THOUGHT. OTHERWISE...PREVIOUS FORECAST IS ON TRACK. JEE //PREV 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 06Z... * NO REAL CONCERNS IN THE NEAR TERM. * OUTSIDE POSSIBILITY FOR FOG/STRATUS TO MOVE NEAR THE TERMINALS LATE TONIGHT/EARLY SUNDAY MORNING. RODRIGUEZ //DISCUSSION...UPDATED 06Z... WITH MID/HIGH LEVEL CLOUD COVER CONTINUING TO SHIFT SOUTH OUT OF THE REGION THIS MORNING...SKIES BECOMING CLEAR ACROSS MUCH OF THE AREA. EXPECT CLEAR/VFR CONDITIONS FOR THE REMAINING OF THE MORNING...BUT WITH THE OUTSIDE POSSIBILITY THAT CURRENT STRATUS/FOG TO THE NORTH TO MOVE NEAR THE TERMINALS LATER THIS MORNING. HAVE NOT INCLUDED ANY MENTION OF THIS STRATUS IN THE TAFS AS CURRENT THINKING KEEPS THIS STRATUS TO THE NORTH AWAY FROM THE TERMINALS. ALTHOUGH...IF THESE CLOUDS WERE TO CONTINUE SOUTH...DISTANCE SPEED TOOL WOULD HAVE THESE CLOUDS REACHING THE TERMINALS NEAR THE 15Z TIME FRAME. WITH HIGH PRESSURE SHIFTING OVERHEAD...EXPECT VFR CONDITIONS FOR THE REMAINING OF THE TAF PERIOD. WINDS TO REMAIN LIGHT OUT OF THE NORTH THIS MORNING AND A PORTION OF SUNDAY BEFORE WINDS SHIFT MORE NORTHWEST AND EVENTUALLY WEST BY SUNDAY EVENING. RODRIGUEZ //ORD AND MDW CONFIDENCE...UPDATED 06Z... * HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM. * HIGH CONFIDENCE IN WIND SPEED AND DIRECTION. * LOW CONFIDENCE FOR FOG/STRATUS TO MOVE OVER HEAD LATE TONIGHT/EARLY SUNDAY MORNING. 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. && $$