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000 FXUS65 KLKN 152256 AFDLKN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ELKO NV 356 PM PDT MON SEP 15 2008 .SYNOPSIS...HIGH PRESSURE WILL REMAIN IN CONTROL THROUGH TOMORROW MORNING...BRINGING CONTINUED DRY AND WARM WEATHER. A SERIES OF LOW PRESSURE SYSTEMS WILL BRING A RISK FOR SHOWERS AND THUNDERSTORMS TO THE GREAT BASIN REGION AREA BEGINNING LATE TOMORROW AND WEDNESDAY... ALONG WITH COOLER TEMPERATURES. && .SHORT TERM...TONIGHT THROUGH WEDNESDAY. CLOUD-LESS SKIES PERSIST OVER THE WESTERN UNITED STATES AT PRESENT. THE UPPER-LEVEL ANALYSIS REVEALS A RIDGE CENTERED OVER NORTHERN UTAH...WITH A CLOSED LOW SITTING WEST OF SAN FRANCISCO AND A TROUGH FURTHER WEST OVER THE EASTERN PACIFIC. HOWEVER...AT LEAST THROUGH TOMORROW MORNING...THE ONLY FEATURE IN OUR WEATHER IS THE RIDGE ALOFT WHICH WILL PROVIDE CONTINUED MOSTLY CLEAR SKIES AND LIGHT WINDS. TOMORROW AFTERNOON...THE SOUTHERLY FLOW ALOFT BETWEEN THE RIDGE TO OUR EAST AND THE LOW TO OUR EAST WILL HELP PUMP SOME MONSOONAL MOISTURE NORTHWARDS INTO THE REGION. HOWEVER...WE`RE STARTING TO GET TO THE TIME OF YEAR WHERE WE NEED SOME UPPER-LEVEL FORCING TO GET THINGS GOING AS THE SUN ANGLE DECREASES...SO ONLY VERY MINIMAL THUNDERSTORM DEVELOPMENT IS EXPECTED MAINLY ALONG THE WESTERN FRINGES OF THE CWA. WITH PW`S STILL PRETTY LOW...EXPECT THOSE FEW T-STORMS THAT DO DEVELOP TO BE DRY...AND LOWERED POPS ACCORDINGLY. WITH THE RIDGE STILL INFLUENCING OUR WEATHER AND THE SOUTHERLY FLOW ALOFT KEEPING MID-LEVEL TEMPERATURES WARM...WE SHOULD HAVE NO PROBLEM REACHING THE UPPER 80S IN MOST VALLEYS...WITH THE NORMALLY HOTTER LOCATIONS PASSING 90. WINDS WILL BE A BIT STRONGER THAN DURING RECENT DAYS...PARTICULARLY ACROSS NORTHERN NYE COUNTY WHERE SOUTHERLY GUSTS MAY APPROACH 30 MPH DURING THE AFTERNOON. ANY STORMS WILL DISSIPATE TOMORROW EVENING AS HEATING DISSIPATES... BUT MOISTURE WILL CONTINUE STREAMING NORTHWARD...AND ACROSS THE NORTHERN AND EASTERN PORTIONS OF THE CWA CLOUD COVER MAY ACTUALLY INCREASE OVERNIGHT. THIS WILL HELP LOW TEMPERATURES STAY A BIT MILDER THAN MANY RECENT NIGHTS. BY WEDNESDAY...THE CLOSED LOW WEST OF SAN FRANCISCO WILL HAVE OPENED UP INTO A NEGATIVELY TILTED SHORT-WAVE TROUGH...AND IT WILL BE APPROACHING OUR CWA. COMBINED WITH THE CONTINUED MONSOONAL INFLUX ON THE SOUTHERLY WINDS...AND WE SHOULD HAVE MUCH MORE WIDESPREAD SCATTERING OF ISOLATED SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON. INSTABILITY WILL BE GREATLY ENHANCED BY THE NEGATIVELY TILTED TROUGH AS IT APPROACHES...SO SOME STORMS MAY GET GOING BY 10 OR 11AM ACROSS THE SOUTHWESTERN FRINGES OF THE CWA. THE INFLUX OF MOISTURE AND RELATIVELY LOW WINDS ALOFT SHOULD ALLOW STORMS OVER MUCH OF THE CWA TO TRANSITION TO WET...BUT ALONG THE WESTERN FRINGES MOISTURE WILL ALREADY BE DIMINISHING BY AFTERNOON AND STORMS MAY REMAIN DRY. HIGH TEMPERATURES WEDNESDAY WILL BE SEVERAL DEGREES LOWER THAN THEY WILL BE TOMORROW...MAINLY DUE TO THE INFLUX OF CLOUDS. RCM && .