Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT" or "AMDAR" received at FSL on 03/16/03

SYNOPTIC SITUATION...A WET PACIFIC STORM SYSTEM IS PASSING THROUGH THE REGION AT THIS TIME. WHILE WESTERN PORTIONS OF SANTA BARBARA AND MOST OF SAN LUIS OBISPO COUNTIES ARE SEEING SOME LATE AFTERNOON SUN...A BAND OF MODERATE TO HEAVY SHOWERS CONTINUES TO POUND PORTIONS OF VENTURA AND LOS ANGELES COUNTIES THIS EVENING. SOME THUNDERSTORMS ARE EMBEDDED WITHIN THE RAIN BAND RESULTING IN LOCALLY HEAVY DOWNPOURS... DANGEROUS LIGHTNING AND GUSTY WINDS.

THE HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DIMINISH SLOWLY THIS EVENING WITH PARTIAL CLEARING IN SOME AREAS. SHOWERS ARE EXPECTED TO LINGER THROUGH THE EVENING...BUT END OVERNIGHT. ON SUNDAY...A WEAK DISTURBANCE APPPROACHES THE CENTRAL COAST. ALONG WITH RESIDUAL MOISTURE AND SOME HEATING DURING THE DAY...THERE IS THE POTENTIAL FOR MORE SHOWERS TOMORROW...BUT THESE SHOULD BE MAINLY OVER THE CENTRAL COAST AND IN THE MOUNTAINS.

SNOW LEVELS ARE EXPECTED TO REMAIN HIGH THROUGH THIS EVENING...BUT DROP SLOWLY OVERNIGHT. ACARS OUT OF LAX SHOWS THE FREEZING LEVEL AT AROUND 8000 FEET THIS AFTERNOON. HOWEVER...EARLIER THERE WAS A REPORT THAT IT WAS BEGINNING TO SNOW IN THE SAN GABRIEL MOUNTAINS AT AROUND 7000 FEET. SNOW LEVELS IN THE MOUNTAINS ARE EXPECTED TO DROP TONIGHT TO BETWEEN 5500 AND 6500 FEET BY TOMORROW MORNING. HEAVY ACCUMULATIONS OF SNOW ARE POSSIBLE ABOVE THE 7000 FOOT LEVEL.

WIND ADVISORIES WILL BE LIFTED EARLY THIS EVENING...BUT REMAIN IN EFFECT FOR THE MOUNTAINS OF VENTURA AND LOS ANGELES COUNTIES INCLUDING THE SANTA MONICA MOUNTAINS. GUSTY WINDS BELOW CRITERIA ARE ALSO OCCURRING AT THIS HOUR ON AVALON...OVER THE CARRIZO PLAIN...AND IN THE ANTELOPE VALLEY. WINDS ARE EXPECTED TO TURN MORE WEST TO NORTHWEST AS AND DIMINISH SLOWLY AS THE EVENING PROGRESSES.

EXTENDED...MEDIUM RANGE MODEL AGREEMENT IS LOOKING PRETTY GOOD FOR NEXT WEEK. LOOKS LIKE A MINOR TROUGH WILL MOVE THROUGH THE REGION EARLY MONDAY PRODUCING SOME LIGHT SHOWER ACTIVITY MONDAY MORNING... BUT THEN A RIDGE BUILDS IN LATER MONDAY AND PERSISTS THROUGH WEDNESDAY. SO LOOK FOR CONDITIONS TO IMPROVE ON MONDAY WITH FAIR WEATHER CONTINUING INTO WEDNESDAY. WHILE THE DETAILS DIFFER...BOTH THE ECMWF AND GFS ARE SUGGESTING AN INSIDE SLIDER FOR THURSDAY WITH ANOTHER RIDGE BUILDING IN FOR FRIDAY. THEREFORE...PERHAPS A SLIGHT CHANCE FOR SHOWERS ON THURSDAY...COOLER AND BREEZY...WITH FAIR SKIES EXPECTED AGAIN ON FRIDAY INTO SATURDAY.

LAX 9420. DANIELSON

.LOX...FLOOD ADVISORY (SEE LAXFLSLOX) FLOOD WATCH (SEE LAXFLSLOX) WIND ADVISORY (SEE LAXNPWLOX) SMALL CRAFT ADVISORY (SEE LAXCWFLOX) HIGH SURF ADVISORY (SEE LAXMWSLOX).



