000 FXUS63 KARX 121605 AFDARX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1105 AM CDT SUN OCT 12 2008 .UPDATE...THIS AFTERNOON AND EVENING LOOKING AT THE 12.12Z UPPER AIR OBSERVATIONS...PLENTY OF WARM AIR CONTINUES TO FEED NORTHWARD INTO THE REGION. THE TOPEKA SOUNDING SHOWED 10C AT 700 MB WITH A 45 KNOT WIND FROM THE SOUTH. IN ADDITION... THE AMDAR SOUNDINGS SHOW CONSIDERABLE CAPPING BETWEEN 800 AND 700 MB. WITH LITTLE FORCING SHOWING UP IN EITHER OF THE MODELS AND NO SIGNIFICANT MID LEVEL WAVE IN THE WATER VAPOR IMAGERY...I DO NOT SEE THIS CAP BREAKING...THUS...I HAVE REMOVED THE PRECIPITATION CHANCES FOR THIS AFTERNOON FROM NORTH CENTRAL WISCONSIN AND SOUTHEAST MINNESOTA. IN ADDITION...I HAVE LOWERED THE PRECIPITATION CHANCES FOR THIS EVENING. THERE ARE INDICATIONS IN THE BOTH THE 12.12Z DETERMINISTIC MODELS /GFS AND WRF/ THAT MUCH OF THE AREA WILL BE DRY TONIGHT. WE WILL LOOK AT THIS FURTHER BEFORE MAKING ANY ADDITIONAL CHANGES. && .PREV DISCUSSION... /ISSUED 311 AM CDT SUN OCT 12 2008/ SHORT TERM...TODAY THROUGH TUESDAY NIGHT MAIN FORECAST FOCUS IS ON RAIN CHANCES FROM THIS AFTERNOON THROUGH TUESDAY NIGHT...ALONG WITH TEMPERATURES ON MONDAY. 07Z SURFACE ANALYSIS SHOWS AN AREA OF LOW PRESSURE OVER COLORADO WITH A WARM FRONT EXTENDING NORTHEAST THROUGH NEBRASKA...INTO CENTRAL MINNESOTA. INFRARED SATELLITE IMAGERY SHOWS MID AND HIGH LEVEL CLOUDS STREAMING ACROSS THE AREA. SOUTHERLY WINDS OVER THE AREA HAVE KEPT TEMPERATURES QUITE MILD. 12.00Z MODELS IN DECENT AGREEMENT WITH THE HANDLING OF THE LONGWAVE TROUGH ACROSS THE WESTERN CONUS AND ITS ATTENDANT COLD FRONT THAT WILL IMPACT THE AREA MONDAY. THUS CONFIDENCE RATHER HIGH IN THE SENSIBLE WEATHER EFFECTS TO THE AREA. MID LEVEL CIRCULATION OVER THE GREAT BASIN LIFTS INTO EASTERN MONTANA TODAY AND INTO SOUTHERN CANADA BY 12Z MONDAY THEN TO NEAR JAMES BAY BY 12Z TUESDAY. IN THE NEAR TERM...EXPECT MID AND HIGH LEVEL CLOUDS TO CONTINUE TO MOVE ACROSS THE AREA TODAY. SOUTHERLY WINDS WILL CONTINUE TO KEEP TEMPERATURES MILD WITH 850MB TEMPERATURES REMAINING AROUND +15 CELSIUS...SO DESPITE THE HIGH CLOUDS SHOULD SEE HIGH TEMPERATURES SIMILAR TO YESTERDAY...PERHAPS A FEW DEGREES COOLER WITH THE CLOUDS. WITH FRONT ENTERING WESTERN MINNESOTA LATE THIS AFTERNOON AND MODELS SHOWING SOME MOISTURE TRANSPORT ACROSS THE FAR WESTERN AND NORTHERN AREAS WILL KEEP THE LOW END POPS GOING FOR LATER THIS AFTERNOON. AS FRONT MOVES ACROSS MINNESOTA TONIGHT...RAIN CHANCES BEGIN TO INCREASE ACROSS THE WEST...BUT MAIN FORCING STILL REMAINS CLOSER TO THE FRONT IN CENTRAL MINNESOTA. SO HAVE KEPT POPS ACROSS THE WEST WITH DRY WEATHER EXPECTED ACROSS THE EASTERN ZONES. BETTER RAIN CHANCES ACCOMPANY THE FRONT ACROSS THE AREA MONDAY/MONDAY EVENING...WITH THE BULK OF THE PRECIPITATION BEING POST FRONTAL. 