Forecast Discussions mentioning "ACARS", "MDCRS", or "AIRCRAFT" received at FSL on 01/22/03

.SYNOPSIS...WEAK UPPER LEVEL DISTURBANCES WILL BRING PERIODS OF MID AND HIGH CLOUDS THIS WEEK...BUT NO PRECIPITATION IS EXPECTED. SOME NIGHT AND MORNING LOW CLOUDS AND FOG WILL ALSO OCCUR...MAINLY NEAR THE COAST. BUILDING HIGH PRESSURE ALOFT COMBINED WITH WEAK OFFSHORE FLOW WILL BRING A GRADUAL WARMING TREND THROUGH THE WEEKEND.

.DISCUSSION...SKIES WERE CLEAR OVER OUR FORECAST AREA...THOUGH STRATOCUMULUS WAS FAIRLY WIDESPREAD FROM CATALINA ISLAND TO NEAR DOWNTOWN LA. ACARS SOUNDINGS SHOW THAT THE MARINE INVERSION HAD BECOME QUITE WEAK AND HAD LIFTED TO AROUND 2500 FEET IN RESPONSE TO A SHORTWAVE MOVING BY TO THE N/NE. THE TREND FOR THE MARINE INVERSION HEIGHT WILL BE DOWN TONIGHT AS THE SHORTWAVE MOVES AWAY. AREAS OF MOSTLY BROKEN STRATUS SHOULD FORM WEST OF THE MTNS OVERNIGHT...WITH FOG BEING A BIT MORE PATCHY THAN LAST NIGHT.

LITTLE SHORTWAVES PERIODICALLY PASS BY TO THE NORTH THROUGHOUT THE ENTIRE 7-DAY PERIOD WITH THE MOST SIGNIFICANT ONE BEING ON THU. HOWEVER...THE MAIN DYNAMICS AND MOISTURE WILL STAY WELL TO THE NORTH...SO PRECIP IS NOT EXPECTED OVER OUR AREA THEN. OFFSHORE SURFACE PRESSURE GRADIENTS WILL OCCUR FRI-SUN...BUT SUPPORT ALOFT BY EITHER SIGNIFICANT WIND OR COLD AIR ADVECTION WILL BE MISSING...SO STRONG WINDS ARE NOT EXPECTED. MILD WEATHER WILL CERTAINLY BE EXPECTED...THOUGH AT LEAST A WEAK NORTHWESTERLY SEA BREEZE WILL PROBABLY STILL OCCUR NEAR THE COAST TO KEEP TEMPS DOWN SOMEWHAT THERE.

.SAN...NONE

MAXWELL



...MAIN FORECAST CONCERN IS LIGHT SNOW/AMOUNTS TODAY...

UPPER AIR ANALYSIS SUITE AND WATER VAPOR IMAGERY SHOWING ELONGATED LARGE SCALE THROUGH ENCOMPASSING MUCH OF EASTERN NORTH AMERICA... WITH HEART OF COLD VORTEX STRETCHING FROM SASKATCHEWAN TO QUEBEC AS MAIN CORE /ACARS INDICATED 130KTS/ OF WESTERLIES ARCS THROUGH THE NORTHERN TIER OF STATES. TO THE WEST...UPPER RIDGING PREVALENT FROM ALONG THE PACIFIC WEST COAST INTO ALASKA...WHILE SEVERAL IMPULSES SLIDE THROUGH THE RELATIVELY WEAK FLOW FROM THE FOUR CORNERS AREA TO THE SOUTHERN PLAINS.

LATEST SUBJECTIVE SURFACE ANALYSIS FEATURING FRONTAL BOUNDARY ALONG THE ROCKIES OF WYOMING AND COLORADO...WITH ASSOCIATED LOW PRESSURE RIPPLE CENTERED ALONG THE WY/CO BORDER. HIGH PRESSURE RIDGE AXIS EXTENDING FROM WESTERN CANADA INTO THE DAKOTAS...WITH E/NE LOW LEVEL FLOW ENCOMPASSING THE CENTRAL PLAINS.