PUBLIC DISCUSSION FOR UPDATED ZONES

UPDATED ZONES COMING SHORTLY TO DEAL WITH LOW TEMPS TONIGHT. CLEAR SKIES AND LIGHT WINDS ALLOWING TEMPS TO DROP OFF ALREADY INTO THE UPPER 30S AT FEW LOCATIONS. EXPECT TEMPS TO CONTINUE TO DROP OFF AS FOG FORMS. VISIBILITIES CURRENTLY RUNNING MAINLY 2-4SM WITH A FEW LOCATIONS DROPPING UNDER 1/2SM BEFORE COMING BACK UP. SATL LOOP SHOWING PATCHES OF FOG/LOW STRATUS FORMING OVER NE IL THEN EAST TO NW OH. ALSO APPEARS FOG/STRATUS IS FORMING AND ADVECTING NORTH. AREAS OF DENSE FOG WILL CERTAINLY FORM OVERNIGHT...BUT UNCERTAIN OF EXTENT AND COVERAGE. WILL UPDATE DENSE FOG WORDING OVERNIGHT AND SUNDAY BUT HOLD OFF ON ADVISORY FOR NOW.

.CHI...NONE.

CMS

AVIATION DISCUSSION FOR 00Z TAFS:

MAIN CONCERN TONIGHT WILL BE POTL FOR REDEVELOPMENT OF FOG. CURRENT ACARS SOUNDINGS...AND FCST SOUNDINGS FROM ALL MODELS SHOW LOW LEVEL INVERSION RELATIVELY UNCHANGED IN STRENGTH OR DEPTH FROM PRESENT THRU TNGT. THIS MEANS THAT SFC WIND FLOW WILL REMAIN RATHER LIGHT...GENLY BLO 10 KTS...FROM SSE OVERNIGHT. CURRENT OBS INDICATE MOIST INVERSION LAYER AS JUST ABOUT ALL TERMINALS REPORT MINOR VIS RESTRICTIONS IN HAZE AS OF 23Z. WITH POOR VENTILATION EXPECTED OVERNIGHT AND CLR SKIES ABV...FOG SHOULD DVLP AGAIN...ESPECIALLY AFT 06Z WITH IFR CONDS MAINLY FROM 09Z-13 OR 14Z. FOG SHOULD BRK UP A BIT QUICKER ON SUN AS INVERSION IS FCST TO BECOME SHALLOWER WITH TIME AND LOW LEVEL WINDS INCRS FROM SSW. EXPECT CIG/VIS TO BE VFR AGN AFT ABT 16Z.



AVIATION DISCUSSION FOR 00Z TAFS:

MAIN CONCERN TONIGHT WILL BE POTL FOR REDEVELOPMENT OF FOG. CURRENT ACARS SOUNDINGS...AND FCST SOUNDINGS FROM ALL MODELS SHOW LOW LEVEL INVERSION RELATIVELY UNCHANGED IN STRENGTH OR DEPTH FROM PRESENT THRU TNGT. THIS MEANS THAT SFC WIND FLOW WILL REMAIN RATHER LIGHT...GENLY BLO 10 KTS...FROM SSE OVERNIGHT. CURRENT OBS INDICATE MOIST INVERSION LAYER AS JUST ABOUT ALL TERMINALS REPORT MINOR VIS RESTRICTIONS IN HAZE AS OF 23Z. WITH POOR VENTILATION EXPECTED OVERNIGHT AND CLR SKIES ABV...FOG SHOULD DVLP AGAIN...ESPECIALLY AFT 06Z WITH IFR CONDS MAINLY FROM 09Z-13 OR 14Z. FOG SHOULD BRK UP A BIT QUICKER ON SUN AS INVERSION IS FCST TO BECOME SHALLOWER WITH TIME AND LOW LEVEL WINDS INCRS FROM SSW. EXPECT CIG/VIS TO BE VFR AGN AFT ABT 16Z.

DISCUSSION FOR AFTERNOON GRIDS

SHORT TERM (TONIGHT-MONDAY) BURNING ISSUE NOW IS RECURRENCE OF FOG AND HOW MUCH IT WILL SUPPRESS MAX TEMPS ON SUNDAY. REDEVLOP OVERNIGHT AFTER AFTERNOON BURNOFF TO A MOSTLY LIGHT HAZE. WE STILL HAVE HIGHER DEWPOINTS ADVECTING OVER GROUND WHICH IS ONLY VERY SLOWLY WARMING ABOVE FREEZING DUE TO DEEP FROST PENETRATION FROM THE OPEN WINTER. ETA MODEL BOUNDARY LAYER 85% RH DID A DECENT JOB DEFINING THIS MORNING'S CLOUD SHIELD AND WOULD SUPPORT A RECURRENCE OVER ABOUT ALL OF THE AREA SATURDAY MORNING. A BIT MORE LOW LEVEL FLOW SHOULD KEEP THINGS STIRRED UP TO WHERE <1/4 MI VISIBILITIES ARE NOT SO WIDESPREAD AS THIS MORNING. BUT CERTAINLY WILL HAVE AREAS OF DENSE FOG DEVELOPING. AS TO ANY HEADLINES...AT PRESENT PLAN TO HOLD OFF WITH EVENING OR EARLY MORNING UPDATE THE BEST TIME TO GET A HANDLE ON PRECISE TIMING AND EXTENT OF HAZARDOUS VISIBILITIES.