800MB-900MB FRONTOGENESIS...THETA-E CONVERGENCE ALONG THE BOUNDARY AND WEAK UPPER LEVEL DIVERGENCE ASSOCIATED WITH 300MB JET MAXIMUM SHOULD AID IN THE LIFT ACROSS THE AREA. MODELS CONTINUE TO SHOW PRECIPITABLE WATER VALUES OF 1.50 TO 1.75 INCHES AVAILABLE TO TAP INTO. THUS WOULD EXPECT SOME DECENT RAINFALL AMOUNTS. HAVE RAISED POPS IN THIS TIME FRAME...BUT HAVE KEPT THEM IN THE LIKELY CATEGORY. FORCING BEGINS TO SLIDE EAST LATER MONDAY NIGHT WITH THE HIGHER POPS ACROSS THE FAR EAST AND JUST CHANCE POPS ACROSS THE FAR WEST. HIGH TEMPERATURES TO BE TRICKY MONDAY WITH FRONT MOVING ACROSS THE AREA...ALONG WITH RAIN AND CLOUDS. DID NOT STRAY TO FAR FROM PREVIOUS GRIDS WITH THE WARMER TEMPERATURES IN THE EAST AND COOLER IN THE WEST. LINGERED POPS INTO TUESDAY MORNING ACROSS THE EASTERN HALF OF THE FORECAST AREA WITH DRY CONDITIONS EXPECTED BY AFTERNOON AS FRONT PUSHES SOUTHEAST OF THE AREA. FOCUS THEN TURNS TO A SECOND PIECE OF ENERGY MOVING OUT OF THE SOUTHWEST CONUS ACROSS THE PLAINS. MODELS DIFFER IN THEIR HANDLING OF THIS...WITH THE GFS KEEPING ITS MAINLY SOUTH OF THE AREA...WHILE THE NAM WANTS TO PUSH MOISTURE BACK ACROSS THE AREA TUESDAY NIGHT. BOTH GEM AND ECMWF SIDES MORE WITH THE NAM IN PUSHING THE MOISTURE NORTHWARD INTO THE AREA. THUS HAVE KEPT CHANCE POPS GOING FOR MUCH OF THE AREA TUESDAY NIGHT. LONG TERM...WEDNESDAY THROUGH SATURDAY 12.00Z GFS/ECMWF DIFFER SLIGHTLY IN HANDLING THE SECOND WAVE MOVING OUT OF THE PLAINS AS REFEREED TO IN THE PREVIOUS SECTION. ECMWF WANTS TO PUSH PRECIPITATION ACROSS THE AREA...WHILE THE GFS KEEPS IT ACROSS MAINLY THE SOUTHERN AREAS. HAVE OPTED TO ADD POPS FURTHER NORTH ACROSS THE EASTERN AND SOUTHERN AREAS OF THE FORECAST AREA. OTHERWISE BRIEF BREAK WITH THE RAIN CHANCES BEFORE NEXT SYSTEM DIVES SOUTHEAST OUT OF CANADA. BOTH MODELS IN AGREEMENT WITH DROPPING WAVE ACROSS THE AREA THURSDAY NIGHT AND PREVIOUS GRIDS HAS THIS WELL IN HAND. HIGH PRESSURE THEN SETTLES IN FOR THE REMAINDER OF THE PERIOD WITH DRY CONDITIONS. TEMPERATURES CONTINUE TO LOOK SEASONAL THROUGH THE PERIOD. AVIATION...TODAY AND TONIGHT BULK OF THE CLOUDS OVER THE AREA TODAY WILL BE HIGH LEVEL AS THE FRONTAL BOUNDARY AND DEEPER SATURATION REMAIN OVER EASTERN NEB TO WESTERN MN. LOW PRESSURE LIFTING NORTHEAST ALONG THE FRONT WILL TIGHTEN THE PRESSURE GRADIENT OVER THE REGION FOR TODAY WITH SOUTH WINDS 15-20KTS...G25KTS OR HIGHER. THIS ONCE THE AIRMASS MIXES LATE THIS MORNING...ESPECIALLY AT KRST AND OTHER OPEN/HIGHER TERRAIN AREAS. WINDS TO DIMINISH QUICKLY WITH SUNSET/DECOUPLING THIS EVENING. THE LOW LIFTING INTO SOUTHERN CAN TONIGHT WILL START THE FRONT MOVING EAST AS A COLD FRONT...WITH THE FRONT AND THE MAIN WEATHER/AVIATION IMPACTS MOVING ACROSS THE KRST/KLSE TAF SITES MONDAY. THE DEEPER MOISTURE/LIFT WITH THE FRONT APPROACHES FROM THE WEST MAINLY LATER TONIGHT AND FOR MON. MAIN IMPACTS...LOWER CIGS...SHRA/ISOLATED TSRA CHANCES REMAIN WITH THE FRONT OR JUST BEHIND IT...SO WILL ONLY BRING 4K FT CIG/VCSH TO KRST LATE IN THE 12Z TAF CYCLE PERIOD FOR NOW. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...RABERDING AVIATION...RRS UPDATE...BOYNE