AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
AFDMLI 238 PM CDT SAT JUN 26 1999
...GLOBALLY...
SLOW PROGRESSIVE 4 WAVE PATTERN CONTINUES ACROSS THE NORTHERN
HEMISPHERE WITH GLOBAL MOSAIC OF WATER VAPOR IMAGERY FROM GMS-5...
GOES 8/10...AND METEOSAT-7 SHOWING BUILDING HEIGHTS ACROSS THE
PACIFIC OCEAN. THIS WILL RESULT IN SOME AMPLIFICATION OF THE
LONGWAVE PATTERN AND THE GLOBAL MODELS CONFIRM THIS BY THE MIDDLE OF
NEXT WEEK. AMPLIFICATION/PROGRESSION OF THE PATTERN PUSHES THE
CURRENT WEST COAST TROF INTO THE CENTER OF THE CONTINENT FOR MUCH OF
THE COMING WEEK. GOES 10/GMS-5 SHOW A SERIES OF SHORTWAVES WITH
ASSOCIATED JET STREAKS LINED UP ACROSS THE PACIFIC WITH THE LEAD ONE
SLIGHTLY WEAKER THAN THE NEXT TWO. DARKNESS ON WATER VAPOR SUGGESTS
THE LEAD ONE BEING 70-80 KNOTS(CONFIRMED BY AIRCRAFT) APPROACHING
THE PAC NORTHWEST WITH THE ONES SOUTH OF THE ALEUTIANS AND EAST OF
JAPAN ON THE ORDER OF 100 KNOTS OR BETTER. ALL OF THESE SHORTWAVES
PLAY SIGNFICANTLY INTO THE COMING WEEKS WEATHER FOR THE AREA.
THE OVERALL PATTERN COMING THIS WEEK SHOULD EVOLVE INTO A FAIRLY
FLAT RIDGE ON THE EAST COAST...TROF IN THE MID-CONTINENT AREA WITH A
SW/NE RIDGE FROM OFF THE WEST COAST INTO WESTERN CANANDA.
NET RESULT FOR THE IMMEDIATE AREA WILL BE TEMPERATURES AT OR
SLIGHTLY BELOW NORMAL FOR MOST OF THE COMING WEEK WITH AN ACTIVE
WEATHER PATTERN. THE GLOBAL MODELS SUGGEST THAT THIS PATTERN SHOULD
CONTINUE PAST THE FOURTH OF JULY WEEKEND AND INTO PART OF THE FIRST
FULL WEEK OF JULY.
...LOCALLY...
MORNING UPPER AIR/WATER VAPOR SHOWED SEVERAL INTERESTING FEATURES. A
SHORTWAVE WAS MOVING SOUTH INTO WESTERN KANSAS IN THE 850-700 MB
LAYER WHILE A CLOSED LOW WAS MOVING SLOWLY NORTHEAST THROUGH
MISSOURI. SHORTWAVES ASSOCIATED WITH THIS LOW WERE MOVING THROUGH
ARKANSAS AND UP THROUGH MISSOURI/ILLINOIS. 15Z RUC INDICATES THAT
THE RAIN ACROSS ILLINOIS IS ASSOCIATED WITH A TROP FOLD...AND AN
AREA OF LOWER CONDESATION PRESSURE DEFICITS/STEEPER LAPSE RATES THAT
IS PROGGED TO REMAIN MAINLY EAST OF THE FORECAST AREA THROUGH THE
AFTERNOON. AN UNSEASONABLY STRONG SHORTWAVE WAS MOVING ALONG THE
U.S./CANANDIAN BORDER WITH WARM/COLD FRONTS EVIDENT UP TO 850 MB.
18Z SURFACE ANALYSIS HAS COLD FRONT ROUGHLY ALONG A KBJI...KONL...
KLIC LINE WITH A WAVE BETWEEN KLAA AND KGCK. NUMEROUS CONVECTIVE
BOUNDARIES WERE ACROSS THE SOUTHERN HALF OF ILLINOIS. MOISTURE
ANALYSIS HAS MID AND UPPER 60 DEW POINTS ACROSS THE FORECAST AREA
WITH 70 DEW POINTS INTO THE MISSOURI VALLEY.
PROBLEMS THIS PACKAGE ARE MANY...TIMING OF COLD FRONT...MESOSCALE
FACTORS...AND THEN CLOUDS/TEMPS/POPS.