AS TODAY...PERSISTENCE OF LOW CLOUDS LIKELY TO SUPRESS TEMPS SOMEWHAT BELOW WHAT WOULD OTHERWISE BE EXPECTED ON SUNDAY'S HIGHS. WILL GO WITH MOS CONSENSUS WHEREAS WITHOUT THE FOG PROBLEM WOULD EXPECTED FORECAST PROFILES TO PRODUCE LOTS OF READINGS NEAR OR ABOVE 70 AND WELL ABOVE THE FWC/MAV #S.

SOME LOW CLOUDS AND FOG LIKELY AGAIN SUNDAY NIGHT AS EVER HIGHER DEWPOINTS CONTINUE TO PUSH NORTHWARD. MONDAY'S MAX TEMPS LIKELY TO BE SIMILAR TO SUNDAYS EVEN AS INCREASED HIGH AND LOW CLOUDS COMPETE WITH CONTINUED LOW LEVEL WARM ADVECTION.

WILL MAINTAIN ARRIVAL TIME OF INTIAL PRECIPITATION THREAT LATE MONDAY NIGHT FOR NOW ALTHOUGH AT MINIMAL POPS ESPECIALLY EASTERN SECTIONS.

LONG TERM (TUES-SAT) AS PER PRELIMINARY HPC EXTENDED DISCUSSION RATHER GOOD AGREEMENT IN MEDIUM RANGE MODELS OUT TO THURSDAY OR SO WITH GFS ENSEMBLE CONSENSUS PREFERRED LATER ON. THIS RESULTS IN EXTENDED PERIOD OF MILD AND THREATENINGLY WET WEATHER UNTIL NEXT WEEKEND. BEST DYANMICS APPEAR IN TUESDAY-WEDNESDAY TIME FRAME TO SUPPORT THUNDERSTORM MENTION ALTHOUGH INCREASINGLY IT APPEARS ANY ORGANIZED SEVERE THREAT WILL REMAIN WELL TO OUR SOUTH WITH BETTER INSTABILITY. HAVE USED HPC TEMPS/POPS WITH LITTLE MODIFICATION SEEN TO BE NEEDED. A MORE SOUTHEAST FLOW WILL KEEP THE NORTH LAKESHORE COOLER

ALL THAT SAID...EXACT POSITION OF DEVELOPING CUT OFF LOW IN CENTRAL U.S. AND TIMING OF SHORT WAVES ROTATING AROUND IT TO PRODUCE SENSIBLE WEATHER IS FAR FROM CERTAIN.

.CHI...NONE

KAPLAN



LATEST WATER VAPOR IMAGERY TELLS THE STORY THIS AFTERNOON WITH STRONG UPPER LEVEL STORM SYSTEM BEGINNING TO DEVELOP ACROSS THE SIERRA NEVADA IN THE LEFT EXIT REGION OF AN INTENSE UPPER LEVEL PACIFIC JET CORE NOSING INTO SW CALIFORNIA. ACARS DATA FROM A FLIGHT FROM ONTARIO CA TO HONOLULU A FEW HOURS AGO ENCOUNTERED A 175KT HEAD WIND IN THE CORE OF THIS JET...ABOUT 20 KNOTS ABOVE ETA MODEL PROG VALID AT 18Z! NEEDLESS TO SAY...THE FORECAST HINGES CLOSELY TO THE EVOLUTION OF THIS JET STRUCTURE AND THE DEVELOPMENT OF A MAJOR STORM SYSTEM OVER THE CENTRAL US.

IN THE SHORT TERM...LARGE TEMPERATURE GRADIENT (PRESENTLY 63 AT UNO AND 76 AT JLN) HAS DEVELOPED ACROSS THE CWA THIS AFTERNOON WITH WEAK SYNOPTIC SCALE WARM AIR ADVECTION UNABLE TO COMPLETELY PENETRATE THE OZARKS. EASTERLY COMPONENT TO LOW LEVEL FLOW CONTINUES ACROSS MUCH OF THE CWA...AND THIS WILL PERSIST FOR TONIGHT. AS A RESULT...WILL ONCE AGAIN INCLUDE AREAS OF FOG WHICH CONTINUES TO BECOME MORE AND MORE SHALLOW EACH NIGHT.

