Forecast Discussions mentioning ACARS, received at FSL on 01/13/00

DEEP LOW OVR SRN IL THIS EVE WITH WARM FRONT EXTENDING EWD ACRS SRN IND TO SW OH. WV LOOP SHOWING VORT MAX ASSOCD WITH THE SFC LOW WAS OVR NW IA AND MOVG ESE AT 45KTS ABT AS FCST BY 12Z/18Z ETA RUNS. SFC OBS INDICATING HVY SNOW JUST NORTH OF VORT MAX, BUT DRY AIR IN LOW LVLS LIMITING PRECIP IN WAA ZN SO FAR. KIWX 88D INDICATING LOW LVL MOISTURE WAS ADVECTING INTO THE AREA ATTM WHICH IS EXPECTED TO LEAD TO PRECIP DVLPMNT OVR MUCH OF CWA IN NEXT FEW HRS. NUMEROUS ACARS REPORTS HEADING EAST AND SOUTHEAST FM ORD THIS EVE SUPPORT FCST OF MAINLY SNOW ACRS MI AND SN/ZR MIX ACRS NRN IND. SHALLOWNESS OF LOW LVL MOISTURE ON SOUNDINGS TO SW ALONG WITH DRY COLD AIR ADVCTG IN FM THE NE AT SFC ALSO SUPPORTS FREEZING PRECIP FCST. THUS, WL KEEP WINTER WX ADVISORY UP FOR NRN IND OVRNGT. WL UPDATE ZNS FOR MINOR CHGS TO WORDING ARND 9PM.

.IWX...WINTER WEATHER ADVISORY TONIGHT INZ003>009-012-014-016>018 AND OHZ001-002-004-005-015-016

JT

.OVERVIEW...THE PATTERN ACROSS THE PACIFIC IS STABLE WITH STRONG HI AMPLITUDE RIDGING ALONG 175W AND TROUGHING ALONG 140W. IR SATELLITE IMAGERY AND OFFSHORE SHIP OBSERVATIONS INDICATE A GOOD DEAL OF COLD AIR FROM THE INTERIOR OF AK...THE BERING SEA...AND ERN SIBERIA DUMPING INTO THE E CENTRAL PACIFIC AND MAINTAINING THE PATTERN. ARCTIC AIR IS FIRMLY ESTABLISHED ACROSS NWRN CANADA AND AK...AND IS BEGINNING TO LOOK LIKE A THREAT TO THE PAC NW TOWARD THE END OF THE EXTENDED PERIOD.

.SHORT TERM... 1...TODAY THE PARENT SFC LOW NEAR 50N/140W CONTINUES TO ROTATE COLD AIR INSTABILITY SHOWERS FROM THE SW. THE AIR MASS IS COLD ENOUGH THAT HEAVIER SHOWERS BRIEFLY LOWER THE SNOW LEVEL FROM ITS FREE AIR STATE OF 500-1000 FT TO THE SURFACE. M2 LIFTED INDICES RESULTING IN ISOLATED THUNDERSTORMS BEING REPORTED NEAR BLAINE AND NEAR THE MOUTH OF THE COLUMBIA RIVER. COULD CONTINUE TO SEE INCH OR SO SNOW ACCUMULATIONS TODAY...BUT WITH LESS IMPACT THAN OVERNIGHT LAST NIGHT AS SOME FILTERED INSOLATION WARMS TEMPS INTO THE MID AND UPPER 30S. 2...TONIGHT...IR AND WATER VAPOR LOOPS SHOW THE DEVELOPMENT OF A BAROCLINIC LEAF ASSOCIATED WITH A 150KT JET STREAK NEAR 41N/136W AT 16Z. THE 12Z ETA/NGM SOLUTIONS ARE WELL INITIALIZED PER SATELLITE AND ACARS DATA...AND INDICATE THAT THIS LEAF WILL DEVELOP SOMEWHAT AS IT TRACKS NE TO THE MOUTH OF THE COLUMBIA RIVER EARLY THIS EVENING...THEN UP THE WA COAST OVERNIGHT. THE LOW LEVEL REFLECTION OF THIS FEATURE IS A NNEWD MOVING NEGATIVELY TILTED OPEN TROUGH WITH RATHER IMPRESSIVE 30KT SSWLY FLOW AT 850 MB OVERRUNNING THE OFFSHORE GRADIENTS AT THE SURFACE. ALTHOUGH TEMPERATURES ALOFT WARM A LITTLE WITH THE APPROACH OF THIS WAVE...EXPECT ANOTHER PERIOD OF MIXED PCPN OR SN WITH SOME AREAS KPAE SWD IN THE INTERIOR SEEING ANOTHER 1-3 INCHES...MAINLY AWAY FROM THE WATER. WILL MAINTAIN/EXPAND THE PREVIOUS SNOW ADVISORY FOR TONIGHTS THREAT. 3...THURSDAY...SHOWERS CONTINUE BUT WITH PASSAGE OF WAVE AND LOW LEVEL SLY FLOW AND A LITTLE MODIFICATION OF AMS...MAYBE LESS THREAT OF LOWLAND ACCUMULATIONS.

.EXTENDED...ANOTHER WAVE PASSES THU EVENING FOR MAYBE A REPEAT OF MIXED PCPN AND THREAT OF A LOWLAND SN ACCUMULATION. THEN UPPER FLOW BACKS FOR COOL/WET PERIOD...BUT PCPN IN FORM OF RA.

UIL +++ SEA 998 OLM 999 ALBRECHT

.KATX...VCP21/CSR21...OPERATIONAL .SEW...SCA COAST...PUGET SOUND/HOOD CANAL. SNOW ADVISORY THROUGH TONIGHT LOWLAND INTERIOR SNOHOMISH COUNTY SOUTH.

WEAK RIDGE OF HIGH PRESSURE AT THE SURFACE WILL CONTINUE OVER SOUTH CAROLINA THIS AFTERNOON. RUC MODEL TRIES TO INCREASE SOUTH TO SOUTHWEST WINDFLOW AND BRING ENOUGH WAA INTO THE STATE TO INCREASE TEMPERATURES INTO THE LOWER 70S. 0819Z ACARS SOUNDING FOR CAE ALSO GIVES THE LOWER 70S. HOWEVER...CURRENT WINDS ARE LIGHT AND VARIABLE AND MESOETA KEEPS WIND FLOW FAIRLY LIGHT ALTHOUGH MODEL SHIFTS WINDS INTO A SOUTHERLY DIRECTION. BELIEVE LIGHT AND VARIABLE WINDS WILL CONTINUE AND HIGHS WILL GENERALLY REMAIN BELOW THE 70 DEGREE MARK. SO WILL NOT CHANGE FORECAST HIGHS AND WILL KEEP LIGHT AND VARIABLE WINDS. .CAE...NONE

TTH



SATELLITE IMAGERY SHOWS LARGE COLD UPPER LEVEL LOW STILL OFF BRITISH COLUMBIA AND PACIFIC NORTHWEST COAST. VORT MAXS CONTINUING TO ROTATE AROUND THE LOW. NEXT ONE CURRENTLY OFF SOUTHERN OREGON COAST NEAR 41N/130W WILL ROTATE THROUGH WESTERN WASHINGTON THIS EVENING. FIRST LOOK AT NEW ETA HAS VORT MAX ALREADY AHEAD OF 18Z MODEL POSITION. WILL SPEED UP TIMING IN FORECAST PACKAGE AND INDICATE RAIN THIS AFTERNOON. ACARS SOUNDINGS OVER KSEA AND KPDX INDICATE 850 MB TEMPS AROUND -4C WITH SOUTHERLY WINDS AT THE LOWER LEVELS. CURRENT TEMPS ACROSS WESTERN WASHINGTON IN THE MID AND UPPER 30S WITH MOST DEW POINTS WELL ABOVE 32 DEGREES. PRECIPITATION IN THE FORM OF RAIN EXCEPT IN A COUPLE OF SMALL COOL POCKETS LEFT...SHELTON AND BELLINGHAM AND PORT ANGELES...WHERE PRECIP COULD BEGIN AS RAIN AND SNOW MIXED BUT NO ACCUMULATIONS EXPECTED. NEXT VORT MAX DUE TO MOVE THROUGH WESTERN WASHINGTON FRIDAY. FELTON

UIL 998 SEA 997 OLM 998

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

.SEW...SCA COAST AND ENTRANCES TO THE STRAIT.