Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT" or "AMDAR" received at FSL on 03/12/03

PUBLIC FORECAST DISCUSSION FOR AFTERNOON ZONES/GRIDS

AFDCHI PATTERN CHANGE UNDERWAY UNDER SPLIT FLOW AS SOUTHERN STREAM

STRENGTHENS AND NORTHERN STREAM MIGRATES NORTHWARD. SOUTHERN STREAM ACTIVITY WILL FOCUS GULF MOISTURE MUCH FURTHER SOUTH...WHILE NORTHERN STREAM ACTIVITY WILL PUSH ARCTIC AIR BACK ACROSS THE CANADIAN BORDER...ALLOWING MUCH MILDER PACIFIC AIR TO WARM OUR TEMPERATURES SIGNIFICANTLY...ESPECIALLY IN THE OUT PERIODS.

SHORT TERM CONCERNS REVOLVE AROUND WEAK NORTHERN STREAM WAVES PUSHING THROUGH AND THE ASSOCIATED SURFACE REFLECTIONS. SMALL CHANCE FOR LIGHT RAIN PERSISTS TONIGHT DESPITE MARGINAL DYNAMICS AND LIMITED MOISTURE...SO WILL LEAVE ANTECEDENT POPS ALONE AND CONTINUING THE LIGHT NATURE OF THE THREAT. GUSTINESS PRESENT ATTM WILL FADE DIURNALLY...AND WEAK BOUNDARY PUSHING THROUGH OVERNIGHT WILL SERVE MAINLY TO FURTHER WEAKEN LOW LEVEL FLOW.

LIGHT FLOW CONTINUES WEDNESDAY...SWINGING NORTHEAST OUT AHEAD OF SLIGHTLY STRONGER WAVE. ONSHORE FLOW WILL IMPACT TEMPERATURES LAKESIDE...BUT ELSEWHERE TEMPERATURES WILL CONTINUE A SLOW CLIMB TOWARD NORMALS.

WAVE KICKS THROUGH WEDNESDAY NIGHT...WITH STRONG HEIGHT RISES BEHIND THE FRONT BRINGING A TASTE OF SPRING TO THE REGION. BY THURS/FRI/SAT EXPECT LITTLE SNOWCOVER LEFT AROUND THE AREA...SO TEMPS SHOULD HAVE NO TROUBLE GETTING 10 TO 15 DEGREES ABOVE NORMAL OVER THE WEEKEND...GIVEN MODEL 8H TEMPS. MODELS HINT AT SOME SORT OF MOISTURE RETURN SAT NIGHT...BUT NOT STRONG ENOUGH TO WARRANT POPS ATTM. OTHERWISE EXTENDED LOOKS MILD AND DRY.

.CHI...GALE WRN LKMICH.

JHV

AVIATION DISCUSSION FOR 18 UTC TAFS

CURRENT SATLT TRENDS SHOW MID LVL CLOUDINESS ASSD WITH WARM ADVECTION GOING THRU A DIURNAL MINIMA. AS A RESULT...WILL JUST GO WITH SOME SCT CLDS AOA 080 FOR THIS AFTN AND TNGT. NO RESTRICTIONS ON VIS THRU FCST PERIOD. MAIN FCST CONCERN IS WITH WIND. ZONE OF SCT-BKN MID LVL CLOUDS FROM MID MS VLY-SRN GRTLKS IS ASSD WITH FAIRLY STOUT SWLY LO LVL FLOW. INVERSION IS BREAKING DOWN SO SOME OF THIS STRONGER WIND WILL BE MAKING DOWN TO THE SFC BY 19Z. THERFORE WILL JUST START OUT WITH GUSTS TO 25 KT IN INITIAL TIME PERIOD OF TAFS. GUSTINESS SHOULD SUBSIDE WITH APCH OF SS. ACARS SOUNDINGS OUT OF ORD SINCE 1630Z HAVE CONFIRMED BREAK DOWN OF INVERSION AND WIND PROFILES SUGGEST GUSTS TO 25 KTS A GOOD BET THRU AFTN. WEAK FRONT IS FCST TO SLIP SWD ACRS TERMINAL AREA ERLY WED MRNG SWITCHING WIND FROM LGT SW INTO LGT NE. SOME LWR CLOUDS PSBL AS WIND TURNS NELY OFF LK MI WED MRNG BUT CIG SHUD STAY MVFR OR BETTER.

MERZLOCK



AREA FORECAST DISCUSSION
NWS LINCOLN IL
AFDILX 210 PM CST TUE MAR 11 2003

FORECAST CONCERNS THIS PERIOD INCLUDE PRECIP CHANCES TNT AND WED NIGHT ALONG WITH TEMPS...WITH LONGER RANGE CONCERNS INVOLVING TIMING OF PRECIP THIS WEEKEND.