12Z MODELS APPEAR TO HAVE INITIALIZED FAIRLY WELL AND SEEMED TO BE
VERIFYING REASONABLY WELL AT 18Z. THE ETA/RUC DOES PLACE THE COLD
FRONT BETTER THAN THE AVN/NGM BUT THE ETA/RUC ARE COMPLETELY MISSING
THE CURRENT RAIN ACROSS CENTRAL ILLINOIS WHERE THE NGM/AVN ARE
BETTER WITH THE AVN BEING OVERDONE AND TOO FAR NORTH. OVERALL THE
AVN APPEARS TO BE SUFFERING FROM CONVECTIVE FEEDBACK AND STRENGTHENS
THE INCOMING SHORTWAVE TOO MUCH. RECENT PERFORMANCE OF THE ETA IS TO
BE TOO WEAK ON SHORTWAVES AND THIS APPEARS TO BE THE CASE HERE. THUS
THE NGM WILL BE FOLLOWED.
CUTOFF LOW ACROSS MISSOURI WILL CONTINUE TO SLOW DRIFT E/ENE AND
REMAIN WELL AWAY FROM THE FORECAST AREA. RUC/NGM SHOW CONDENSATION
PRESSURE DEFICITS TO REMAIN HIGH SO DRY CONDITIONS TONIGHT LOOK
RIGHT ON WITH A MOSTLY CLEAR/PARTLY CLOUDY SKY. COLD FRONT IN THE
PLAINS SHOULD STALL AT SOME POINT TONIGHT/EARLY SUNDAY AS A WAVE
MOVES UP ALONG IT. QG FORCING AND THERMAL/MOISTURE GRADIENTS SUGGEST
THAT AN MCS SHOULD DEVELOP ACROSS NEBRASKA WHICH WOULD ANCHOR THE
FRONT INITIALLY AND THEN MOVE IT EAST. SUNDAY FRONT SLOWLY
APPROACHES THE AREA AND THUS WILL INTRODUCE POPS FROM WEST TO EAST
USING AFTERNOON/LATE IN THE DAY WORDING.
MAIN PRECIPITATION EVENT TO OCCUR SUNDAY NIGHT/MONDAY AS COLD FRONT
SLOWLY MOVES THROUGH THE FORECAST AREA WITH ADDITIONAL WAVES
TRAVELING ALONG IT. GOOD DRYING/DOWNWARD MOVEMENT BEHIND THE FRONT
INDICATES CLEARING SKIES FROM WEST TO EAST DURING THE DAY MONDAY.
FWC/FAN ARE A GOOD STARTING POINT FOR TONIGHT BUT WILL GO ABOVE
GUIDANCE FOR TONIGHT AND MAKE ADJUSTMENTS ACCORDINGLY FOR LATER
PERIODS.
...EXTENDED...
HIGH PRESSURE TO BUILD INTO THE AREA MONDAY NIGHT/TUESDAY ALLOWING
THE ONLY QUIET PERIOD OF WEATHER. CURRENT SHORTWAVE/JET STREAK SOUTH
OF THE ALEUTIANS TO BE THE FOCUS FOR THE START OF ACTIVE WEATHER FOR
THE WEDNESDAY/THURSDAY TIME PERIOD. WEDNESDAY/THURSDAY TIME PERIOD
COULD GET QUITE INTERESTING AS THIS SHORTWAVE AMPLIFYS. FAIRLY
WIDESPREAD CONVECTIVE RAINS APPEAR LIKELY WITH AMOUNTS BEING
MODERATE TO POSSIBLY HEAVY.
COORDINATED WITH DSM...LSE...CHI...SPI...STL.
.DVN...NONE.
NC
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
AFDGRB 300 PM CDT SAT JUN 26 1999
LINES OF CU ACROSS WI AT 20Z BUT WARM 700MB TEMPS (+10 AT MKE AND MSP AT
18Z ACCORDING TO ACARS) KEEPING A LID ON CONVECTION IN WISCONSIN. SOME
CONVECTION FIRING ACROSS CENTRAL MN NOW THANKS TO COLD FRONT. UPPER
SYSTEM OVER IL/MO PRODUCING RW AND TRW IN IL BUT IT FIZZLES AS IT MOVES
N INTO DRIER AIR AND CONFLUENT UPPER FLOW. MODELS PRETTY CLOSE AS FAR AS
FIRST 30-36 HOURS GO BUT THEN DIVERGE. AVN HAS 999MB SFC LOW OVER THE UP
OF MI AT 48 HOURS WHILE ETA HAS A TROF ACROSS SRN ONTARIO AND SRN LWR
MI. NGM IS SOMEWHERE IN BETWEEN. TEND TO BELIEVE THE SLOWER AVN/NGM
MODELS AS MAIN UPPER SYSTEM IS FAR BEHIND SFC FRONT.
SO WILL KEEP A 30 PCNT CHANCE OF RW/TRW IN WRN ZONES TONIGHT AND GO WITH
60 PERCENT POPS SUNDAY AS SFC FRONT APPROACHES. WILL KEEP FCST PRETTY
MUCH AS IS FOR EASTERN WISCONSIN. THINK BEST CHANCE FOR TRW IS SUNDAY
NIGHT.
.GRB...NONE.
RDM
WWW.CRH.NOAA.GOV/GRB