Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT" or "AMDAR" received at FSL on 03/31/03

AVIATION DISCUSSION FOR 18Z TAFS

NOT MUCH GOING ON. WITH COOL TEMPS ALOFT WILL SEE SOME SCT CU . ALL MODELS STILL INSIST ON BRINING HIGH RH IN TONIGHT AOA 060 SO WILL CARRY BKN CIGS WHICH SHOULD CLEAR TOMORROW MORNING. WINDS LIGHT NW TIL TOWARD SS WHEN GO VARIABLE. SMALL CHANCE LAKE BREEZE BUT DO NOT THINK LAND WILL WARM ENOUGH TO TRIGGER IT.

AF

PUBLIC DISCUSSION FOR THE 11 AM ZONE UPDATE.

USING THE ACARS SOUNDING FROM ORD AT 1430 UTC AND THE SOUNDING AT DVN AT 1200 UTC WE CALCULATE A CONVECTIVE TEMPERATURE OF 41 F. WE EXPECT CUMULUS TO FORM WHEN THE TEMPERATURE REACHES 40 TO 42 DEGREES. WILL FORECAST MOSTLY CLOUDY SKIES FOR LATER THIS AFTERNOON. AT 43 DEGREES AND GREATER THERE IS ENOUGH CAPE TO PRODUCE SOME SUBSTANTIAL CUMULUS. THE MESOETA FORECAST SOME POSITIVE DIFFERENTIAL VORTICITY ADVECTION FROM 15 UTC TO 18 UTC. OMEGA IS FORECASTED TO BE NEGATIVE AT THE SAME TIME. THE MODEL FORECAST CLOUD COVER AS WELL THIS AFTERNOON. WILL FORECAST SOME SPRINKLES AND FLURRIES THIS AFTERNOON. SATELLITE VISIBLE PICTURES SHOW THE INCREASING CUMULUS FIELD JUST WEST OF ILLINOIS AND JUST EAST OF THE FORECAST AREA. SEEING CUMULUS DEVELOPMENT OUT OUR WINDOW AS WELL.

.CHI...NONE. WHW



THIN FAST MOVING MID DECK WILL PASS OVER THE TAF SITES THIS MORNING...THEN VFR SC WILL DEVELOP IN COLD POOL CYCLONIC FLOW THIS AFTERNOON ACCENTUATED BY A WEAK IMPULSE DROPPING IN FROM THE NORTHWEST. A STRAY FLURRY OR TWO IS POSSIBLE...BUT LOW LEVELS ARE QUITE DRY AND EXPECT MOST ANY PRECIP THAT DEVELOPS WOULD BE VIRGA.

WILL KEEP THE CIGS GOING OVERNIGHT DESPITE SOME BOUNDARY LATER STRATIFICATION BASED ON MOISTURE POOL PER ETA/GFS TIME SECTIONS FROM 31/03Z OR SO UNTIL 12Z. AS CIGS SHOULD BE VFR THIS SHOULD HAVE LITTLE PRACTICAL IMPACT.

LIGHT NORTHWEST WINDS SHOULD BACK SLIGHTLY DURING THE DAY TODAY...THEN DECOUPLE OVERNIGHT AND BECOME NEARLY CALM BY MORNING.

JHV



.SYNOPSIS...A FEW SHOWERS WILL REMAIN OVER THE AREA THIS MORNING IN THE WAKE OF A COLD FRONT THAT MOVED THROUGH LAST NIGHT. A SECOND COLD FRONT WILL MOVE ACROSS THE AREA LATE TODAY FOR MORE SHOWERS THIS AFTERNOON AND TONIGHT. COLD AIR WILL MOVE OVER THE REGION ALOFT AND WILL BRING COOL...SHOWERY...AND UNSTABLE CONDITIONS TO THE AREA FOR THE REMAINDER OF THE WEEK. SNOW LEVELS WILL DROP BELOW PASS LEVEL BY TUESDAY MORNING AND BOTTOM OUT TUESDAY NIGHT BEFORE SLOWLY RISING TOWARD THE WEEKEND.

