Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 05/17/08

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
521 AM PDT THU MAY 15 2008 ...NEAR RECORD HIGH TEMPERATURES EXPECTED FOR INLAND AREAS TODAY THROUGH SATURDAY... .UPDATE...HIDDEN BENEATH THE HIGH LEVEL MOISTURE APPEARS TO BE PATCHES OF LOW CLOUDS AND FOG. WITH THE MARINE INVERSIONS AT 500 FT OR LESS FROM ACARS SOUNDINGS...THIS FOG COULD BECOME DENSE...BUT OBSERVATIONS AT KLAX AND KSMO INDICATE OTHERWISE AT THIS TIME. FORECAST HAS BEEN UPDATED TO ADD LOW CLOUDS AND FOG TO THE LOS ANGELES COUNTY COAST. && .SHORT TERM (TODAY-SATURDAY)...SATELLITE IMAGERY REVEALS SIGNIFICANT AMOUNT OF HIGH LEVEL MOISTURE CONTINUING TO PUSH OVER THE AREA THIS MORNING. HIGH LEVEL MOISTURE WILL CONTINUE TO STREAM OVER THE AREA TODAY...GRADUALLY DIMINISHING THROUGHOUT THE DAY. WITH DECREASING HIGH LEVEL MOISTURE...WEAK OFFSHORE FLOW ESTABLISHING OVER THE AREA...AND 850 MB TEMPERATURES WARMING BY ABOUT 2 TO 4 DEGREES CELSIUS TODAY...THE MAIN STORY WILL BE THE HEAT WAVE DEVELOPING OVER THE AREA FOR LATE WEEK. TEMPERATURES WILL INCREASE TO NEAR RECORD LEVELS THIS AFTERNOON. NEAR RECORD OR RECORD LEVELS COULD BE REACHED IN THE MOUNTAIN AREAS...THE WESTERN SAN FERNANDO VALLEY...EASTERN VENTURA COUNTY VALLEYS...AND THE SANTA CLARITA VALLEY THIS AFTERNOON. FRIDAY WILL LIKELY PRODUCE ADDITIONAL AREAS REACHING OR EXCEEDING RECORD LEVELS SOUTH OF POINT CONCEPTION. 850 MB TEMPERATURES STAY THE ABOUT SAME ON FRIDAY OVER LOS ANGELES AND VENTURA COUNTIES...BUT 950 MB TEMPERATURES INCREASE AND OFFSHORE SURFACE GRADIENTS TIGHTEN SOME FRIDAY MORNING. THIS SHOULD BRING A WARMER START TO THE MORNING ON FRIDAY. TEMPERATURES MAY APPROACH OR EXCEED RECORD LEVELS ON FRIDAY IN THE SAME AREAS AGAIN...BUT FRIDAY WILL LIKELY BE THE WARMEST DAY SOUTH OF POINT CONCEPTION. NORTH OF POINT CONCEPTION...SURFACE GRADIENTS WEAKEN ALLOWING FOR A SLIGHT INCREASE IN THE INTRUSION IN THE AFTERNOON SEA BREEZE. SATURDAY WILL LIKELY PRODUCE THE WARMEST AND NEAR RECORD TEMPERATURES FOR THE SAN LUIS OBISPO COUNTY VALLEYS AND MOUNTAINS...AND THE SANTA BARBARA MOUNTAINS AND CUYAMA VALLEY AS THE HIGH REPOSITIONS NORTHWARD. THIS WILL CONCENTRATE THE BEST OFFSHORE FLOW REGIME ALONG THE CENTRAL PART OF THE STATE. THROUGHOUT THE REMAINDER OF THE WEEK..OFFSHORE WINDS SHOULD REMAIN BELOW ADVISORY LEVELS. WINDS COULD REACH LOCALIZED ADVISORY LEVELS LATER THIS MORNING OR EARLY THIS AFTERNOON. HOWEVER WITH KLAX-KDAG CURRENTLY 1.2 MB ONSHORE CURRENTLY AND BEST THERMAL GRADIENTS EXPECTED TO OCCUR WHEN THE UPPER-LEVEL WINDS ARE AT A MINIMUM...THESE WINDS SHOULD BE LOCALIZED AND NOT WIDESPREAD. IT IS CONCERNING THAT ETA MOS GUIDANCE VALUES INDICATE 25 KNOTS AT KVNY AND 29 KNOTS AT KSDB AROUND 21Z. NAM-WRF TIME HEIGHT SECTIONS AT KVNY INDICATE GUSTS AT KVNY TO BE 35 KNOTS...OR AROUND 40 MPH. NAM-WRF IS USUALLY TOO AGGRESSIVE WITH THE WINDS...AND ETA MOS VALUES ARE OCCASIONALLY OVERDONE AT KSDB. WINDS WILL HAVE TO BE MONITORED FOR POSSIBLE STRENGTHENING...AND ADVISORY WILL ISSUED IF NECESSARY. .LONG TERM (SUNDAY-WEDNESDAY)...A COOLING TREND SHOULD START TO TAKE SHAPE LATE IN THE WEEKEND. MODELS ARE DIVERGING A BIT WITH GFS SOLUTION INDICATING A LATE SEASON CUT-OFF TROUGH APPROACHING THE CALIFORNIA COAST MIDWEEK NEXT WEEK...BUT ECMWF SOLUTIONS ARE MORE PROGRESSIVE WITH TROUGH PUSHING IT THROUGH THE PACIFIC NORTHWEST. WITH IT BEING THE MONTH OF MAY...GFS SOLUTIONS WOULD NORMALLY BE EMBRACED...BUT GFS STRENGTHENS THE TROUGH IN A STRANGE WAY. THE MODEL SOLUTION PUSHES A WEAK TROUGH INTO THE NORTHERN CALIFORNIA COAST...AND THEN RETROGRADES AND STRENGTHENS THE TROUGH OFFSHORE. A BLEND OF MODEL SOLUTION MAY BE MORE REALISTIC...WITH THE TROUGH DROPPING SOUTH THROUGH THE GREAT BASIN AND CUTTING OFF OVER THE COASTAL WATERS. COOLER AND MORE MOIST CONDITIONS WILL LIKELY DEVELOP WITH A RETURN OF THE MARINE LAYER FOR THE EARLY PART OF NEXT WEEK. LOW CONFIDENCE SHOULD PLACED IN FUTURE FORECASTS FOR LATTER PART OF NEXT WEEK. && .AVIATION...15/1220Z. VFR CONDITIONS WILL PERSIST THROUGH THIS EVENING...EXCEPT FOR EARLY MORNING IFR CEILINGS AND VISIBILITIES NEAR THE WESTERN LOS ANGELES COUNTY COASTAL TERMINALS. THERE WILL BE MODERATE UDDF ACROSS THE LOCAL MTNS AND LLWS POSSIBLE NEAR WINDY PASSES AND CANYONS...ESPECIALLY AT KBUR AND KVNY TODAY. KLAX...HIGH CONFIDENCE THAT VFR CONDITIONS WILL REMAIN PREDOMINANT AFTER IFR TO MVFR CONDITIONS IN LOW CLOUDS AND FOG. IFR CONDITIONS WILL LIKELY GIVE AWAY TO VFR CONDITIONS BY 1430Z. KBUR...HIGH CONFIDENCE IN CLEAR SKIES AND GOOD VISIBILITIES THROUGH THU NIGHT. GOOD CONFIDENCE IN LOCALLY GUSTY WINDS AND LLWS THIS MORNING THROUGH THIS AFTERNOON. && .LOX WATCHES/WARNINGS/ADVISORIES... SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && $$ PUBLIC...HALL AVIATION...HALL/KAPLAN WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1021 PM EDT FRI MAY 16 2008 .UPDATE... THE LATEST WATER VAPOR LOOP SHOWS A WELL DEFINED SHORT WAVE MOVING INTO WESTERN UPPER MICHIGAN. REGIONAL RADAR DATA SHOWS A BAND OF SHOWERS AHEAD OF THIS FEATURE...ROUGHLY ALONG A SURFACE TROUGH AXIS OVER WESTERN UPPER MI AND NORTHERN WI. THE 00Z GRB SOUNDING DID SHOW A LITTLE HIGHER MOISTURE IN THE MID LEVELS IN