Forecast Discussions mentioning ACARS, received at FSL on 01/12/00

SHORT TERM DISCUSSION: AS HAS BEEN THE CASE THE LAST SEVERAL DAYS HIGH WINDS AND MOUNTAIN SNOWS ARE THE PROBLEMS TO BE DEALT WITH. FIRST THE MOUNTAIN SNOW. SATELLITE IMAGERY...RADAR...SNOTELS... ROAD REPORTS...SURFACE OBS AND PHONE CALLS TO THE HILLS ALL SUGGEST THAT SNOW HAS TAPERED OFF IN MANY MOUNTAIN AREAS. THIS SUPPORTS WHAT THE MODELS ARE TELLING ME...THAT IS LESS PRECIPITATION THAN YESTERDAY...SO WILL GO WITH NO HIGHLIGHTS BUT KEEP HIGH POPS AND SOME WIND GOING...ESPECIALLY IN THE HIGHER AREAS. IF DAY SHIFT DEEMS IT NECESSARY THEY CAN HOIST SOMETHING AS APPROPRIATE. AS REGARDS HIGH WINDS...LAPS ANALYSIS IS SHOWING THE LEE TROUGH DEVELOPING DEEP IN THE FOOTHILLS LAST SEVERAL HOURS. FURTHERMORE LAPS ANALYSIS IS ALSO SHOWING POTENTIALLY COLDER AIR SITTING OVER THE PLAINS AT THIS HOUR. METEOROLOGICAL TOWER OBSERVATIONS AT ROCKY FLATS AND LAPS SOUNDINGS SHOWING A DECENT INVERSION AROUND 1000 FEET DEEP ALSO EXISTS OVER THE PLAINS. ALTHOUGH AN ACARS SOUNDING AT 08Z DID SHOW A DECENT STABLE LAYER NEAR MOUNTAIN TOP LEVEL IT ALSO INDICATED SIGNIFICANT VERTICAL SHEAR OF THE CROSS MOUNTAIN WIND COMPONENT. PROFILER AND LAPS ANALYSES ALSO SHOW THIS SHEAR ALTHOUGH LAPS DID NOT CAPTURE THE UPPER LEVEL INVERSION (NO SURPRISE). IMAGERY FROM THE KFTG RADAR SUGGESTS THE PRESENCE OF A MOUNTAIN WAVE AND SOME OF THE FOOTHILLS RAWS ARE SHOWING SOME GUSTS IN EXCESS OF 50 MPH AT 09Z. AT THE PRESENT TIME THEN WITH THE COLD AIR ON THE PLAINS AND SUBSTANTIAL VERTICAL SHEAR FEEL THAT MOUNTAIN WAVE STRONG WINDS WILL BE CONFINED TO THE FOOTHILLS. AS THE DAY PROGRESSES... DON'T EXPECT MUCH TO CHANGE. VERTICAL SHEAR SHOULD REMAIN STRONG AND BELIEVE LEE TROUGH WILL STAY IN/NEAR THE FOOTHILLS. ALSO FEEL THAT THE SHALLOW COLD AIRMASS ON THE PLAINS WILL HAVE A TOUGH TIME SCOURING OUT COMPLETELY. FOR THIS REASON HAVE UNDERCUT MOS TEMPS A BIT ON THE PLAINS AND WILL DROP HIGH WIND WATCH FOR THE URBAN CORRIDOR ZONES. AS REGARDS THE WATCH IN THE FOOTHILLS...AM RELUCTANT TO GO EITHER WAY WITH THAT. DON'T WANT TO DROP THE WATCH COMPLETELY AS IT SHOULDN'T BE TOO HARD FOR A FEW FOOTHILLS SPOTS TO GET SOME GUSTS IN THE HIGH WIND CATEGORY. HOW WIDESPREAD THEY WILL GET AND THE NECESSITY OF A WARNING IS NOT CLEAR RIGHT NOW. SANGSTER VALUES WERE RISING LAST SEVERAL HOURS BUT DROPPED SOME AT 10Z. CONSEQUENTLY DON'T HAVE GOOD ENOUGH FEEL FOR HOISTING A WARNING JUST YET. ET

