Forecast Discussions mentioning ACARS, received at FSL on 02/04/01

SYNOPSIS...HIGH PRESSURE STACKED INTO THE UPPER LEVELS OF THE ATMOSPHERE WILL PROVIDE THE REGION WITH DRY AND WARM WEATHER THROUGH EARLY NEXT WEEK. CONDITIONS WILL TURN MUCH COOLER AND MORE UNSETTLED DURING THE SECOND HALF OF THE WEEK AS A COUPLE OF WINTER STORMS MOVE THROUGH THE SOUTHERN ROCKIES.

DISCUSSION...SHORT TERM FORECAST LOOKING VERY GOOD. CWA GETTING CLIPPED BY HIGH CLOUDS AS FAST-MOVING SHORT WAVE DIVES INTO THE MS VALLEY. WITH WEAKLY CLOSED UPPER HIGH DRIFTING E TOWARD AZ, THOSE CLOUDS WILL BE GONE ON SUN. AGREE WITH DAY SHIFT THAT IF WE MIX ON MON, WE COULD CAUSE THREATEN A FEW RECORD HIGHS. WE'LL HAVE TO SEE BECAUSE MIXING TODAY WASN'T ALL THAT GOOD, AND WITH THE UPPER HIGH OVERHEAD SUN/MON, IT PROBABLY WON'T GET ANY BETTER UNTIL THE 700-500MB LAYER STARTS TO COOL A BIT. NO UPDATES.

STILL SCRATCHING MY HEAD ABOUT WHY MODELS ARE HAVING SUCH A HARD TIME WITH INITIALIZING UPPER JET SPEEDS. OVER 10 UPPER AIR SITES IN JAPAN/KOREA/CHINA HAD 250MB WINDS OF 170-190KTS AT 00Z THIS EVENING. THERE'S ALSO A 170KT JET TOPPING THE W COAST RIDGE PICKED UP BY ACARS DATA. THE ONLY MODEL THAT'S EVEN CLOSE WAS THE 12Z AVN (AVERAGING 30KTS TOO WEAK), AND THAT DROVE ONE OF THE COLDEST WINTER STORMS IN OVER 10 YEARS INTO THE 4-CORNERS AT 120HRS (5280M 500MB HEIGHTS IN THE 4 CORNERS). THAT LOOKS EXTREME, BUT WITH 190KT JET MAXES IN AN INCREASINGLY AMPLIFIED AND RETROGRESSIVE PATTERN, ANYTHING IS POSSIBLE. INTERESTING TO NOTE THAT THE 00Z AVN INITIALIZED 30-40KTS TOO WEAK ALONG THE WA/BC BORDER, BUT ONLY 20KTS TOO WEAK OVER JAPAN. THE MAIN THING TO WATCH WILL BE WHERE THE NEW LONGWAVE RIDGE ANCHORS. IF IT'S W OF 140W, WE'RE IN TROUBLE. IF IT'S E, WE'LL BE CLIPPED WITH WINDY/COLD INSIDE SLIDERS, AND ANY SIGNIFICANT SNOW WILL STAY TO THE E. RIGHT NOW, A THIN MAJORITY OF MEDIUM RANGE MODELS, FOR WHAT THEY'RE WORTH, HAVE IT JUST E OF 140W. AS DAY SHIFT NOTED, THOUGH, EACH RUN HAS BEEN FURTHER W SINCE THU. WHO KNOWS IF THIS IS BECAUSE THE MODELS ARE NOT AS FAR OFF WITH THE JET SPEEDS (THEY WERE 70KTS TOO WEAK ON THU), OR SOMETHING ELSE. CONSIDERING ALL THE UNCERTAINTIES, THE TREND MY PREDECESSORS STARTED IS A GOOD STARTING POINT, WITH BEST SNOW THREAT IN THE WHITES, A DECENT CHANCE OF AT LEAST ONE CWA-WIDE WIND EVENT SOMETIME AFTER TUE, AND TEMPS SINKING BACK BELOW NORMAL. PYTLAK

.TWC...NONE.