18Z SFC ANALYIS INDICATING BROAD SWLY FLOW ACRS THE MIDWEST AS THE LARGE CANADIAN HIGH CONTINUES TO SHIFT AWAY FROM THE REGION. IMPRESSIVE LOW LVL WARM ADVECTION PATTERN ACRS THE MIDWEST THIS AFTN WITH A SCATTERING OF SOME MID LVL CLOUDS FROM CNTRL IA EWD INTO IL. MODELS DIFFERENCES CONTINUE THIS FORECAST PACKAGE...ALTHOUGH NOT NEARLY AS PRONOUNCED AS YESTERDAY. ETA MODEL COMING MORE IN LINE WITH WHAT THE GFS HAS BEEN ADVERTISING FOR THE PAST SVL RUNS WITH THE PRECIP EVENT WED NIGHT INTO THU. THOUGHT WITH AS MUCH AMPLITUDE AS DEPICTED ON THE MODELS WITH THE NRN STREAM WAVE LATER WED...A SLOWER SOLUTION WOULD BE THE WAY TO GO. HOWEVER AS THE PATTERN CONTINUES TO EVOLVE MORE TOWARDS A FAST ZONAL FLOW...AT LEAST INTO FRIDAY...THE GFS SOLUTION SEEMS MORE REASONABLE SO WL FOLLOW IT THIS FCST PACKAGE.

FIRST SHORTWAVE OF INTEREST SEEN STREAKING OUT OF THE HIGH PLAINS WITH SCT TSRA OCCURRING IN THE WARM ADVECTION ZONE AHEAD OF IT. SFC MAP SHOWING MOISTURE RETURNING ACRS THE SRN PLAINS IN ADVANCE OF THE SHORTWAVE WITH SOME LIGHTNING DETECTED OVR ERN KS. WL INCLUDE CHCS OF THUNDER ACRS THE SE TNT WITH SHOWER CHANCES FOR THE REMAINDER OF THE FCST AREA. GUID VALUES LOOK REASONABLE TONIGHT. RAIN CHANCES DECREASE FROM WEST TO EAST WED MORNING HOWEVER ENOUGH LOW LVL MOISTURE AROUND TO KEEP IT MO CLDY DURING THE DAY. WL LEAN MORE TOWARDS THE COOLER GUID VALUES ON WED DUE TO THE EXPECTED CLOUD COVER. NRN STREAM SHORTWAVE THEN WL BEGIN TO AFFECT THE AREA WED NIGHT INTO THU. FAIRLY DECENT WARM ADV DVLPG AHD OF SHORTWAVE WITH WARM AXIS ORIENTATED NE TWDS CENTRL IL BY EVENING. AVN NOT NEARLY AS AGGRESSIVE WITH THE QPF WED NIGHT AS INITIAL WAVE TNT MAY PUSH DEEPER MOISTURE AWAY FROM MIDWEST ON WEDNESDAY. CHANCE TO LIKELY POPS GOING WED NIGHT INTO THU WITH BEST THREAT FOR RAIN AND THUNDER ACRS THE SRN HALF OF THE FCST AREA.

ONCE AGAIN...RAIN CHANCES DECREASE DURING THE FIRST HALF OF THE DAY ON THU WITH MODELS CONSISTENT IN BUILDING RIDGE ACRS THE CNTRL U.S. FOR THU AND FRI. THIS SHOULD BRING MILD TEMPERATURES WITH LITTLE IN THE WAY OF UPPER OR LOWER LVL FORCING TO PRODUCE PRECIP IN OUR AREA. THAT WL PROBABLY BEGIN TO CHANGE OVER THE WEEKEND...AT LEAST DURING THE SECOND HALF. MODELS CONTINUE TO SHOW A DEEP TROF EVOLVING ACRS THE WESTERN US WHILE RIDGING...ALBEIT NOT HAS AMPLIFIED AS PREVIOUSLY INDICATED ON THE MODELS...HOLDS OVER THE CNTRL US. SVL WEAK OR LEAD SHORTWAVES ARE EJECTED OUT OF THE MAIN LONG WAVE TROF DURING THE WEEKEND. WL FOLLOW THE ECMWF DEPICTION/SOLUTION WITH THE SHORTWAVE ENERGY CLOSE ENOUGH TO OUR AREA TO START INCLUDING THUNDER CHANCES ON SUNDAY...AND CONTINUING THE CHANCE OF PRECIP INTO DAY 7/TUESDAY. QUESTION BECOMES JUST WHEN THE MAIN/MAJOR PIECE OF ENERGY COMES OUT ACRS OUR AREA. APPEAR THE MRF MAY BE EJECTING THE MAJOR PORTION OF THE UPPER LOW OUT TOO QUICKLY WITH THE ECMWF SHOWING ABOUT 3 DIFFERENT WAVES ROTATING OUT OF THE TROF EARLY NEXT WEEK...EACH ONE INCHING CLOSER TO ILLINOIS. APPEARS THE BEST CHANCES FOR ORGANIZED CONVECTION WILL BE IN THE TUE-WED TIME FRAME WITH A CHANGE TO COLDER WX BY THE SECOND HALF OF THE WEEK.

.ILX...NONE. $$

SMITH



 
 

NATIONAL WEATHER SERVICE CHICAGO IL 1155 AM TUESDAY MARCH 11 2003

AVIATION DISCUSSION FOR 18 UTC TAFS

CURRENT SATLT TRENDS SHOW MID LVL CLOUDINESS ASSD WITH WARM ADVECTION GOING THRU A DIURNAL MINIMA. AS A RESULT...WILL JUST GO WITH SOME SCT CLDS AOA 080 FOR THIS AFTN AND TNGT. NO RESTRICTIONS ON VIS THRU FCST PERIOD. MAIN FCST CONCERN IS WITH WIND. ZONE OF SCT-BKN MID LVL CLOUDS FROM MID MS VLY-SRN GRTLKS IS ASSD WITH FAIRLY STOUT SWLY LO LVL FLOW. INVERSION IS BREAKING DOWN SO SOME OF THIS STRONGER WIND WILL BE MAKING DOWN TO THE SFC BY 19Z. THERFORE WILL JUST START OUT WITH GUSTS TO 25 KT IN INITIAL TIME PERIOD OF TAFS. GUSTINESS SHOULD SUBSIDE WITH APCH OF SS. ACARS SOUNDINGS OUT OF ORD SINCE 1630Z HAVE CONFIRMED BREAK DOWN OF INVERSION AND WIND PROFILES SUGGEST GUSTS TO 25 KTS A GOOD BET THRU AFTN. WEAK FRONT IS FCST TO SLIP SWD ACRS TERMINAL AREA ERLY WED MRNG SWITCHING WIND FROM LGT SW INTO LGT NE. SOME LWR CLOUDS PSBL AS WIND TURNS NELY OFF LK MI WED MRNG BUT CIG SHUD STAY MVFR OR BETTER.

MERZLOCK

PRELIMINARY DISCUSSION FOR 4 AM ZONES/GRIDS

AT 06Z VERY WEAK TROF MOVING THRU AREA. MID CLOUDS WITH SOME ECHOES ALOFT, NOTHING REPORTED AT SFC TIL CENTRAL WI. THIS QUICKLY GONE BY MORNING. ANOTHER WEAK WIGGLE MIDDLE OF TONIGHT. THIS ALL IN THE ZONAL FLOW NOW OVERHEAD SO THE ARTIC AIR FINALLY CUT OFF. BY THURSDAY MORNING VORT DIVING SE COMES OVERHEAD WITH THE X NR CHI AS TROF SWINGS THRU SE CANADA AND RIDGE BUILDS OVER N ROCKIES. THIS VORT LOOKS STRONG SO SHOULD PRODUCE SOME SHOWERS WEDNESDAY NIGHT. UPPER RIDGE THEN OVER AREA SATURDAY AS STORM APPROACHES WEST COAST.

WIGGLE TONIGHT WEAK. POPS ALL OVER PLACE. SINCE 30% CHANCE ALREADY IN WILL LEAVE IN BUT IF ANYTHING OCCURS SHOULD BE VERY LIGHT. ALL MODELS DO SHOW SOME OMEGA OVER AREA TONIGHT ESPECIALLY AOA 070 ALONG WITH MID LEVEL RH AND SOME Q-VECTOR CONVERGENCE SO A LITTLE BIT POSSIBLE. WEDNESDAY LATE NW THEN AT NIGHT LOOKS LIKE THE MOST REALISTIC PRECIP CHANCE. GOOD DYNAMICS AND EVEN UNSTABLE ENOUGH FOR ISO TSTMS. FOR NOW WILL NOT PUT IN. UNTIL THEN CLOUDS MOVING THRU FROM TIME TO TIME.