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. THE EXTENDED PERIOD COULD BE A FAIRLY ACTIVE TIME. THE MODELS ARE NOT IN VERY GOOD AGREEMENT...ESPECIALLY GOING INTO THE WEEKEND. WED NIGHT INTO THU WILL SEE SOME LINGERING MONSOON MOISTURE ACROSS THE EASTERN CWA WHICH COULD LEAD TO SOME SHOWERS AND THUNDERSTORMS. TEMPERATURES WILL CONTINUE TO BE ABOVE NORMAL AS WARM AIR WILL REMAIN IN PLACE WITH SOUTHERLY FLOW AHEAD OF A CUTOFF LOW MOVING IN FROM THE PACIFIC. THIS CUTOFF LOW IS WHERE THERE IS GREAT DISCREPANCY IN THE MODELS. ECMWF IS FURTHER NORTH AND MORE PROGRESSIVE THAN THE GFS. THE GFS SOLUTION BRINGS UPPER LOW INTO SOUTHERN NV AND JUST SLOWLY MOVES IT NE INTO THE EARLY PART OF NEXT WEEK. THE ECMWF BRINGS LOW ACROSS NORTHERN NV AND HAS IT MOVING OUT OF AREA BY SUN. MOST OF THE GFS ENSEMBLE MEMBERS SUPPORT MORE OF A ECMWF SOLUTION WHICH IS ALSO SIMILAR TO THE CANADIAN SO WILL FOLLOW THIS SOLUTION GOING INTO THE WEEKEND. KEPT MENTION OF SHOWERS ACROSS MOST OF CWA FOR SAT WITH HIGHER POPS ACROSS THE NORTHERN ZONES. TEMPERATURES WILL COOL OFF WITH SOME AREAS POSSIBLY REMAINING IN THE 60S ACROSS THE NORTH WITH 70S ELSEWHERE ON SAT. EXPECT A SHORTWAVE RIDGE TO MOVE ACROSS THE REGION ON SUN WHICH WILL HELP TO WARM TEMPERATURES BACK UP A BIT BEFORE ANOTHER STORM SYSTEM WITH A FAIRLY STRONG COLD FRONT MOVES IN FOR MONDAY. TIMING OF THE FRONT MONDAY WILL BE CRITICAL TO THE TEMPERATURE FORECAST. RIGHT NOW THE ECMWF DOES NOT HAVE FRONT PASSING THROUGH SOUTHERN ZONES UNTIL MONDAY NIGHT WHICH COULD ALLOW HIGHS TO GET INTO THE 80S SOUTH WITH JUST 70S AND POSSIBLY 60S NORTH. RIGHT NOW DO NOT HAVE A REAL STRONG TEMPERATURE GRADIENT ACROSS THE CWA AND WILL WAIT TO SEE IF THERE IS BETTER MODEL CONSENSUS AND CONSISTENCY WITH TIMING ISSUES IN LATER RUNS. JMG && .AVIATION...UPPER LEVEL RIDGE WILL GRADUALLY MOVE EASTWARD OVER THE NEXT 24 HOURS. THIS WILL KEEP SKIES MOSTLY CLEAR SKIES EAST AND SOME CUMULUS BUILDUPS OVER THE WEST BY TUE AFTERNOON. WINDS WILL GENERALLY REMAIN LIGHT THROUGH TUE MORNING AND THEN START TO TURN MORE SOUTHERLY TUE AFTERNOON. JMG && .FIRE WEATHER...HIGH PRESSURE WILL KEEP DRY CONDITIONS AND LIGHT WINDS PREVALENT THROUGH TOMORROW MORNING. AN APPROACHING TROUGH COMBINING WITH A LATE-SEASON PUSH OF MONSOONAL MOISTURE WILL CAUSE SOME ISOLATED DRY THUNDERSTORMS LATE TOMORROW IN ZONES 451...454... AND 457...BUT THEY SHOULD BE VERY FEW AND FAR BETWEEN. AS SOUTHERLY WINDS PICK UP BETWEEN THE RIDGE TO OUR EAST AND THE LOW TO OUR WEST...GUSTS MAY BRIEFLY REACH" onClick="return popup(this, 'notes')">REACH 30 MPH ACROSS ZONE 457. RH WILL NOT RECOVER MUCH TONIGHT AND WILL BE VERY LOW DURING THE DAY TOMORROW IN ALL ZONES. THE TROUGH MOVES ACROSS THE REGION ON WEDNESDAY AND COUPLED WITH THE MONSOONAL MOISTURE PUSH...WIDESPREAD ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED. MANY STORMS WILL LEAN TOWARDS BEING WET THANKS TO THE ADDITIONAL MOISTURE AND STRONGER DYNAMICS WITH THE TROUGH...BUT THE WESTERN PORTIONS OF ZONES 451 AND 457 MAY SEE MORE DRY STORMS AS MOISTURE WILL ALREADY BE EXITING THESE ZONES AS WINDS ALOFT TURN MORE WESTERLY BY AFTERNOON. WINDS WILL NOT BE AS STRONG ON WEDNESDAY AFTERNOON AS THEY ARE EXPECTED TO BE TOMORROW AFTERNOON...AND RH`S WILL GENERALLY BE HIGHER BOTH TOMORROW NIGHT AND WEDNESDAY...AT LEAST COMPARED TO THE RH`S EXPECTED TONIGHT AND TOMORROW. RCM && .LKN WATCHES/WARNINGS/ADVISORIES...NONE. $$