Forecast Discussions mentioning ACARS, received at FSL on 02/19/01

THE NEXT RAINMAKER FOR THE AREA HAS DEVELOPED NICELY OFFSHORE AND IS PRODUCING STRONG RADAR RETURNS...FREQUENT LIGHTNING AND HAS BECOME NEGATIVELY TILTED. A 100 KNOT PLUS JET IS NOW ROUNDING THE BOTTOM OF THE TROUGH WITH EXCELLENT DIFFLUENCE EXPECTED OVER THE SAN FRANCISCO BAY AREA AND CENTRAL CALIFORNIA AT THE ARRIVAL OF THE RAIN...ABOUT 3 TO 4 AM AT THE COAST. PACJET P-3 AIRCRAFT DATA INSTRUMENTAL IN DETERMINING THE STRENGTH OF THIS FRONT WITH RADAR IMAGERY AND PILOT REPORTS INFLUENCING THE UPDATE OF THE PUBLIC FORECAST. WILL UPDATE THE FORECAST TO INCREASE POPS AND MOVE UP TIMING. ALSO HAVE ADDED THUNDERSTORMS FOR THE EARLY MORNING HOURS AS THE RAIN ENTERS THE CWA. PACJET P-3 AIRCRAFT RADAR INDICATES THUNDERSTORM TOPS NEAR 30000 FEET.

ANOTHER CONCERN ASSOCIATED WITH THE FRONT IS STRONG WIND. CURRENTLY WIND AHEAD OF THE FRONT IS SOUTHERLY AT 25 TO 35 KNOTS. A GALE WARNING HAS BEEN POSTED FOR THE COASTAL WATERS. AS FOR THE LAND PORTION...THE CURRENT FORECAST KEEPS THE WIND JUST BELOW WIND ADVISORY CRITERIA AND WILL STICK WITH THIS FOR NOW. THE SURFACE PRESSURE GRADIENTS FROM SAN FRANCISCO TO WINNEMUCCA...AND FROM SAN FRANCISCO TO ARCATA ARE FORECAST TO ONLY INCREASE TO 6 MB...NOT IMPRESSIVE FOR A WIND ADVISORY ISSUANCE. A FEW LOCATIONS...ESPECIALLY THE HIGHER TERRAIN...MAY EXPERIENCE WINDS OF 30 TO 40 KNOTS...BUT SHOULD BE SHORT-LIVED.

GOES WEST RSO HAS BEEN REQUESTED FROM 08Z TONIGHT THROUGH 02Z MONDAY EVENING MAINLY DUE TO REPORTS FROM THE PACJET P-3 AIRCRAFT PERSONNEL OF POSSIBLE SUPERCELLS IN THE APPROACHING FRONT. STS +++7 SFO +++6 SJC 8+86 MRY 9++6 LVK 7+86. EVANS

.SFO...TNGT...GALE WRNG...PT ARENA TO PIGEON PT. ...SCA...SAN FRANCISCO AND MONTEREY BAYS.



IR IMAGERY SHOWING WARMING CLOUD TOPS OVER SOUTHWESTERN OR/EXTREME NORTHERN CA AS A WEAK SHORTWAVE OVER THE REGION DISSIPATES THUS NIL WEATHER FOR THE TIME BEING...HOWEVER...THIS IS JUST THE CALM BEFORE THE STORM. IR IMAGERY ALSO SHOWING STRONG UPPER LOW IN THE VICINITY OF 39N/135W SLOWLY DRIFTING TO THE EAST-SOUTHEAST WITH A SPOKE OF ENERGY IN THE FORM OF AN INCREASINGLY NEGATIVELY TILTED TROUGH HEADING FOR THE CENTRAL CA COAST. PAC-JET P-3 AIRCRAFT WAS MEASURING 50 DBZ STRONG CELLS IN ASSOCIATION WITH JET MAXIMA TOWARDS THE BASE OF THIS TROUGH. UPPER LOW TO PUSH EASTWARD TONIGHT WITH ENERGY FROM THIS SYSTEM BEGINNING TO IMPACT THE FORECAST AREA MONDAY MORNING. WINTER STORM WARNING FOR FAVORED UPSLOPE AREAS OF WESTERN AND SOUTHERN SISKIYOU COUNTY STILL LOOKING ON TRACK FOR MONDAY AND MONDAY NIGHT. WIND ADVISORY FOR THE SHASTA VALLEY FOR LATE TONIGHT AND MONDAY ALSO LOOKING ON TRACK.

UPPER LOW TO DRIFT NORTHWARD OFFSHORE OF THE OREGON COAST MONDAY NIGHT AND TUESDAY WHILE THIS FEATURE WEAKENS. WILL BE BACK IN A WET PATTERN...IF ONLY FOR A LITTLE WHILE...BEFORE UPPER RIDGING AND DRYING TAKES OVER FOR A BRIEF PERIOD ON WEDNESDAY. WILL GET BACK TO THE WET STUFF THU-FRI AS ANOTHER SYSTEM IMPACTS THE AREA.

IN THE NEAR-TERM...JUST SOME MINOR TWEAKS TO FIRST PERIOD TEMPS/POPS AND FORECAST WORDING.

REYNOLDS

.MFR...WINTER STORM WARNING MONDAY AND MONDAY NIGHT ABOVE 3500 FEET CAZ080/082. WIND ADVISORY LATE TONIGHT AND MONDAY FOR THE SHASTA VALLEY IN CAZ081. OTH RW 043/057 043/056 044 192787 4BK RW 045/059 045/058 045 193977 RBG EW 041/058 040/052 040 191366 MFR EW 040/060 039/054 036 191466 LMT EW 031/044 027/045 028 191254 LKV EW 029/042 028/042 027 191133 MHS SO 033/039 032/041 031 193++8



A VIGOROUS FRONT IS JUST OFFSHORE AT 300 AM WITH NUMEROUS LIGHTNING STRIKES ALONG A BAND OF 55+ DBZ REFLECTIVITIES. WINDS HAVE PICKED UP TO GALE FORCE OVER THE COASTAL WATERS JUST AHEAD OF THE FRONT. PIGEON POINT ON THE SAN MATEO COUNTY COAST HAS REPORTED GUSTS AS HIGH AS 44 MPH. WINDS AT OTHER LAND STATIONS ARE STILL RELATIVELY LIGHT...BUT EXPECT THEM TO PICK UP JUST AHEAD OF THE FRONT. PRIOR TO RETURNING TO THE MONTEREY AIRPORT...THE PACJET P-3 AIRCRAFT REPORTED WINDS AT 1000 FEET ABOVE THE SURFACE AS HIGH AS 49 KNOTS FROM THE SSE. THE AIRCRAFT-MEASURED WINDS WERE STRONGER THAN WHAT THE MODELS WERE FORECASTING AND THESE REPORTS WERE INSTRUMENTAL IN THE DECISION TO ISSUE A WIND ADVISORY LATE LAST EVENING. WITH THE FRONT MOVING ALONG AT A FAST PACE OF ABOUT 30 KNOTS...EXPECT THE FRONT TO BE THROUGH THE ENTIRE AREA BY MID MORNING...OR EVEN SOONER...AND WINDS WILL DIMINISH AFTER FRONTAL PASSAGE. THE FRONT WILL WEAKEN QUICKLY AS IT MOVES INLAND FOR A COUPLE OF REASONS. FIRST...IT IS MOVING WELL OUT AHEAD OF THE UPPER LOW (CURRENTLY OUT NEAR 38N/132W) AND IS LOSING ITS UPPER LEVEL SUPPORT. SECOND...MOST INSTABILITY IS NEAR THE COAST AND AS THE FRONT MOVES INTO A MORE STABLE AIRMASS...CONVECTION WILL DIE OUT. 09Z OAK SOUNDING WAS QUITE UNSTABLE WITH A RELATIVELY ROBUST SHEAR PROFILE. THUS...EXPECT SCATTERED THUNDERSTORMS FOR MOST OF THE AREA AHEAD OF AND WITH THE FRONT. WE ARE CURRENTLY SEEING NUMEROUS LIGHTNING STRIKES HERE AT THE FORECAST OFFICE IN MONTEREY. BRIEF HEAVY RAIN WILL OCCUR WITH THE FRONT EARLY THIS MORNING AND THEN SCATTERED SHOWERS AND PERHAPS A FEW THUNDERSTORMS WILL CONTINUE THROUGH THE REMAINDER OF THE DAY. WHEREAS MOST THUNDERSTORM ACTIVITY IS CURRENTLY FROM SANTA CRUZ COUNTY SOUTH...THE MOST INSTABILITY THIS AFTERNOON WILL BE ACROSS THE NORTHERN PART OF THE DISTRICT WHERE THE COLDEST AIR ALOFT WILL BE.

THE HIGH PRESSURE RIDGE OVER THE PACIFIC NW WILL ACT TO BLOCK THE OFFSHORE LOW'S EASTWARD PROGRESSION. IN FACT...BOTH THE UPPER AND SURFACE LOWS ARE FORECAST TO REMAIN OFF THE NORTHERN CALIFORNIA COAST THROUGH MIDDAY TUESDAY...KEEPING US IN A MOIST ONSHORE FLOW PATTERN WITH WEAK IMPULSES MOVING THROUGH THE FLOW ALOFT...TRIGGERING NUMEROUS SHOWERS THROUGH TUESDAY AND POSSIBLY INTO TUESDAY NIGHT. ON WEDNESDAY...THE NEXT SYSTEM WILL BE DIGGING OFFSHORE...AND A SHORTWAVE RIDGE WILL DEVELOP OUT AHEAD OF IT OVER CENTRAL CA. THIS WILL GIVE US A SHORT DRY PERIOD BEFORE THE NEXT ROUND OF RAIN MOVES IN WEDNESDAY NIGHT AND THURSDAY. THE FOCUS OF HEAVIEST RAIN WITH THIS NEXT SYSTEM...ACCORDING TO THE AVN...WILL BE A LITTLE FURTHER SOUTH THAN THE CURRENT SYSTEM. THE MRF BRINGS YET ANOTHER SYSTEM INTO CENTRAL CALIFORNIA OVER THE COMING WEEKEND. STS ++7 SFO ++6 SJC +86 MRY ++6 LVK +86. DYKEMA

.SFO...TDA...GALE WRNG...PT ARENA TO PT PIEDRAS BLANCAS...OUT 20 NM. GALE WRNG...PT ARENA TO PIGEON PT...20 TO 60 NM OFFSHORE. GALE WRNG...MONTEREY BAY. SCA...PIGEON PT TO PT PIEDRAS BLANCAS 20-60 NM OFFSHORE AND SAN FRANCISCO BAY. TIL MID MORNING...WIND ADVISORY...ALL ZONES.