AS FLOW GOES ZONAL FINALLY A NICE WARMUP IN THE 850 TEMPS. VIS PICS SHOW SNOW COVER ROUGHLY FROM ABOUT VPZ-C09-S PNT SO S COUNTIES SHOULD REALLY WARM UP. THICK COVER STILL UP AROUND RFD THEN W THRU E IA.

TEMPS NEXT FEW DAYS A CHALLANGE. SNOW COVER NW VS BARE SE. PERIODS OF MOSTLY MID CLOUDS. AND THEN WIND OFF LAKE WEDNESDAY AND THURSDAY. THE REAL WARMUP FRIDAY AND SATURDAY.

.CHI...GALE LM N 1/2

AF



AREA FORECAST DISCUSSION
NWS LINCOLN IL
AFDILX 1030 AM CST TUE MAR 11 2003

LATEST SATELLITE IMAGERY INDICATES MOSTLY SUNNY SKIES ACROSS CWA...WITH ONLY HIGH THIN CLOUDS NOTED. SOUTHERLY WIND FLOW HAS BEEN INCREASING ALL MORNING...ALLOWING WARMER AIR TO FILTER INTO THE REGION. AFTER CHILLY MORNING LOWS IN THE SINGLE DIGITS AND TEENS...TEMPS HAVE REBOUNDED BY 15 TO 20 DEGREES. GIVEN ABUNDANT SUNSHINE AND SOUTHERLY WINDS...EXPECT THIS TREND TO CONTINUE INTO THE AFTERNOON...WITH HIGH TEMPS TOPPING OUT WELL INTO THE 40S. THEREFORE...WILL MAKE NO UPDATES TO ZONES AT THIS TIME.

.ILX...NONE. $$ BARNES



 
 

NATIONAL WEATHER SERVICE CHICAGO IL 600 AM TUESDAY MARCH 11 2003

AVIATION DISCUSSION FOR 12 UTC TAFS

THE WARM AIR ADVECTION INTO THE NORTHEAST ILLINOIS AND NORTHWEST INDIANA HAS BEGUN. PROFILERS AT 850 MB AND 925 MB ILLINOIS...WISCONSIN AND INDIANA SHOW A WEST TO SLIGHTLY SOUTHWEST WIND. THE ACARS SOUNDING AT ORD 0812 UTC SHOWS A SHARP INVERSION FROM 703 MB TO 677 MB AND AT ROCKFORD TEMPERATURES INCREASE WITH HEIGHT FROM THE SURFACE TO 900 MB AND 850 TO 750 MB. VEERING WINDS ARE NOTED AT BOTH ACARS SOUNDING. CLOUDS AND PRECIPITATION ALOFT SHOWS THAT THE ISENTROPIC LIFT FORECASTED BY THE ETA MODEL ON THE 290K SURFACE IS OCCURRING. WILL PUT CLOUDS IN AT 5000 FT AND 9000 TO 10000 FT. THE CEILINGS WILL BE VARIABLE FROM THOSE HEIGHTS TODAY. USING THE ETA AS A MODEL OF CHOICE. THERE IS SOME NEGATIVE OMEGA STARTING FROM ABOUT 06 UTC TO AROUND 10 UTC AND COINCIDING WITH THE MAXIMUM RELATIVE HUMIDITY ALOFT. WILL ADD A PROBABILITY OF 30 PERCENT 4 MILES IN LIGHT RAIN FOR THOSE TIMES. STRONG WARM AIR ADVECTION AND DIVERGENCE ALOFT SEEN ON THE 250 MB WIND FORECASTS GIVE SUPPORT FOR THE UPWARD VERTICAL MOTION PREVIOUSLY MENTIONED.

WHW

PRELIMINARY DISCUSSION FOR 4 AM ZONES/GRIDS

AT 06Z VERY WEAK TROF MOVING THRU AREA. MID CLOUDS WITH SOME ECHOES ALOFT, NOTHING REPORTED AT SFC TIL CENTRAL WI. THIS QUICKLY GONE BY MORNING. ANOTHER WEAK WIGGLE MIDDLE OF TONIGHT. THIS ALL IN THE ZONAL FLOW NOW OVERHEAD SO THE ARTIC AIR FINALLY CUT OFF. BY THURSDAY MORNING VORT DIVING SE COMES OVERHEAD WITH THE X NR CHI AS TROF SWINGS THRU SE CANADA AND RIDGE BUILDS OVER N ROCKIES. THIS VORT LOOKS STRONG SO SHOULD PRODUCE SOME SHOWERS WEDNESDAY NIGHT. UPPER RIDGE THEN OVER AREA SATURDAY AS STORM APPROACHES WEST COAST.

