043 FXUS65 KGGW 230953 AFDGGW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 353 AM MDT MON APR 23 2012 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH WEDNESDAY... SYNOPTIC SET UP... A LARGE TROUGH SETS OVER THE EASTERN HALF OF THE US AND CANADA WHILE AN EQUALLY LARGE TROUGH SITS OVER THE WESTERN HALF OF THE TWO COUNTRIES. MEANWHILE ANOTHER TROUGH HAS SET ITSELF UP OFF THE WEST COAST AND IS IN THE PROCESS OF SEPARATING WITH A DETACHED LOW OFF OF THE CALIFORNIA. TODAY THROUGH TONIGHT... THE RIDGE IS ANTICIPATED TO REMAIN IN PROMINENCE. HOWEVER... A FEW ISOLATED SHORTWAVES EMBEDDED IN THE FLOW WILL PASS BY THE TOP OF THE RIDGE AND FLATTEN IT DESTABILIZING IT BY THE LATE AFTERNOON HOURS LEADING INTO THE EVENING. ISOLATED SHOWERS AND THUNDERSTORMS ARE ANTICIPATED TO FIRE OVER THE HIGHER TERRAIN AND OF CENTRAL MONTANA MOUNTAINS AND THEN SPREAD OVER THE HIGH PLAINS. THE ONLY ISSUE IS THE LOW RHS NEAR THE SURFACE WHICH WILL LIMIT SHOWER ACTIVITY TO SMALL AREAS. AS PER THE INVERTED V SOUNDING VIRGA WILL BE A COMMON SITE FOR MOST PLACES. TUESDAY THROUGH WEDNESDAY... ON THE LARGE SCALE FOUR LOW PRESSURE CENTERS SPACED AROUND THE RIDGE WILL BEGIN TWISTING... CONTORTING... AND FINALLY BREAKING DOWN THE RIDGE OVER THE CENTRAL PLAINS. THE FIRST POINT OF THIS WILL BE TO SEND MOST OF THE HARSH CONTINENTAL HEAT BACK INTO THE NEW MEXICO AND TEXAS. A SUBTLE WEAK COLD FRONT WILL THEN BE CAPABLE OF OVER RUNNING THE REMAINDER OF WARM TEMPS IN EASTERN MONTANA TUESDAY NIGHT. THIS WILL PLACE NORTHEAST MONTANA INTO A NORTHWESTERN FLOW PATTERN AND REDUCE TEMPERATURES AND ALLOW FOR SLIGHT CHANCES AT SHOWERS AND THUNDERSTORMS THROUGHOUT THE THREE PERIODS. MOISTURE WILL BE LIMITED DUE TO NO SOURCE TAP SUCH AS THE PACIFIC OR GULF OF MEXICO. THEREFORE... SIGNIFICANT QPF AMOUNTS WILL BE VERY HARD TO COME BY FOR ANY STORMS THAT DO FORM. GAH .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY... CONTINUED REASONABLY GOOD MODEL AGREEMENT THROUGH THE EXTENDED PERIOD WITH A NEGATIVELY TILTED TROF MOVING INTO THE WESTERN STATES. THIS WILL REPLACE THE WARM DRY AIRMASS CURRENTLY IN PLACE WITH A COOLER AND WETTER AIRMASS AND MORE UNSETTLED CONDITIONS. STRONG LOW LEVEL JET DEVELOPS ON THURSDAY ACROSS THE HIGH PLAINS AS PRESSURE FALLS OVER THE NORTHERN ROCKIES WITH TROF MOVING ACROSS ONSHORE. MODELS BEGINNING TO SPLIT OFF THE SOUTHERN PORTION OF THE TROF INTO A PARTIALLY CLOSED LOW TRACKING FROM THE FOUR CORNERS REGION INTO THE CENTRAL PLAINS LATE IN THE WEEK WHILE THE NORTHERN PORTION OF THE TROF ROTATES ACROSS MONTANA. MODELS PUTTING BEST CHANCE OF PRECIPITATION WITH THE COLD FRONT PASSAGE THURSDAY NIGHT INTO FRIDAY...THEN KEEPING INSTABILITY SHOWERS OVER THE REGION INTO THE WEEKEND. RELUCTANT TO GO TOO HIGH WITH POPS GIVEN RECENT POOR PERFORMANCE OF MODELS WITH OVER FORECASTING PRECIPITATION EVENTS IN NORTHEAST MONTANA. MODEL TREND TOWARD DEVELOPING A STRONGER SOUTHERN SYSTEM ALSO PROBLEMATIC FOR POPS AS IT COULD LIMIT NORTHWARD MOISTURE TRANSPORT. THUS BACKED OFF SLIGHTLY ON POP FORECAST. EBERT && .AVIATION... VFR. MOSTLY CLEAR SKIES WITH LIGHT WINDS BECOMING WEST BY THE AFTERNOON. CLOUDS WILL INCREASE LATE IN THE DAY AND ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE OVERNIGHT AS A COLD FRONT MOVES THROUGH THE AREA. && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW