Forecast Discussions mentioning ACARS, received at FSL on 04/28/01

.OVERVIEW... A RATHER HIGH ZONAL INDEX IS DEVELOPING OVER THE PACIFIC WITH A MEAN TROUGH NEAR 140W. FAST MOVING SHORT WAVE SYSTEMS MOVING THROUGH THE MEAN OFFSHORE TROUGH PROMISE TO BRING COOL AND UNSETTLED CONDITIONS THROUGH TUE NIGHT. SATELLITE IMAGERY AND AIRCRAFT DATA SHOW VARIOUS SHORT WAVE FEATURES AND THE STRENGTH OF THE JET WELL INITIALIZED. MODELS SHOW GOOD CONSISTENCY AND CONTINUITY THROUGH TUE NIGHT. FROM WED ONWARD NEW MRF/ECMWF/CANADIAN/AVN/AVNX SHOW MORE TENDENCY FOR RIDGING OVER THE PAC NW...WITH THIS RIDGING PERSISTING THROUGH NEXT FRI.

.SHORT TERM... CMAN/BUOY OBS SHOW FRONT MOVING ONTO THE N COAST AT 19Z. EXPECT THIS TO MOVE THRU THE INTERIOR EARLY THIS EVENING BRINGING A PERIOD OF LIGHT RA. ONSHORE GRADIENTS INCREASE BEHIND THE FRONT AND THE AIR MASS DESTABILIZES AS COLD AIR ALOFT MOVES IN. AFTER SOME -SHRA TONIGHT AND EARLY SAT...ALL MODELS BRING A POCKET OF H5 TEMPERATURES M30C-M32C SAT AFTN WITH THE UPPER TROUGH PASSAGE. COLD AIR ALOFT...PVA...AND THE INTERACTION OF LOW LEVEL MOIST ONSHORE FLOW WITH THE TERRAIN WILL PRODUCE LOCAL TSTM ACTIVITY AS CAPES APPROACH 700J/KG AND LIS GO TO M2 OR SO PER MESOETA. BUT INSTABILITY WILL BE SHORT LIVED AS OVERRUNNING FROM THE NEXT RAPIDLY MOVING FRONT NOW 160W MAKES IT INTO WRN WA AFTER MIDNIGHT SAT NIGHT. WARM ADVECTION PRECIPITATION MOST OF THE DAY SUN WILL BE FOLLOWED BY FROPA DURING THE AFTN. GALES COULD ACCOMPANY THE WARM ADVECTION ALONG THE COAST SUN MORNING.

.EXTENDED... AFTER ONSHORE FLOW AND SCT SHOWERS MON-TUE...ALL EXTENDED MODELS NOW SHOW RIDGING WED-FRI TIME FRAME WITH ECMWF MOST EMPHATIC. BUT OPERATIONAL MRF SHOWS ENOUGH FLOW OVER THE RIDGE TO JUSTIFY MORE CLOUDS AND A CHANCE OF RAIN N PART.

UIL 898+ SEA 6769 OLM 676+ ALBRECHT .SEW...NONE. .KATX...VCP21/CSR21...OPERATIONAL



SHORT TERM DISCUSSION: LATEST SATELLITE IMAGERY SHOWS A WIDE SWATH OF MID AND HIGH LVL CLOUDS STRETCHING NWRD OVR WRN NM...WRN CO...ERN UT AND SWRN WY ASSOCIATED WITH A WK MID-LVL SHORTWV TROF. TROF AXIS AS OF 12Z/SAT NR CO/UT BORDER IS PROGD TO LIFT NEWRD ACRS STATE REACHING ERN CO BORDER SOMETIME THIS EVE. LATEST RADAR COMPOSITE ALSO INDICATING SVRL SHWRS OF LGT INTENSITY IN WRN CO DRFTG N-NEWRD. IN ERN CO SKIES ERLY THIS MRNG PRETTY MUCH CLOUD-FREE...BUT THIS WILL CHANGE AS RUC AND ETA MODELS SHOW MID AND UPR LVL RHS RISING QUICKLY AFT 18Z AS TROF AXIS PASSES OVR THE MTNS. WARMEST AIR OVR CWFA ERLY THIS MRNG WITH H7 TEMP OFF LATEST ACARS SOUNDINGS NR 9C. MODELS SHOW H7 TEMP LOWERING TO NR 7C BY 18Z TODAY IN RESPONSE TO INCREASING MID-LVL MOISTURE AND FM COOLING ALOFT. WHILE MID AND UPR LVLS MOISTEN TODAY...LOW LVLS PROGD TO REMAIN RELATIVELY DRY. THIS LOOKS REASONABLE SINCE LATEST SFC DEW PTS UPWIND IN SRN CO/WRN KS ONLY IN THE 30S AND LOWER 40S. AND YET MODELS SHOW 600-1200 J/KG SFC BASED CAPES ALONG A WIND CONVERGENCE BNDRY XTNDG NEWRD FM DOUGLAS CTY THRU CNTRL ARAPAHOE...CNTRL ADAMS...WELD AND MORGAN CTYS ARND MIDDAY TODAY. HIGHEST CAPE VALUES SHOW UP ALG BNDRY IN CNTRL WELD CTY INVOF GREELEY AS OF 18Z. ALG AND E OF THIS BNDRY IS WHERE WE/LL LKLY SEE BEST CHANCE FOR HIGH BASED CNVCTN TODAY. MODEL INVERTED-V SOUNDINGS SUGGEST STG DOWNBURST WINDS MAIN THREAT FM WITH THE POTENTIAL FOR ISOLD GUSTS TO 60 MPH. OTWS...CHANCE FOR MEASURABLE RAINFALL LOOKS LOW ON THE PLAINS AND ONLY SLIGHTLY BETTER IN MTN AREAS. BAKER