WIGGLE TONIGHT WEAK. POPS ALL OVER PLACE. SINCE 30% CHANCE ALREADY IN WILL LEAVE IN BUT IF ANYTHING OCCURS SHOULD BE VERY LIGHT. ALL MODELS DO SHOW SOME OMEGA OVER AREA TONIGHT ESPECIALLY AOA 070 ALONG WITH MID LEVEL RH AND SOME Q-VECTOR CONVERGENCE SO A LITTLE BIT POSSIBLE. WEDNESDAY LATE NW THEN AT NIGHT LOOKS LIKE THE MOST REALISTIC PRECIP CHANCE. GOOD DYNAMICS AND EVEN UNSTABLE ENOUGH FOR ISO TSTMS. FOR NOW WILL NOT PUT IN. UNTIL THEN CLOUDS MOVING THRU FROM TIME TO TIME.

AS FLOW GOES ZONAL FINALLY A NICE WARMUP IN THE 850 TEMPS. VIS PICS SHOW SNOW COVER ROUGHLY FROM ABOUT VPZ-C09-S PNT SO S COUNTIES SHOULD REALLY WARM UP. THICK COVER STILL UP AROUND RFD THEN W THRU E IA.

TEMPS NEXT FEW DAYS A CHALLANGE. SNOW COVER NW VS BARE SE. PERIODS OF MOSTLY MID CLOUDS. AND THEN WIND OFF LAKE WEDNESDAY AND THURSDAY. THE REAL WARMUP FRIDAY AND SATURDAY.

.CHI...GALE LM N 1/2

AF



SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NWS BILLINGS MT
AFDBIL 208 PM MST TUE MAR 11 2003

.SHORT TERM...VALID FOR WED AND THU...

TOUGH FORECAST TODAY WITH MODELS OUT OF SYNC WITH COLD AIR THAT HAS INVADED THE EASTERN 2/3 OF CWA. 12Z MODEL GUIDANCE FOR BOTH MODELS FAILED TO BRING COLD AIR INTO BILLINGS TODAY AND WAS ABOUT 15 DEGREES TOO WARM WITH THE AIRMASS ACROSS THE EAST. THIS GUIDANCE ALSO SUGGESTS 60S FOR TOMORROW AND 70S BY THURSDAY. GIVEN THE POOR PERFORMANCE OVER THE LAST SEVERAL DAYS WILL NOT LEAN TOO HEAVILY ON GUIDANCE OR MODELS AND GO MORE WITH ANALYSIS...TRENDS...AND PATTERN RECOGNITION FOR THE NEXT 24 HOURS AND LEAVE PERIODS 3 AND 4 PRETTY MUCH ALONE.

WATER VAPOR INDICATING NEXT SHORTWAVE ENTERING NORTHERN IDAHO ATTM BEGINNING TO DROP PRESSURES AROUND CUT BANK AND GREAT FALLS. AS IT CONTINUES TO ADVANCE INTO THE REGION SHOULD SEE LOW PRESSURE DEVELOP OVER NORTH-CENTRAL MONTANA AND MOVE INTO THE EASTERN ZONES OVERNIGHT TONIGHT DRAGGING A WARM FRONT WITH IT. WESTERLY WINDS WILL PICK UP BEHIND THE WARM FRONT AND RANGE FROM 15 TO 25 MPH. AS A RESULT LOW TEMPERATURES WILL OCCUR EARLY THIS EVENING AND RISE THROUGHOUT THE NIGHT. THE EXCEPTION WILL BE THE EXTREME EASTERN ZONES WHERE TEMPERATURES MAY DROP A COUPLE OF DEGREES BUT GENERALLY WILL REMAIN STEADY UNTIL MORNING. AS FOR PRECIPITATION CHANCES...LATEST ACARS INDICATING GOOD WARM ADVECTION AT 500 MB WITH A VERY UNSTABLE LAYER JUST ABOVE THE FRONT EXTENDING UP TO AROUND 600 MB. WOULD EXPECT SOME STEEPENING OF THE LAPSE RATES ALOFT OVERNIGHT AS SHORTWAVE PASSES AND FOR THIS REASON WILL GO WITH CHANCE POPS FOR THE WEST. IN THE EAST WILL GO WITH CHANCE POPS EVERYWHERE THROUGH EARLY WEDNESDAY AS WARM ADVECTION OVER THE RETREATING COLD AIR DOME SHOULD SQUEEZE OUT A FEW SNOW SHOWERS...WITH OCCASIONAL AREAS OF FREEZING DRIZZLE NOT OUT OF THE QUESTION GIVEN THE THERMODYNAMIC PROFILE.