COMPARISON TO DTX AND APX. THE MID LEVEL THETA E ADVECTION AND ISENTROPIC ASCENT IS LEADING TO A SECOND AREA OF SHOWERS CURRENTLY MOVING ACROSS NORTHWEST LOWER MI. THIS REGION OF ISENTROPIC ASCENT IS EXPECTED TO BRUSH THE NORTHERN SAGINAW VALLEY AND THUMB OVER THE NEXT COUPLED OF HOURS. FAIRLY DECENT QG FORCING AND EXIT REGION JET DYNAMICS IS STILL EXPECTED TO OVERSPREAD SE MI LATE TONIGHT AS THE MID LEVEL WAVE ROTATES ACROSS THE NORTHERN LAKES. THUS THE CURRENT FORECAST WHICH HAS AN IN INCREASE IN POPS AFTER 06Z STILL LOOKS ON TRACK. ONLY MINOR ADJUSTMENTS WILL BE MADE TO SKY COVER AND MIN TEMPS IN THE UPDATE. && .PREV DISCUSSION...ISSUED 708 PM EDT FRI MAY 16 2008 AVIATION... CLOUD BASES ARE GENERALLY ABOVE 6K FT THIS EVENING ALONG A WEAKENING SURFACE TROUGH AXIS ACROSS THE THUMB REGION. THIS IS A RESULT OF FAIRLY DRY LOWER LEVELS...PER RECENT TAMDAR SOUNDINGS OUT OF DTW. THE SURFACE TROUGH AXIS CURRENTLY OVER THE ARROWHEAD OF MINNESOTA IS FORECAST TO MOVE INTO THE SAGINAW VALLEY AROUND 09Z...THEN INTO METRO DETROIT BETWEEN 12Z AND 15Z. DEEPER MOISTURE ALONG THIS BOUNDARY AS WELL AS STRONGER LARGE SCALE FORCING WILL PROVIDE A BETTER CHANCE FOR SOME SHOWERS EARLY SAT MORNING. MODEL SOUNDINGS STILL SUGGEST THAT CEILINGS AND VISIBILITIES WILL REMAIN PREDOMINATELY IN THE VFR CATEGORY AS THIS TROUGH MOVES THROUGH. PREV DISCUSSION...ISSUED 358 PM EDT FRI MAY 16 2008 SHORT TERM...THROUGH TONIGHT BAND OF MID CLOUDS OVER CENTRAL LOWER MICHIGAN WILL SLIDE DOWNWARD THROUGH SOUTHEAST MICHIGAN LATE THIS AFTERNOON AND EVENING AS THE AXIS OF A SURFACE TROUGH MOVES ACROSS LAKE HURON AND WEAKENS. MODELS CONTINUE TO HINT THERE MAY BE A FEW SHOWERS OUT OF THIS BAND THIS EVENING...BUT WITH VERY MINIMAL FORCING AND VERY DRY AIR BELOW 9000 FEET WILL CONTINUE DRY FORECAST WITH INCREASING CLOUDS. BEHIND THIS BAND...WILL SEE A BRIEF BREAK IN CLOUD COVERAGE BEFORE CLOUDS INCREASE ONCE AGAIN AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. SURFACE LOW PRESSURE SYSTEM WILL MOVE INTO CENTRAL ONTARIO LATE TONIGHT AS THE FIRST IN A SERIES OF STRONG UPPER SHORTWAVES RACES DOWN INTO THE NORTHERN GREAT LAKES. PRECIPITATION IS EXPECTED TO DEVELOP AFTER MIDNIGHT AS A COLD FRONT APPROACHES SOUTHEAST MICHIGAN. BEST CHANCES FOR PRECIPITATION WILL BE FROM 06Z-14Z AS MODELS SHOW A GOOD BAND OF MOISTURE AND ISENTROPIC ASCENT (295-300K) PROGRESSING SOUTHEASTWARD ACROSS THE FORECAST AREA DURING THIS TIMEFRAME...WITH SOME HELP FROM LEFT EXIT REGION DYNAMICS. WITH AMPLE CLOUD COVER AND SOME WIND...TEMPERATURES OVERNIGHT WILL REMAIN FAIRLY MILD...FALLING TO ONLY AROUND 50. LONG TERM...SATURDAY THROUGH FRIDAY MODEL SOLUTIONS ARE A BIT DIFFERENT (TODAY AS COMPARED TO THIS TIME YESTERDAY) IN REGARDS TO THE SURFACE LOW PASSING NORTH OF THE LAKES REGION AND THE COLD FRONT THAT IT SENDS SOUTHEAST THROUGH THE AREA. THIS LOW IS NOW MUCH FURTHER NORTH AND HENCE THE THE DEGREE OF COLD AIR PUSHING INTO THE STATE ON SATURDAY IS MINIMIZED TO SOME DEGREE. OVERNIGHT FORECAST HAD THIS PRETTY WELL IN HAND...AND DO NOT EXPECT ANY MAJOR ADJUSTMENTS TO TEMPERATURES. ANOTHER MAJOR DIFFERENCE IN THE FORECAST IS A STRONG SHORTWAVE THAT DIVES SOUTH FROM THE ARCTIC CIRCLE IN BEHIND THIS INITIAL SYSTEM. THIS RESULTS IN ANOTHER LOW PRESSURE SWINGING AROUND THE FIRST ONE NORTHEAST OF LAKE HURON...WITH A MUCH STRONGER SURGE OF COLD AIR ON THE WAY FOR SUNDAY...WITH TEMPERATURES ONLY IN THE LOW/MID 50S IN MANY LOCATIONS. ALTHOUGH THE COLDEST SURGE OF AIR PROGRESSES SOUTHEAST OF THE AREA RATHER QUICKLY...A RELATIVELY COOL PATTERN REMAINS IN PLACE EARLY NEXT WEEK...WITH TEMPERATURES ONLY EDGING BACK INTO THE 60S MONDAY INTO TUESDAY. BY THIS TIME...THE FORECAST BECOMES UNCERTAIN AS THE CURRENT UPPER PATTERN BREAKS DOWN. BASICALLY...A STRONG UPPER LEVEL TROUGH WILL BE DIGGING INTO THE WESTERN CONUS...WHICH FORCES THE CURRENT UPPER RIDGE EAST INTO THE MISSISSIPPI VALLEY AND PARTS OF THE GREAT LAKES REGION. THE VORTEX OVER SOUTHEAST CANADA THAT WILL BE FEEDING THE COOL AIR INTO THE AREA WEAKENS SOME...BUT REMAINS STRONG ENOUGH TO INFLUENCE THE WEATHER IN SOUTHEAST MICHIGAN BY BLOCKING THE WARMER AIR THAT WILL BE ENCROACHING ON THE AREA WITH THE BUILDING RIDGE. THE BATTLE GROUND WILL BE A NEARLY STATIONARY SURFACE FRONT THAT WILL BECOME DRAPED FROM THE WESTERN GREAT LAKES SOUTHEAST INTO THE OHIO VALLEY. THE POSITIONING OF THIS FRONT WILL EVENTUALLY DETERMINE THE DEGREE OF WARMING (OR LACK THEREOF). THIS FEATURE WILL ALSO BE THE FOCUS FOR SHOWERS/THUNDERSTORMS FROM MID/LATE NEXT WEEK. WILL MAINTAIN SOMEWHAT OF A CONSERVATIVE FORECAST ATTM...ASSUMING THIS FRONTAL BOUNDARY WILL HAVE TROUBLE LIFTING COMPLETELY NORTH THROUGH THE AREA. THIS WILL FOCUS THE WARMEST AND WETTEST OF THE WEATHER JUST SOUTH/SOUTHWEST OF THE REGION. MARINE... WINDS WILL INCREASE TONIGHT AS THE PRESSURE GRADIENT TIGHTENS IN ADVANCE OF THE NEXT COLD FRONT. NORTHWEST WINDS WILL INCREASE FURTHER IN THE WAKE OF THIS FRONT ON SATURDAY...LEADING TO GUSTS AROUND 25 KNOTS OVER ALL NEARSHORE WATERS ON SATURDAY. THE SETUP IS NOT QUITE AS FAVORABLE FOR GALES OVER NORTHERN LAKE HURON...BUT IT APPEARS WEST/NORTHWEST FLOW WILL BE IDEAL OF FUNNELING OVER THE FAR NORTHERN PART OF THE LAKE...WITH SOME DEGREE OF INSTABILITY AIDING IN MIXING AS WELL. WILL UPGRADE THE WATCH TO A WARNING FOR THE TWO NORTHERN ZONES FROM LATE SATURDAY AND RUN IT INTO SUNDAY MORNING AS A SECOND STRONGER COLD FRONT SWEEPS THROUGH THE REGION. EVEN THOUGH THERE WILL BE A LULL IN WINDS EARLY SATURDAY NIGHT IN BETWEEN THE TWO COLD FRONTAL PASSAGES...SMALL CRAFT ADVISORY CONDITIONS WILL BE THE RULE OVER MOST OF THE WEEKEND...AND WILL KEEP THE ADVISORIES IN PLACE AS IS. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... GALE WARNING...LHZ361-LHZ362...FROM 5 PM SATURDAY TO 10 AM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON INCLUDING SAGINAW BAY...FROM 4 AM SATURDAY TO 8 AM MONDAY. LAKE ST CLAIR... SMALL CRAFT ADVISORY...FROM 8 AM SATURDAY TO 8 PM SUNDAY. MI WATERS OF LAKE ERIE... SMALL CRAFT ADVISORY...FROM 8 AM SATURDAY TO 8 PM SUNDAY. && $$ UPDATE.......SC AVIATION.....SC SHORT TERM...HLO LONG TERM....DG MARINE.......HLO YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
708 PM EDT FRI MAY 16 2008 .AVIATION... CLOUD BASES ARE GENERALLY ABOVE 6K FT THIS EVENING ALONG A WEAKENING SURFACE TROUGH AXIS ACROSS THE THUMB REGION. THIS IS A RESULT OF FAIRLY DRY LOWER LEVELS...PER RECENT TAMDAR SOUNDINGS OUT OF DTW. THE SURFACE TROUGH AXIS CURRENTLY OVER THE ARROWHEAD OF MINNESOTA IS FORECAST TO MOVE INTO THE SAGINAW VALLEY AROUND 09Z...THEN INTO METRO DETROIT BETWEEN 12Z AND 15Z. DEEPER MOISTURE ALONG THIS BOUNDARY AS WELL AS STRONGER LARGE SCALE FORCING WILL PROVIDE A BETTER CHANCE FOR SOME SHOWERS EARLY SAT MORNING. MODEL SOUNDINGS STILL SUGGEST THAT CEILINGS AND VISIBILITIES WILL REMAIN PREDOMINATELY IN THE VFR CATEGORY AS THIS TROUGH MOVES THROUGH. && .PREV DISCUSSION...ISSUED 358 PM EDT FRI MAY 16 2008 SHORT TERM...THROUGH TONIGHT BAND OF MID CLOUDS OVER CENTRAL LOWER MICHIGAN WILL SLIDE DOWNWARD THROUGH SOUTHEAST MICHIGAN LATE THIS AFTERNOON AND EVENING AS THE AXIS OF A SURFACE TROUGH MOVES ACROSS LAKE HURON AND WEAKENS. MODELS CONTINUE TO HINT THERE MAY BE A FEW SHOWERS OUT OF THIS BAND THIS EVENING...BUT WITH VERY MINIMAL FORCING AND VERY DRY AIR BELOW 9000 FEET WILL CONTINUE DRY FORECAST WITH INCREASING CLOUDS. BEHIND THIS BAND...WILL SEE A BRIEF BREAK IN CLOUD COVERAGE BEFORE CLOUDS INCREASE ONCE AGAIN AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. SURFACE LOW PRESSURE SYSTEM WILL MOVE INTO CENTRAL ONTARIO LATE TONIGHT AS THE FIRST IN A SERIES OF STRONG UPPER SHORTWAVES RACES DOWN INTO THE NORTHERN GREAT LAKES. PRECIPITATION IS EXPECTED TO DEVELOP AFTER MIDNIGHT AS A COLD FRONT APPROACHES SOUTHEAST MICHIGAN. BEST CHANCES FOR PRECIPITATION WILL BE FROM 06Z-14Z AS MODELS SHOW A GOOD BAND OF MOISTURE AND ISENTROPIC ASCENT (295-300K) PROGRESSING SOUTHEASTWARD ACROSS THE FORECAST AREA DURING THIS TIMEFRAME...WITH SOME HELP FROM LEFT EXIT REGION DYNAMICS. WITH AMPLE CLOUD COVER AND SOME WIND...TEMPERATURES OVERNIGHT WILL REMAIN FAIRLY MILD...FALLING TO ONLY AROUND 50. LONG TERM...SATURDAY THROUGH FRIDAY MODEL SOLUTIONS ARE A BIT DIFFERENT (TODAY AS COMPARED TO THIS TIME YESTERDAY) IN REGARDS TO THE SURFACE LOW PASSING NORTH OF THE LAKES REGION AND THE COLD FRONT THAT IT SENDS SOUTHEAST THROUGH THE AREA. THIS LOW IS NOW MUCH FURTHER NORTH AND HENCE THE THE DEGREE OF COLD AIR PUSHING INTO THE STATE ON SATURDAY IS MINIMIZED TO SOME DEGREE. OVERNIGHT FORECAST HAD THIS PRETTY WELL IN HAND...AND DO NOT EXPECT ANY MAJOR ADJUSTMENTS TO TEMPERATURES. ANOTHER MAJOR DIFFERENCE IN THE FORECAST IS A STRONG SHORTWAVE THAT DIVES SOUTH FROM THE ARCTIC CIRCLE IN BEHIND THIS INITIAL SYSTEM. THIS RESULTS IN ANOTHER LOW PRESSURE SWINGING AROUND THE FIRST ONE NORTHEAST OF LAKE HURON...WITH A MUCH STRONGER SURGE OF COLD AIR ON THE WAY FOR SUNDAY...WITH TEMPERATURES ONLY IN THE LOW/MID 50S IN MANY LOCATIONS. ALTHOUGH THE COLDEST SURGE OF AIR PROGRESSES SOUTHEAST OF THE AREA RATHER QUICKLY...A RELATIVELY COOL PATTERN REMAINS IN PLACE EARLY NEXT WEEK...WITH TEMPERATURES ONLY EDGING BACK INTO THE 60S MONDAY INTO TUESDAY. BY THIS TIME...THE FORECAST BECOMES UNCERTAIN AS THE CURRENT UPPER PATTERN BREAKS DOWN. BASICALLY...A STRONG UPPER LEVEL TROUGH WILL BE DIGGING INTO THE WESTERN CONUS...WHICH FORCES THE CURRENT UPPER RIDGE EAST INTO THE MISSISSIPPI VALLEY AND PARTS OF THE GREAT LAKES REGION. THE VORTEX OVER SOUTHEAST CANADA THAT WILL BE FEEDING THE COOL AIR INTO THE AREA WEAKENS SOME...BUT REMAINS STRONG ENOUGH TO INFLUENCE THE WEATHER IN SOUTHEAST MICHIGAN BY BLOCKING THE WARMER AIR THAT WILL BE ENCROACHING ON THE AREA WITH THE BUILDING RIDGE. THE BATTLE GROUND WILL BE A NEARLY STATIONARY SURFACE FRONT THAT WILL BECOME DRAPED FROM THE WESTERN GREAT LAKES SOUTHEAST INTO THE OHIO VALLEY. THE POSITIONING OF THIS FRONT WILL EVENTUALLY DETERMINE THE DEGREE OF WARMING (OR LACK THEREOF). THIS FEATURE WILL ALSO BE THE FOCUS FOR SHOWERS/THUNDERSTORMS FROM MID/LATE NEXT WEEK. WILL MAINTAIN SOMEWHAT OF A CONSERVATIVE FORECAST ATTM...ASSUMING THIS FRONTAL BOUNDARY WILL HAVE TROUBLE LIFTING COMPLETELY NORTH THROUGH THE AREA. THIS WILL FOCUS THE WARMEST AND WETTEST OF THE WEATHER JUST SOUTH/SOUTHWEST OF THE REGION. MARINE... WINDS WILL INCREASE TONIGHT AS THE PRESSURE GRADIENT TIGHTENS IN ADVANCE OF THE NEXT COLD FRONT. NORTHWEST WINDS WILL INCREASE FURTHER IN THE WAKE OF THIS FRONT ON SATURDAY...LEADING TO GUSTS AROUND 25 KNOTS OVER ALL NEARSHORE WATERS ON SATURDAY. THE SETUP IS NOT QUITE AS FAVORABLE FOR GALES OVER NORTHERN LAKE HURON...BUT IT APPEARS WEST/NORTHWEST FLOW WILL BE IDEAL OF FUNNELING OVER THE FAR NORTHERN PART OF THE LAKE...WITH SOME DEGREE OF INSTABILITY AIDING IN MIXING AS WELL. WILL UPGRADE THE WATCH TO A WARNING FOR THE TWO NORTHERN ZONES FROM LATE SATURDAY AND RUN IT INTO SUNDAY MORNING AS A SECOND STRONGER COLD FRONT SWEEPS THROUGH THE REGION. EVEN THOUGH THERE WILL BE A LULL IN WINDS EARLY SATURDAY NIGHT IN BETWEEN THE TWO COLD FRONTAL PASSAGES...SMALL CRAFT ADVISORY CONDITIONS WILL BE THE RULE OVER MOST OF THE WEEKEND...AND WILL KEEP THE ADVISORIES IN PLACE AS IS. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... GALE WARNING...LHZ361-LHZ362...FROM 5 PM SATURDAY TO 10 AM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON INCLUDING SAGINAW BAY...FROM 4 AM SATURDAY TO 8 AM MONDAY. LAKE ST CLAIR... SMALL CRAFT ADVISORY...FROM 8 AM SATURDAY TO 8 PM SUNDAY. MI WATERS OF LAKE ERIE... SMALL CRAFT ADVISORY...FROM 8 AM SATURDAY TO 8 PM SUNDAY. && $$ AVIATION.....SC SHORT TERM...HLO LONG TERM....DG MARINE.......HLO YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
730 AM EDT THU MAY 15 2008 UPDATED AVIATION SECTION FOR 12Z TAFS .DISCUSSION (405 AM EDT)... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW UPR TROFFING ACRS ONTARIO E OF HI AMPLITUDE RDG OVER THE W COAST. A NW FLOW OF COLD AIR ALF (00Z H5 TEMPS -25C AT INL/-29C AT YPL) DOMINATES THE UPR GRT LKS EARLY THIS MRNG ARND THE ONTARIO TROF. THE 00Z APX RAOB/TAMDAR SDNG FM SAW SHOW A VERY DRY/STABLE AIRMASS ASSOCIATED WITH HI PRES CENTERED OVER NRN LK MI AT 03Z...SO THE WX THIS EVNG HAS BEEN MOCLR. BUT THERE IS MORE CLD AND EVEN SOME SHRA UPSTREAM IN AREA OF DIFFERENTIAL TEMP ADVCTN/STEEPER LAPSE RATES ALG LO PRES TROF/AXIS OF H85-7 FGEN OVER ONTARIO N OF THE MN BORDER. SOME OF THE CLD HAS SPILLED TOWARD THE KEWEENAW PENINSULA. THERE WAS EVEN A TS OR TWO UPSTREAM EARLIER IN THE EVNG BEFORE LOSS OF DIURNAL HTG. SFC DWPTS WERE AS HI AS 45 WHERE THE TS OCCURRED. 00Z INL/YPL/YQD RAOBS SHOW DEEP...WELL MIXED PBLS TYPICAL OF THE WARM SEASON WITH VARIOUS DEPTHS OF MID LVL MSTR ABV THE RATHER DRY PBL. MAIN FCST CONCERNS THIS PACKAGE ARE SHRA CHCS/TIMING ASSOCIATED WITH DISTURBANCES PROGGED TO DROP SE INTO THE UPR GRT LKS IN PERSISTENT NW FLOW ALF ON SW FLANK OF TROF CENTERED NEAR JAMES BAY. FOR TDAY...NAM/GFS HINT SFC TROF TO THE NW WL SWING INTO THE UPR LKS UNDER NW FLOW ALF. FCST LLVL TRAJECTORIES TDAY WL BE COMING FM THE WSW...WHERE 00Z MPX RAOB SHOWED LLVLS DRY ENUF TO MIX THE SFC DWPT OUT TO NEAR 30. THE FLY IN THE OINTMENT IS POTENTIAL FOR LK MI MSTR TO STREAM INTO THE ERN ZNS IN MORE SW FLOW AHEAD OF INCOMING TROF/ ACCOMPANYING SHRTWV. THE SFC DWPT REACHED 45 AT GRB IN THE LK BREEZE YDAY AFTN OFF THE 44 DEGREE BAY OF GREEN BAY...AND NAM/GFS/RUC13 HINT SIMILAR SFC DWPTS NEAR 45 WL IMPACT AREAS DOWNWIND OF LK MI. 00Z NAM/RUC13/LOCAL WRF-ARW MODEL INDICATE SOME AFTN SHRA WL DVLP OVER MAINLY THE ERN ZNS IN CONFLUENCE BTWN LK BREEZES OF SUP/MI. SINCE EXPECTED DIFFERENTIAL TEMP ADVCTN PATTERN IS CONDUCIVE FOR DIURNAL SHRA ESPECIALLY WITH SYNOPTIC SCALE TROFFING (ALBEIT WEAK) ARND...WL GO WITH A 20 POP IN THIS AREA. NAM FCST CAPE CLOSE TO 2000J/KG SEEMS OVERDONE WITH FCST DWPTS IN THAT AREA POOLING ARND 50 IN LK BREEZE CNVGC. MODIFIED NAM SDNG AT ERY FOR T/TD OF 64/44 YIELDS CAPE ARND 325 J/KG. SHALLOW NATURE OF MSTR INFLUX FM NRN GREEN BAY SUGS ANY SHRA WL BE ISOLD...SO NO MORE THAN A 20 POP IS APPROPRIATE. TEMPTED TO ADD MENTION OF TS AS WELL SINCE TS WERE OBSVD UPSTREAM WHERE SFC DWPTS REACHED ARND 45...BUT LIMITED CAPE SHOWN BY MODIFIED NAM SDNG AND SHALLOW NATURE OF MSTR RETURN THAT MAY MIX OUT WITHIN OTRW DRY AIRMASS SUG HOLDING OFF IS THE BETTER STRATEGY. PLUS...GFS FCST SDNG MODIFIED FOR SIMILAR SFC T/TD SHOWS ONLY 200 CAPE. OTRW...WL GO WITH A 20 POP OVER WRN/CNTRL LK SUP LATE IN THE DAY WITH APRCH OF BETTER DPVA/DEEP LYR H85-3 QVECTOR CNVGC/H7-5 LAPSE RATES AOA 7C/KM IN ADVANCE OF STRONGER SHRTWV DIGGING THRU NW ONTARIO. BUT ABSENCE OF LLVL MSTR ENHANCEMENT AS MIGHT BE PSBL FARTHER E WARRANTS NOTHING MORE THAN A SCHC POP IN THAT AREA W OF LIMITING LK MI STREAMLINE. IN FACT...WITH SFC TEMPS TOPPING OUT IN THE MID-UPR 60S AWAY FM LK MODERATION OVER THE INTERIOR W AND SFC DWPTS MIXING OUT TO ARND 30...EXPECT MIN RH TO SINK NEAR 25 PCT. FOR TNGT...STRONGER SHRTWV APRCHG FM THE NW PROGGED TO SWING THRU ONTARIO...WITH SHARPER DPVA/DEEP LYR H85-3 QVECTOR CNVGC/UPR DVGC/ H85-7 FGEN/STEEPER H7-5 LAPSE RATES SWIPING THE N TIER ZNS AS ATTENDANT SFC TROF/COLD FNT MOVES N TO S ACRS THE FA AFT MIDNGT. WL RETAIN FLAVOR OF GOING FCST SHOWING HIER POPS ARRIVING OVER THE NW IN THE EVNG THEN SWINGING E OVERNGT WITH LOWER POPS TO THE S. LACK OF DEEP MSTR/DIURNAL MIN HTG TIME OF FROPA WARRANTS NOTHING MORE THAN A 30 POP. THERE SEEMS TO BE DECENT AGREEMENT AMONG NUMERICAL MODELS THERE WL BE BRIEF PD OF DRY AIR INFLUX WITH SOME SHRTWV RDGING/DNVA/MID LVL DRYING IN THE WAKE OF THE SHRTWV/SFC TROF RESPONSIBLE FOR SHRA CHCS TNGT. SO DECIDED TO CUT POPS IN THE 12Z-18Z TIME TO JUST 20. NEXT SHRTWV OF CONCERN EMBEDDED WITHIN NW FLOW ALF IS FCST TO BARREL INTO THE UPR GRT LKS SOMETIME LATER ON FRI. GFS/UKMET ARE FASTER THAN THE NAM WITH THIS IMPULSE. CONSIDERING EXCELLENT RUN-TO-RUN CONTINUITY DISPLAYED BY THE GFS AND FAST NATURE OF THE UPPER FLOW...WL TEND TOWARD THE GFS SCENARIO. THIS MODEL SHOWS THE SHRTWV MOVING TO NEAR CYQT BY 00Z SAT...WITH IMPRESSIVE DPVA/DEEP LYR H85-3 QVECTOR CNVGC/ UPR DVGC IN LEFT EXIT OF SUPPORTING 120KT H3 JET MAX SWINGING ACRS THE FA. AVBL MSTR WOULD SEEM TO BE A PROBLEM BASED ON LACK OF GLFMEX INFLOW...BUT IMPRESSIVE LLVL CNVGC ALONG SHARP WSHFT/COLD FROPA MIGHT POOL ENUF MSTR TO JUSTIFY INCRS IN PWAT TO 0.8-0.9 INCH SHOWN BY BOTH GFS/NAM. BASED ON GFS MOS...WL BUMP UP POPS TO 60 OVER THE E IN THE AFTN...WITH LOWER POPS TOWARD THE W CLOSER TO THE JET AXIS. CONSIDERED MENTION OF TS GIVEN STRENGTH OF DYNAMICS...BUT INITIAL DEARTH OF MSTR APPEARS TO LIMIT MAGNITUDE OF LAPSE RATES (H7-5 LAPSE RATE FCST NO HIER THAN 6.5C/KM EVEN OVER THE E). GFS INDICATES DRY SLOTTING WL IMPACT THE FA LATER FRI EVNG BEHIND THE INITIAL COMMA CLD PATTERN ASSOCIATED WITH THE SHRTWV...WITH THE DRYING MOST EMPHATIC OVER THE W HALF CLOSER TO JET SURGE. BUT MODEL SHOWS SOME RELATIVE MOISTENING OVERNGT IN DVLPG CYC FLOW AS COOLER AIR ARRIVES...ENUF TO MAINTAIN LOWER CHC POPS DESPITE THE DRYING ALF. MAINTAINED HIER POPS OVER THE E DEEPER INTO THE LOWER HGTS. GFS/UKMET/ECMWF HINT AT REINFORCING SHRTWV ON SAT...SO MAINTAINED CHC POPS. APRNT STRENGTH OF THIS SYS AND ARRIVAL DURING DAYTIME HTG MAY EVENTUALLY REQUIRE HIER POPS...BUT TIMING UNCERTAINTIES AS WELL AS MORE LIMITED MSTR JUSTIFY MAINTAINING JUST CHC POPS ATTM. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... ESSENTIALLY A VFR/MID CLOUD FORECAST NEXT 24 HRS. KSAW MAY SEE LOW VFR CU THIS AFTN AS WEAK LAKE BREEZE OFF LAKE SUPERIOR RUNS INTO STRONGER LAKE BREEZE OFF LAKE MICHIGAN. EXPECT BUILD UP OF CU AND POSSIBLE SHRA/TSRA TO REMAIN EAST OF KSAW WHERE BETTER LOW LEVEL CONVERGENCE IS PROJECTED. WEAK TROUGH COMES THROUGH BOTH SITES LATE IN THE TAF PERIOD...AFT 06Z TONIGHT. COULD BE A SHOWER ALONG THE TROUGH...BUT COVERAGE IS TOO LOW TO MENTION IN THE TAFS RIGHT NOW. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC RIDGE/LIGHT WINDS TO START BUT STRENGTHENING W FLOW AHEAD OF APPROACHING TROUGH MAY LEAD TO WINDS TO 25 KT THIS AFTN MAINLY OVR NORTH CENTRAL. LACK OF PRESSURE GRADIENT WITH THE TROUGH ALLOWS THE STRONGER WINDS TO DIMINISH LATER TONIGHT. LOW PRESSURE OVER NORTHERN MANITOBA ON FRIDAY AFTERNOON WILL DEEPEN AS IT DIVES TO GEORGIAN BAY BY SATURDAY MORNING. SOUTH/SOUTHWEST WINDS TO 25 KNOTS...PERHAPS EVEN STRONGER...BRIEFLY AS LOW PRESSURE SYSTEM PASSES BY TO NORTH FRIDAY NIGHT...THEN A SHIFT TO NORTHWEST WINDS TO 30 KT IN ITS WAKE ON SATURDAY. COLDER WATER TEMPS WILL LIMIT INSTABILITY FOR GALE FORCE WINDS TO COME TO THE SFC...BUT HIGHER OBSERVATION PLATFORMS MAY SEE SOME GALES THIS WEEKEND. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...JLA MARINE...JLA
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
405 AM EDT THU MAY 15 2008 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW UPR TROFFING ACRS ONTARIO E OF HI AMPLITUDE RDG OVER THE W COAST. A NW FLOW OF COLD AIR ALF (00Z H5 TEMPS -25C AT INL/-29C AT YPL) DOMINATES THE UPR GRT LKS EARLY THIS MRNG ARND THE ONTARIO TROF. THE 00Z APX RAOB/TAMDAR SDNG FM SAW SHOW A VERY DRY/STABLE AIRMASS ASSOCIATED WITH HI PRES CENTERED OVER NRN LK MI AT 03Z...SO THE WX THIS EVNG HAS BEEN MOCLR. BUT THERE IS MORE CLD AND EVEN SOME SHRA UPSTREAM IN AREA OF DIFFERENTIAL TEMP ADVCTN/STEEPER LAPSE RATES ALG LO PRES TROF/AXIS OF H85-7 FGEN OVER ONTARIO N OF THE MN BORDER. SOME OF THE CLD HAS SPILLED TOWARD THE KEWEENAW PENINSULA. THERE WAS EVEN A TS OR TWO UPSTREAM EARLIER IN THE EVNG BEFORE LOSS OF DIURNAL HTG. SFC DWPTS WERE AS HI AS 45 WHERE THE TS OCCURRED. 00Z INL/YPL/YQD RAOBS SHOW DEEP...WELL MIXED PBLS TYPICAL OF THE WARM SEASON WITH VARIOUS DEPTHS OF MID LVL MSTR ABV THE RATHER DRY PBL. MAIN FCST CONCERNS THIS PACKAGE ARE SHRA CHCS/TIMING ASSOCIATED WITH DISTURBANCES PROGGED TO DROP SE INTO THE UPR GRT LKS IN PERSISTENT NW FLOW ALF ON SW FLANK OF TROF CENTERED NEAR JAMES BAY. FOR TDAY...NAM/GFS HINT SFC TROF TO THE NW WL SWING INTO THE UPR LKS UNDER NW FLOW ALF. FCST LLVL TRAJECTORIES TDAY WL BE COMING FM THE WSW...WHERE 00Z MPX RAOB SHOWED LLVLS DRY ENUF TO MIX THE SFC DWPT OUT TO NEAR 30. THE FLY IN THE OINTMENT IS POTENTIAL FOR LK MI MSTR TO STREAM INTO THE ERN ZNS IN MORE SW FLOW AHEAD OF INCOMING TROF/ ACCOMPANYING SHRTWV. THE SFC DWPT REACHED 45 AT GRB IN THE LK BREEZE YDAY AFTN OFF THE 44 DEGREE BAY OF GREEN BAY...AND NAM/GFS/RUC13 HINT SIMILAR SFC DWPTS NEAR 45 WL IMPACT AREAS DOWNWIND OF LK MI. 00Z NAM/RUC13/LOCAL WRF-ARW MODEL INDICATE SOME AFTN SHRA WL DVLP OVER MAINLY THE ERN ZNS IN CONFLUENCE BTWN LK BREEZES OF SUP/MI. SINCE EXPECTED DIFFERENTIAL TEMP ADVCTN PATTERN IS CONDUCIVE FOR DIURNAL SHRA ESPECIALLY WITH SYNOPTIC SCALE TROFFING (ALBEIT WEAK) ARND...WL GO WITH A 20 POP IN THIS AREA. NAM FCST CAPE CLOSE TO 2000J/KG SEEMS OVERDONE WITH FCST DWPTS IN THAT AREA POOLING ARND 50 IN LK BREEZE CNVGC. MODIFIED