FXUS63 KARX 010222 AAA AFDARX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE LA CROSSE WI 921 PM CDT SAT JUL 31 2010 .UPDATE... CONCERN IS ON DENSE FOG OVERNIGHT. DEW POINTS DID NOT MIX OUT THIS AFTERNOON AND CURRENTLY TEMP/DEW POINT SPREADS ARE RUNNING FROM 5 TO 8 DEGREES. SOUNDINGS INDICATE DEEP LAYER OF LIGHT WINDS AND CROSS OVER METHOD WOULD SUGGEST WIDESPREAD DENSE FOG DEVELOPING OVERNIGHT. THUS HAS OPTED TO ISSUE A DENSE FOG ADVISORY FOR THE ENTIRE AREA. PRODUCTS WILL BE OUT SHORTLY. && JLR .PREV DISCUSSION... .SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT FORECAST CONCERNS CONTINUE TO BE FOCUSED ON DENSE FOG POTENTIAL TONIGHT AND PRECIPITATION CHANCES THROUGH THE PERIOD. VIS SATELLITE THIS AFTERNOON SHOWING AN EXPANSIVE FIELD OF CUMULUS/STRATOCUMULUS ACROSS THE FORECAST AREA AS A MID-LEVEL TROUGH AND ASSOCIATED COLD POOL MAKES ITS WAY EAST INTO THE WESTERN GREAT LAKES REGION. RIDGE AND ASSOCIATED SUBSIDENCE PRODUCING MOSTLY SUNNY SKIES JUST TO OUR WEST ACROSS WESTERN MN/EASTERN DAKOTAS. UNDER PARTLY SUNNY SKIES EARLY THIS AFTERNOON...TEMPERATURES MANAGING TO WARM INTO THE MID 70S TO LOWER 80S. 31.12Z NAM/GFS AND THE 31.09Z SREF ALL IN REASONABLY GOOD OVERALL AGREEMENT THROUGH THE SHORT TERM. MID-LEVEL/SURFACE RIDGE SLIDES OVER THE REGION TONIGHT FOR CLEARING SKIES AND LIGHT TO CALM WINDS. WITH LITTLE VERTICAL MIXING THIS AFTERNOON...ANTICIPATED CROSSOVER TEMPERATURES THIS AFTERNOON SHOULD REMAIN IN THE MID 60S ACROSS MUCH OF THE AREA. FOG FORMATION IS EXPECTED AS A RESULT TONIGHT...SOME POSSIBLY BECOMING LOCALLY DENSE ESPECIALLY IN RIVER VALLEY AREAS. NOT CERTAIN HOW WIDESPREAD THE DENSE FOG WILL GET...SO WILL HOLD OFF ON ANY HEADLINES FOR NOW AS PASS ONTO THE EVENING SHIFT TO ASSESS FURTHER. MODELS SHOWING THE HIGH PRESSURE RIDGE SHIFTING EAST OF THE AREA ON SUNDAY WITH A WARM FRONT LIFTING NORTHWARD INTO THE DAKOTAS. NAM SHOWING MODERATE AMOUNT OF ISENTROPIC LIFT/MOISTURE TRANSPORT ON THE 310K THETA SURFACE CROSSING THE WARM FRONT AND BENDING INTO CENTRAL MN/NORTHWEST WI. AS A RESULT...COULD SEE ONGOING WEAKENING MCS/POSSIBLE NEW CONVECTION MOVING INTO AREAS MAINLY NORTH OF I-94 BY AFTERNOON. HAVE RE-INTRODUCED SOME SHRA/TS CHANCES ACROSS THAT AREA AS A RESULT OF THIS SIGNAL. THIS MAINLY ELEVATED CONVECTION NOT ANTICIPATED TO BE SEVERE AS 1-3KM MUCAPE ONLY IN THE 1000-1500J/KG RANGE WITH MARGINAL 1-3 BULK SHEAR. WILL SEE SHRA/TS CHANCES OVERSPREAD THE AREA FROM SUNDAY NIGHT THROUGH MONDAY NIGHT AS A WEAK COLD FRONT MAKES ITS WAY ACROSS THE UPPER MISSISSIPPI RIVER VALLEY REGION. WILL HAVE TO KEEP AN EYE ON MONDAY FOR POSSIBLE SEVERE THREAT AS 0-3KM MUCAPE //PER THE NAM// PUSH INTO THE 1500-3000J/KG RANGE WITH INCREASING BULK SHEAR. FROM MONDAY NIGHT THROUGH TUESDAY NIGHT...THE MID-UPPER LEVEL FLOW PARALLELS AND SLOWS SOUTHWARD PUSH OF THE COLD FRONT. MOISTURE TRANSPORT/CONVERGENCE ALONG THE