Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000 FXUS65 KVEF 021353 AFDVEF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAS VEGAS NV 700 AM PDT MON MAY 2 2016 .SYNOPSIS...A WEAK CIRCULATION WILL MOVE OVER SOUTHERN NEVADA AND SURROUNDING AREAS MONDAY ENHANCING THE CHANCES OF SHOWERS AND THUNDERSTORMS ESPECIALLY OVER THE HIGHER TERRAIN OF SOUTHERN NEVADA AND NORTHWEST ARIZONA. A STEADY WARMUP WILL OCCUR AS THE AREA BRIEFLY DRIES OUT TUESDAY AND WEDNESDAY BEFORE ANOTHER POTENT SLOW- MOVING SYSTEM BRINGS MORE INCLEMENT WEATHER AND COOL TEMPERATURES TO THE REGION BY THE END OF THE UPCOMING WEEK. && .UPDATE...
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MADE A FEW CHANGES TO THE GRIDS THIS MORNING BASED ON LATEST RADAR/SATELLITE TRENDS AS WELL AS UPDATED HI-RES GUIDANCE. AREA OF SHOWERS HAS PERSISTED MUCH OF THE NIGHT IN SOUTHERN INYO AND NORTHERN SAN BERNARDINO COUNTIES IN CLOSE PROXIMITY TO WEAK LOW- LEVEL CONVERGENCE AND LARGE-SCALE ASCENT ASSOCIATED WITH A VORT MAX MOVING INTO SOUTHEAST CALIFORNIA THIS MORNING. MESOANALYTICAL TRENDS SUGGEST THIS LARGE-SCALE ASCENT IS WEAKENING, PARTICULARLY IN ADJACENT SOUTHERN NEVADA, WHERE MORE ISOLATED SHOWERS HAVE ALSO OCCURRED. NEVERTHELESS, HI-RES MODELS HAVE HANDLED THIS PRECIP POORLY OVERNIGHT, WITH MOST SIMULATIONS SHOWING LITTLE OR NO PRECIP AND THOSE THAT DO (NAMELY, THE HRRR) WEAKENING THIS PRECIP TOO RAPIDLY. AS SUCH, INCREASED POPS AND ASSOCIATED SKY COVER IN THESE AREAS THIS MORNING. IN ADDITION...RECENT HI-RES SIMULATIONS HAVE SUBTLY INCREASED SCATTERED PRECIP BREAKING OUT THIS AFTERNOON ACROSS THE AREA. GIVEN THE UNDER-PREDICTION OF PRECIP TONIGHT, FELT INCLINED TO INCREASE POPS A BIT MORE ACROSS THE AREA THIS AFTERNOON, ESPECIALLY GIVEN THE VORT MAX MOVING THROUGH THE AREA. 12Z KVEF SOUNDING SHOWS SUBTLE COOLING IN THE MIDLEVELS, SUGGESTING AFTERNOON INSTABILITY MAY BE SOMEWHAT IMPROVED COMPARED TO YESTERDAY. STILL THINK PRECIP WILL BE SPOTTY AND MOSTLY LIGHT...WITH MOST VALLEY LOCATIONS REMAINING DRY...BUT FELT THAT INCREASING POPS A TAD BETTER MATCHES TRENDS.
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&& .PREVIOUS DISCUSSION...
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241 AM PDT MON MAY 2 2016 .SHORT TERM...THROUGH WEDNESDAY NIGHT. WV AND IR SATELLITE IMAGERY DEPICT A WEAK SHORTWAVE TROUGH BEGINNING TO PIVOT EASTWARD IN CENTRAL CALIFORNIA THIS MORNING. MODELS HAVE FORECAST THE TRACK OF THIS CIRCULATION WELL SO FAR AND CONTINUE TO AGREE ON ITS TRACK ESE TODAY INTO SOUTHERN NEVADA AND INTO NORTH- CENTRAL ARIZONA BY 12Z TUESDAY. THE PRESENCE OF THIS COLD TROUGH AND ASSOCIATED (ALBEIT WEAK) LARGE-SCALE ASCENT SHOULD AID IN THE DEVELOPMENT OF MORE ISOLATED-SCATTERED SHOWERS AND STORMS ACROSS THE AREA DURING THE LATE MORNING THROUGH EARLY EVENING HOURS TODAY. SUSPECT THAT SHOWER ACTIVITY MAY GET GOING A LITTLE EARLIER TODAY GIVEN THE CLOSER PROXIMITY OF THE TROUGH. HI-RES GUIDANCE KEEPING MOST PRECIP IN THE HIGHER TERRAIN AGAIN TODAY, WHICH IS WHERE THE HIGHEST POPS RESIDE. HOWEVER, WAS INCLINED TO KEEP POPS A LITTLE HIGHER THAN GUIDANCE IN THE VALLEYS GIVEN THE SYSTEM`S TRACK OVER THE AREA TODAY. HOWEVER, SHOWERS WILL BE SPOTTY AND ANY PRECIP AMOUNTS WILL BE LIGHT. KEPT THUNDER IN THE GRIDS GIVEN EXPECTED SUFFICIENT CAPE DURING THE PEAK HEATING HOURS. AS LOCALIZED PROCESSES WILL ONCE AGAIN BE IMPORTANT IN THE DEVELOPMENT OF CONVECTION, ANY PRECIP SHOULD RAPIDLY DIMINISH WITH THE LOSS OF DAYTIME HEATING AND NO MENTIONABLE POPS ARE IN THE GRIDS AFTER 06Z TUESDAY. DEEP SOUTHERLY TO SOUTHWESTERLY FLOW DEVELOPS OVER THE AREA BEGINNING TUESDAY AS THE AREA