LONG TERM DISCUSSION: MDLS CONSISTENT IN MAINTAINING STRONG ZONAL FLOW ALF OVR CO WITH FLOW BECOMING MORE WLY TNGT AND WED. MDLS MAINTAIN FAIR AMT OR MID LVL INSTBY, MSTR AND WIND IN THE MTNS TNGT AS ANOTHER DISTURBANCE EMBEDDED IN THE FLOW CLIPS NRN CO AS AXIS OF THE UPPER LEVEL JET RIDES ALG THE CO/WY BDR. SNOW MDL CAME UP WITH 4-6 INCHES WITH INCRG POT VORT IN THE 06-12Z TIME FRAME AS UPPER LEVL JET STRENGTHENS. EXPECT WINDS SHUD CONTINUE IN THE MTNS AND HIR FOOTHILL AREAS. ALTHO WINDY ...HIGH WIND POTENTIAL SHOULD BE MARGINAL AT BEST FOR THE URBAN CORRIDOR AND LOWER ELEVATION FOOTHILL AREAS. STRONG WINDS THAT DEVELOP WL NOT BE THE PRODUCT OF AN AMPLIFIED MTN WAVE AS THE VERTICAL SHEAR SHUD BE TOO STG DUE TO THE CLOSE PROXIMITY OF THE UPPER LEVEL JET. NO STRONG DOWNWARD H5-H3 DIV-Q APPARENT EITHER TO AID INTO DOWNWARD TRANSPORT OF MOMENTUM. HIGHLIGHTS MAY NEED TO BE ISSUED LATE TNGT FOR THE MTNS AND MAYBE THE FOOTHILLS DUE TO INCRS IN WIND AND SNOW. SINCE BEST POTENTIAL APPEARS TO BE AFT 06Z TNGT ...WL LET THE DAY CREW MAKE THE DECISION TO HOIST ANY ADDITIONAL HIGHLIGHTS. IN THE PLAINS DOWNSLOPE SHUD ALLOW FOR ISOLD POPS AT BEST. MID AND UPPER LEVEL MSTR CONTINUES TO STREAM OVER THE AREA...BUT THE LOWER LVLS RMN DRY. FOR WED...MSTR DEPTH DECREASES IN THE MTNS AS BUT OROGRAPHICS SHUD BE STRONG ENUF TO KEEP SOME LGT SNOW GOING IN THE MTNS. EXPECT BREEZY-WINDY CONDITIONS IN THE PLAINS BUT SHUD SEE SOME MORE SUNSHINE UPPER LVL RIDGE STARTS TO DVLP OVR CO WED NGT INTO THU. IN THE EXTENDED PD...MEAN RIDGE TO CONTINUE OVR CO WITH WSWLY FLOW OVR THE STATE. WL TINKER WITH THE WORDING OF THE EXTENDED A BIT...BUT THAT SHUD BE ABOUT IT. COOPER

.DEN...HIGH WIND WATCH TODAY FRONT RANGE FOOTHILLS ZONES 35...36

CLEAR SKIES OVER SOUTH CAROLINA. WINDS LIGHTER PRESENTLY THAN THE FORECAST. HOWEVER...CAE VWP WINDS SHOW PRETTY GOOD FLOW AT 1 AND 2 THSD FT. 1 THSD FT WINDS 25KT AND 2 THSD FT 40KT. SO WILL KEEP WIND ADVY FOR THE AREA LAKES. AS LOW LEVEL INVERSION BREAKS...THERE SHOULD BE PRETTY GOOD MIXING. SO THINK STRONGER WINDS WILL COME DOWN CLOSER TO SURFACE. HIGHS IN THE LOWER 70S SEEM A BIT HIGH SINCE CAE STARTS GETTING WEAK CAA THIS AFTERNOON. ALSO 0829Z ACARS SOUNDING FOR CAE GIVES A HIGH OF ABOUT 70. SO WILL CUT HIGHS ONE CAT MIDLANDS...CSRA AND PIEDMONT. OTHERWISE NO MORE CHANGES.

