000 FXUS63 KBIS 121622 AFDBIS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 1122 AM CDT SUN OCT 12 2008 .UPDATE... LOWER THAN FORECAST SNOW AMOUNTS ACROSS PARTS OF THE WEST MAY HAVE BEEN UNDER-FORECAST FOR TODAY. SOME REPORTS OF MODERATE TO HEAVY SNOW HAVE BEEN RECEIVED ALONG THE MONTANA/NORTH DAKOTA BORDER THIS MORNING...WITH OVER 6 INCHES ON THE GROUND IN THE WATFORD CITY AREA AND A FOOT OF ACCUMULATION JUST WEST OF BEACH ND IN EASTERN MONTANA. IT LOOKS LIKE THE BULK OF WILLISTON SNOW WILL COME FROM THE COMMA HEAD DEFORMATION SNOWS LATER TODAY AS THE AREA OF FORCING MOVES EASTWARD OUT OF MONTANA. HAVE LOWERED PRECIPITATION CHANCES A BIT OVER TH SOUTHWESTERN PART OF THE STATE. THE DRY SLOT IS FILLING IN WITH LIGHT PRECIPITATION...BUT EXPECT TROPOPAUSE FOLD TO EXPAND AND SQUASH FORCING THERE. OTHERWISE...FORECAST LOOKS GOOD. && .PREV DISCUSSION... /ISSUED 344 AM CDT SUN OCT 12 2008/ SHORT TERM...TODAY THROUGH TUESDAY NIGHT... FORECAST CONCERNS/HIGHLIGHTS IN THE SHORT TERM PERIOD CONTINUE TO CENTER ON THE STRONG CLOSED UPPER LOW AND ITS RESULTANT WEATHER ACROSS THE NORTHERN PLAINS OVER THE NEXT 36 HOURS. SPECIFICALLY WILL FOCUS ON PRECIPITATION TYPE AND AMOUNTS OVER THE NEXT 12-24 HOURS. MODELS ARE IN DECENT AGREEMENT EARLY THIS PERIOD SO WILL UTILIZE A GENERAL BLEND. MONDAY INTO MONDAY NIGHT THE NAM BECOMES THE OUTLIER SO WILL SIDE CLOSER TO THE LATEST VERSIONS OF THE GFS AND ECMWF HERE AND AFTERWARD. CURRENT SYNOPSIS...THE CLOSED MID/UPPER LOW REMAINS CENTERED OVER THE INTERMOUNTAIN WEST REGION OF SOUTHEASTERN ID/NORTHERN UT. A 150 KT UPPER LEVEL JET STREAK ROTATING AROUND THE BASE OF THE LOW HAS STARTED ITS NORTHEASTWARD MIGRATION TOWARDS THE NORTHERN PLAINS. AHEAD OF THIS STREAK IN ITS LEFT EXIT REGION DIVERGENCE ALOFT HAS ENHANCED VERTICAL MOTION ACROSS THE LOCAL REGION WITH LIGHT TO MODERATE PRECIPITATION OVER THE ENTIRE FORECAST AREA THIS MORNING. PRECIPITATION IS IN THE FORM OF RAIN CENTRAL AND EAST WHERE WEAK WAA IS COUNTERING THE AFFECTS OF DYNAMIC COOLING. FURTHER WEST AND ACROSS THE NORTH CENTRAL WAA IS VIRTUALLY NON-EXISTENT AND HAS ALLOWED THE DYNAMIC COOLING PROCESSES TO QUICKLY CHANGE ALL PRECIP OVER TO SNOW. FURTHERMORE...PRECIPITATION INTENSITY IS BEING ENHANCED IN THE LOW/MID LEVELS BY STRONG MOISTURE ADVECTION AND 35-50KTS OF ISENTROPIC LIFT ACROSS THE DAKOTAS. A STRONG UPPER LEVEL S/WV IMPULSE IS FORECAST TO EJECT NORTHEAST FROM THE PARENT LOW INTO THE NORTHERN HIGH PLAINS OVER THE NEXT FEW HOURS AND WILL FURTHER ENHANCE PRECIPITATION INTENSITIES ACROSS WESTERN NORTH DAKOTA. IN ADDITION...UPPER LEVEL DIVERGENCE AND ISENTROPIC UPGLIDING REMAIN MODERATE TO STRONG THROUGHOUT THE MORNING HOURS SO EXPECT LIGHT TO MODERATE RAIN AND SNOW TO CONTINUE WITH A FEW HEAVIER AREAS WEST CLOSER TO WHERE THE STRONG IMPULSE WILL TRACK. GIVEN THAT DYNAMIC COOLING HAS ALREADY CHANGED PRECIP OVER TO SNOW WEST AND WITH POSSIBLE HEAVIER BANDS OVER THE NEXT SEVERAL HOURS...SEE NO REASON TO MAKE ANY CHANGES TO THE CURRENT WINTER STORM WARNING. OBSERVATIONS OF LIGHT SNOW IN THE MINOT AREA ARE EXPECTED TO CHANGE BACK OVER TO ALL RAIN...OR PERHAPS SOME -FZRA...BETWEEN 12-18Z AS MID LEVEL WAA PUSHES SLOWLY FURTHER WEST AND NORTHWEST. THUS STILL