LONG TERM DISCUSSION: WEAK SHORTWAVE WILL DRIFT ACROSS THE PLAINS THIS EVENING WITH CLEARING IN ITS WAKE. THERE DOES NOT APPEAR TO BE ENOUGH FORCING TO OVERCOME THE DIURNAL DECREASE IN ENERGY...SO THINGS SHOULD QUIET DOWN BY MIDNIGHT. THE MODELS ARE TRENDING SLOWER WITH THE NEXT SHORTWAVE FOR LATE SUNDAY. IT STILL LOOKS LIKE WE WILL BE DRY AT THE LOW LEVELS...ETA SEEMS A BIT TOO MOIST. BEST THREAT OF SIGNIFICANT STORMS APPEARS TO BE TO OUR NORTH AND EAST. CAVEAT IS THAT WITH THE SLOWER MOTION WE SHOULD HAVE MORE SUN. I WILL TRIM THE POPS ALONG THE FRONT RANGE...AND HOLD ON TO SCATTERED EVENING POPS IN THE NE CORNER. IF THE SUN PANS OUT IT SHOULD BE A BIT WARMER ON SUN.

BEHIND THE SHORT WAVE THINGS REALLY DRY OUT...AND WARMING ALOFT SHOULD PRETTY WELL SHUT DOWN THE CONVECTION FOR MON/TUE. THERE IS A BETTER CONSENSUS ON THE MID WEEK SYSTEM WITH A LOW DEVELOPING OVER THE GREAT BASIN. DETAILS OF COURSE IMPORTANT AS WE COULD STILL BE RATHER MILD AND SHOWERY IF THE LOW WOBBLES WEST...OR RAINY/SNOWY IF IT PARKS OVER THE FOUR CORNERS. WEDNESDAY MAY BE TOO SOON FOR PRECIP...BUT THE THREAT DOES EXIST. I WILL LOWER TEMPERATURES TO MATCH MRF GUIDANCE...IF THE MRF MODEL ITSELF WERE CORRECT IT WOULD BE EVEN COLDER. GIMMESTAD

.DEN...NONE.



IT LOOKS LIKE AN ACTIVE WEATHER PERIOD ACROSS WRN WA THRU MON.

.TODAY...AN UPPER TROUGH WILL SWING E THROUGH WRN WA BRINGING SHOWERS. THE H5 VORT MAX AT THE BASE OF THE TROUGH IS ALREADY MOVING INTO NW OREGON AND THE S WA COAST THIS MORNING. COLD H5 TEMPERATURES AROUND M30C...FREEZING LEVELS AT OR BELOW 4KFT... AFTERNOON LIFTED INDICES NEAR M5...AFTN CAPES 700-900J/KG...AND ONSHORE GRADIENTS INTERACTING WITH THE TERRAIN WILL PROVIDE SCATTERED THUNDERSTORMS... SOME WHICH WILL CONTAIN HAIL. IT ALSO APPEARS THAT CONVECTIVE DOWNDRAFTS AND LEE SIDE TROUGHING E OF THE OLYMPICS WILL PROVIDE LOCALLY WINDY CONDITIONS. WILL BUMP WINDS...INCREASE TSTM COVERAGE...AND MENTION SOME HAIL IN THE AFTN PACKAGE.

.TONIGHT...A STRONG UPSTREAM FRONT NOW NEARING 140W IS BEING PUSHED VERY RAPIDLY EWD BY A 185KT 300 MB JET. ACARS DATA ALONG 50N IN THE E CENTRAL PAC CONFIRM THE STRENGTH OF THE JET SHOWN BY THE AVN. NEW 12Z GUIDANCE AND SATELLITE IMAGERY SHOW THE FRONT NOW REACHING THE COAST AROUND 6 AM...FASTER THAN CURRENT FORECASTS WOULD INDICATE. SO WILL SPEED UP ONSET OF STEADY WARM ADVECTION RAIN IN THE LOWLANDS AND WINDY CONDITIONS LATE TONIGHT. PREFRONTAL WARM ADVECTION ALSO APPEARS SUFFICIENT FOR THE ISSUANCE OF A SNOW ADVISORY FOR THE MOUNTAINS LATER TONIGHT.

.SUN...THE FRONT MOVES THRU DURING THE MORNING HOURS AND BEHIND IT WE FIND OURSELVES WITH IMPRESSIVE ONSHORE FLOW AND THE APPROACH OF A 150+ KT H3 JET. WILL NEED TO MAINTAIN SN ADVISORIES FOR THE MOUNTAINS...BUMP POST FRONTAL WINDS...AND INCLUDE A RISK OF TSTMS DURING THE AFTN HOURS.

.EXTENDED... ONSHORE FLOW GRADUALLY RELAXES TUE THEN RIDING AND DRYING COMMENCES WED. NO CHANGES.

UIL 7++ SEA 799 OLM +++ ALBRECHT

.SEW...GALE WARNING COAST...ENTRANCES TO THE STRAIT...ADMIRALTY INLET...NORTHERN INLAND WATERS...HOOD CANAL. .SMALL CRAFT ADVISORY PUGET SOUND. .SNOW ADVISORY TONIGHT AND SUNDAY FOR THE WEST SLOPES OF THE CASCADES AND OLYMPICS. GALE COAST/ENTRANCES TO STRAIT/ADMIRALTY INLET/HOOD CANAL

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