000 FXUS65 KVEF 191135 AFDLAS MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAS VEGAS NV 435 AM PDT SUN MAY 19 2002 SYNOPSIS...A VERY STRONG STORM SYSTEM ALONG THE WEST COAST IS FORECAST TO MOVE OVER NORTHERN NEVADA MONDAY NIGHT AND TUESDAY. THIS WILL RESULT IN A DRAMATIC CHANGE TO THE WEATHER ACROSS THE SOUTHERN GREAT BASIN AND MOJAVE DESERT. THE MAIN CHANGE WILL BE WINDY TO VERY WINDY CONDITIONS THIS AFTERNOON AND MONDAY ALONG WITH A 10 TO 20 DEGREE TEMPERATURE DROP IN THE DAYTIME HIGHS FOR MONDAY AND TUESDAY. DISCUSSION...THE APPROACHING PACIFIC LOW WAS CENTERED NEAR 41N/132W WITH A SHORTWAVE SWING THROUGH THE BASE OF THE TROUGH NEAR 35N/130W. BOTH THE ETA AND AVN INITIALIZED THE SYSTEM WELL AND ARE QUITE SIMILAR IN THE FORECAST EVOLUTION THROUGH 60 HOURS. THE MAIN EFFECT THIS SYSTEM TODAY WILL TAKE THE FORM OF FAIRLY STRONG SURFACE WINDS ACROSS EASTERN CALIFORNIA AND CENTRAL NEVADA. A SURFACE LOW RAPIDLY DEEPENS OVER NORTHEAST NEVADA THIS AFTERNOON COMBINED WITH A STRONG WEST TO EAST THERMAL GRADIENT ORIENTED OVER NORTHERN CALIFORNIA AND NEVADA. THIS SYSTEM IS NOT AS TYPICAL AS THOSE WE HAVE SEEN THIS SPRING WHICH HAVE PRODUCED STRONG WINDS WITHIN THE FORECAST AREA. INSTEAD OF APPROACHING FROM THE NORTHWEST WITH STRONG COLD AIR ADVECTION...IT SWINGS INLAND WITH A NEGATIVE TILT AND A WEST TO EAST MIGRATION OF THE COLD FRONT ON MONDAY. THE LATEST GUIDANCE DOES NOT INDICATE WIND SPEEDS APPROACHING HIGH WIND WARNING (SUSTAINED OVER 40 MPH WITH GUSTS TO 60 MPH) OVER SOUTHEAST CALIFORNIA AND SOUTHERN NEVADA. A MSLP GRADIENT OF 12-14 MB IS FORECAST MONDAY AFTERNOON BETWEEN THE SOUTHERN CA COAST AND SOUTHERN NV BUT THE 700 MB THERMAL GRADIENT WAS ONLY ABOUT 12 DEGREES C. FORECAST SPEEDS AT 850 AND 700 MB BY THE ETA AND AVN DID NOT APPEAR OVERLY IMPRESSIVE...GENERALLY IN THE 25-35 KNOT RANGE. WE BELIEVE ADVISORY LEVEL WINDS (SUSTAINED 30 MPH OR MORE WITH GUSTS OVER 40 MPH) WILL BE OBSERVED BUT CONFIDENCE IS NOT REAL HIGH AT THIS TIME IN AN EXCEPTIONALLY STRONG WIND EVENT FOR MONDAY IN SE CA/SRN NV. LATER SHIFTS WILL MONITOR CLOSELY OF COURSE. AS THE COLD POOL SWINGS ACROSS CENTRAL AND NORTHERN NEVADA MONDAY NIGHT...UPWARD FORCING SHOULD COMBINE WITH ENOUGH MOISTURE AND INSTABILITY FOR SHOWERS ACROSS CENTRAL NEVADA. ADDED WORDING ACCORDINGLY. COOLEST TEMPERATURES BEHIND THE TROUGH OCCUR TUESDAY ALONG WITH INSTABILITY SHOWERS OVER THE NORTHERN ZONES. NO CHANGE TO THE EXTENDED PERIOD AS THE LATEST ECMWF AND MRF ARE IN FAIR AGREEMENT WITH THE IDEA OF FLAT RIDGE OVER THE WEST AND A WEAK TROUGH OFF THE SRN CA COAST AND OUR AREA IN THE MIDDLE FOR NEAR NORMAL CONDITIONS. ADAIR .LAS...A WIND ADVISORY IS IN EFFECT TODAY FOR CA ZONES 26-27 AND NV ZONES 13-15. PLEASE SEE WWUS45 FOR DETAILS.