A MIXED BAG OF PRECIP TYPE POSSIBLE ALONG A CORRIDOR FROM HETTINGER NORTH TO DICKINSON...THEN NORTH- NORTHEAST TO AROUND MINOT WHERE MID LEVEL WAA AND DYNAMIC COOLING WILL BATTLE EACH OTHER. MAYBE SOME LIGHT TO MODERATE SNOW ACCUMULATIONS ALONG THIS LINE ALSO THIS MORNING GIVEN LIGHT SNOW HAS BEEN REPORTED AT DIK FOR SEVERAL HOURS NOW. THUS WILL ALSO LEAVE THE WINTER WEATHER ADVISORY AS IS. THE UPPER LOW TRACKS INTO EASTERN MT/NORTHWESTERN ND TONIGHT. DRY AIR IS PULLED NORTH-NORTHEAST AND SHOULD BRING TO AN END ANY LINGERING PRECIPITATION ACROSS MY CENTRAL COUNTIES. WRAP AROUND SNOW SHOWERS WILL BE POSSIBLE THROUGHOUT TONIGHT WEST CLOSER TO THE UPPER LEVEL VORTEX. CHANCE TO SLIGHT CHANCE POPS FOR SNOW WEST AND SNOW AND RAIN MIX CENTRAL MONDAY DAYTIME AS THE UPPER LOW PUSHES ACROSS THE STATE. THEREAFTER...A MORE ZONAL GENERAL FLOW PATTERN IS FORECAST TO DIRECT SEVERAL WEAK SHORTWAVES THROUGH THE NORTHERN PLAINS. MAINLY DRY MONDAY NIGHT THROUGH TUESDAY NIGHT WITH TEMPERATURES SLOWLY RECOVERING. MAY NEED A FREEZE WARNING FOR THE ENTIRE CWA OVER THE NEXT SEVERAL NIGHTS. FOR NOW WILL LEAVE ALONE AND DEFER TO THE DAY CREW UNTIL OUR CURRENT HEADLINES EXPIRE. LONG TERM...WEDNESDAY THROUGH SUNDAY... MAIN PROBLEM IN THE DAY 4-5 PERIOD WILL BE A SYSTEM MOVING THROUGH THE LOCAL AREA ON THURSDAY. GFS IS QUICKER WITH THIS SYSTEM THAN THE ECMWF AND GLOBAL GEM. WILL UTILIZE A BLEND WITH A NOD TO THE SLOWER SOLUTION. ON WEDNESDAY...WE START OUT WITH SURFACE HIGH PRESSURE OVER THE AREA AND A ZONAL FLOW ALOFT. IT WILL BE COOL ON WEDNESDAY WITH 85H TEMPS BELOW ZERO ACROSS THE NORTH AND INCREASING MID LEVEL CLOUDINESS SOUTHWEST BY AFTERNOON. GFS ALREADY BRINGS SOME LIGHT QPF INTO THE WEST DURING THE AFTERNOON BUT WILL KEEP THINGS DRY...SIDING WITH THE SLOWER ECMWF/GLOBAL GEM SOLUTIONS. WEDNESDAY NIGHT...PRECIPITATION SPREADS INTO THE WEST. ECMWF 85H TEMPS SUPPORT FROZEN PRECIPITATION NORTHWEST AND LIQUID SOUTHWEST. WILL STICK WITH A MIX OF RAIN AND SNOW. HOWEVER...WITH SURFACE TEMPERATURES BELOW FREEZING...WILL HAVE TO MONITOR FOR A MENTION OF FREEZING RAIN SOUTHWEST AS WE GET CLOSER TO THIS PERIOD. ON THURSDAY...WILL MENTION A SLIGHT CHANCE OF RAIN SHOWERS ACROSS MUCH OF THE CWA. PRECIP EXITS THE AREA BY THURSDAY AFTERNOON. COULD POSSIBLY SEE A LINGERING SHOWER IN THE EAST EARLY THURSDAY EVENING...BUT ACCUMULATIONS WOULD BE MINIMAL AT BEST. WILL CONTINUE WITH A DRY FORECAST ON THURSDAY NIGHT. MODELS CONTINUE TO INDICATE A WARMING TREND INTO THE WEEKEND WITH LITTLE IF ANY SIGNIFICANT PRECIPITATION. AVIATION... WIDESPREAD MVFR-IFR CIGS AND VSBYS ACROSS THE FORECAST AREA THIS MORNING WITH PRECIP COVERING THE ENTIRE CWA. WILL SEE SOME DRYING IN THE MID LEVELS AS THE DAY PROGRESSES BUT WITH ABUNDANT LOW LEVEL MOISTURE...LOW CEILINGS WILL BE SLOW TO IMPROVE. NORTH TO NORTHEAST FLOW THIS MORNING WILL EVENTUALLY SHIFT WEST AS THE SURFACE LOW MOVES INTO EASTERN NORTH DAKOTA BY 00Z MONDAY...AND SOUTHERN ONTARIO BY 12Z MONDAY. && .BIS WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 1 AM CDT /MIDNIGHT MDT/ MONDAY FOR NDZ002-003-010-011-018-021-033-041-044. WINTER STORM WARNING UNTIL 1 AM CDT /MIDNIGHT MDT/ MONDAY FOR NDZ001-009-017-031-032-040-043. && $$ NH/TWH/SCHECK