WATER VAPOR IMAGERY AND RUC VORT FIELD CONTINUES TO ILLUSTRATE A WELL DEFINED N-S UPPER TROUGH THAT RUNS THE LENGTH OF THE EASTERN ROCKIES...AND CONTINUES A SLOW EASTWARD PROGRESSION. THIS FEATURE WILL SPILL HIGH CLOUDINESS ACROSS THE REGION ON SUNDAY...AND THEREFORE HAVE KEPT TEMPERATURES STATUS QUO. MID LEVEL HEIGHT WEAKNESS ASSOCIATED WITH THIS SYSTEM DRAWS SOME CONCERN AS STEEP MID LEVEL LAPSE RATES MAY SUPPORT WIDELY SCATTERED AFTN/EVENING STORMS ACROSS FAR WRN MO/SE KS. LACK OF LOW LEVEL MOISTURE ADVECTION IS THE LARGE NEGATIVE FACTOR WITH STUBBORN UPPER LEVEL LOW OVER THE SOUTHEAST US PREVENTING GULF MOISTURE RETURN. DESPITE ALL THIS...SUFFICIENT SUNSHINE SHOULD ERODE CAP BY MID AFTERNOON AND SUPPORT AT LEAST ISOLATED ACTIVITY WITH MAIN THREAT BEING GUSTY WINDS WITH DRY SUBCLOUD LAYER.

ON MONDAY...RAPID LEE CYCLOGENESIS WILL OCCUR ACROSS THE HIGH PLAINS AS INCREASINGLY NEGATIVE TILT UPPER TROUGH INTERSECTS LEFT EXIT REGION OF UPPER JET. THIS WILL FINALLY ALLOW A STRONG INFLUX OF GULF MOISTURE AS LOW LEVEL JET STRENGTHENS AHEAD OF A SHARPENING DRY LINE. AT THIS POINT...I FEEL RATHER CONFIDENT THAT STORMS WILL DEVELOP ALONG THE DRY LINE ACROSS CENTRAL KS AND OK DURING THE MID/LATE AFTERNOON MONDAY...AND ORGANIZE INTO A CURVILINEAR COMPLEX AS THEY APPROACH THE OZARKS DURING THE NIGHTTIME HOURS. STRONG VERTICAL SHEAR ENHANCED BY 40 KNOT LOW LEVEL JET AND APPROACHING UPPER JET STREAK SUGGESTS THAT SEVERE STORMS ARE LIKELY.

EXPECT SOME CLEARING TO TAKE PLACE TUESDAY IN WAKE OF CONVECTION MONDAY NIGHT/EARLY TUES MORNING AS SYSTEM TO THE WEST GETS RE-ENERGIZED BY A SECOND SHORTWAVE THAT WILL ROTATE UNDERNEATH THE BASE OF LONGWAVE TROUGH STILL OVER THE WESTERN HIGH PLAINS. THIS WILL INDUCE SECONDARY CYCLOGENESIS ACROSS THE PLAINS...FORCING ADDITIONAL MOISTURE NORTH INTO THE REGION. VERTICAL SHEAR PROFILES AGAIN BECOME INCREASINGLY FAVORABLE FOR SEVERE THUNDERSTORM DEVELOPMENT TUESDAY AFTERNOON AND EVENING...AND NOW WITH THE ADDTIONAL BENEFIT OF A BITTERLY COLD -24C 500MB LOW. BACKED LOW LEVEL FLOW AHEAD OF OCCLUDING SURFACE FRONTAL ZONE COULD PLAY A SIGNIFICANT ROLE IN THE EVOLUTION OF CONVECTIVE MODE. WILL ALSO HAVE TO KEEP IN MIND THREAT FOR HEAVY RAINFALL WITH TWO POTENTIAL ROUNDS OF SEVERE CONVECTION TAPPING INTO INCREASING DEEP LAYER MOISTURE.

EVEN AFTER OCCLUDED FRONTAL PASSAGE TUESDAY NIGHT...THE FORECAST DOES NOT GET ANY EASIER AS COLD CORE UPPER LOW REMAINS ENTRENCHED OVER THE REGION THROUGH LATE WEEK. WILL OPT FOR A DRY DAY WEDNESDAY WITH EXTENSIVE STRATO-CUMULUS...BUT WILL KEEP A CHANCE FOR INSTABILITY SHOWERS DURING THE DAYTIME THURSDAY/FRIDAY AS CUTOFF COLD CORE LOW MIGRATES SLOWLY THROUGH THE AREA. WOULD NOT BE SURPRISED TO EVEN SEE SOME HAIL OR EVEN COLD AIR FUNNELS SOMEWHERE ACROSS THE REGION GIVEN THE MAGNITUDE OF COLD AIR ALOFT AND STRONG CYCLONIC SHEAR. MEDIUM RANGE TEMPS LOOK OK.

A VERY INTERESTING AND DIFFICULT FORECAST INDEED.

.SGF... MO...NONE. KS...NONE.

BOOKBINDER



.SYNOPSIS...A COOL...MOIST...AND UNSTABLE AIR MASS WILL GIVE SHOWERS AND A CHANCE OF AFTERNOON THUNDERSTORMS TO THE AREA THROUGH SUNDAY. A SERIES OF SPLITTING AND DIFFICULT TO TIME FRONTAL SYSTEMS WILL MOVE THROUGH THE AREA MONDAY THROUGH NEXT WEEKEND. WHILE UNSETTLED WEATHER WILL DOMINATE...SOME CLEARING IS POSSIBLE AT TIMES IN THE INTERIOR BETWEEN SYSTEMS.