.OVERVIEW... A SLOWLY FILLING 1000 MB LOW NEAR 45N/140W AT 18Z APPEARS TO STILL BE ABOUT 5 MB DEEPER THAN THE 12Z MODELS 6 HR MODEL FORECASTS...BUT SATELLITE IMAGERY SHOWS MODEL GUIDANCE TO BE COMING MORE IN LINE WITH REALITY CONCERNING ITS DEPTH AND POSITION. WILL USE THE 18Z MESOETA FOR THE SHORT TERM TODAY. THE EXTENDED MODELS APPEAR TO BE STILL HAVING PROBLEMS RESOLVING AN UPCOMING PATTERN CHANGE. ON A HEMISPHERIC SCALE IT APPEARS THAT THE LONG WAVE RIDGE OR SPLIT THAT HAS BEEN OVER THE COASTAL WATERS OR WEST COAST FOR MOST OF THE WINTER IS SHOWING SIGNS OF RETROGRADING BACK TO 160W BY LATE NEXT WEEK. A CONSOLIDATED FLOW WITH LONG WAVE RIDGING AT THAT LONGITUDE AS SHOWN BY THE AVN EXTENSION/UKMO/ECMWF MODELS WOULD BE A MAJOR BLESSING TO OUR MOUNTAINS AS RAPIDLY MOVING EMBEDDED SHORTWAVE TROUGHS IN A ROBUST NWLY FLOW WOULD ALLOW THE SNOWPACK TO BUILD SOMEWHAT. GIVEN THE DIFFICULTY IN TIMING FAST MOVING SYSTEMS IN THIS PATTERN...LOW RUN-TO-RUN CONTINUITY...AND A TOO WEAK 300 MB JET ALONG 50N IN THE CENTRAL PAC PER AIRCRAFT REPORTS...WILL NOT ATTEMPT TO TIME INDIVIDUAL FORECASTS BEYOND TUE.

.SHORT TERM...MODEL CONSENSUS IS TO SLOWLY FILL THE LOW NEAR 45N/140W AS IT MOVES ONTO N CENTRAL VANCOUVER ISLAND MIDDAY SUN. WARM ADVECTION PCPN IN ADVANCE OF ITS ASSOCIATED WARM OCCLUSION HAS ALREADY BEGUN IN CENTRAL/SRN OREGON. THIS SHOULD SPREAD NE INTO THE AREA AFTER MIDNIGHT. THE OCCLUSION MOVES TO THE COAST 15Z THEN TO THE CASCADES BY NOON...WITH IT THE SNOW LEVELS BRIEFLY JUMP TO 4500 FEET IN THE CENTRAL CASCADES BEFORE DROPPING BACK TO 2000 FEET LATE SUN NIGHT AND MON MORNING. AVN/MESOETA MODEL QPF IN THE MOUNTAINS SUGGEST THE NEED FOR A SNOW ADVISORY FOR 5-10 INCH ACCUMULATIONS 12Z SUN-00Z MON...BUT CONFIDENCE IS LOW ENOUGH THAT WILL LET LATER SHIFTS EXERCISE THE OPTION WHEN THE NEW 00Z GUIDANCE COMES IN. EXPECT WIDESPREAD POST FRONTAL SHOWER ACTIVITY SUN AFTN GRADUALLY TAPERING OFF TO OROGRAPHIC AND CONVERGENCE ZONE SHOWER ACTIVITY IN WNW FLOW ALOFT SUN NIGHT AND MON MORNING. MON WILL SEE GRADUAL DRYING AS THE LOW AND ASSOCIATED SHORTWAVE TROUGH DEPART TO THE E AND HIGH PRES BUILDS IN.

.EXTENDED...TUE SEES INCREASING CLOUDS WITH MAYBE SOME CHANCE OF PCPN LATE IN THE DAY...MAINLY COAST...AS A RAPIDLY MOVING SHORTWAVE TROUGH IN THE GULF OF AK MOVES SE ALONG THE AK/BC COAST. THEN WILL BROADBRUSH WED THRU NEXT SAT FOR A COOL PERIOD WITH SOME SHRA AT TIMES AND SN IN THE MTNS.

UIL 7+73 SEA 5963 OLM 6962 ALBRECHT

.SEW...SMALL CRAFT ADVISORY COAST.

.KATX...VCP31/CSR31...OPERATIONAL.



.OVERVIEW... A SLOWLY FILLING 1000 MB LOW NEAR 45N/140W AT 18Z APPEARS TO STILL BE ABOUT 5 MB DEEPER THAN THE 12Z MODELS 6 HR MODEL FORECASTS...BUT SATELLITE IMAGERY SHOWS MODEL GUIDANCE TO BE COMING MORE IN LINE WITH REALITY CONCERNING ITS DEPTH AND POSITION. WILL USE THE 18Z MESOETA FOR THE SHORT TERM TODAY. THE EXTENDED MODELS APPEAR TO BE STILL HAVING PROBLEMS RESOLVING AN UPCOMING PATTERN CHANGE. ON A HEMISPHERIC SCALE IT APPEARS THAT THE LONG WAVE RIDGE OR SPLIT THAT HAS BEEN OVER THE COASTAL WATERS OR WEST COAST FOR MOST OF THE WINTER IS SHOWING SIGNS OF RETROGRADING BACK TO 160W BY LATE NEXT WEEK. A CONSOLIDATED FLOW WITH LONG WAVE RIDGING AT THAT LONGITUDE AS SHOWN BY THE AVN EXTENSION/UKMO/ECMWF MODELS WOULD BE A MAJOR BLESSING TO OUR MOUNTAINS AS RAPIDLY MOVING EMBEDDED SHORTWAVE TROUGHS IN A ROBUST NWLY FLOW WOULD ALLOW THE SNOWPACK TO BUILD SOMEWHAT. GIVEN THE DIFFICULTY IN TIMING FAST MOVING SYSTEMS IN THIS PATTERN...LOW RUN-TO-RUN CONTINUITY...AND A TOO WEAK 300 MB JET ALONG 50N IN THE CENTRAL PAC PER AIRCRAFT REPORTS...WILL NOT ATTEMPT TO TIME INDIVIDUAL FORECASTS BEYOND TUE.

