755  
FXUS65 KREV 211250 AAA  
AFDREV  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE RENO NV  
450 AM PST THU FEB 21 2019  
   
UPDATE
 
 
WE ISSUED A WINTER WEATHER ADVISORY FOR THE LAKE EFFECT SNOW BAND  
COMING OFF PYRAMID LAKE UNTIL NOON, FOR THE RENO AND NORTH VALLEYS.  
THIS BAND EXTENDED SOUTH ALONG THE PAH RAH RANGE AND WAS  
AFFECTING EAST SPARKS AND EAST RENO INCLUDING I-80 TO PATRICK  
WHERE WEB CAMS SHOWS SNOW ON THE ROADWAY. THIS BAND IS EXPECTED TO  
REMAIN INTACT THROUGH THE MORNING AS AN UPPER LEVEL DISTURBANCE  
ROTATES THROUGH THE AREA IN AN UNSTABLE AIRMASS. AS WINDS TURN  
MORE NORTHEAST DURING THE MORNING, THE BAND WILL SHIFT WEST INTO  
RENO AND THE NORTH VALLEYS WHERE UP TO 3" OF SNOW ARE POSSIBLE.  
AMOUNTS IN THE PALOMINO VALLEY AND POSSIBLY SPANISH SPRINGS WILL  
BE HIGHER WHERE OVER 6" ARE POSSIBLE.  
 

 
   
PREVIOUS DISCUSSION
 
/ISSUED 325 AM PST THU FEB 21 2019/  
 
SYNOPSIS...  
 
LIGHT SNOW SHOWERS WITH HEAVIER LAKE-EFFECT SNOW BANDS ARE LIKELY  
TODAY. COLD CONDITIONS WILL CONTINUE INTO THIS WEEKEND WITH  
A POSSIBLE TRANSITION TO A MILDER AND WETTER PATTERN NEXT WEEK.  
 
SHORT TERM...  
 
A COLD UPPER LOW PRESSURE SYSTEM WILL REMAIN OVER THE REGION TODAY  
AS THE CENTER OF THE LOW SETTLES SLOWLY SOUTH ACROSS SOUTHERN NV.  
MODEL DATA INDICATED AN UPPER LEVEL DISTURBANCE ROTATING AROUND THE  
BACK SIDE OF THIS LOW INTO WESTERN NV TODAY AND SATELLITE DATA  
SUPPORTS THIS. UNSTABLE CONDITIONS WILL PROMOTE ISOLATED-SCATTERED  
SNOW SHOWERS MOST AREAS WITH CONDITIONS FAVORABLE FOR LAKE  
EFFECT/ENHANCED SNOW BANDS OFF THE SOUTH AND SOUTHWEST SIDES OF  
LARGER LAKES.  
 
A BAND DEVELOPING EARLY THIS MORNING TO THE SOUTH OF PYRAMID LAKE  
WAS SHOWING DECENT IR ENHANCEMENT AND BASED ON A BRIEF SNOW  
SHOWER THAT MOVED ACROSS THE RENO-TAHOE INTL AIRPORT AROUND  
MIDNIGHT AND PUT DOWN A QUICK DUSTING OF SNOW, THESE SNOW BANDS  
ARE GOING TO PRODUCE DECENT ACCUMULATION OF DRY FLUFFY SNOW WHERE  
THEY DEVELOP. SOME HIGH RESOLUTION MODELS AND EVEN THE 00Z/06Z GFS  
SHOWED THIS BAND SHIFTING WEST INTO RENO/NORTH VALLEYS LATER THIS  
MORNING AND THIS WILL HAVE TO BE WATCHED CLOSELY. IF IT SHIFTS  
EARLY ENOUGH THIS MORNING, SNOW ACCUMULATIONS WOULD CAUSE IMPACTS  
TO AREA ROADWAYS. SNOW LATER IN THE MORNING AND AFTERNOON MAY NOT  
BE AS IMPACTFUL UNLESS THE SNOW IS ONGOING FROM THIS MORNING AND  
REMAINS HEAVY ENOUGH TO MITIGATE MELTING ON ROADS. MOST AREAS  
TODAY WILL SEE ACCUMULATIONS LESS THAN AN INCH. HOWEVER, MUCH  
HIGHER ACCUMULATIONS ARE LIKELY IN THESE LAKE EFFECT BANDS (2-6"  
OR POSSIBLY MORE).  
 
AS THE LOW PULLS AWAY TONIGHT, SNOW SHOWERS WILL DIMINISH. LAKE  
EFFECT SNOW BANDS MAY CONTINUE, BUT INTENSITY AND AREAL EXTENT  
SHOULD DECREASE. QUIET CONDITIONS WILL PREVAIL FRIDAY-SATURDAY  
WITH UNSEASONABLY COLD CONDITIONS PREVAILING. LOWS FRIDAY AND  
SATURDAY MORNING WILL BE IN THE SINGLE DIGITS AND TEENS WITH SUB-  
ZERO READINGS FOR COLDER SIERRA VALLEYS. HOHMANN  
 
LONG TERM...SUNDAY THROUGH FRIDAY AND BEYOND...  
 
MADE SOME MINOR ADJUSTMENTS TO THE GOING FORECAST, MAINLY TO  
INCREASE THE CHANCES OF PRECIP NEAR THE OREGON BORDER AND THE SIERRA  
NORTH OF ALPINE COUNTY MON-TUE. THE MODELS ARE IN REASONABLY GOOD  
AGREEMENT WITH AN ACTIVE PATTERN FOR EARLY NEXT WEEK. THEY DO DIFFER  
ON THE DETAILS WITH HOW WET AND WHO GETS HIT THE WORST.  
 