.DISCUSSION...THE DEEP LOW HAS NOW MOVED TO NW OF THE CHARLOTTES AND THIS MORNINGS FRONT IS WELL EAST OF THE AREA. A COOL/UNSTBL AIR MASS IS NOW IN PLACE GIVING TYPICAL SHOWER ACTIVITY AND EVEN A FEW TSTMS. AS USUALLY OCCURS IN THE SPRING...AREAS TO THE NE OF THE OLYMPICS AND VRISL ARE GETTING SOME RAIN SHADOWING. HIGH SWELLS THAT DEVELOPED IN THE BENT BACK OCCLUSION S OF THE DEPARTING LOW ARE DECAYING ONTO THE COAST NEAR 25 FT THIS AFTN. THESE SHOULD SLOWLY RELAX TONIGHT BUT WILL NEED TO MAINTAIN THE HIGH SURF ADVISORY THERE TONIGHT.

CONVECTIVE TEMPS THIS AFTN ARE 53-55F AND AIRCRAFT SOUNDINGS OUT OF SEATAC AIRPORT SHOW 500 MB TEMPS AROUND -28C. SURFACE-BASED LIFTED INDICES ARE BETWEEN 0 AND -3 WHILE CAPES PER THE MESOETA ARE AROUND 400J/KG. THIS SUGGESTS THE NEED TO KEEP A CHANCE OF THUNDER IN THE FORECAST THRU THE EARLY EVENING HOURS. A FEW STROKES HAVE BEEN OBSERVED ON THE N COAST TODAY. LITTLE CHANGE IN THE AIR MASS THROUGH SUNDAY SUGGEST THAT A CHANCE FOR A TSTM SUN AFTN SHOULD REMAIN.

THE STRONG MEAN LONG WAVE TROUGH ALONG 150W IS EXPECTED TO CONTINUE THROUGH THE WEEK. WHILE THE LARGE SCALE PATTERN IS HANDLED WELL BY THE MODELS...RUN-TO-RUN CONSISTENCY WITH THE TIMING AND STRENGTH OF INDIVIDUAL SHORT WAVE TROUGHS IS NOT REAL HIGH. HOWEVER...THE GLOBAL MODELS HAVE BEEN TRENDING TOWARD A SOLUTION THAT KEEPS A GOOD DEAL OF ENERGY IN THE JET TO OUR S WITH SPLITTING SYSTEMS MOVING INTO OUR AREA. ONE SUCH SYSTEM SEEMS TO COME IN MON NIGHT/TUE...WITH STRONGER BUT MORE NEG TILT SYSTEMS MOVING THRU LATE WED AND AGAIN LATE FRI. NOT A LOT OF CONFIDENCE IN THE EXACT TIMING...BUT IT SEEMS THAT THERE IS A CHANCE THAT THERE COULD BE A COUPLE OF DRY AND MILD DAYS IN THE INTR IN THE OFFSHORE FLOW AHEAD OF THESE SYSTEMS...ESPECIALLY WED AND FRI. FOR NOW WILL MAINTAIN AT LEAST A CHANCE OF RAIN IN THE INTR DURING THESE PERIODS...WITH TEMPS NEAR OR JUST A BIT ABOVE CLIMO. BUT IF LATER SOLUTIONS KEEP LOCKING IN ON THE TIMING OF FEATURES...LATER FORECAST SHIFTS MAY BE ABLE TO KEY INTO POSSIBLE DRY DAYS AND 60+ MAX TEMPS IN THE INTR WED AND FRI.

UIL 7867 OLM 7667 SEA 6666

.KSEW...HIGH SURF ADVISORY COAST. .SMALL CRAFT ADVISORY ALL WATERS EXCEPT ADMIRALTY INLET.

.KATX...VCP21/CSR21...OPERATIONAL. $$



.SYNOPSIS...A DEEP LOW PRESSURE SYSTEM OFF CENTRAL VANCOUVER ISLAND WILL MOVE NORTH TOWARD THE QUEEN CHARLOTTE ISLANDS TODAY. GUSTY SOUTH WINDS ALONG THE COAST WILL DIMINISH TODAY AS THE LOW MOVES AWAY. AN UNSTABLE AIR MASS IN THE WAKE OF THIS LOW WILL GIVE SHOWERS AND A CHANCE OF THUNDERSTORMS. A SERIES OF SPLITTING FRONTS WILL MOVE THROUGH THE AREA TONIGHT THROUGH LATE NEXT WEEK BRINGING UNSETTLED WEATHER.