.SHORT TERM...MODEL CONSENSUS IS TO SLOWLY FILL THE LOW NEAR 45N/140W AS IT MOVES ONTO N CENTRAL VANCOUVER ISLAND MIDDAY SUN. WARM ADVECTION PCPN IN ADVANCE OF ITS ASSOCIATED WARM OCCLUSION HAS ALREADY BEGUN IN CENTRAL/SRN OREGON. THIS SHOULD SPREAD NE INTO THE AREA AFTER MIDNIGHT. THE OCCLUSION MOVES TO THE COAST 15Z THEN TO THE CASCADES BY NOON...WITH IT THE SNOW LEVELS BRIEFLY JUMP TO 3500 FEET IN THE CENTRAL CASCADES BEFORE DROPPING BACK TO 2000 FEET LATE SUN NIGHT AND MON MORNING. AVN/MESOETA MODEL QPF IN THE MOUNTAINS SUGGEST THE NEED FOR A SNOW ADVISORY FOR 5-10 INCH ACCUMULATIONS 12Z SUN-00Z MON...BUT CONFIDENCE IS LOW ENOUGH THAT WILL LET LATER SHIFTS EXERCISE THE OPTION WHEN THE NEW 00Z GUIDANCE COMES IN. EXPECT WIDESPREAD POST FRONTAL SHOWER ACTIVITY SUN AFTN GRADUALLY TAPERING OFF TO OROGRAPHIC AND CONVERGENCE ZONE SHOWER ACTIVITY IN WNW FLOW ALOFT SUN NIGHT AND MON MORNING. MON WILL SEE GRADUAL DRYING AS THE LOW AND ASSOCIATED SHORTWAVE TROUGH DEPART TO THE E AND HIGH PRES BUILDS IN.

.EXTENDED...TUE SEES INCREASING CLOUDS WITH MAYBE SOME CHANCE OF PCPN LATE IN THE DAY...MAINLY COAST...AS A RAPIDLY MOVING SHORTWAVE TROUGH IN THE GULF OF AK MOVES SE ALONG THE AK/BC COAST. THEN WILL BROADBRUSH WED THRU NEXT SAT FOR A COOL PERIOD WITH SOME SHRA AT TIMES AND SN IN THE MTNS.

UIL 7+73 SEA 5963 OLM 6962 ALBRECHT

.SEW...SMALL CRAFT ADVISORY COAST.

.KATX...VCP31/CSR31...OPERATIONAL.



.OVERVIEW... THE MODELS APPEAR TO BE HAVING SOME PROBLEM HANDLING THE INITIALIZATION OF COMPLEX FEATURES IN THE NE PACIFIC. THIS WILL LEAD TO FORECAST DIFFICULTIES...PARTICULARLY IN THE EXTENDED WHERE THE GULF OF ALASKA SHOWS THE LARGEST ENSEMBLE SPREAD. IN THE SHORT TERM TWO MAIN PROBLEMS APPEAR AT THE 12Z INITIAL TIME. THE AVN INITIALIZED THE 998 MB LOW NEAR 42N/143W A LITTLE TO THE SE OF ITS POSITION AT 1006 MB. WHILE BETTER THAN THE 00Z SOLUTION...SHORT TERM MODELS ARE STILL IN CATCH UP MODE. THE SECOND PROBLEM AREA IS ALONG 50N FROM THE DATELINE TO 160W. THE 12Z AVN IS 10 DEG SLOW WITH THE PROGRESSION OF THE STRONG 150+KT 300 MB JET PER AIRCRAFT DATA. THIS STRONG JET ALONG 50N SUPPORTS THE IDEAS OF THE MORE ENERGETIC UKMO/ECMWF SOLUTIONS IN TIME OVER THE MRF IN THE NE PAC.

