AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 238 PM CST MON MAR 27 2000
LARGE VORTEX OVER EASTERN LK SUPERIOR ABOUT STATIONARY WITH ROTATING
LOBE OF ENERGY SWINGING SEWD ACROSS MINN THIS AFTERNOON. LAPSE RATES
VIEWED THROUGH ACARS DATA HAVE BECOME ADIABATIC BELOW ABOUT 750MB WITH
LOWER ATMOSPHERE TURNING OVER WELL NOW. RADAR SHOWS MEASLES ACROSS
ALL OF WESTERN LAKES INTO SCENTRAL ILLINOIS WITH SOME SHORT LINES.
MODELS GENERALLY OK AND ARE CONSISTENT IN SHOWING SHEAR LOBE OF
VORTICITY OVER WESTERN MINN AT THIS TIME MOVING SEWD JUST TO S AND
WEST OF CHICAGO TUE MORNING. PROFILER DATA HAS 120+KT WIND AT SLATER
IA ALONG WEST EDGE OF CLOUD FIELD AND CLOUD MOTION SUGGESTS A WEAK
ROTATION SHOWING UP OVER CNTRAL MINN. WITH MOST OF NRN ILLINOIS AND NW
INDIANA REMAINING ON CYCLONIC SHEAR SIDE OF THIS FEATURE THROUGH AT
LEAST MIDDAY TUE WE CAN EXPECT AREAS OF RAIN SHOWERS TO PERSIST THIS
EVE LIKELY CONVERTING THE SNOW SHOWERS IN SOME AREAS LATER IN THE
NIGHT.
AFTERNOON SUN IS HELPING SHOWERS THIS AFTERNOON BUT DYNAMICS WILL COME
INTO PLAY TONIGHT AS COLDEST POCKET SLIDES TO SE DOWN THE MISS RIVER.
RH PROGS AND CONTINUED CYCLONIC CURVATURE IN FLOW SUGGEST CLEARING
WILL BE SLOW TUE NIGHT STRETCHING INTO WED.
AS LARGE GREAT LAKES VORTEX REFORMS UNDER CYCLOGENESIS ALONG EAST
COAST TUE THE WHOLE CIRCULATION SHOULD EDGE EWD A BIT THRU MIDWEEK BUT
STILL KEEP NRN ILLINOIS IS COOL NW ALBEIT WEAKING FLOW. REBOUND IN
TEMPS SHOULD BE SLOW UNTIL AT LEAST THURSDAY. BY THEN ANOTHER SYSTEM
IS FORECAST TO EDGE SEWD FROM NRN PLAINS TO PROVIDED ANOTHER THREAT OF
SHOWERS TOWARD THE WEEKEND.
MOS/FAN NUMBERS GENERALLY PRETTY GOOD BUT WILL BE A LITTLE
MOREPLENTIFUL WITH POPS TONIGHT AND TUE ESPECIALLY CHI AREA AND NW
INDIANA. LAKE EFFECT RAIN/SNOW SHOWERS MAY BE MORE EVIDENT TOWARD
LAKE CO INDIANA TUE INTO TUE NIGHT DEPENDING UPON WIND DIRECTION..MORE
NORTHERLY OR MORE WESTERLY. KML
.CHI...NONE.