Forecast Discussions mentioning "ACARS", "MDCRS", or "AIRCRAFT" received at FSL on 01/18/02

...MAIN FORECAST CONCERNS ARE POSSIBILITIES FOR LIGHT SNOW/FLURRIES ON FRIDAY...

UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY CONTINUING TO INDICATE SUBTLE BROAD SCALE TROUGHING ACROSS THE CONUS...AS POLAR VORTEX REMAINS LOCKED OVER HUDSON BAY. A LOW AMPLITUDE/PROGRESSIVE FLOW REGIME PREVAILS...AS MEAN UPPER JET/WESTERLIES BRANCH EXTENDS FROM THE DESERT SOUTHWEST TO THE OHIO VALLEY...WITH MORNING ACARS DATA INDICATING EMBEDDED 180+ KNOT JET STREAK ACROSS KANSAS. OTHERWISE... MEAN RIDGE IN THE EASTERN PACIFIC CONTINUING TO GRADUALLY DAMPEN.

AFTERNOON SUBJECTIVE SURFACE ANALYSIS INDICATING AN ARCTIC COLD FRONT DROPPING SOUTHWARD FROM CENTRAL MN...THROUGH SD...AND THEN EXTENDING BACK INTO CENTRAL MT. BEHIND THE FRONT...HIGH PRESSURE WAS LOCATED OVER SASKATCHEWAN.

COLD FRONT WILL CONTINUE TO DROP SOUTHWARD TONIGHT. AFTER A GENERALLY PARTLY CLOUDY EVENING FOR MOST OF THE CWA...CLOUDS WILL INCREASE IN ASSOCIATION WITH THE FRONT. NOT OUT OF THE QUESTION TO SQUEEZE OUT A FEW FLURRIES OVERNIGHT.

12Z ETA/AVN NOW IN VERY GOOD AGREEMENT WITH THE ADVANCEMENT OF THE UPPER TROUGH OUT OF THE SOUTHWEST UNITES STATES ON FRIDAY. AMPLE FORCING PRESENT AS EMBEDDED SHORTWAVE ENERGY APPROACHES THE AREA FRIDAY AFTERNOON...IN ASSOCIATION WITH DEEP ASCENT ZONE EVIDENT IN ISENTROPIC DIAGNOSTICS UP THROUGH 315K. AT LEAST LOW SNOW PROBABILITIES ARE WARRANTED...NAMELY FRIDAY AFTERNOON AND NIGHT. BEST CHANCES SEEMINGLY IN NCNTRL KS AND THE EASTERN PORTIONS OF THE NEB CWA. THE OVERALL QUICK PROGRESSION OF THE UPPER WAVE AND QUESTIONABILITY OF EFFECTIVE SATURATION REMAIN HINDRANCES FOR MUCH IN THE WAY OF MEASURABLE SNOW.

PASSAGE OF THE MEAN TROUGH AXIS EARLY SATURDAY WILL RESULT IN CLEARING/WARMING CONDITIONS FOR THE WEEKEND.

IN THE EXTENDED...LATEST MRF AND EUROPEAN MODELS IN VERY GOOD AGREEMENT INTO THE MIDDLE OF NEXT WEEK...AS LARGE SCALE TROUGH/ PROGRESSIVE PATTERN PERSISTS ACROSS THE CONUS. SEASONABLY MILD DAYS EARLY NEXT WEEK AS BROAD SOUTHWESTERLY FLOW DOMINATES...BEFORE A UPPER TROUGH HEADS OUT OF THE SOUTHWEST CONUS AROUND MID WEEK.

.GID...NONE.

GUYER



.SYNOPSIS...A PAIR OF WEAK WEATHER SYSTEMS WILL MOVE ACROSS SOUTHERN NEVADA THROUGH THE WEEKEND. THIS WILL BRING SOUTHWEST CALIFORNIA A FEW HIGH CLOUDS AT TIMES AND LOCALLY GUSTY WINDS BELOW PASSES AND CANYONS NIGHTS THROUGH MORNINGS...WITH PATCHY NIGHT AND MORNING LOW CLOUDS AT THE COAST. TEMPERATURES WILL REMAIN A LITTLE BELOW AVERAGE THROUGH THE WEEKEND...THEN WARM A LITTLE MONDAY AHEAD OF A STRONGER TROUGH OF LOW PRESSURE FOR TUESDAY AND WEDNESDAY.

.DISCUSSION...TWO "INSIDE SLIDER" SYSTEMS WL BRING ALTERNATING WK ONSHR/OFFSHORE FLOW THRU SUNDAY WITH HIGHER RESOLUTION MDLS SHOWING A WK CSTL EDDY THIS MORNING AND AGAIN SAT NIGHT INTO SUN MORNING. PK OFFSHORE FLOW WL BE LATE TONIGHT INTO SAT MORNING AND LATE SAT NIGHT INTO SUN MORNING. WINDS AT WINDIER LOCATIONS BELOW CAJON PASS AND IN THE SNA MTNS AND FOOTHILLS MAY LCLLY REACH THE LOW END OF WIND ADV CRITERIA DURG THESE PDS. ACARS SOUNDINGS SHOW A SUBSIDENCE INVERSION AROUND 4000 FT WITH HINTS OF A VRY WK MARINE INVERSION NR 1500 FT. WKNESS OF THE MARINE INVERSION SHOULD KP STRATUS COVERAGE QUITE PATCHY THIS MORNING WITH WK OFFSHORE FLOW TO THE N KPG STRATUS CONFINED PRIMARILY TO SRN CSTL SXNS TONIGHT AND SATURDAY NIGHT. OTHERWISE...ONLY A FEW HIGH CLOUDS AT TIMES THRU MON.

TEMPERATURES WL REMAIN A LTL BLO AVERAGE THRU THE WEEKEND...THEN RETURN TO NR AVERAGE MON AHEAD A STRONGER UPR TROUGH FOR TUE AND WED. AVN/MRF HAVE BEEN TRENDING TOWARD THE MORE AMPLIFIED ECMWF WITH SOME LIGHT PRECIPITATION NOT OUT OF THE QUESTION. WL KEEP THE FORECAST DRY FOR NOW AND JUST EMPHASIZE COOLER AND BREEZY WITH GREATER CLOUD COVER. FOR THU...DRY AND A LTL WARMER WITH OFSHR FLOW AS THE UPR TROUGH MOVES E. THE MORE AMPLIFIED ECMWF WOULD SUPPORT A MDT-STG OFFSHORE FLOW EVENT FOR THU WITH THE LESS AMPLIFIED AND MORE PROGRESSIVE MRF WKR WITH THE OFFSHORE FLOW. FOR NOW...HAVE TRENDED SLIGHTLY TOWARD THE ECMWF.

.SAN...NONE.

MARTIN