RSS FeedsIssued by NWS Sioux Falls, SD
000 FXUS63 KFSD 210241 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 830 PM CST FRI NOV 20 2009 .DISCUSSION... TEMPERATURES DROPPING OFF QUICKLY IN OUR EAST THIS EVENING WITH WINDS NEARLY CALM...AND HAD TO DROP MINS A COUPLE OF DEGREES IN THE LOWEST ELEVATIONS. EXPECT TEMPERATURES TO STEADY OUT OR EVEN A RISE A BIT OVERNIGHT WITH WINDS PICKING UP IN A TIGHTENING GRADIENT...AND HIGH TO MID CLOUDS ROUNDING THE CENTRAL U.S. RIDGE. MINOR UPDATES OUT WITH NO CHANGE TO ZFP. /JM && .PREV DISCUSSION... QUIET NIGHT ACROSS THE AREA AS WINDS GRADUALLY SWING AROUND TO THE SOUTH AND SOUTHEAST AND INCREASE...ESPECIALLY OVER THE WEST. WENT WITH NON DIURNAL TEMPERATURES ALONG AND WEST OF THE JAMES RIVER AS WINDS BEGIN TO INCREASE MORE STEADILY. EVEN HAVE TEMPERATURES RISING A LITTLE TOWARDS 12Z IN THE FAR EAST. OTHERWISE...DECREASED LOWS A LITTLE FROM ABOUT INTERSTATE 29 EAST WITH LIGHT FLOW AND CLEAR SKIES THROUGH MUCH OF THE NIGHT. LOWS SHOULD RANGE FROM THE MID TO UPPER 20S EAST OF INTERSTATE 29 TO THE LOWER 30S WEST OF THE JAMES RIVER. SATURDAY SHOULD PROVE TO BE A MILD BUT BREEZY DAY AS WINDS INCREASE TO SOMETHING AROUND 20 TO 30 MPH ON A STRONG SOUTHERLY GRADIENT. MOISTURE ALSO SET TO INCREASE ALONG INCOMING LLJ SO HAVE PARTLY TO MOSTLY CLOUDY SKIES IN THE EAST DURING THE AFTERNOON. QUIET A BIT OF MOISTURE RETURN JUST OFF THE SFC AND THIS LOOKS REASONABLE GIVEN HIGHER DEW POINT AIR IN EASTERN OKLAHOMA. HIGHS MAINLY IN THE 50S. SATURDAY NIGHT WILL SEE A WIND SHIFT WORK INTO THE AREA AHEAD OF AN ENTRANCE REGION TO A RELATIVELY WEAK UPPER LEVEL JET STREAK. MAY BE JUST ENOUGH LIFT ALOFT AND JUST ENOUGH MOISTURE CONVERGENCE IN THE LOW TO MID LEVELS TO SUPPORT A LITTLE LIGHT RAIN OVER THE EASTERN CWA...BUT WILL HOLD OFF ON BETTER CHANCES UNTIL SUNDAY. EXPECT CLOUDS TO ALSO INCREASE DURING THIS TIME AS THE UPPER WAVE APPROACHES THE DECENT LOW TO MID LEVEL MOISTURE. LOWS WILL BE MILD...ESPECIALLY IN THE EAST WHERE THE STRONGER SOUTHERLY FLOW REMAINS IN PLACE...AND SHOULD RANGE FROM THE LOWER 40S IN NW IA TO 30 TO 35 IN CENTRAL SD. AS STATED EARLIER...WILL MAINTAIN SOME LOWER END POPS IN THE EAST FOR A FEW RAIN SHOWERS WITH INCOMING WEAK ENTRANCE REGION AND WEAK MID TO LOW LEVEL MOISTURE CONVERGENCE. THIS SHOULD KEEP CLOUD COVER IN PLACE MUCH OF THE DAY...BUT DECREASE SLOWLY FROM WEST TO EAST. A LITTLE COOLER BUT A LOT LESS WIND SO STILL MILD...WITH HIGHS FROM THE UPPER 40S TO LOWER 50S. /08 HEADING INTO SUNDAY NIGHT...AFTER SOME HINT OF A DYNAMIC DOWNTIME AFTER WAVE SHEARS BY TO THE NORTHEAST...THE TRAILING SYSTEM STARTS TO INCREASE LOW LVL FLOW AGAIN WITH ISENTROPIC TRANSPORT INCREASING THRU THE CWA FROM S TO N. A LITTLE LOWER TO MID LVL CONVERGENCE AXIS LOOKS TO SET UP FROM SW TO NE ACRS THE AREA LIFTING SLOWLY NE...AND ENOUGH TO PERHAPS FOCUS A SMALL POP LATER IN THE