.CAE...LAKE WIND ADV FOR CAE CWA.

TTH

...SYNOPSIS... STRONG FLOW ALOFT WILL CAUSE WINDY CONDITIONS ACROSS THE HIGHER MOUNTAINS AND DESERTS THROUGH WEDNESDAY AFTERNOON. WIND ADVISORIES AND HIGH WINDS WATCHES ARE IN EFFECT. WEST OF THE MOUNTAINS... ONSHORE FLOW WILL CONTINUE TO DEEPEN THE MARINE LAYER THROUGH WEDNESDAY. NIGHT AND MORNING LOW CLOUDS AND FOG WILL BE WIDESPREAD. OFFSHORE FLOW WILL BRIEFLY RETURN THURSDAY. INCREASING CLOUDS ARE EXPECTED ACROSS SOUTHWEST CALIFORNIA THIS WEEKEND AS A COLD FRONT APPROACHES.

...DISCUSSION... ACARS SOUNDINGS ACROSS SW CALIFORNIA THROUGH 0330Z SHOWED WNW WINDS 25 KT AT 4000 FT INCREASING TO 40 KTS AT 10000 FT. THE 11/18Z MESOETA MODEL WAS THE CLOSEST TO THESE OBSERVED WIND SPEEDS WHILE THE SYNOPTIC SCALE MODELS WERE ABOUT 10-20 KTS WEAKER. THE 12/00Z RUC AND ETA MODEL BOTH INCREASE WIND SPEEDS IN THIS LAYER ANOTHER 10-15 KTS BY 12/18Z. ADDING THIS INCREASE TO THE CURRENT OBSERVATIONS WOULD YIELD HIGH WINDS ACROSS HIGHER MOUNTAINS... THROUGH CANYONS...AND ALONG LEE SLOPES AND ADJACENT VALLEY FLOORS WEDNESDAY MORNING. LOCAL WIND SCHEME USING THE NUMBERS FROM THE MODELS HOWEVER ONLY SUPPORTS WIND ADVISORIES FOR THE APPLE/YUCCA VALLEYS. WILL LET HIGH WIND WATCH RIDE FOR NOW BUT ADVISE MIDNIGHT SHIFT MAY WANT TO CHANGE IT TO A WIND ADVISORY VERSUS HIGH WIND WARNING AND MOVE EXPIRATION TIME UP TO THE MID AFTERNOON.

THE OTHER SHORT TERM WEATHER PRODUCER IS THE DEEPENED MARINE LAYER. THE 12/00Z KVBG RAOB SHOWS IT DEEPENDED ANOTHER 2000 FEET IN THE PAST 24 HOURS. METARS ACROSS COASTAL SECTIONS AND INLAND VALLEYS SHOW FAIRLY UNIFORM DEWPOINTS...IN THE LOW 50S...SO MODIFICATION OF THE AIR MASS APPEARS COMPLETE. FORECASTS ALREADY HAVE MENTION OF DENSE FOG AND LOW CLOUDS SO NO UPDATE NEEDED.

IN THE MEDIUM RANGE ALL THE MODELS CONTINUE TO DIG A TROUGH ALONG 140 WEST LONGITUDE BY WEDNESDAY NIGHT WHICH SHOULD PULL THE BAROCLINIC ZONE NORTHWARD AND DIMINISH THE STRONG WINDS ALOFT. THE TROUGH IS THEN MOVED SLOWLY EASTWARD. THE LATEST MRF IS IN AGREEMENT WITH THE OTHER MODELS IN KEEPING THE TROUGH AXIS WEST OF 130 WEST LONGITUDE THROUGH THE WEEKEND....SO THREAT OF RAIN AT THIS TIME APPEARS MINIMAL FOR EXTREME SOUTHWEST CALIFORNIA. SAN 000

.SAN...WIND ADVISORIES CAZ060 THROUGH 330 AM PST WED HIGH WIND WATCH CAZ055-056-060-061 WEDNESDAY...SEE LAXNPWSAN. BALFOUR