AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 600 AM CDT TUE APR 22 2003
AVIATION DISCUSSION FOR 12Z TAFS...
SC DECK DIVING DUE SOUTH FROM ERN WISCONSIN DELAYING CLEARING IN
NERN IL/NWRN INDIANA TIL AFTER DAYBREAK. RFD CLEAR ALREADY. CIGS AOB
3K NOW AND JUST ABOUT TO CLEAR MKE. ESTIMATING CLEARING AT ORD AT
1415Z AND DPA AT 14Z. MDW PROBLY 15Z FOLLOWED BY 17Z AT GYY. WINDS
GENERALLY NORTH. CURRENT WIND VALUES ARND 10 KTS ON OBSERVATIONS
WITH ACARS SHOWING INVERSION STARTING AT 5K AND SPEED BELOW THAT
FROM 18 TO 26 KTS. SUSPECT SURFACE WINDS STRONGER THAN OBS INDICATE
AND WILL CARRY 15 TO 20 KTS THRU MIDDAY TODAY...THEN SLACK OFF AS
GRADIENT WEAKENS THRU AFTN. DECOUPLING INVERSION SETTLING IN AFTER
SUNSET WITH WINDS DROPPING OFF TO LIGHT AND VARIABLE. OTHERWISE WUD
VEER TO NORTHEAST OFF LAKE MICH. TEMPS DROPPING DOWN TO OR NEAR
FREEZING AND FROST A GOOD BET AWAY FROM LK MICH.
RLB
DISCUSSION FOR MORNING GRIDS AND ZFP...
UPR TROF TO CONT TO ROTATE E INTO ERN GRTLKS TODAY WITH RISING
HEIGHTS TODAY THRU WED EVE WITH RIDGE MOVG E FM PLAINS ACROSS MS VLY
AHEAD OF GREAT BASIN UPR LOW MOVG ACROSS 4 CORNERS TO KS BY 12Z THU.
THEN FCST TO TRACK E OR ESE ACROSS MID MS VALLEY TO LWR OH VALLEY ON
FRI. FCST PROBLEM IS RA CHANCES INTO CWA THU WITH INITIAL SURGE OF
WAA...AND FRI AS SYSTEM TRACKS ACROSS SRN IL. MOISTURE FM WRN GULF
TO BE DRAWN RAPIDLY NWRD AHEAD OF SYSTEM INTO CNTRL PLAINS WED AND
TO MID MS VLY THU. E TO SE DRY BNDRY LYR FLO SHUD KEEP PCPN ALOFT
FOR THRU MOST OF DAY...WITH COLUMN OVER FAR SWRN PORTION OF CWA
EVENTUALLY MOISTENING ENUF TO SEE -RA BY 00Z FRI. WHILE ETA .1 TO
.45 INCH QPF OVER CWA FOR THU NIGHT APPEARS OVERDONE...ENUF OF A
THREAT FOR CHC MENTION ALL BUT FAR NE CORNER OF IL. CONT CHC ACROSS
ALL BUT FAR NRN COUNTIES FRI AS SYSTEM MOVES ACROSS SRN IL...WITH
BEST CHANCE FROM FAR SRN CWA INTO CNTRL IL.
SHORT TERM...BACK EDGE OF SC FM GRB TO ARR TO CMI WILL CONT
CLRG OUT THIS MORNING WITH DRYING AND SUBSIDENCE. NW IND LAST TO CLR
BUT SHUD STILL SEE SUNNY BY MID MORNING. GUID TEMPS FAIRLY IN
LINE...GENERALLY FROM LWR 50S E TO UPR 50S W. WITH SFC RDG TO BE
PARKED OVER ERN IL BY 12Z WED WDSPRD FROST LIKELY OVERNIGHT...XCP IN
CHI AND CLOSE IN SUBURBS. FROST ADVISORY ISSUED AS APR 23RD
CONSIDERED AVG START OF LOCAL GROWING SEASON.
.CHI...FROST ADVISORY ENTIRE CWA.
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 815 AM PDT TUE APR 22 2003
.SYNOPSIS...CLOUDS WILL DECREASE TODAY AND TEMPERATURES WARM AS A
WEAK RIDGE OF HIGH PRESSURE BUILDS INTO THE AREA. A FRONTAL SYSTEM
WILL MOVE THROUGH THE AREA WEDNESDAY FOR ANOTHER ROUND OF RAIN. AN
UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE INTO THE REGION THURSDAY
THEN REMAIN NEAR THE AREA THROUGH EARLY NEXT WEEK. THIS WILL BRING
PARTLY SUNNY DAYS AND SEASONABLE TEMPERATURES...BUT A CHANCE OF
SHOWERS AT TIMES.
.DISCUSSION...THE BACK EDGE OF MID LEVEL CLOUDS WITH TOPS AT 8000
FEET...THE REMNANT OF YESTERDAYS FRONTAL SYSTEM AS SHOW ON THIS
MORNING'S ACARS SOUNDINGS FROM SEATAC...LIES FROM JUST E OF BLAINE TO
KOLM-KTDO. THIS LINE IS SLOWLY PULLING E AND SHOULD MOVE OUT OF THE
GREATER SEATTLE AREA BY NOON. A SC DECK ALONG THE COAST MOVING INTO
THE CHEHALIS GAP SHOULD PERSIST THRU EARLY AFTN...AND MAY BUBBLE UP
SOME CU IN THE INTR THIS AFTN. BUT OVERALL CLOUDS SHOULD DECREASE BY
MID AFTN AS ONSHR PRES GRADIENTS DECREASE THIS AFTN AS THE HIGH
BUILDS IN THEN PUSHES E IN ADVANCE OF THE INCOMING FRONT NOW APCHG
135W.
THE INCOMING FRONT WILL SPREAD LIGHT PCPN ONTO THE COAST BEFORE
DAYBREAK. CURRENT CHANCE POPS PER SATELLITE TIMING AND 12Z GUIDANCE
APPEARS A LITTLE LOW. OTHERWISE PCPN WAITS TIL DURING THE DAY INLAND
AS THE FRONT WEAKENS WHILE MOVING ONSHR.
AFTER SOME POST FRONTAL SHOWER ACTIVITY WED NIGHT...AN UPPER LEVEL
LOW SETTLES INTO THE AREA UNDER A BLOCK JUST E OF YUKON...LEAVING THE
AREA IN A WEAKLY UNSTABLE AMS AND OCNL LOW LVL ONSHR FLOW. DETAILS OF
VORT MAXES/IMPULSES ROTATING AROUND THE BROAD UPPER LOW WILL BE
DIFFICULT TO HANDLE...SO THE CURRENT BROAD BRUSH FCST LOOKS GOOD.
UIL 178 SEA 117 OLM 117 ALBRECHT
.KSEW...NONE.
.KATX...VCP32/CSR32...OPERATIONAL.
$$