.SHORT TERM... RADAR AND OBSERVATIONS SHOW SHOWERS ALL BUT OVER AS MID/HI LVL OVERRUNNING AHEAD OF THE OFFSHORE LOW STABILIZES THE AIR MASS. NEW GUIDANCE SHOWS OVERRUNNING PCPN SPREADING INTO THE AREA FROM THE SW AFTER MIDNIGHT WITH LIKELY POPS ON THE COAST AND A CHANCE IN THE INTERIOR. THEN PCPN SUN MORNING AS THE OFFSHORE OCCLUSION SWINGS THRU AND INTO THE CASCADES BY NOON. POST FRONTAL SHOWERS SUN AFTN FOLLOWED WILL BE FOLLOWED BY MORE OROGRAPHIC PCPN AND CONVERGENCE ZONE ACTIVITY SUN NIGHT AND EARLY MON.

.EXTENDED... THE TUE DRY SPELL MAY BE IN TROUBLE GIVEN FASTER AND MORE ENERGETIC FLOW PATTERN. THEN GIVEN THE VERY LONG WAVELENGTH BETWEEN THE MEAN TROUGH ANCHORED OFF NE ASIA AND THE TROUGH OVER THE ERN US...EXPECT RETROGRESSION OF THE ERN US TROUGH WWD TO THE INTERMOUNTAIN US...MORE IN LINE WITH UKMO/ECMWF. THE MRF KEEPS WANTING TO POP A RIDGE JUST OFF THE W COAST. HOPEFULLY A MORE ENERGETIC NW FLOW WILL OPEN US UP TO VIGOROUS SYSTEMS THAT CAN BUILD UP THE MTN SNOWPACK. BUT GIVEN EXTENDED MODEL PERFORMANCE OVER THE NE PAC THE PAST FEW DAYS...CONFIDENCE IN ANY EXTENDED FORECAST IS GENERALLY LOW. WILL AWAIT AFTN PACKAGE BEFORE MAKING ANY EXTENDED FORECAST CHANGES.

UIL 27+ SEA 149 OLM 149 ALBRECHT

.SEW...SMALL CRAFT ADVISORY COAST FOR HEAVY SWELL.

.KATX...VCP31/CSR31...OPERATIONAL.



VIGOROUS JET DIVING SOUTHEAST ACROSS THE EASTERN SLOPES OF THE ROCKIES AND WESTERN HIGH PLAINS WILL HELP UPPER LOW FORM OVER MIDWEST TODAY AS MODELS HAVE BEEN PREDICTING. 160KT WINDS OVER ERN BRITISH COLUMBIA AROUND 06UTC ACCORDING TO AIRCRAFT (ACARS) REPORTS. THIS QUITE A BIT STRONGER THAN 00UTC AVN/ETA/NGM. 06UTC ETA HAS THE WINDS INITIALIZED BETTER AND WILL GO MORE OR LESS WITH IT...ESPECIALLY AS IT LOOKS QUITE A BIT LIKE THE 00UTC ETA AS FAR AS THE NEXT VORT MAX FOR MONDAY NIGHT. AVN MUCH STRONGER AND SLOWER WITH NEXT SYSTEM COMING DOWN FROM THE NW...BUT NCEP FORECASTER (SEE PMDHMD DISCUSSION) THINK THAT FASTER ETA MODEL MORE LIKELY IN THE QUICK PATTERN WE ARE IN. SINCE THEY ARE USUALLY RIGHT... AND 06UTC ETA AGREES WITH THEM WILL GO IN THAT DIRECTION.

AS FAR AS TODAY GOES...LOW WILL MOVE ACROSS WI/IL BORDER TO SRN LK MI BY THIS EVENING. LIGHT SNOW SHOULD FALL IN THE SE PART OF THE FCST AREA IN THE AREA OF DIFFLUENT UPPER FLOW AND LOW LEVEL WARM ADVECTION. THE BIG QUESTION IS HOW MUCH? THINK ABOUT AN INCH IS LIKELY FROM GREEN BAY THROUGH THE FOX VALLEY TO OSHKOSH...WITH PERHAPS TWO INCHES IN SOUTHERN MANITOWOC COUNTY. ELSEWHERE THERE SHOULD BE SOME LIGHT SNOW OR FLURRIES WITH A DUSTING. TEMPERATURE FORECAST LOOKS FINE FROM PREVIOUS FORECAST. TONIGHT THE LIGHT SNOW IN THE SE PART SHOULD END THIS EVENING...LEAVING SKIES MOSTLY CLOUDY. WILL GO WITH MOSTLY CLOUDY MONDAY. WILL KEEP MENTION OF LIGHT SNOW MONDAY NIGHT AND TUESDAY BUT WILL NOT MENTION ACCUMULATIONS AT THIS TIME.

.GRB...NONE.

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