.DISCUSSION...FIRST COLD FRONT OVER THE SE PORTION OF THE FA EARLY THIS AM AND WILL SHIFT OUT OF OUR CWA IN THE NEXT 2 TO 4 HOURS. COOLER AIR MOVING INTO THE REGION AS SFC TEMPS BEHIND THE FRONT HAVE DROPPED BACK INTO THE MID 40S. ALSO NOTED NICE DROP IN THE FREEZING LEVEL. ACARS DATA SHOWED FREZZING LEVEL DROPPED 1000 FEET IN ONE HOUR BETWEEN 0630Z AND 0730Z. FORGET ABOUT MID 60 TO MID 70 TEMPS FOR AWHILE. WILL HAVE A LIMITED AMOUNT OF SHOWER ACTIVITY DURING THE MIDDLE PART OF THE DAY BETWEEN THE FRONTS WITH SOME SUNSHINE BREAKING THROUGH THE CLOUD COVER AT TIMES. SHOWER ACTIVITY WILL INCREASE AGAIN LATER THIS AFTERNOON AS THE NEXT FRONT APPROACHES.

SHOWERS LIKELY TONIGHT...MAINLY DURING THE EVENING AS THE SECOND FRONT MOVES THROUGH. THIS FRONT WILL USHER IN EVEN COLDER AIR FOR ALL TO ENJOY FOR THE REMAINDER OF THE WEEK. SNOW LEVELS WILL FALL TO AROUND 1500 FEET BY LATE TUESDAY AND EVEN LOWER TUE NIGHT. LOOKS AS THOUGH THE SNOW LEVEL COULD DROP TO AROUND 500 FEET LATE TUESDAY NIGHT...ESPECIALLY IN HEAVIER SHOWERS. HAVE MADE MENTION OF THAT IN THE ZONES. ALSO TUE...HAVE FAIRLY DECENT DYNAMICS MOVING OVER THE REGION AS NEXT TROF MOVES ON IN AS UPPER LOW SETTLES IN NEARBY. AIR MASS UNSTABLE ENUF BELOW 600 MB (CAPE VALUES NEARING 400) THAT MAY SEE SOME THUNDERSTORM ACTIVITY LATE IN THE DAY WITH THE TROF. THESE WOULD BE MOST LIKELY ALONG THE COAST AND THE OLYMPICS...BUT DECIDED TO PUT THEM INTO THE OTHER ZONES AS WELL.

WED AND THU...UPPER LOW OVER THE AREA WITH COLD MID LEVEL TEMPS. THE RESULT BEING AN UNSTABLE AIRMASS AND PLENTY OF SHOWERS AROUND. SHOWERS MAINLY DURING THE DAY AND EXPECT SOME RANDOM THUNDERSTORM ACTIVITY. OF THE THREE DAYS (TUE-THU) THU APPEARS TO BE THE LEAST LIKELY DAY FOR THUNDERSTORMS TO OCCUR AS AIR ALOFT BEGINING TO MODERATE AND LIMITED FORCING. TEMPS THROUGH THIS PERIOD BELOW SEASONAL NORMS.

FRIDAY THROUGH SUN...UPPER LOW BEGINS TO LOOSEN UP AND MID LEVEL TEMPS CONTINUE TO MODERATE. PLENTY OF ENERGY ROLLING DOWN THE BACKSIDE OF THIS TROF HOWEVER WILL INPACT THE WEST WELL DOWN THE COAST AND WILL NOT BE A PROBLEM FOR US. MAIN THEME WILL BE A GRADUAL DECREASE IN SHOWER ACTIVITY AND VERY SLOW MODERATION IN TEMPERATURES. BY THE TIME WE GET TO SUNDAY...MODELS HINTING (ESP THE ECMWF) AT SOME RIDGING OVER THE AREA FOR A POSSIBLE DRY DAY.

UIL 678 OLM 578 SEA 578

.KSEW....SMALL CRAFT ADVISORY COAST.

.KATX...VCP21/CSR21...OPERATIONAL. $$

CERNIGLIA