999 FXUS65 KBYZ 020826 AFDBIL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 222 AM MDT SUN MAY 2 1999 LOOKING AT 500MB THIS MORNING...THE HIGHEST PRESSURE RISES OF THE U.S. APPEAR OVER THE GREAT LAKES STATES AND THE SOUTHEAST. THIS WOULD INDICATE THE RIDGE WILL CONTINUE TO GRADUALLY SLIDE EAST. THE SLOW EASTWARD PROGRESSION HAS ALLOWED THE SOUTHWEST CUTOFF LOW TO MOVE INTO NE NEW MEXICO/SE COLORADO. MODELS SIMILAR IN KICKING LOW NORTHEAST INTO THE NORTHERN PLAINS TONIGHT. NORTHERN PART OF THIS SYSTEM BRUSHES THE SOUTHEAST CORNER OF FORECAST AREA. ATMOSPHERE WILL BE MARGINALLY UNSTABLE...THUS WILL MAINTAIN SCATTERED POPS. THE LOW WILL BE KICKED NORTHEAST COURTESY OF JET ENERGY DIVING SOUTHEAST AT 45N 135W. THIS ENERGY PENETRATING A LOT FARTHER SOUTH THEN PREVIOUS WAVE...SO WILL HAVE MUCH MORE OF A KICK. HANDLING OF THIS ENERGY IS WHERE THE MODELS DIFFER. THE ETA/NGM KEEP THE ENERGY FARTHER NORTH WITH THE AVN DIVING IT MORE SOUTHEAST. THE AVN THUS DEEPENS THE DEVELOPING TROUGH MORE THAN THE OTHER TWO MODELS. THIS DIFFERENCE WOULD LEAD TO THE AVN BEING SLOWER WITH THE EASTWARD ADVANCEMENT OF THE TROUGH AXIS AND RELATED SURFACE COLD FRONT. WATER VAPOR POINTS TO A FARTHER SOUTHWARD PUSH OF THE JET. UPPER LOW AT 35N 160W RETROGRADING...OPENING THE DOOR FOR THIS WAVE. PLUS THE DESERT SOUTHWEST UNDER WEAK TROUGHINESS AT THE MOMENT OFFERING LITTLE RESISTENCE. AT ANY RATE...WILL GO WITH THE AVN THIS PACKAGE. THUS WILL GO WARMER MONDAY THAN MOS GUIDANCE. DEEPENING CYCLONIC FLOW WILL ALLOW FOR CONTINUATION OF SCATTERED POPS WITH A SLIGHTLY BETTER CHANCE MONDAY. HUMPHREY UK AND EURO NEWEST MEDIUM RANGE MODELS TO LOOK AT WHILE STILL AWAITING ARRIVAL OF THE MRF. MODELS CONTINUE TO SHOW STRONG WESTERLIES DIVING ACROSS THE GULF OF AK AND INTO THE PACIFIC NW/NORTHERN CA. EVENTUALLY THIS STRETCHES ACROSS THE CENTRAL AND NORTHERN ROCKIES. VERY DIFFICULT FOR MODELS TO RESOLVE EACH AND EVERY SHORTWAVE IN SHORT TERM...LET ALONE THE EXTENDED. THUS THE 3 TO 5 DAY PERIOD LOOKS TO BE SLIGHTLY COOLER THAN NORMAL WITH A CONTINUED CHANCE FOR SHOWERS. UK IS AGGRESSIVE AT MOVING THE LONG WAVE PATTERN ALONG...KEEPING EASTERN MT UNDER CYCLONIC UPPER FLOW TUE AND WED WITH RIDGING FOLLOWING ON THU. THIS FOLLOWED BY ANOTHER BLOCKY TYPE PATTERN FROM THE E PACIFIC TO THE STATES. EURO MOSTLY IN AGREEMENT WITH THIS SCENARIO EARLY THEN DIVERGES GREATLY LATER IN THE PERIOD DEVELOPING BROADER UPPER RIDGING OVER THE AREA. CANEPA BIL BE 066/042 061/040 049 55234 LVM .. 062/038 057/... ... 55344 HDN .. 070/040 065/... ... 55234 MLS .. 073/046 067/044 ... 55334 4BQ .. 071/044 065/... ... 55334 BHK .. 070/043 065/... ... 55334 SHR BE 066/040 061/038 049 55234 BUR BE 050/030 045/026 036 55234