FOR WEDNESDAY...COLD AIR CONTINUES TO RETREAT IN THE EAST WHILE STRONG 500 MB RIDGE BUILD OVER THE DIVIDE. UNDER THIS RIDGE EXPECT PARTLY CLOUDY SKIES...WINDY AND WARM CONDITIONS WITH 50S MOST LOCATIONS. IN THE EAST TIMING OF COLD AIR RETREAT WILL DICTATE HIGHS BUT FOR NOW UPPER 30S TO NEAR 40 LOOKS REASONABLE. WEDNESDAY NIGHT LOOKS TRANQUIL WITH WINDS ABATING SOMEWHAT...EXCEPT IN LIVINGSTON WHERE WINDS WILL BE GUSTY THROUGH THE NIGHT UNDER 700MB THERMAL RIDGING. OTHER WISE PARTLY CLOUDY SKIES WITH LOWS IN THE 20S AND 30S.

THURSDAY COULD BE INTERESTING...AS MENTIONED PREVIOUSLY MODEL GUIDANCE FORECASTING 60S AND 70S ACROSS THE AREA. CURRENT WATER VAPOR IS SHOWING A VERY STRONG VORTICITY LOBE AND A STRONG NORTHERLY JET PUSHING SOUTH OUT OF THE NORTH POLE AND ALREADY INTO NORTHERN BC. GFS INDICATES A COLD POOL WITH -40C AIRMASS AT 850MB BUILDING BEHIND THIS FEATURE. CURRENT TRACKING WOULD BRING A COLD FRONT INTO THE AREA BY THURSDAY...BUT MODELS ARE DOING WHAT THEY HAVE DONE WITH LAST SEVERAL COLD AIR INTRUSIONS AND PUSHING IN PACIFIC SYSTEMS WHICH HOLD COLD AIR IN PLACE AND DILUTE IT RAPIDLY OVER TIME. THIS SCENARIO HAS NOT WORKED OUT WELL RECENTLY AND AM A BIT CONCERNED THAT THIS COLD POOL WILL WORK ITS WAY IN HERE. AGAIN...WITH MODELS FORECASTING 70S EVEN A WEAK COLD POOL COULD BUST FORECAST A GOOD 40 DEGREES. AS A RESULT WILL NOT MAKE ANY CHANGES TO GOING FORECAST AND WILL STAY A GOOD BIT BELOW GUIDANCE FOR THURSDAY AND THURSDAY NIGHT. CHAMBERS

.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE... MODELS CONTINUE TO AGREE ON SOUTHWEST FLOW PATTERN DOMINATING FIRST HALF OF EXTENDED. SEVERAL WAVES ROTATING NORTHEAST AROUND TROUGH WILL EACH BRING A CHANCE OF SHOWERS TO WESTERN PORTION OF CWA. WILL BEGIN TO TWEAK TIMING FOR FRIDAY WITH AFTERNOON/EVENING EVENT GIVEN WAVE POSITION AND INSTABILITY PROFILE. EXPECT FRIDAY TO BE WARMEST DAY OF EXTENDED AS WELL AS MODELS CONSISTENT WITH SHOWING 8-12 DEGREE AIR AT 850 WITH GOOD MIXING PROFILE. FOR THE WEEKEND WILL KEEP CHANCE OF SHOWERS IN WEST ON SATURDAY...AND ADD A CHANCE OF SHOWERS TO HIGHER TERRAIN SUNDAY WITH MORE WAVES TRANSVERSING SOUTHWEST FLOW. WAVES WILL ALSO WORK TO BREAK DOWN THERMAL RIDGE...ESPECIALLY IN THE WEST. ATTM IT APPEARS WAVES WILL HAVE LESS IMPACT ON TEMPS ACROSS SOUTHEAST...SO WILL WARM THINGS UP A FEW DEGREES HERE WITH 850MB TEMPS REMAINING AROUND 10 DEGREES. TROUGH SWINGS INTO WESTERN US ON MONDAY...WITH PACIFIC COLD FRONT PUSHING THROUGH AREA...SO CHANCE POPS HERE LOOK ON TRACK. WITH FRONT PUSHING THROUGH WILL TREND TEMPS TO ADVERTISE COOL DOWN INTO EARLY NEXT WEEK... THOUGH DO NOT EXPECT TEMPS TO DROP TOO FAR GIVEN PACIFIC ORIGIN OF FRONT. WILL ALSO ADD CHANCE POPS ON TUESDAY WITH DEEP SURFACE LOW FORMING JUST TO THE EAST AND FOR BETTER COORDINATION WITH OTHER OFFICES. JZ