LIGHT SNOW CONTINUES TO SLIDE EASTWARD THROUGH NORTHERN/CENTRAL NEBRASKA EARLY THIS MORNING...AIDED BY MID LEVEL FRONTOGENETICAL FORCING /ROUGHLY IN 800MB-600MB LAYER/ AND COUPLED UPPER JET STRUCTURE. BEST NET LIFT COINCIDENT WITH FAVORABLE DENDRITIC GROWTH EXPECTED TO PERSIST AT LEAST UNTIL MIDDAY...WITH SNOW LIKELY TAPERING OFF AND/OR TO FLURRIES IN THE AFTERNOON. GIVEN EARLY MORNING TREND AND ETA/RUC DIAGNOSTICS...BEST SNOWFALL PROSPECTS STILL APPEAR ROUGHLY FROM THE TRI-CITIES AND AREAS NORTH AND EAST. ONE TO TWO INCH AMOUNTS SHOULD SUFFICE IN THE AFOREMENTIONED AREAS...ALTHOUGH PROBABLY NOT OUT OF THE QUESTION TO SEE ISOLD POCKET OF THREE INCHES. SNOW AMOUNTS ARE EXPECTED TO TAIL OFF MARKEDLY THROUGH THE SOUTHWEST CWA...WHERE LITTLE IN THE WAY OF SNOW ACCUMULATION IS EXPECTED. GIVEN EXPECTED SNOW AMOUNTS GENERALLY IN THE ONE TO TWO INCH RANGE AND ABSENCE OF ADDITIONAL NUSSIANCE FACTORS -- STRONG WINDS FOR INSTANCE -- WILL NOT ISSUE ADVISORY FOR THE NORTH/EAST CWA UNLESS PRE-ISSUANCE TRENDS/REPORTS DICTATE OTHERWISE.

WITH ENDING OF SNOW THIS AFTERNOON/EARLY EVENING...QUESTION TURNS TO EVENTUAL POSITIONING OF LOW CLOUDS TONIGHT -- AND SUBSEQUENT IMPACTS ON LOW TEMPERATURES -- AS 1044MB HIGH PRESSURE DEVELOPS SOUTHWARD THROUGH THE NORTHERN PLAINS. 00Z ETA GUIDANCE WOULD SUGGEST AMPLE CLEARING THROUGH THE EASTERN CWA...WITH UPSLOPE TRAJECTORIES MAINTAINING CLOUD COVER FROM THE WESTERN CWA WESTWARD INTO THE HIGHER TERRAIN. IN CONTRAST...00Z GFS PORTRAYS A MUCH MORE CLOUD-PESSIMISTIC SCENARIO. A VERY TOUGH CALL AT THIS TIME AS VERY EASY FOR MOISTURE TO BECOME TRAPPED UNDERNEATH THE RIDGE IN PRESENCE OF WEAKENING AMBIENT LOW LEVEL FLOW...BUT EITHER WAY...CLOUDS OR NOT...A VERY COLD NIGHT IN STORE. SINGLE DIGITS BELOW ZERO...AT LEAST...ARE A SAFE BET FOR MUCH OF THE CWA. IF CLEARING MATERIALIZES IN THE EAST/NORTH CWA TONIGHT...AND GIVEN ADDITIONAL BOUT OF SNOW TODAY...THESE AREAS COULD SEE TEMPERATURES EVEN DIP AS LOW AS 10 TO 15 BELOW ZERO. OTHERWISE... WOULD THINK LIGHT WINDS ASSOCIATED WITH THE RIDGE AXIS WILL PROBABLY NEGATE NECESSITY FOR WIND CHILL HEADLINE...NEVERTHELESS WILL STILL NEED TO BE CLOSELY EVALUATED BY NEXT SHIFT.

SURFACE HIGH TO GRADUALLY SLIDE SOUTH/EASTWARD DURING THE DAY ON THURSDAY...WITH SOUTHERLY FLOW DEVELOPING THURSDAY NIGHT INTO FRIDAY. AS SUCH...SHOULD SEE A DECENT TEMPERATURE REBOUND DURING THE DAY ON FRIDAY. WILL MAINTAIN LIGHT SNOW CHANCES THURSDAY NIGHT IN PRESENCE OF LOW TO MID LEVEL WAA/THETA-E ADVECTION REGIME ASSOCIATED WITH PASSING MID LEVEL SHORTWAVE TROUGH.

IN THE EXTENDED...REMNANT COLD VORTEX ACROSS WESTERN CANADIAN STILL EXPECTED TO PIVOT TOWARD EASTERN CANADA THIS WEEKEND. THIS WILL BRING A REINFORCING SHOT OF COLDER AIR AND POSSIBLY A SLIGHT SNOW CHANCE SOMEWHERE IN THE SATURDAY TIMEFRAME. PATTERN CERTAINLY LOOKS TO TURN MILDER/DRY BY EARLY NEXT WEEK WITH LOW AMPLITUDE/NEARLY ZONAL FLOW DEVELOPING FROM THE EASTERN PACIFIC THROUGH THE WESTERN CONUS. GOING FORECAST HAS THE AFOREMENTIONED IDEAS WELL IN HAND...THUS ANY OUTER PERIOD ADJUSTMENTS WILL BE MINIMAL.

COORDINATED WITH OAX.

.GID...NONE.

GUYER