.DISCUSSION...SATELLITE IMAGERY SHOWS DEEP 960 MB LOW MOVING N TOWARD THE NRN TIP OF VANCOUVER ISLANDS. THE ASSOCIATED BENT BACK OCCLUSION IS NICKING THE N COAST WITH HIGH END MARINE GALES IN THE COASTAL WATERS...POSSIBLE STORM FORCE WINDS A LITTLE OFF THE COAST...AND 20- 24 FT SWELL BASHING THE COASTAL BEACHES. CURRENT WARNINGS AND ADVISORIES LOOK GOOD.

THE COLD FRONT HAS MOVED E OF THE AREA ALREADY LEAVING WRN WA IN A COOL AND UNSTABLE AMS. ACARS SOUNDINGS SHOW 500 MB TEMPERATURES NOW AT -24C AND FCST MODELS SHOW THEM REACHING -28 TO -29C THIS AFTN AS THE COLD AIR NOW IN THE OFFSHORE WATERS SHIFTS NE OVER THE AREA. THAT GIVES CONVECTIVE TEMPS 53-55F THIS AFTN WITH CAPES NEAR 500J/KG. SOME CLEARING AS SHOWN ON EARLY MORNING VISIBLE IMAGERY SHOWS THAT CONVECTIVE TEMPS WILL LIKELY TO BE REACHED BY NOON. BOTTOM LINE IS THAT I WILL LEAVE THE CHANCE OF THUNDERSTORMS IN THE FORECAST FOR THIS AFTERNOON.

CONVECTIVE TEMPS ARE ACTUALLY A LITTLE LOWER AND CAPES A BIT HIGHER ON SUN AS MORE COLD AIR ALOFT MOVES OVER THE AREA TO THE N OF THE STG JET PLOWING INLAND TO THE S. WHILE HIGH TEMPS WILL BE A DEG OR TWO LOWER WITH A COOLER START TONIGHT...STILL NEED TO HAVE A CHANCE OF THUNDERSTORMS IN FOR SUN AFTN.

BEYOND SUNDAY THE MODELS ARE HAVING RUN-TO-RUN CONTINUITY PROBLEMS IN THIS INCREASINGLY SPLIT PATTERN...PARTICULARLY WITH THE TIMING OF INDIVIDUAL TROUGHS OR WEAK FRONTAL SYSTEMS ROTATING AROUND THE MEAN UPPER LEVEL TROUGH AT 150W. FOR NOW WILL CONTINUE WITH THE BROAD BRUSH FORECAST.

UIL 988 OLM 986 SEA 886

.KSEW...HIGH SURF ADVISORY COAST. .STORM WARNING COAST. .GALE WARNING REMAINDER OF THE MARINE AREAS EXCEPT SMALL CRAFT ADVISORY PUGET SOUND AND HOOD CANAL AND CENTRAL STRAIT. .A FLOOD WARNING IS IN EFFECT FOR THE SKOKOMISH RIVER.

.KATX...VCP21/CSR21...OPERATIONAL. $$



PRECIPITATION CHANCES THROUGH MID WEEK CONTINUES TO THE BE PRIMARY FORECAST CHALLENGE.

ANALYSIS OF 00Z DATA SHOWED MAIN JET IN THE CONUS VICINITY SCREAMING SOUTHEAST INTO BAJA WITH 170KT AIRREP WET OF SAN FRANCISCO. THERE WERE A FEW 70K CORES MOVING NORTHEAST OVER THE REMAINDER OF THE CONUS WITH ONE FROM WESTERN KANSAS INTO CENTRAL NEBRASKA VIA ACARS. SHORTWAVE ENERGY MAKING ITS WAY THROUGH THE PLAINS WITH LOW SPINNING THROUGH SOUTH DAKOTA AND ANOTHER SHOT THROUGH NORTHERN KANSAS. ANOTHER SPOKE OF ENERGY FROM THE WESTERN COAST TROF WAS WORKING ITS WAY NORTH THROUGH THE GREAT BASIN. 850MB LEVEL HAS MOISTENED CONSIDERABLY SINCE 24 HRS PRIOR WITH 3C DEWPOINT ON KTOP SOUNDING. 08Z SURFACE MAP SHOWED LOW FROM DAKOTA UPPER WAVE ALONG THE SOUTHERN SD/MN BORDER BUT 60F DEWPOINTS STILL IN SOUTH TEXAS.

RADAR LOOP SHOWING THUNDERSTORM BAND MOVING SLOWLY NORTHEAST ON NOSE OF 850MB JET PER PROFILER DATA AS THE UPPER WAVE MAKES ITS WAY EAST. THIS BATCH SHOULD BE EXITING THIS MORNING BUT THE SOUTHERN END OF THE WAVE MAY LINGER OVER THE EASTERN ZONES ENOUGH TO BRING A FEW AFTERNOON STORMS. WILL LIMIT POPS TO THIS AREA WHICH JIVES WELL WITH SURROUNDING OFFICES. WESTERN ZONES SHOULD SEE DECENT SUNSHINE AND WILL KEEP THEM THE WARMEST. RECORD TEMPS APPEAR THREATENED AGAIN TODAY WITH STANDING MARKS OF 79 AT TOP AND 80 AT CNK.

