Issued by NWS Bismarck, ND
000 FXUS63 KBIS 210927 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 420 AM CDT SUN SEP 21 2008 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT... THE SHORT TERM LOOKS TO GET QUITE ACTIVE WITH THUNDERSTORM CHANCES AS THE WEST COAST NEGATIVELY TILTED TROF ADVANCES EAST. SOUTHEAST FLOW INCREASES TODAY IN TIGHTENING PRESSURE GRADIENT... RESULTING IN DEWPOINTS IN THE MID 50S. SOUTHERN AREAS SHOULD BE CLOSE TO WIND ADVISORY CRITERIA BUT ENOUGH UNCERTAINTY REMAINS TO HOLD OFF ON ANY HEADLINES FOR THAT. A SERIES OF SHORT WAVES ROUND THE BASE OF THE TROF AND BRING OUR RECENT DRY / WARM SPELL TO AN END. WILL EXPECT STORM CHANCES TO BE PROLONGED AS THE SURFACE FRONT IS SLOW TO MOVE...PROVIDING A PROLONGED PERIOD OF CONVERGENCE AND LIFT ALONG / AHEAD OF IT. SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA ARE IN A SLIGHT RISK FOR SEVERE STORMS DAY 1...AND CENTRAL AND EASTERN FOR DAY 2. WILL HIGHLIGHT SEVERE RISK IN THE HAZARDOUS WEATHER OUTLOOK PRODUCT. OTHER CONCERN RAISED AMONG THE FORECAST STAFF THIS MORNING IS HEAVY RAIN. PRECIPITABLE WATER VALUES INCREASE TO OVER AN INCH...TO NEAR 1.50 INCHES...LATER TODAY AND HOLD THERE INTO MONDAY. TO SUPPORT THIS...K INDEX VALUES NEAR THRESHOLD VALUES TONIGHT. UNSETTLED WEATHER CONTINUES THROUGH MONDAY AS A RESULT OF THE SLOW MOVING SURFACE SYSTEM...AND EVEN INTO TUESDAY IN CYCLONIC FLOW SURFACE AND ALOFT. A MORE ZONAL FLOW SETS UP FOR WEDNESDAY WITH DRYING CONDITIONS THEN. BEST CHANCES OF RAIN LOOK TO BE TONIGHT...AND AGAIN LATER MONDAY ...BASED ON VORTICITY MAXIMA TIMING. TEMPERATURES THROUGH THE PERIOD...HIGHEST TODAY AHEAD OF THE FRONT ...ABOUT NORMAL BY TUESDAY AND WEDNESDAY. && .LONG TERM...THURSDAY THROUGH SATURDAY NIGHT... MAINLY WESTERLY UPPER LEVEL FLOW CONTINUES FOR THURSDAY WITH SHORTWAVE ENERGY SKIMMING TO THE NORTH IN SRN CANADA THROUGH FRIDAY. NEW SHORTWAVE ENERGY DEVELOPS OFF THE PACIFIC NW STATES ON SATURDAY THOUGH THERE IS SOME DISPARITY WITH THE GFS AND ECMWF RUNS. OVERALL TREND IS TO CONTINUE WARM THOUGH PRECIPITATION CHANCES SMALL AT BEST. && .AVIATION... SYSTEM COMING INTO THE REGION TODAY WILL OFFER INCREASING MID-LEVEL CLOUDS FROM 8,000 TO 10,000 FEET AND A CHANCE OF SHOWERS AND THUNDERSTORMS PARTICULARLY IN THE AFTERNOON. THIS CHANCE WILL CONTINUE INTO THE NIGHT AND INTO THE DAY ON MONDAY. EXPECT MAINLY VFR TO OCCASIONALLY MVFR CEILINGS. && .FIRE WEATHER... THERE IS SOME CONCERN OVER DRY LIGHTNING TODAY...BUT NOT ENOUGH TO WARRANT ANY HEADLINES FOR IT. ALL AREAS SHOULD RECEIVE ENOUGH RAIN LATER TODAY / TONIGHT TO DIMINISH THAT RISK. OTHERWISE...NO FIRE WEATHER CONCERNS. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ JPM/VJ