LINGERING FRONTAL BOUNDARY WILL CONTINUE SHRA/TS CHANCES. .LONG TERM...WEDNESDAY THROUGH SATURDAY 31.06Z GFS AND 31.00Z ECMWF SHOWING SOME SUBTLE DIFFERENCES IN THE LONG TERM BUT IN PRETTY GOOD AGREEMENT OVERALL WITH GENERAL SYNOPTIC SETUP ACROSS THE REGION. GENERALLY USED A BLEND OF THE TWO MODELS FOR THE FORECAST. WILL CONTINUE TO SEE THE LINGERING FRONTAL BOUNDARY JUST TO THE SOUTH OF THE AREA WITH EMBEDDED MID-LEVEL SHORTWAVE TROUGHS ACTING ON THE BAROCLINICITY FOR SHRA/TS CHANCES. THESE CHANCES SHOULD REMAIN CONFINED SOUTH OF I-90. FINALLY BY WEDNESDAY NIGHT...THE FRONT SHOULD BE PUSHED FAR ENOUGH SOUTH OF THE AREA TO END SHRA/TS CHANCES. THURSDAY THROUGH FRIDAY LOOK DRY FOR NOW AS MID-LEVEL RIDGING REBOUNDS ACROSS THE MIDWEST/UPPER MISSISSIPPI RIVER VALLEY REGION. SHRA/TS CHANCES RETURN BY FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY AS BOTH MODELS BRINGING IN A MID-LEVEL/SURFACE TROUGH INTO THE AREA FROM THE NORTHERN PLAINS. ECMWF IS A BIT MORE AGGRESSIVE WITH 850MB MOISTURE TRANSPORT AND PRECIPITATION GETTING INTO THE AREA WHEREAS THE GFS KEEPS IT WEAKER AND MORE WEST OF THE AREA. WILL CARRY A 20-30 POP IN THE FRIDAY NIGHT-SATURDAY TIME FRAME FOR NOW AS A COMPROMISE. TEMPERATURE-WISE...LOOKS LIKE WE SHOULD STICK RIGHT AROUND SEASONAL NORMALS THROUGH THE PERIOD WITH FAIRLY HIGH-ZONAL FLOW. && .AVIATION...TONIGHT THROUGH SUNDAY MORNING AVIATION CONCERNS FOCUS ON FOG/STRATUS POTENTIAL LATE TONIGHT/EARLY SUN MORNING. PRETTY GOOD SETUP FOR A WIDESPREAD FOG ACROSS THE REGION AS AN AREA OF HIGH PRESSURE CENTERS ITSELF ACROSS THE REGION. LIGHT SFC/NEAR SFC WIND FIELD TONIGHT...PER BUFKIT SOUNDINGS...ALONG WITH AMPLE BOUNDARY LAYER MOISTURE LINGERING. SHOULD GET A BUMP IN SFC DEW POINTS AFTER SUNDOWN TOO...THANKS TO EVAPOTRANSPORATION...ADDING MORE MOISTURE...AND FUELING THE FOG POTENTIAL. IF THERE WERE SOME RAINFALL TODAY...FOG/STRATUS WOULD BE A VIRTUAL CERTAINTY. AN UPPER LEVEL SHORTWAVE CONTINUES TO EXIT TO THE EAST THIS EVENING...BUT THERE COULD BE A FEW ISOLATED/SCT SHRA OVER EASTERN WI LATE THIS AFTERNOON/EVENING. DON/T EXPECT ANY PCPN CONCERNS FOR KRST/KLSE. WILL CONTINUE TO TREND THE MVFR/IFR CONDITIONS OVERNIGHT FOR KRST/KLSE...FAVORING LOWER VSBYS IN THE RIVER VALLEYS...AND THUS KLSE. CAN/T RULE OUT DENSE FOG BECOMING MORE WIDESPREAD...AND TRENDS WILL BE MONITORED THROUGH TONIGHT...AND UPDATES MADE AS NECESSARY. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...DENSE FOG ADVISORY FROM 3 AM TO 9 AM CDT SUNDAY FOR WIZ017- WIZ029-WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043-WIZ044- WIZ053-WIZ054-WIZ055-WIZ061. MN...DENSE FOG ADVISORY FROM 3 AM TO 9 AM CDT SUNDAY FOR MNZ079- MNZ086-MNZ087-MNZ088-MNZ094-MNZ095-MNZ096. IA...DENSE FOG ADVISORY FROM 3 AM TO 9 AM CDT SUNDAY FOR IAZ008- IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030. && $$ SHORT/LONG TERM...DAS AVIATION...RIECK