AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 349 AM CDT SAT APR 14 2001
SYNOPSIS...WEAKENING CLOUD BAND AND SURFACE FRONT SHOULD EXIT NRN
ILLINOIS THIS MORNING WITH WEAK RIDGING THIS AFTERNOON AND EARLY
TONIGHT. DEVELOPING WAVE THROUGH MID MISSISSIPPI VALLEY TONIGHT AND
SUNDAY WILL SHORT CIRCUIT ANY RETURN MOISTURE AHEAD OF NEXT PLUNGE OF
UNSEASONABLY COLD AIR SUNDAY NIGHT. FIRST HALF OF THE WEEK WILL SEE
SCATTERED SNOW SHOWERS.
DISCUSSION...FRONTAL BAND MOVING THROUGH NRN ILLINOIS DURING PREDAWN
HRS CONTINUING TO WEAKEN. ONLY LIGHT SPRINKLES ARE LIKELY TOWARD WISC
BORDER AND THOSE WIL BE GONE BY DAWN. MODEST SUBSIDENCE IN MODELS OVER
REGION TODAY WILL MEAN ONE LAST FINE SPRING DAY BEFORE WINTER TRIES A
RETURN ON MONDAY. ACARS PROFILES SUGGEST MAX TEMPS TODAY WILL BE AT
LEAST IN THE MID 60S PERHAPS A BIT HIGHER IN SPOTS. 850 MB TEMPS
PROGGED TO CONT A SLOW RISE. WHILE SURFACE WINDS WILL COME ARND TO NW
DURING THE DAY PRETTY GOOD TEMP CONTRAST WITH LM WATER SUGGESTS NEAR
SHORE NEIGHBORHOODS WILL SEE COOLER TEMPS..PERHAPS IN THE MID OR UPPER
50S...WITH ONSHORE FLOW THIS AFTERNOON.
EASTERN CANADIAN VORTEX CONTINUES TO BE FORECAST SOUTHWARD ACROSS THE
GT LAKES SUN NIGHT THROUGH ABOUT TUE. MODELS SHOW QUITE STEEP LAPSE
RATES LATER SUN NIGHT AND MON WITH ONSET OF COLDER AIR AND WINDS JUST
OFF THE SURFACE FORECAST TO BE ARND 30KT. THUS MOST OF MON SHOULD BE
AT LEAST BREEZY AND FEEL QUITE COLD AS TEMPS BEGIN TO SLIDE OFF LATER
SUNDAY NIGHT.
WHILE ETA A BIT MORE AGGRESSIVE IN TIMING WITH FROPA THAN AVN NEITHER
SUGGEST ANY SIGNIFICANT THREAT OF PRECIP. DEVELOPMENT OF SOUTHERN LO
MOVING THROUGH OHIO VALLEY SUN NIGHT WILL KILL ANY MOISTURE FLUX
NORTHWARD AND APPROACHING FRONT FROM NW SHOWS VERY MINIMAL IF ANY
SURFACE TROUGHING. MID LVL Q-VEC FORCING ALSO APPEARS MORE AIMED AT
LWR MICH THAN NRN ILLINOIS. THUS WILL DOWNPLAY ANY PRECIP ALONG AND
PREFRONTAL SUNDAY AND SUNDAY NIGHT. TEMPS MON-WED LOOK QUITE COLD
WITH GOOD CHC OF SNOW SHOWERS IN UNSTABLE AIRMASS. BEST BET FOR THESE
SHOULD BE MON NIGHT AND TUE. PERHAPS SOME LAKE EFFECT SNOW BANDS OVER
NW INDIANA LATER TUE AND WED AS FLOW TURNS MORE NORTHERLY AND BEFORE
CAPPING SETS IN.
CURRENT MOS NUMBERS GENERALLY GOOD TODAY AND TONIGHT BUT APPEAR TOO
HIGH FOR SUN GIVEN EXPECTATION OF CLOUDS AND PERHAPS A SE WIND. KML
.CHI...NONE