Forecast Discussions mentioning ACARS, received at FSL on 04/19/00

FORECAST CONCERNS AGAIN REVOLVE AROUND TEMPERATURES AND PRECIPITATION TRENDS THROUGH THIS PACKAGE. SPLIT FLOW CONTINUES ALOFT WITH NORTHERN STREAM UPPER LOW SPINNING OVER JAMES BAY...AND SOUTHERN BRANCH UPPER SYSTEM MOVING INTO THE NEBRASKA PANHANDLE REGION THIS MORNING. 06Z SURFACE ANALYSIS SHOWS COLD FRONT FROM NORTHERN SYSTEM FROM MQT TO LSE AND TO SURFACE LOW ASSOCIATED WITH COLORADO UPPER SYSTEM IN SOUTH CENTRAL NEBRASKA. COLD FRONT CONTINUES TO SLIP SOUTH ALONG LAKE MICHGAN...WITH WIND SHIFT NOTED AT SHEBOYGAN AT 07Z. VARIABLE WINDS WITH WEAK HIGH PRESSURE OVER NORTHERN INDIANA SHOULD GIVE WAY TO SOUTHEAST FLOW AS LOW MOVES EAST TODAY...AND BOUNDARY CONTINUES SOUTH ALONG THE LAKE.

RADAR SHOWING INITIAL WAVE OF PRECIP SPREADING INTO FORECAST AREA THIS MORNING...AS WEAK VORTICTY MAX AND LEADING EDGE OF LO LEVEL THREMAL ADVECTION GO TO WORK. MAIN LO LEVEL INFLOW AND MOISTURE ADVECTION REMAINS FARTHER WEST...OVER IOWA AND NEBRASKA AHEAD OF 960 MB SFC LOW. LO LEVELS INITIALLY SOMEWHAT DRY SEEN IN ACARS TEMP/VAPOR SOUNDING OUT OF RFD THIS MORNING...BUT SURFACE OBS HAVE INDICATED SOME LIGHT PRECIP REACHING THE GROUND EVEN INTO CHICAGO AREA.

ETA MODEL NAILED THE 6 HR POSITION AND STRENGTH OF THE NEBRASKA SURFACE LOW CENTER...AND CONTINUES TO BE MODEL OF CHOICE. PERIOD OF SHOWERS/FEW THUNDERSTORMS DURING THE MORNING AS 850 MB THERMAL BOUNDARY LIFTS NORTHEAST ACROSS THE AREA. THEN A LULL INDICATED BY NUMERICAL FORECASTS UNTIL EARLY THIS EVENING/TONIGHT...WHEN PRECIPITATION BREAKS OUT AHEAD OF MAIN SHORT WAVE. MODELS HINT AT A SOME DRY SLOTTING THURSDAY MORNING BEFORE SURFACE AND UPPER LOWS MOVE ACROSS THE AREA DURING THE DAY. AVN 52 HOUR FORECAST SHOWS A SHARP BACK EDGE TO LAYER MOISTURE FIELDS...WITH DRYING AND SUBSIDENCE ENDING PRECIPITATION EARLY FRIDAY MORNING.

TEMP GUIDANCE GOES ALONG WITH CURRENT FORECAST THINKING...WITH SURFACE BOUNDARY LAYING OUT OVER NORTHERN ILLINOIS. COOL EAST/SOUTHEAST WINDS NORTH OF THE BOUNDARY ACROSS FAR NORTH SHOULD LIMIT MAX TEMPS TO THE 55 TO 60 RANGE...AND AROUND 50 NEAR LAKE MICHIGAN SHORE WHERE WILL UNDERCUT GUIDANCE. FWC/FAN FORECAST TEMPS NEAR 70 IN THE SOUTHERN ZONES TODAY...WHICH LOOKS OK PROVIDED THEY SEE SOME SUN AFTER MORNING PRECIP. MAXES THURSDAY WILL COME EARLY BEFORE FRONT/SURFACE LOW PASS THROUGH IN THE AFTERNOON.

.CHI...NONE

RATZER



MORNING AIRCRAFT SOUNDINGS AT BFL/FAT SHOW 3-5 DEGS WARMING FROM 24HRS AGO. NEW ETA/NGM INDICATE SIGNIFICANT WARM ADVECTION TO CONTINUE TODAY...ON THE ORDER OF 8 DEGS C. THUS SHOULD SEE NICE TEMP RECOVERY TODAY ALL AREAS AS SHORTWAVE RIDGE MOVES IN. TROF APPROACHING 130W FCST TO SPLIT...WITH SOUTHERN PORTION DIGGING SE OFF THE CENTRAL CA COAST THURS MORNING AND FORMING A CLOSED LOW OFF THE SOCAL COAST FRI MORNING. VERY LITTLE LOW OR MID LEVEL MOISTURE INDICATED FOR CENTRAL CA AND DYNAMICS STAY OFFSHORE. WILL REVISIT POPS IN AFTERNOON PACKAGE. FAT 001 BFL 000 YNP 003 BINGHAM

.HNX...NONE.