SUNDAY, THEY DRAG A COLD FRONT DOWN FROM THE NORTH THAT WILL STALL  
NEAR THE OREGON BORDER. THEN, THEY HAVE WEAK, BUT MOIST,  
UNDERCUTTING IMPULSES IN THE SOUTHERN STREAM MERGING WITH THE  
BOUNDARY. THE EC KEEPS THE FRONT THERE, WHILE THE GFS BRINGS IT  
SOUTH TUESDAY BEFORE RIDING NORTH AGAIN WEDNESDAY. THE EC HAS THE  
BRUNT ACROSS THE NORTH AND IS WARMER, WHILE THE GFS KEEPS IT WET  
INTO THURSDAY WITH MOST AREAS AT LEAST SEEING LIGHT PRECIP.  
 
AS MENTIONED ABOVE, ONLY INCREASED POPS ACROSS THE NORTH (AND TO  
A LESSER EXTENT THE SIERRA) WHERE THE HIGHEST CONFIDENCE LIES. THE  
GEFS SHOWS CONSIDERABLE SPREAD WHILE THE EC ENSEMBLES GIVES MORE  
SUPPORT FOR ITS SOLUTION. THIS FORECAST LEANS MORE TOWARD THE EC  
AND IS NOT AS WET. THAT SAID, CONFIDENCE IS LOW WITH THE MULTITUDE  
OF MODEL CHANGES OVER THE PAST 48 HOURS SO THINGS WILL LIKELY  
CHANGE.  
 
I HAVE SOME MENTION OF PRECIP AT LEAST NORTH OF HIGHWAY 50 THROUGH  
THURSDAY, BUT CHANCES GRADUALLY DWINDLE EACH DAY WED-THURS. THERE  
WILL BE RIDGING BEHIND THIS SYSTEM THAT WOULD DRY US OUT FOR 2-3  
DAYS, BUT HOW QUICKLY IS YET TO BE DETERMINED WITH MY GUT SAYING  
IT STARTS LATE WED.  
 
BEYOND THIS SHORT WAVE RIDGE, IT CONTINUES TO LOOK ACTIVE INTO EARLY  
MARCH. THE EAST PACIFIC RIDGE IS FORECAST TO BE UNDERCUT WITH AR  
TOOLS SHOWING THE CHANCE OF AT LEAST WEAK ARS ALONG THE WEST COAST  
THROUGH THE FIRST WEEK OF MARCH. THE FLAVOR OF THESE WILL BE  
DETERMINED OVER TIME. X  
 
AVIATION...  
 
MAIN CONCERN THIS MORNING WILL DEAL WITH LAKE EFFECT SNOW COMING OFF  
TAHOE AND PYRAMID. THIS WILL CONTINUE INTO THE AFTERNOON. UPSLOPE  
SNOW SHOWERS ARE ALSO EXPECTED IN MONO COUNTY, WITH GENERAL  
INSTABILITY -SHSN THIS AFTERNOON AND EVENING. VFR BY  
MIDNIGHT TONIGHT AND INTO FRIDAY. TERMINAL DETAILS:  
 
KRNO: AS OF THIS WRITING A STRONG BAND IS SEEN OFF PYRAMID AND  
STRETCHING JUST TO THE EAST OF THE TERMINAL. WE EXPECT THIS BAND TO  
REMAIN JUST EAST OF THE TERMINAL THROUGH 14Z, BUT THEN SHIFT OVER  
THE TERMINAL AT TIMES FROM 14-19Z WITH ACCUMULATIONS UP TO 2 INCHES.  
IFR TO LIFR CONDITIONS ARE OCCURRING IN THIS BAND WITH VISIBILITY  
DOWN TO 1/4 TO 1/2 SM AT TIMES. AFTER 19Z, EXPECT VFR CONDITIONS  
WITH NORTH WINDS 10-15 KTS WITH BRIEF PERIODS OF MVFR VIS IN  
INSTABILITY SHOWERS.  
 
KTVL: THE LAKE TAHOE BAND IS EXPECTED TO REMAIN WEST OF THE TERMINAL  
THROUGH THE MORNING WITH VFR CONDITIONS. AFTER 19Z, BRIEF PERIODS OF  
IFR VIS ARE POSSIBLE IN SHOWERS, MAINLY FROM 21-24Z WITH NORTH WINDS  
AROUND 10 KTS.  
 
KTRK: SOME LOW CLOUDS AND FZFG THIS MORNING WITH IFR CONDITIONS  
ENDING AROUND 16Z. AFTER 19Z, BRIEF PERIODS OF IFR VIS ARE POSSIBLE  
IN SHOWERS, MAINLY FROM 21-24Z WITH NORTH WINDS AROUND 10 KTS.  
 
KCXP: VFR WITH JUST A FEW INSTABILITY SHOWERS THIS AFTERNOON THAT  
COULD BRIEFLY CONTAIN MVFR VIS.  
 
KMMH: LIGHT UPSLOPE -SHSN WILL CONTINUE THROUGH 20Z WITH MVFR  
CIGS/VIS. AFTER 20Z, MORE VFR CONDITIONS WITH BRIEF PERIODS OF MVFR  
VIS IN ANY SHOWERS. X  
 

 
   
REV WATCHES/WARNINGS/ADVISORIES
 
 
NV...WINTER WEATHER ADVISORY UNTIL NOON PST TODAY NVZ003.  
 
CA...NONE.  

 
 

 
 
FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...  
HTTP://WEATHER.GOV/RENO  
 
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