EXPERIENCES TRANSIENT HIGH-AMPLITUDE RIDGING DOWNSTREAM OF A DEEP EASTERN PACIFIC TROUGH. TEMPERATURES WILL WARM RAPIDLY IN THIS REGIME, WITH MAX TEMPS TUESDAY AND WEDNESDAY 3-10 DEGREES ABOVE NORMAL GENERALLY. SLIGHTLY HIGHER TEMPS ARE FORECAST WEDNESDAY AS STRONGER SOUTHERLY SURFACE FLOW BECOMES ESTABLISHED, INDUCING STRONGER MIXING. THOUGH MOST OF THE AREA WILL BECOME BREEZY ON WEDNESDAY, FORECAST SPEEDS SO FAR MERELY APPROACH ADVISORY LEVELS (ESPECIALLY IN THE SOUTHERN GREAT BASIN). NEVERTHELESS, THIS WILL REQUIRE MONITORING AS THE LARGE PACIFIC TROUGH APPROACHES THE AREA. REGARDING THE APPROACH OF THIS SYSTEM...MODELS ARE IN DECENT AGREEMENT ON TIMING/AMPLITUDE, WITH THE NAM PERHAPS THE SLOWEST AND THE MOST AMPLIFIED. THIS IS TIED TO THE STRENGTH OF THE DOWNSTREAM RIDGING IN THE INTERMOUNTAIN WEST, WHICH IS GENERALLY DEPICTED TO BE FLATTEST WITH THE GFS (THUS MAKING IT THE FASTER SOLUTION). SUSPECT REALITY WILL FAVOR THE DEEPER/MORE AMPLIFIED SOLUTIONS...SO NOT ENTIRELY SOLD ON THE GFS TIMING OF THE SYSTEM`S APPROACH TO THE AREA. REGARDLESS, WEAK VORTICITY LOBES EMBEDDED IN THE LARGE-SCALE TROUGH WILL BEGIN AFFECTING THE SIERRA BY WEDNESDAY AFTERNOON AND HAVE MAINTAINED/SLIGHTLY INCREASED POPS IN THIS AREA WEDNESDAY AFTERNOON AND NIGHT. .LONG TERM...THURSDAY THROUGH MONDAY. THURSDAY WILL BEGIN WITH THE LARGE CLOSED PACIFIC LOW MEANDERING EASTWARD ACROSS CALIFORNIA. BREEZY TO LOCALLY WINDY CONDITIONS WILL CONTINUE THURSDAY, AS MOISTURE AND ASSOCIATED SHOWERS AND A FEW THUNDERSTORMS SPREAD INTO OUR WESTERN FORECAST AREA. CHANCES SPREAD EAST THURSDAY NIGHT AND FRIDAY AS THE LOW SLOWLY MAKES ITS WAY TO SOUTHERN NEVADA. MODELS SEEM TO BE IN BETTER AGREEMENT THIS MORNING PUSHING THE LOW INTO NORTHWEST ARIZONA FRIDAY NIGHT AND SATURDAY, THEN FINALLY INTO UTAH AND COLORADO SATURDAY NIGHT AND SUNDAY. EXPECT UNSETTLED WEATHER, INCREASING FROM WEST TO EAST THURSDAY AND THURSDAY NIGHT, ACROSS MUCH OF THE AREA FRIDAY AND SATURDAY, THEN DIMINISHING CHANCES FROM WEST TO EAST SUNDAY. SNOW LEVELS WILL DROP TO AROUND 6500-7000 FEET IN THE FRIDAY THROUGH SATURDAY TIME FRAME. EVEN WITH THE LOW EAST OF OUR AREA, MOISTURE SHOULD LINGER INTO MONDAY, BEFORE RIDGING ALOFT SETTLES INTO THE REGION. SO, THE DEVELOPMENT OF SHOWERS AND STORMS REMAIN POSSIBLE MONDAY AFTERNOON AND EARLY EVENING, MAINLY NORTH AND EAST OF LAS VEGAS. TEMPERATURES WILL TREND COOLER HEADING INTO THE WEEKEND, WITH READINGS SOME 5-10 DEGREES BELOW NORMAL EXPECTED. TEMPS WILL THEN TREND WARMER MONDAY.
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&& .AVIATION...FOR MCCARRAN...SKC-FEW CLOUDS AROUND 10K FEET OVERNIGHT WITH SOUTH TO SOUTHWEST WINDS AROUND 5-7 KTS. FEW-SCT CLOUDS AROUND 8-10K FEET MONDAY WITH ISOLATED SHOWERS OVER THE HIGHER TERRAIN. WINDS WILL TRANSITION TO A NORTHEAST DIRECTION AFTER 18Z WITH SPEEDS AROUND 7 KTS. SOME OF THE HIGHER PEAKS COULD BE OBSCURED. FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA...FEW-SCT CLOUDS AROUND 10K FEET OVERNIGHT ALONG WITH WINDS UNDER 10KTS. ISOLD SHRA OVER THE HIGHER TERRAIN AFTER 18Z MONDAY WITH WINDS REMAINING UNDER 10 KTS. SHOWER ACTIVITY IS EXPECTED TO DIMINISH AFTER SUNSET. LOCAL MOUNTAIN OBSCURATIONS NEAR SHOWERS. && .SPOTTER INFORMATION STATEMENT...ACTIVE WEATHER IS EXPECTED TODAY. SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER ACCORDING TO STANDARD OPERATING PROCEDURES. && $$ UPDATE/SHORT TERM...SHAFER LONG TERM...PADDOCK AVIATION...GORELOW FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE: HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER

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