NAM SDNG AT ERY FOR T/TD OF 64/44 YIELDS CAPE ARND 325 J/KG. SHALLOW NATURE OF MSTR INFLUX FM NRN GREEN BAY SUGS ANY SHRA WL BE ISOLD...SO NO MORE THAN A 20 POP IS APPROPRIATE. TEMPTED TO ADD MENTION OF TS AS WELL SINCE TS WERE OBSVD UPSTREAM WHERE SFC DWPTS REACHED ARND 45...BUT LIMITED CAPE SHOWN BY MODIFIED NAM SDNG AND SHALLOW NATURE OF MSTR RETURN THAT MAY MIX OUT WITHIN OTRW DRY AIRMASS SUG HOLDING OFF IS THE BETTER STRATEGY. PLUS...GFS FCST SDNG MODIFIED FOR SIMILAR SFC T/TD SHOWS ONLY 200 CAPE. OTRW...WL GO WITH A 20 POP OVER WRN/CNTRL LK SUP LATE IN THE DAY WITH APRCH OF BETTER DPVA/DEEP LYR H85-3 QVECTOR CNVGC/H7-5 LAPSE RATES AOA 7C/KM IN ADVANCE OF STRONGER SHRTWV DIGGING THRU NW ONTARIO. BUT ABSENCE OF LLVL MSTR ENHANCEMENT AS MIGHT BE PSBL FARTHER E WARRANTS NOTHING MORE THAN A SCHC POP IN THAT AREA W OF LIMITING LK MI STREAMLINE. IN FACT...WITH SFC TEMPS TOPPING OUT IN THE MID-UPR 60S AWAY FM LK MODERATION OVER THE INTERIOR W AND SFC DWPTS MIXING OUT TO ARND 30...EXPECT MIN RH TO SINK NEAR 25 PCT. FOR TNGT...STRONGER SHRTWV APRCHG FM THE NW PROGGED TO SWING THRU ONTARIO...WITH SHARPER DPVA/DEEP LYR H85-3 QVECTOR CNVGC/UPR DVGC/ H85-7 FGEN/STEEPER H7-5 LAPSE RATES SWIPING THE N TIER ZNS AS ATTENDANT SFC TROF/COLD FNT MOVES N TO S ACRS THE FA AFT MIDNGT. WL RETAIN FLAVOR OF GOING FCST SHOWING HIER POPS ARRIVING OVER THE NW IN THE EVNG THEN SWINGING E OVERNGT WITH LOWER POPS TO THE S. LACK OF DEEP MSTR/DIURNAL MIN HTG TIME OF FROPA WARRANTS NOTHING MORE THAN A 30 POP. THERE SEEMS TO BE DECENT AGREEMENT AMONG NUMERICAL MODELS THERE WL BE BRIEF PD OF DRY AIR INFLUX WITH SOME SHRTWV RDGING/DNVA/MID LVL DRYING IN THE WAKE OF THE SHRTWV/SFC TROF RESPONSIBLE FOR SHRA CHCS TNGT. SO DECIDED TO CUT POPS IN THE 12Z-18Z TIME TO JUST 20. NEXT SHRTWV OF CONCERN EMBEDDED WITHIN NW FLOW ALF IS FCST TO BARREL INTO THE UPR GRT LKS SOMETIME LATER ON FRI. GFS/UKMET ARE FASTER THAN THE NAM WITH THIS IMPULSE. CONSIDERING EXCELLENT RUN-TO-RUN CONTINUITY DISPLAYED BY THE GFS AND FAST NATURE OF THE UPPER FLOW...WL TEND TOWARD THE GFS SCENARIO. THIS MODEL SHOWS THE SHRTWV MOVING TO NEAR CYQT BY 00Z SAT...WITH IMPRESSIVE DPVA/DEEP LYR H85-3 QVECTOR CNVGC/ UPR DVGC IN LEFT EXIT OF SUPPORTING 120KT H3 JET MAX SWINGING ACRS THE FA. AVBL MSTR WOULD SEEM TO BE A PROBLEM BASED ON LACK OF GLFMEX INFLOW...BUT IMPRESSIVE LLVL CNVGC ALONG SHARP WSHFT/COLD FROPA MIGHT POOL ENUF MSTR TO JUSTIFY INCRS IN PWAT TO 0.8-0.9 INCH SHOWN BY BOTH GFS/NAM. BASED ON GFS MOS...WL BUMP UP POPS TO 60 OVER THE E IN THE AFTN...WITH LOWER POPS TOWARD THE W CLOSER TO THE JET AXIS. CONSIDERED MENTION OF TS GIVEN STRENGTH OF DYNAMICS...BUT INITIAL DEARTH OF MSTR APPEARS TO LIMIT MAGNITUDE OF LAPSE RATES (H7-5 LAPSE RATE FCST NO HIER THAN 6.5C/KM EVEN OVER THE E). GFS INDICATES DRY SLOTTING WL IMPACT THE FA LATER FRI EVNG BEHIND THE INITIAL COMMA CLD PATTERN ASSOCIATED WITH THE SHRTWV...WITH THE DRYING MOST EMPHATIC OVER THE W HALF CLOSER TO JET SURGE. BUT MODEL SHOWS SOME RELATIVE MOISTENING OVERNGT IN DVLPG CYC FLOW AS COOLER AIR ARRIVES...ENUF TO MAINTAIN LOWER CHC POPS DESPITE THE DRYING ALF. MAINTAINED HIER POPS OVER THE E DEEPER INTO THE LOWER HGTS. GFS/UKMET/ECMWF HINT AT REINFORCING SHRTWV ON SAT...SO MAINTAINED CHC POPS. APRNT STRENGTH OF THIS SYS AND ARRIVAL DURING DAYTIME HTG MAY EVENTUALLY REQUIRE HIER POPS...BUT TIMING UNCERTAINTIES AS WELL AS MORE LIMITED MSTR JUSTIFY MAINTAINING JUST CHC POPS ATTM. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... AVIATION WEATHER WILL CONTINUE TO BE QUIET WITH VFR CONDITIONS THROUGH THE PERIOD. SOME MID LEVEL CLOUDINESS ASSOCIATED WITH A WEAK WAVE ALOFT WILL MOVE THROUGH THE REGION OVERNIGHT...BUT CIGS SHOULD STAY NEAR 10 KFT. AS THE HIGH SHIFTS EAST OF THE AREA ON THURSDAY...SW WINDS WILL DEVELOP AND BECOME GUSTY ESPECIALLY AT CMX. THE NAM...RUC13 AND LOCAL WRF-ARW ALSO SUGGEST SOME ISOLATED SHOWER ACTIVITY NEAR THE LAKE SUPERIOR LAKE BREEZE EAST OF MARQUETTE. WILL NOT INCLUDE ANY SHOWER MENTION IN THE SAW TAF THU AFTN...BUT THERE IS A SMALL CHANCE FOR SHOWERS AND EVEN A RUMBLE OF THUNDER WITH COLD TEMPERATURES ALOFT. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... SFC RIDGE/LIGHT WINDS TO START BUT STRENGTHENING W FLOW AHEAD OF APPROACHING TROUGH MAY LEAD TO WINDS TO 25 KT THIS AFTN MAINLY OVR NORTH CENTRAL. LACK OF PRESSURE GRADIENT WITH THE TROUGH ALLOWS THE STRONGER WINDS TO DIMINISH LATER TONIGHT. LOW PRESSURE OVER NORTHERN MANITOBA ON FRIDAY AFTERNOON WILL DEEPEN AS IT DIVES TO GEORGIAN BAY BY SATURDAY MORNING. SOUTH/SOUTHWEST WINDS TO 25 KNOTS...PERHAPS EVEN STRONGER...BRIEFLY AS LOW PRESSURE SYSTEM PASSES BY TO NORTH FRIDAY NIGHT...THEN A SHIFT TO NORTHWEST WINDS TO 30 KT IN ITS WAKE ON SATURDAY. COLDER WATER TEMPS WILL LIMIT INSTABILITY FOR GALE FORCE WINDS TO COME TO THE SFC...BUT HIGHER OBSERVATION PLATFORMS MAY SEE SOME GALES THIS WEEKEND. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...MRD MARINE...JLA
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