NIGHT. THE INCREASING SELY FLOW...CLOUDS...AND MOISTURE LKLY TO KEEP TMPS WARM ENOUGH AT TIME OF PCPN THREAT FOR ALL RAIN...BUT ANY QUICKER APPROACH WOULD PERHAPS BRING SOME LIGHT FREEZING RAIN TO THE MIX. MONDAY GETS SOME BETTER DIV Q IN THE MIX ADVANCING OUT AHEAD OF THE TROUGH DIGGING INTO THE CNTRL/SRN PLAINS. MAIN MID LVL BNDRY/CONVERGENCE STARTS TO LOCK INTO THE NRN/SWRN CWA...AND WOULD SEEM TO BE A SLIGHTLY BETTER FOCUS FOR MID TO HIGH CHC POPS. START TO LIMIT DIURNAL RANGE SOMEWHAT MORE WITH HIGH AMT OF CLDS. FOR THE EXTENDED RANGE /MON NIGHT THRU FRI/ ALMOST FUNNY HOW CHANGES IN THE LONG RANGE GUIDANCE...ESPECIALLY AFFECTING THE START OF THE PERIOD...WAS PREDICTABLE. FOR THE MOST PART THE VARIOUS CAMPS HAVE NOT ABANDONED THEIR RESPECTIVE SLNS...WITH GFS CONTINUING AS THE PROGRESSIVE POSTER CHILD...BUT THE CANADIAN/ECMWF/UKMET ALL ON THE SLOW AND DIGGY SIDE...WITH 12Z RUNS OF THE FORMER PAIR EVEN MORESO. ENCOURAGING WAS GFS HALF STEP BACK TOWARD MORE DIGGING. THEREFORE... HARD TO DENY THAT THERE WILL NOT BE A PRECIPITATION EVENT IN THE MONDAY NIGHT TO TUESDAY NIGHT WINDOW /ALTHOUGH LATEST GUIDANCE TRENDS WOULD PERHAPS PUSH BACK A PERIOD OR SO FOR BEST FORCING/. INTRODUCED SOME LKLY POPS THRU THE NWRN HALF OF THE CWA FOR THE MOMENT...TAPERING OFF SLIGHTLY TOWARD THE FAR SE. WRAPPED UP LOWS NOTORIOUS FOR SLOW PROGRESSION AND LOOKS TO BE ONE WHERE AN EVENTUAL TROWAL STRUCTURE IS PROBABLE...ALONG WITH A HEALTHY INVERTED TROUGH...FAVORING PCPN ALG/BEHIND. THESE TYPES OF SYSTEM ALSO SEEM TO HAVE A TENDENCY TO BRING UP WARMER AND MOIST AIR...WRAPPING WELL WESTWARD FOR A WHILE. CERTAINLY THE BETTER OF THE SNOW THREAT WOULD BE BACK ALG/W OF THE INVERTED TROUGH...AND DO NOT HAVE SUGGESTIONS OF A DRIER ELY TRAJECTORY TO HELP WET BULB THINGS. THEREFORE...KEPT ANY SNOW MENTION LIMITED TO THE EXTREME WEST...WITH MIX TOWARD THE JAMES VALLEY MONDAY NIGHT...THEN ON A BIT EASTWARD TUE...BEFORE STARTING A WHOLE SCALE CHANGEOVER TUE NIGHT. SOME LINGERING POPS CONTINUED THRU THE NE/E ON WEDNESDAY. THE END OF THE WEEK IS FEATURED DRY AT THIS POINT AS RIDGING REBOUNDS THRU THE NRN PLAINS. SFC RIDGE MOVING OVER THU INTO EARLY FRI COULD LEAD TO SOME CHILLY LOWS...ESPLY IF WRN AREAS HAVE ANY DECENT SNOWCOVER. SOME COLD AIR SC MAY BE AROUND ON THU THRU ERN CWA...BUT MAINLY CLEAR TO MO CLR EXPECTED BY THU NIGHT/FRI. FOR NOW...DID NOT FULLY ACCEPT THE RAPIDITY OF THE WARMUP ON FRIDAY... BUT WL BE SOMETHING TO WATCH FOR ONCE THE EVOLUTION OF THE EARLY TO MID WEEK SYSTEM IS DEFINED. /CHAPMAN && .AVIATION... PRETTY MUCH VFR THROUGH 0Z SUNDAY. NOT OUT OF THE QUESTION TO SEE SOME VALLEY FOG LATE TONIGHT...BUT COVERAGE SHOULD BE MINIMAL. WE WILL SEE AN INFLUX OF MOISTURE ON SATURDAY AFTERNOON...WITH THE POTENTIAL FOR HIGH END MVFR CEILINGS AT SUX...AND POSSIBLY FSD. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. $$
