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Area Forecast Discussion

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...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.
&&

.PREVIOUS DISCUSSION...
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.
&&

.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

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