MODELS SHOWING NEXT SPOKE OF ENERGY TO SWING INTO THE REGION LATE TONIGHT AND INTO MONDAY AND ANOTHER LATE TUESDAY AFTERNOON WHICH SHOULD BRING BETTER OPPORTUNITIES FOR WIDESPREAD RAINFALL. MODEL SOLUTIONS ARE TRENDING A LITTLE SLOWER AND FARTHER SOUTH WITH THE UPPER LOW WHICH APPEARS REASONABLE AND THE SEVERE WEATHER THREAT HAS DIMINISHED SOMEWHAT THOUGH ENOUGH MOISTURE AND INSTABILITY WILL BE PRESENT FOR SOME HAILERS. TROWAL POSITION WHICH WAS OVER NORTHERN NEBRASKA WITH YESTERDAYS RUNS HAS SLIPPED TO THE KS/NE BORDER WHICH MATCHES QPF FORECASTS WELL. SHOULD STILL BE ENOUGH SUN MONDAY TO PUSH HIGHS AROUND 70 BUT EXPECT MORE CLOUDS AND A MORE EASTERLY FLOW TO KEEP HIGHS IN THE 55-65 RANGE TUESDAY.

WITH UNCERTAINTY HIGH WITH THE TRACK AND SPEED OF THE UPPER LOW HAVE LEFT THE LATER PERIOD UNCHANGED.

.TOP...NONE.

$$

65



AVIATION DISCUSSION FOR 12Z ISSUANCE...

SLUGGISH AIRMASS WITH INCREASED DEW PTS AND COLD GROUND HAS ALLOWED ANOTHER NIGHT OF DENSE FOG IN SOME SPOTS. WHERE SFC TEMPS HAVE STAYED UP IN THE UPPER 30S TO NEAR 40 THE VSBYS HAVE HELD IN THE 2-3 MI RANGE. THIS IS TRUE FOR ORD AND MDW. ELSEWHERE TEMPS DOWN IN THE LOW 30S COINCIDE WITH VSBYS BELOW 1/4 MI AND CIGS BELOW 300 FT. ACARS PROFILE FROM ORD SHOWS THE INVERSION PRETTY SOLID TO 2000FT ALTHOUGH SW WINDS INCREASE THROUGH THIS LYR. EXPECT SIMILAR DISSIPATION OF FOG TODAY AS PER YESTERDAY WITH IMPROVING CONDS THROUGH MID MORNING. LOCAL SPOTS MAY STAY IFR UNTIL NOON BUT IF WINDS CAN MIX DOWN THE CLEARING TREND SHOULD BE STEADY ONCE STARTED. PATCHES OF HIGH CLOUDS ABOVE CONTINUING AND WE MAY SEE ANOTHER SPELL OF RADIATION FOG SUN NIGHT-MON MRNG. IF MORE CLOUDS WORK INTO THE REGION LATER TODAY AND TONIGHT AS THE VORTEX NEAR FSD DRIFTS EAST THE FOG MAY NOT BE AS DENSE TONIGHT. KL

PUBLIC DISCUSSION FOR 400 AM ZONES

DENSE FOG AGAIN A BIG CONCERN TODAY. WHERE WILL IT BE THICKEST AND WHERE WILL IT BREAK UP FIRST AND LAST IS ALWAYS A GUESS. SO MAX TEMPS AGAIN ARE IN JEOPARDY. FOG NOT ALL THAT DENSE IN NWRN INDIANA OR SOUTH OF KANKAKEE RIVER THIS TIME...BUT THE NIGHT IS STILL YOUNG. MAY NEED TO EXPAND AREA OF DENSE FOG BEFORE ZONE ISSUANCE. ASSUMING A CLEARING BY NOONTIME...MAY NEED TO CURTAIL HIGH TEMPS A SHAVE OR TWO AT LEAST IN AREAS WHERE FOG IS DENSE NOW. ANY UPDATES BEFORE DAWN TO ADD DENSE FOG ADVISORY COUNTIES WILL RESULT IN CURBED MAXES AS WELL.

AFTER FOG LIFTS...SHUD BE ANOTHER DECENT DAY WITH SOME CI DEBRIS FROM SRN PLAINS SPREADING THRU THE AREA...ESPECIALLY WRN PORTION OF CWA IN N CENTRAL IL. PARTLY CLOUDY MAY BE A BIT TOO PESSIMISTIC. PERHAPS MOSTLY SUNNY IN THE AFTN. ANOTHER CLEAR EVENING WITH FOG DEVELOPING YET AGAIN WITH QUESTIONS OF WHERE AND HOW MUCH AND FOR HOW LONG.