250 PM CDT FRI MAY 16 2008 .SYNOPSIS... AT 18Z...SURFACE ANALYSIS SHOWED A TROUGH ACROSS THE DAKOTAS AND INTO NORTHEAST WYOMING. HIGH PRESSURE DOMINATED THE SCENE FROM SOUTHWEST U.S. NEAR THE FOUR CORNERS REGION UP INTO BRITISH COLUMBIA AND THE YUKON TERRITORY. IN UPPER LEVELS...6.7 MICRON WATER VAPOR IMAGERY INDICATED A HIGH AMPLITUDE RIDGE FROM SOUTHERN BRITISH COLUMBIA TO THE SOUTHERN TIP OF THE BAJA PENINSULA. THIS RESULTS IN NORTH TO NORTHEAST FLOW ALOFT OVER THE HIGH PLAINS. SATELLITE DERIVED PRODUCT IMAGERY INDICATED SOME ZERO TO -1C VALUES IN NORTHWEST NEBRASKA AND VISIBLE IMAGERY HAD SOME SCATTERED CUMULUS BUILDING IN THE NEBRASKA PANHANDLE. && .SHORT TERM...TONIGHT THROUGH TUESDAY. THE TROUGH OR WEAK FRONT WILL PIVOT THROUGH WESTERN NEBRASKA THIS EVENING AND TONIGHT BRINGING SOME MIDDLE AND HIGH CLOUDS AND A POSSIBILITY OF AN ISOLATED SHOWER IN THE NORTHWEST. THE POSITIVE AREA IN THE PHASE CHANGE LAYER IS NOT REAL HIGH AND MAY NOT BE ENOUGH FOR LIGHTNING. THE PROBABILITY IS VERY LOW FOR MEASURABLE PRECIPITATION THOUGH. THAT SHOULD KEEP TEMPERATURES IN THE UPPER 40S TO LOWER 50S. AFTER SATURDAY...THE BIG ISSUE IS THE HEAT ASSOCIATED WITH THE WESTERN RIDGE AS IT MAKES ITS WAY ONTO THE PLAINS. VERY WARM TEMPERATURES ARE LIKELY AS THE WESTERN RIDGE POKES IN OVER THE PLAINS FROM THE SOUTHWEST. HOWEVER...A SEQUENCE OF UPPER WAVES RUNNING AROUND IT WILL WEAKEN IT SOME AND KEEP THE WARMEST TEMPERATURES CONFINED TO THE SOUTHWEST U.S. AND SOUTHERN PLAINS. AT THIS TIME THEN...IT APPEARS UNLIKELY THAT THE CENTRAL PLAINS WILL EXPERIENCE THE RECORD-BREAKING HEAT THAT THE WESTERN U.S. HAS NOW. FOR SUNDAY THROUGH TUESDAY...DAYTIME HIGHS ARE EXPECTED TO RANGE FROM AROUND 90 IN SOUTHWEST NEBRASKA TO AROUND 80 IN NORTH CENTRAL NEBRASKA. WINDY CONDITIONS ARE EXPECTED SATURDAY AFTERNOON WITH 20 TO 25 GUSTY NORTHWEST WIND. GUSTY NORTH WIND IS POSSIBLE AGAIN MONDAY AFTERNOON. .LONG TERM...WEDNESDAY THROUGH FRIDAY. BIG QUESTION FOR THIS PERIOD WILL BE THE EVOLUTION OF THE UPPER TROUGH FORECAST TO DIG INTO THE WESTERN UNITED STATES. ECMWF HAS BEEN VERY CONSISTENT WITH ITS SOLUTION OF DIGGING A DEEP TROUGH INTO THE WESTERN CONUS...AND IN TURN VERY STRONG CYCLOGENESIS COMMENCES SOMEWHERE IN THE HIGH PLAINS OF COLORADO...WESTERN NEBRASKA OR WESTERN SOUTH DAKOTA. OPERATIONAL RUN OF THE GFS HAS BEEN TRENDING TOWARD THIS SOLUTION...WITH THE 06Z AND NOW THE 12Z SEEMING MORE IN AGREEMENT WITH ITS OWN ENSEMBLE AND THE ECMWF. THIS LEADS TO A LITTLE MORE CONFIDENCE THAT THUNDERSTORMS SEEM POSSIBLE BY THE MIDDLE AND LATER PARTS OF NEXT WEEK. HAVE MAINTAINED THE 20 AND 30 PERCENT POPS GOING FROM PREVIOUS FORECAST. STILL A LOT OF UNCERTAINTY WHERE BOUNDARIES ETC. WILL SET UP FOR THE FOCUS OF THIS CONVECTION. TEMPERATURES APPEAR QUITE WARM...ESPECIALLY ON WEDNESDAY AHEAD OF THE TROUGH. THURSDAY AND FRIDAY A BIT MORE UNCERTAINTY...SO HAVE OPTED TO COOL THINGS JUST A BIT FROM WEDNESDAY FOR THE EXPECTED CLOUD INCREASE AND WHERE LOW LEVEL BOUNDARIES SET UP. && .AVIATION... VFR CONDITIONS LOOK TO REMAIN IN PLACE ACROSS WESTERN AND NORTH CENTRAL NEBRASKA THROUGH THE OVERNIGHT AND MORNING HOURS ON SATURDAY. A SCATTERED-BROKEN DECK OF HIGH BASED CU/AC MAY PERSISTS NEAR 10KFT AGL THROUGH SUNSET...THEN QUICKLY DISSIPATED...WITH VSBYS REMAINING UNLIMITED. ISOLATED THUNDERSTORMS WILL BE POSSIBLE DOWNSTREAM OF THE BLACK HILLS INTO THE NORTHERN PANHANDLE. THIS WOULD CONTAIN SOME VERY GUSTY LOW LEVEL WINDS AND SHOULD BE AVOIDED BY SMALL AIRCRAFT. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SPRINGER/TAYLOR/13
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
315 AM PDT SAT MAY 17 2008 ...UPDATED AVIATION DISCUSSION... .SHORT TERM (TONIGHT-MON)...THREE MORE RECORD HI TEMPS WERE TIED OR BROKEN TODAY OVER THE DISTRICT (SANDBERG AT 85 DEGREES...WOODLAND HILLS AT 101 DEGREES AND OJAI AT 101 DEGREES.) THE HOTTEST OFFICIAL TEMP OVER THE REGION TODAY WAS 102 DEGREES AT BOTH VAN NUYS AND FILLMORE. QUIET WX CONTINUES THIS EVENING ACROSS THE DISTRICT WITH MOSTLY CLEAR SKIES IN ALL AREAS...WHICH WILL CONTINUE THRU THE NIGHT. TEMPS IN MANY AREAS WERE STILL INTO THE MID 70S TO MID 80S...AND SOME FOOTHILL AREAS MAY HAVE LOWS IN THE LOWER 70S TONIGHT. LATEST ACARS SOUNDING FROM LAX SHOWS 1200 FT TEMP AROUND 85 DEGREES...WITH A SURFACE BASED INVERSION. LOW CLOUDS...NO DOUBT WITH DENSE FOG...EXTENDED FROM THE OUTER COASTAL WATERS WESTWARD...BUT THERE HAS BEEN LITTLE EASTWARD MOVEMENT IN THE LOW CLOUD SHIELD OVER THE PAST HOUR OR TWO. IT APPEARS LOW CLOUDS AND DENSE FOG MAY HAVE A TOUGH TIME MAKING IT EVEN TO THE CENTRAL COAST LATE TONIGHT. HAVE UPDATED THE ZONES TO TAKE OUT ANY MENTION OF LOW CLOUDS AND DENSE FOG FOR THE VTU/L.A. COASTAL AREAS LATE TONIGHT AND SAT MORNING. STRONG UPPER HI CENTERED OVER NRN CA WILL MOVE SLOWLY SSW TO THE CENTRAL CA COAST FOR SAT...AND OFF THE SBA COUNTY COAST WHILE SLOWLY WEAKENING SUN THRU MON. A BROAD NE FLOW ALOFT WILL CONTINUE OVER THE FORECAST AREA THRU SUN...THEN BECOME WEAKER AND TURN NORTHERLY FOR MON. THE POSITION OF THE UPPER HI WILL NOT BE CONDUCIVE TO THE DEVELOPMENT OF LOWER LEVEL STRONG NE FLOW DURING THE PERIOD...SO GENERALLY WEAK NIGHT AND MORNING OFFSHORE FLOW CAN BE EXPECTED OVER THE REGION. HOWEVER...THE LATEST WRF IS FORECASTING STRONGER NORTHERLY FLOW OVER SLO/SBA COUNTIES AND THE MOUNTAINS OF VTU COUNTY SAT NIGHT INTO SUN MORNING. THE HEAT WILL CONTINUE THRU SUN WITH THE