Issued by NWS Twin Cities, MN
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000 FXUS63 KMPX 081102 AFDMPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 502 AM CST SUN FEB 8 2009 .UPDATE... UPDATED TO INCLUDE 12Z AVIATION DISCUSSION. && .DISCUSSION... SURFACE RIDGE WAS NEARLY OVERHEAD EARLY THIS MORNING WINDS WERE LIGHT FROM THE WEST UNDER 8 KTS. TEMPERATURES HAVE FALLEN INTO THE TEENS...WITH 20S AROUND THE TWIN CITIES...AND NEAR 10 ABOVE AT ALEXANDRIA. THIS WILL BE THE LAST COLD NIGHT FOR A FEW DAYS AS A SURGE OF UNSEASONABLY WARM MOIST AIR MOVES NORTHWARD ACROSS THE UPPER MIDWEST LATER TONIGHT. IN THE SHORT TERM...VERY DRY AIR IN THE WAVE OF SATURDAY SYSTEM WILL BRING MAINLY CLEAR SKIES TODAY WITH OPTIMAL SOLAR RADIATION. HOWEVER...GUIDANCE HAS TEMPERATURES ALREADY TOO WARM AS OF 1 AM...SO OPTED TO LOWER A FEW DEGREES EVEN WITH FULL SUNSHINE. FORECAST CONCERNS REMAIN WITH THE UPCOMING STORM SYSTEM MOVING INTO FAR SOUTHERN CALIFORNIA. SUBTLE DIFFERENCES REMAIN IN THE OVERALL EVOLUTION OF THE UPPER LOW PROGGED TO MOVE INTO THE UPPER MIDWEST/NORTHERN PLAINS MONDAY. ALTHOUGH THESE DIFFERENCES ARE NOTED ON THE SURFACE AND ALOFT...SENSIBLE WEATHER PARAMETERS REMAIN THE SAME WITH FREEZING RAIN DEVELOPING ACROSS WESTERN MINNESOTA LATE TONIGHT...THEN SLOWLY SPREADING NORTH/NORTHEAST ACROSS THE REST OF OUR CWA BY NOON MONDAY. THE INITIAL VERY DRY ATMOSPHERE IN THE UPPER MIDWEST WILL LIKELY PRECLUDE SUBSTANTIAL PRECIPITATION AMOUNTS AT THE BEGINNING OF THIS EVENT. THEREFORE...FREEZING RAIN AND THE ANTICIPATION OF ACCUMULATING ICE IS BECOMING LESS LIKELY OF A FACTOR ACROSS SOUTHERN MINNESOTA...EXCEPT IN FAR SOUTHWEST/WEST CENTRAL MINNESOTA WHERE BETTER DYNAMICS AND MOISTURE FEED WILL ALLOW FOR MORE MOISTURE TO REACH THE SURFACE. CENTRAL MINNESOTA WILL ALSO HAVE A PERIOD OF FREEZING RAIN WITH ICE ACCUMULATION LIKELY. BUT AGAIN...AS STRONG WARM AIR ADVECTION BEGINS TO OVERSPREAD OUR REGION...SURFACE TEMPERATURES WILL LIKELY RISE ABOVE FREEZING BY NOON...OR EARLY AFTERNOON. HPC DOES DEPICT < 0.10" OF ICE ACCUMULATION FOR AREAS NORTH OF A REDWOOD FALLS TO TWIN CITIES LINE FOR LATE TONIGHT...AND INTO MONDAY MORNING. THIS IS SUBSTANTIALLY LESS AGGRESSIVE THAN PREVIOUS AMOUNTS FORECASTED FOR AREAS AROUND ALEXANDRIA AND ST. CLOUD EARLIER. ADVISORY CRITERIA WILL LIKELY BE OBTAINED SOMETIME LATE TONIGHT ACROSS WESTERN MINNESOTA...AND FOR AREAS ACROSS CENTRAL MINNESOTA MONDAY MORNING. DUE TO SOME UNCERTAINTIES OF TIMING AND QPF AMOUNTS...WILL HOLD OFF ON ANY HEADLINES OR ADVISORIES. WILL UPDATE THE MORNING HWO AND ELABORATE MORE ON THE ICE INFORMATION. SEVERAL OF PREVIOUS RUNS OF THE GFS HAS BEEN MORE CONSISTENT WITH THE SLOW PROGRESSION OF THE UPPER LOW ACROSS THE UPPER MIDWEST AND NORTHERN PLAINS. NAM...ECMWF AND OTHER SHORT RANGE MODELS ARE A BIT MORE UNORGANIZED IN TERMS OF PLACEMENT OF THIS FEATURE. THEREFORE...HAVE LEANED TOWARD THE GFS WITH THE SLOWER PROGRESSION OF THE UPPER LOW WHICH MEANS A SLOWER SCENARIO OF THE PRECIPITATION EXITING OUR AREA. HAVE LEFT TUESDAY WEATHER THE