WED THU FRI SAT SUN MON TUE ----------------------------------------------------------- BIL 022/050 035/059 039/060 036/056 035/055 035/053 033/045 30/B 00/B 02/W 23/W 30/B 03/W 33/O LVM 038/055 035/059 037/059 035/053 034/054 035/050 031/044 40/B 00/N 03/W 33/W 30/E 03/W 33/O HDN 023/047 032/061 036/062 034/057 033/056 034/054 031/046 30/B 00/B 02/W 20/E 00/B 03/W 33/O MLS 015/041 028/055 034/061 031/056 031/057 032/055 030/043 40/E 00/B 00/B 00/B 00/B 03/W 33/O 4BQ 025/049 030/060 034/064 033/060 034/059 033/057 031/044 40/E 00/B 00/B 00/B 00/B 03/W 33/O BHK 015/038 026/051 033/058 029/055 031/057 031/055 029/042 42/J 00/U 00/B 00/B 00/B 03/W 33/O SHR 034/053 030/060 035/063 032/061 032/057 033/055 031/045 30/B 00/U 02/W 23/W 30/E 03/W 33/O

.BYZ... MT...NONE. WY...NONE.



AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 845 PM PST TUE MAR 11 2003

.SYNOPSIS...A SERIES OF WEATHER SYSTEMS WILL ARRIVE IN WESTERN WASHINGTON OVER THE NEXT THREE DAYS. RAIN WILL BE HEAVY AT TIMES... TEMPERATURES WILL BE MILD...AND THE COAST WILL BE WINDY. A MORE SHOWERY...BUT STILL WET...PATTERN TAKES OVER BY THE WEEKEND.

.DISCUSSION...WITH THE EXCEPTION OF THE CENTRAL CASCADES THE PRECIP HAS ENDED FOR THE TIME BEING. LOOKING AT THE MOISTURE PROFILE ON A BFI ACARS FLIGHT AND THE UIL SOUNDING...RATHER DRY AIR MASS BELOW 12000 FEET. THIS WOULD BE EXPECTED BETWEEN SYSTEMS. IT IS ALSO SHOWING UP IN THE LACK OF CLOUD COVER MANY HOURS AT THIS TIME. IT LOOKS AS THO WILL NEED TO WAIT UNTIL THE PRE-DAWN HOURS BEFORE THE NEXT ROUND OF PRECIP BEGINS. CURRENT FORECAST DOES NOT HAVE THE CURRENT OR EXPECTED OVERNIGHT WEATHER COVERED WELL AND AN UPDATE WILL BE ISSUED VERY SHORTLY.

ALSO HAD TO TWEAK THE WIND FORECAST NORTHERN AREAS. STRONG SURGE DOWN THE STRAIT BEHIND THIS SYSTEM AND NEARLY MADE GALE IN THE STRAIT AND THE WIND WENT NW IN ADMIRALTY INLET AND AS FAR SOUTH AS KPAE. ONSHORE PRES GRAD QUICKLY DIMINISHING AND EXPECT THE STRAIT TO SHUT OFF COMPLETELY OVERNIGHT AND THE WIND TO BECOME SLY INLAND AGAIN AS THE NEXT SYSTEM APPROACHES.

FURTHER IN THE FORECAST PERIOD HAVE NOT MADE ANY CHANGES AT THIS TIME. WILL LEAVE THE WATCH AS SUCH AND NOT HOIST A WIND WARNING AS I STILL FEEL THIS IS A MARGINAL EVENT.

UIL ++++ OLM 8+++ SEA 8+++ .KSEW...HIGH WIND WATCH COAST WED AFTERNOON THROUGH THURSDAY. GALE WARNING COAST...WEST ENTRANCE TO STRAIT...CAMANO ISLAND TO POINT ROBERTS. SMALL CRAFT ADVISORY EAST ENTRANCE TO STRAIT...ADMIRALTY INLET...PUGET SOUND/HOOD CANAL. .KATX...VCP21/CSR21...OPERATIONAL. $$

CERNIGLIA



AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 545 AM CST WED MAR 12 2003

AVIATION DISCUSSION FOR 12 UTC TAFS

THE FORECAST PROBLEM WITH TAFS IS THE COLD FRONT MOVING SOUTH INTO NORTHEAST ILLINOIS THIS MORNING. THE FRONT IS OVER CENTRAL MICHIGAN TO SOUTHERN WISCONSIN TO CENTRAL IOWA AT 10 UTC. THE WIND WILL SHIFT TO THE NORTH AFTER FRONTAL PASSAGE. ISENTROPIC CROSS SECTION ACROSS THE FRONT SHOWS THE COLD AIR IS BELOW 850 MB. ACARS SOUNDING AT ORD AT 0922 UTC SHOWS TWO INVERSIONS WITH BASES AT 530 FT AND 4600 FT. UNTIL THE FRONT PASSES SOUTH WILL FORECAST MIDLEVEL CLOUDS. THE WINDS WILL BE LIGHT BECAUSE OF THE INVERSIONS. THE HIGHER INVESION MAY NOT MIX DOWN WHEN THE COOL AIR ARRIVES. SURFACE WINDS THIS AFTERNOON WILL BE FORM THE NORTHEAST. COOL AIR FROM THE LAKE WILL ENHANCE THE THERMAL PROPERTIES OF THE AIR MASS BEHIND THE FRONT. A WEAK SHORT WAVE SEEN ON THE 700 MB FORECASTS USING THE ETA AND AVN MODEL WILL MOVE THROUGH TONIGHT. OMEGA FORECASTS SHOW LIFT WITH THIS WAVE AND THERE WILL BE MOISTURE AVAILABLE. WILL FORECAST RAIN. THE BUFKIT AND MODEL SOUNDINGS SHOW A LAYER OF TEMPERATURES ABOVE FREEZING FROM THE SURFACE TO 7100 FT AT 02 UTC. BY 06 UTC THE ETA MODELS SHOW ISENTROPIC LIFT ON THE 285K SURFACE. WILL FORECAST LOWER CEILINGS TO 1000 TO 1500 WITH THE COOL LOW LEVEL AIR...INVERSION AND EASTERLY WINDS.

WHW

PRELIMINARY DISCUSSION FOR 4 AM ZONES/GRIDS

AT 06Z JUST CI CLOUDS N WITH MID LEVEL STUFF S AND SOME WEAK ECHOES ALOFT EXTREME S FRINGE OF THE AREA. SOME MVFR CIGS THRU N MO/CENTRAL IL. LOT OF 850 MOISTURE COMING N. MVFR CIGS AGAIN TO NW OF AREA BEHIND THE COLD FRONT FROM S GRB-LNR-OMA. 925 CHART SHOWS STRONG STREAMLINE CONVERGENCE VCNTY OF THE FRONT.

VAPOR PIC SUGGESTS WEAK UPPER LEVEL TROF NE WI-W IA WITH SOMETHING MUCH STRONGER VCNTY ID. MODELS ALL TAKE THE ID SYSTEM AND DEVELOP IT WHILE IT MOVES TO SW TIP MI BY MORNING. THIS A LITTLE FARTHER NE AND FASTER THAN LAST NIGHTS RUN WHICH HAD THE VORT CENTER OVER NE IL.

AFTER THIS SYSTEM PASSES WARM RIDGE ALOFT FINALLY MOVES E OVER AREA AHEAD OF COMPLEX SYSTEM COMING INTO W COAST. THIS WILL BE NEXT WX MAKER EARLY NEXT WEEK. WILL HAVE TO WATCH FOR COLD FRONT ON SUNDAY AFTERNOON TO SLIDE DOWN LAKE AS UPPER TROF JUST TO OUR NE BUCKLES THE RIDGE SOME. VERY USUAL TO SEE THIS IN MARCH/APRIL/MAY AROUND HERE.

MODELS SHOW IA TROF MOVING E. WILL PROBABLY JUST HAVE SOME WEAK ECHOES ALOFT EARLY THIS MORNING WITH MAIN RA AREA JUST TO OUR S. RH INCREASES AGAIN LATE AFTERNOON AND THRU ABOUT 3/4 TONIGHT AS ID SYSTEM COMES INTO PLAY. DECENT 700 VORTICITY OVER AREA BY 00Z ALONG WITH INCREASING Q-VECTOR CONVERGENCE. HEAVIER RH SHOULD BE E OF AREA BY MORNING AS TROF AXIS PASSES TO THE E.

CLEARING THRU MIDDAY AND EARLY AFTERNOON OVER AREA ON THURSDAY WITH NICE SUN FRIDAY WITH SOME CLOUDS SATURDAY AND GENERAL INCREASE IN CLOUDS ON SUNDAY. WILL HAVE TO WATCH SUNDAY FOR PRECIP CHANCE BUT FOR NOW WILL LEAVE DRY.

EXPECT SOME LAST MINUTE DECISIONS ON ANY EARLY MORNING PRECIP CHANCES BASED ON LATEST RADAR.

IN SHORT TERM WILL HAVE LAKESIDE COOLING NEXT 2 DAYS WITH NE WINDS ONCE FRONT GOES THRU THIS MORNING.

COORD WITH ILX

.CHI...NONE

AF