VALLEYS REACHING WELL INTO THE 90S TO LOW 100S...AND A FEW MORE RECORD HIGH TEMPS WILL BE POSSIBLE. THE SEABREEZE WILL DEVELOP BY LATE MORNING ALONG THE IMMEDIATE COAST TO KEEP THE BEACHES COOLER...MAINLY IN THE 70S TO LOWER 80S. A QUICKER RETURN TO ONSHORE FLOW ON MON ALONG WITH LOWER BOUNDARY LAYER TEMPS WILL RESULT IN TEMPS TURNING SEVERAL DEGREES COOLER...BUT THE WARMEST VALLEYS SHOULD STILL REACH INTO THE LOWER TO MID 90S. THE COOLING TREND WILL BE MUCH SLOWER TO RETURN TO THE MOUNTAINS AND ANTELOPE VALLEY... HOWEVER. PLEASE SEE THE LATEST SPECIAL WEATHER STATEMENT (LAXSPSLOX) FOR DETAILS ON THE EXTENDED PERIOD OF HOT WEATHER THRU THE WEEKEND OVER SOUTHWESTERN CALIFORNIA. ...FROM PREVIOUS DISCUSSION... .LONG TERM (TUE-FRI)...MODELS IN GENERAL AGREEMENT NEXT WEEK, THOUGH SPECIFICS REMAIN A QUESTION MARK. OVERALL COOLING TREND LOOKS GOOD, THOUGH TO WHAT DEGREE STILL REMAINS TO BE SEEN. ECMWF IS MUCH FARTHER WEST WITH THE NEXT TROF AND COOLER THAN THE GFS. HAVE TRENDED THE FORECAST SOMEWHERE IN THE MIDDLE FOR NOW. EITHER WAY, HEAT WAVE SHOULD BE OVER BY TUESDAY WITH TEMPS FALLING AT LEAST TO NEAR NORMALS BY MID WEEK. A POTENTIALLY WINDY PATTERN SETTING UP FOR THE END OF THE WEEK AS A STRONG NORTHWEST FLOW ALOFT AND STRONG ONSHORE SURFACE FLOW DEVELOPS. && .AVIATION...17/1015Z. HIGH CONFIDENCE FOR VFR CONDS THROUGH TONIGHT. VERY LOW CONFIDENCE FOR LOW CLOUDS TO AFFECT PORTIONS OF IMMEDIATE CENTRAL COAST WITH LIFR/IFR CIGS AND VSBYS BETWEEN 12-15Z. KLAX...HIGH CONFIDENCE CAVU THROUGH TONIGHT. KBUR...HIGH CONFIDENCE CAVU THROUGH TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && $$ PUBLIC...SIRARD/WOFFORD AVIATION...KAPLAN WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1000 PM PDT FRI MAY 16 2008 .SHORT TERM (TONIGHT-MON)...THREE MORE RECORD HI TEMPS WERE TIED OR BROKEN TODAY OVER THE DISTRICT (SANDBERG AT 85 DEGREES...WOODLAND HILLS AT 101 DEGREES AND OJAI AT 101 DEGREES.) THE HOTTEST OFFICIAL TEMP OVER THE REGION TODAY WAS 102 DEGREES AT BOTH VAN NUYS AND FILLMORE. QUIET WX CONTINUES THIS EVENING ACROSS THE DISTRICT WITH MOSTLY CLEAR SKIES IN ALL AREAS...WHICH WILL CONTINUE THRU THE NIGHT. TEMPS IN MANY AREAS WERE STILL INTO THE MID 70S TO MID 80S...AND SOME FOOTHILL AREAS MAY HAVE LOWS IN THE LOWER 70S TONIGHT. LATEST ACARS SOUNDING FROM LAX SHOWS 1200 FT TEMP AROUND 85 DEGREES...WITH A SURFACE BASED INVERSION. LOW CLOUDS...NO DOUBT WITH DENSE FOG...EXTENDED FROM THE OUTER COASTAL WATERS WESTWARD...BUT THERE HAS BEEN LITTLE EASTWARD MOVEMENT IN THE LOW CLOUD SHIELD OVER THE PAST HOUR OR TWO. IT APPEARS LOW CLOUDS AND DENSE FOG MAY HAVE A TOUGH TIME MAKING IT EVEN TO THE CENTRAL COAST LATE TONIGHT. HAVE UPDATED THE ZONES TO TAKE OUT ANY MENTION OF LOW CLOUDS AND DENSE FOG FOR THE VTU/L.A. COASTAL AREAS LATE TONIGHT AND SAT MORNING. STRONG UPPER HI CENTERED OVER NRN CA WILL MOVE SLOWLY SSW TO THE CENTRAL CA COAST FOR SAT...AND OFF THE SBA COUNTY COAST WHILE SLOWLY WEAKENING SUN THRU MON. A BROAD NE FLOW ALOFT WILL CONTINUE OVER THE FORECAST AREA THRU SUN...THEN BECOME WEAKER AND TURN NORTHERLY FOR MON. THE POSITION OF THE UPPER HI WILL NOT BE CONDUCIVE TO THE DEVELOPMENT OF LOWER LEVEL STRONG NE FLOW DURING THE PERIOD...SO GENERALLY WEAK NIGHT AND MORNING OFFSHORE FLOW CAN BE EXPECTED OVER THE REGION. HOWEVER...THE LATEST WRF IS FORECASTING STRONGER NORTHERLY FLOW OVER SLO/SBA COUNTIES AND THE MOUNTAINS OF VTU COUNTY SAT NIGHT INTO SUN MORNING. THE HEAT WILL CONTINUE THRU SUN WITH THE VALLEYS REACHING WELL INTO THE 90S TO LOW 100S...AND A FEW MORE RECORD HIGH TEMPS WILL BE POSSIBLE. THE SEABREEZE WILL DEVELOP BY LATE MORNING ALONG THE IMMEDIATE COAST TO KEEP THE BEACHES COOLER...MAINLY IN THE 70S TO LOWER 80S. A QUICKER RETURN TO ONSHORE FLOW ON MON ALONG WITH LOWER BOUNDARY LAYER TEMPS WILL RESULT IN TEMPS TURNING SEVERAL DEGREES COOLER...BUT THE WARMEST VALLEYS SHOULD STILL REACH INTO THE LOWER TO MID 90S. THE COOLING TREND WILL BE MUCH SLOWER TO RETURN TO THE MOUNTAINS AND ANTELOPE VALLEY... HOWEVER. PLEASE SEE THE LATEST SPECIAL WEATHER STATEMENT (LAXSPSLOX) FOR DETAILS ON THE EXTENDED PERIOD OF HOT WEATHER THRU THE WEEKEND OVER SOUTHWESTERN CALIFORNIA. ...FROM PREVIOUS DISCUSSION... .LONG TERM (TUE-FRI)...MODELS IN GENERAL AGREEMENT NEXT WEEK, THOUGH SPECIFICS REMAIN A QUESTION MARK. OVERALL COOLING TREND LOOKS GOOD, THOUGH TO WHAT DEGREE STILL REMAINS TO BE SEEN. ECMWF IS MUCH FARTHER WEST WITH THE NEXT TROF AND COOLER THAN THE GFS. HAVE TRENDED THE FORECAST SOMEWHERE IN THE MIDDLE FOR NOW. EITHER WAY, HEAT WAVE SHOULD BE OVER BY TUESDAY WITH TEMPS FALLING AT LEAST TO NEAR NORMALS BY MID WEEK. A POTENTIALLY WINDY PATTERN SETTING UP FOR THE END OF THE WEEK AS A STRONG NORTHWEST FLOW ALOFT AND STRONG ONSHORE SURFACE FLOW DEVELOPS. && .AVIATION...17/0500Z...HIGH CONFIDENCE IN CLEAR SKIES THROUGH SAT AT ALL AIRFIELDS...EXCEPT LOW CONFIDENCE IN A PERIOD OF IFR CIGS/VSBYS AT KSMX LATE TONIGHT AND EARLY SAT. NO WIND ISSUES EXPECTED. KLAX AND KBUR...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH SAT. && .LOX WATCHES/WARNINGS/ADVISORIES... SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && $$ PUBLIC...SIRARD/WOFFORD AVIATION...SIRARD WWW.WEATHER.GOV/LOSANGELES