SAME AS THE UPPER LOW AND RESIDUAL WRAP AROUND MOISTURE CONTINUES TO PLAGUE MY NORTHERN FORECAST AREA. THERE REMAINS SOME QUESTION ON CONVECTION MONDAY AFTERNOON AS MODELS TRY TO DEPICT A DRY SLOT MOVING NORTHWARD ACROSS IOWA. ALTHOUGH MID LEVEL LAPSE RATES ARE FAIRLY HIGH AND PRECIPITABLE WATER VALUES ARE INCREDIBLE FOR THIS TIME OF YEAR...HAVE NOT ADDED THUNDER INTO THE FORECAST...BUT THIS SCENARIO IS PLAUSIBLE DUE TO THE STRENGTH AND MOISTURE PARAMETERS WITH THIS SYSTEM. NOT TOO MANY CHANGES PAST TUESDAY AS ANOTHER STRONG STORM SYSTEM MOVES ACROSS THE CENTRAL PLAINS/MID MISSISSIPPI VALLEY REGION. OUR AREA WILL LIKELY BE ON THE FRINGE OF ANY TYPE OF SUBSTANTIAL QPF AMOUNTS...SO LEFT LIGHT SNOW IN THE FORECAST. THE OVERALL TREND IN THE MEDIUM RANGE ENSEMBLES AND MEANS HAS A VERY PROGRESSIVE AND ACTIVE PATTERN ACROSS THE CENTRAL AND SOUTHERN U.S. OUR AREA WILL LIKELY BE DRY AS THE MAIN STORM TRACK REMAINS TOO FAR SOUTH OF ANY SUBSTANTIAL/ORGANIZED SYSTEM TO AFFECT THE UPPER MIDWEST. && .AVIATION.../12Z TAF ISSUANCE/ A REASONABLY QUIET AVIATION FORECAST PERIOD WITH THIS MORNING/S TAFS. A RIDGE OF HIGH PRESSURE CENTERED OVER IOWA IS HELPING TO KEEP THINGS MOSTLY CLEAR ACROSS THE AREA AT THE CURRENT TIME. THERE IS SOME PATCHY FOG AROUND GIVEN THE LIGHT WINDS AND SOMEWHAT MOIST BOUNDARY LAYER... ALTHOUGH IT HAS ONLY BEEN PERSISTENT IN LOW LYING AREAS/RIVER VALLEYS/ETC... PARTICULARLY TO THE NORTH WHERE A WEAK SHORTWAVE COULD BE SEEN RIPPLING THROUGH THE NORTHWEST MID-LEVEL FLOW. ALONG WITH THE LIGHT FOG... THERE IS A SMALL AREA OF STRATUS APPARENT ON THE 11-3.9 MICRON IMAGERY. THIS AREA OF LOW CLOUDS HAS MOVED SLOWLY EAST-SOUTHEAST THROUGH THE NIGHT... AND IS NOW LOCATED NEAR AND EAST OF KSTC. EXPECT IT TO CONTINUE TO SHIFT EAST AND LIKELY DISSIPATE AFTER SUNRISE... SO AT THIS POINT WILL PROBABLY ONLY INCLUDE THE LOWER CEILINGS AND VISIBILITIES AT KSTC... AND JUST MENTION SOME SCT LOW CLOUDS AND MARGINAL MVFR VISIBILITIES AT THE OTHER SITES. OTHERWISE... WE WILL SEE MOSTLY SUNNY SKIES THROUGH THE DAY WITH RETURN FLOW SETTING UP BY THIS AFTERNOON... THEN AN INCREASE IN MID-HIGH CLOUDS BY EARLY EVENING FOLLOWED BY STEADILY LOWERING AND THICKENING CLOUDS FROM SOUTHWEST TO NORTHEAST THROUGH THE NIGHT. THE WARM ADVECTION WILL HAVE A TOUGH TIME SATURATING THE LOWER LEVELS... BUT HAS A REASONABLE CHANCE OF DOING SO BY 12Z OVER THE WEST AND SOUTH... SO INCLUDED SOME TEMPO PCPN CHANCES AND SUB 3K FT CEILINGS IN TEMPO GROUPS TOWARD MORNING. PCPN TYPE OVER THE WEST AND SOUTH WOULD LIKELY BE FZRA PRIOR TO 12Z... WITH A TRANSITION MORE TOWARD RAIN AS THE MORNING UNFOLDS... ALTHOUGH KAXN COULD SEE SUB-FREEZING TEMPERATURES LINGER INTO THE AFTERNOON HOURS. AT THIS POINT... THINK THE PCPN MAY STAY OUT OF KMSP LONG ENOUGH FOR TEMPERATURES TO WARM ABOVE FREEZING SO DID NOT INCLUDE ANY FZRA FOR KMSP ALTHOUGH THAT WILL CERTAINLY BE SOMETHING TO WATCH... PARTICULARLY IF THINGS ARRIVE A BIT SOONER DURING THE HIGH TRAFFIC TIME ON MONDAY MORNING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ JLT/TRH