AFTER THAT...ITS THE SAME SCENARIO WITH ONTARIO LOW MOVING EAST INTO QUEBEC TDA TRAILING COLD FRONT DOWN THRU LAKE SUPERIOR...THEN DOWN LAKE MICHIGAN ON LT TNGT AND MONDAY...DISSIPATING ALONG WI BORDER MONDAY EVENING. LARGE HIGH PRESSURE OVER HUDSON BAY RIDING SOUTH BEHIND THIS FRONT OVER THE LAKES AND INTO THE MIDWEST. THIS TURNS SLOW MORE EASTERLY OFF LAKE MICHIGAN FOR CHI AREA...PROMOTING COOLER TEMPS THAN ELSEWHERE. THIS HAPPENING WHILE LO IN LEE OF CENTRAL ROCKIES DEEPENS AND DIVES TO TX PANHANDLE LT MON NGT AND TUESDAY. MODELS REFLECTING A WAVE SWINGING NWD AROUND THE DEEP VORTEX VERY LT MONDAY NIGHT AND TUESDAY ALTHO OMEGA QUITE WEAK. CHC OF RAIN MAY BE WORTH KEEPING MON NGT ALTHO TSTMS ADDED FOR TUESDAY SOMEWHAT SHAKY. HOWEVER WITH STRONG LOW LVL JST FEEDING MORE MOISTURE INTO MIDWEST AND STRONG OMEGA FIELD SURGING NWD INTO CENTRAL IL LT TUESDAY...IS NOT WORTH REMOVING RISK.

BEST RISK STILL LOOKS LIKE WEDNESDAY AS STRONG WARM FNT SWINGS NEWD FROM VORTEX (WHICH MOVES INTO KANSAS BY THAT TIME). VERY STRONG SWLY LOW LVL JET PUSHING FNT THRU AREA BY WED AFTN...THEN DRYING WED NGT BEFORE WRAPAROUND DEVELOP THURSDAY.

.CHI...NONE

RLB



.SYNOPSIS...A COOL...MOIST...AND UNSTABLE AIR MASS WILL PROMOTE SHOWERS AND THE THREAT OF THUNDERSTORMS THROUGH MONDAY. A SERIES OF INCOMING PACIFIC WEATHER SYSTEMS WILL MAINTAIN A GENERALLY WET WEATHER PATTERN WITH SEASONABLE TEMPERATURES FOR THE REST OF THE WEEK.

.DISCUSSION...THE DEEP/MATURE LOW IN THE GULF OF ALASKA WILL CONTINUE TO SHOOT UPPER LEVEL IMPULSES THROUGH OUR AREA EVERY 12 HOURS OR SO THRU MON AFTN...LOWERING MID TROP TEMPS A COUPLE OF DEG C AS THEY PASS. 500 MB TEMPERATURES ARE AROUND -29C NOW PER ACARS SOUNDINGS AND ARE EXPECTED TO REACH -31C WITH PASSING SHORTWAVES. SO WITH DAYTIME HEATING ALLOWING MAX TEMPS IN THE MID 50S THE CONVECTIVE TEMPS 50-52F WILL BE EASILY REACHED...LIFTED INDICES WILL GO TO -1 TO -4 AND CAPES WILL APPROACH 400 J/KG. FORCING IS WEAK...SO EXPECT ONLY ISOLD AIR MASS ONE-STROKE WONDER TSTMS THRU MON EVENING PER PREVIOUS FCST.

THE 12Z MESOETA IS A LITTLE WEAKER WITH THE MORE POTENT SHORT WAVE TROUGH AND ASSOCIATED FRONTAL SYS THAT DRAGS THRU TUE THAN THE PREVIOUS SOLUTION. THE GFS CONTINUES TO BRING A MORE CONSOLIDATED SYSTEM THRU TUE AFTN. THE MIDNIGHT FORECASTER BROUGHT POPS DOWN A BIT WITH TUESDAYS SYSTEM FROM PREVIOUS DAYS THINKING...WHICH LOOKS GOOD.

A STRONGER BUT STRETCHING SYSTEM APPROACHES THE COAST WED AND MOVES INLAND LATE WED INTO THU. OFFSHORE FLOW AHEAD OF THIS SYS ON WED COULD GIVE QUITE MILD CONDITIONS TO THE INTR IF THE FRONT STALLS ON THE COAST. WILL AWAIT NEW GFS GUIDANCE BEFORE MAKING ANY CHANGES.

CURRENT ZONES LOOK GOOD...NO UPDATES PLANNED.

UIL 868 OLM 767 SEA 667 ALBRECHT

.KSEW...SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT.

.KATX...VCP21/CSR21...OPERATIONAL. $$