RSS FeedsIssued by NWS Des Moines, IA
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000 FXUS63 KDMX 231135 AFDDMX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 534 AM CST MON NOV 23 2009 .SHORT TERM /TODAY/... MOIST SELY FLOW CONT OVR THE STATE...HOWEVER DRIER AIR IS BEING DRAWN NWWD INTO THE SERN ZNS. PCPN AREA WILL CONT TO LIFT NWD THIS MRNG AND WITH COMBO OF UPR TROF PASSAGE AND SOMEWHAT DRIER AIR ADVN EXPECT PCPN TO TAPER OFF FM THE S BTWN 12Z AND 15Z. THIS FITS BEST WITH GEM-REGIONAL/WRF-EX 4.5/FIM SOLNS. FOR THE E HLF OF THE STATE...THE REST OF THE DAY SHOULD BE DRY. NXT SYS WILL PUSH CLOUDS AND PCPN INTO WRN IA THIS AFTN. TEMPS WILL BE A BIT TRICKY WITH THE THINNING CLOUDS. DO NOT EXPECT TO SEE THE LOW CLOUDS TO PREVAIL AND WOULD NOT BE SURPRISED TO SEE BKN CONDS OVR MUCH OF THE E HLF OF IA. FOR THAT REASON...RAISED MAX TEMPS TDA A FEW DEG FM GOING FCST. .LONG TERM /TONIGHT THROUGH SUNDAY/... 00Z GFS/EC/CANADIAN/SREF...AND NOW THE 06Z NAM ARE IN GOOD AGREEMENT REGARDING THE SYSTEM SET TO AFFECT THE REGION THROUGH TUESDAY NIGHT. AT 00Z TONIGHT THE UPPER LEVEL LOW SHOULD HAVE CLOSED OFF OVER THE WESTERN CENTRAL PLAINS...AND A SFC LOW SHOULD BE OVER CENTRAL KS WITH OLD STALLED FRONTAL BOUNDARY ANGLING NORTH INTO WRN MN. WITH THE UPPER LEVEL SYSTEM FINISHING ITS DIG TONIGHT AND CONVERGENCE NEAR THE SFC LOW TO OUR SW AND ALONG SFC TROUGH/FRONT OVER WRN IA...HAVE ADJUSTED POPS TONIGHT TO BE HIGHEST...NEARLY 100 PERCENT ACROSS WRN ZONES...BUT ONLY CHC POPS FARTHER EAST. MIN TEMPS TONIGHT WILL BE MILD...WARMER THAN NORMAL MAX TEMPS...AS DEWPOINTS IN THE LOWER TO MID 40S REMAIN IN PLACE AHEAD OF THE SYSTEM. TUESDAY PROMISES TO BE WET AS THE UPPER LEVEL AND SFC SYSTEM MIGRATE ACROSS CENTRAL IA. STRONG KINEMATIC FORCING MOVES OVER IOWA...BUT THE FRONTOGENETICAL FORCING ORIENTED NORTH-SOUTH OVER WRN IOWA WILL DISSIPATE. MEANWHILE A SECONDARY BUT WEAKER BAND OF FRONTOGENESIS ALIGNED UNDER THE DEFORMATION ZONE SETS UP MORE WEST-EAST ACROSS CENTRAL IOWA. ESSENTIALLY...WITH A LOW TRACKING FROM NW MO INTO SE IA...EXPECT COMMA HEAD PRECIP SHIELD TO AFFECT MOST OF THE AREA THROUGH THE DAY. THERE IS THE POTENTIAL FOR SOME DECENT RAINFALL IN THE ONE HALF INCH TO ONE INCH RANGE. TEMPS WILL SHOW LITTLE RECOVERY DURING THE DAY...BUT COULD RISE A FEW DEGREES. EXPECT SOME AFTERNOON COOLING IN THE WEST AS COLD ADVECTION STARTS TO KICK IN. THUNDER CHANCES STILL APPEAR HIGH ENOUGH TO MENTION TONIGHT AND TUESDAY MORNING ACROSS THE SOUTHERN HALF OR SO...AND THE AREA MAY NEED TO BE EXPANDED. MID LEVEL LAPSE RATES NOT AS STEEP AS SHOWN 24 HOURS AGO...BUT TQ INDEX VALUES SUPPORT EMBEDDED CONVECTION AND THERE IS STILL SOME NEGATIVE EPV SHOWING UP. WHILE THE FIRST SYSTEM PULLS OUT TUESDAY NIGHT...ANOTHER UPPER LEVEL LOW DIVES OUT OF SOUTHERN CANADA AND CROSSES IOWA WEDNESDAY. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM IS WHAT WILL USHER IN THE COLDER AIR FOR THE END OF THE WEEK. HAVE MAINTAINED LIKELY POPS IN THE NORTHEAST WEDNESDAY...BUT MUCH LOWER POPS FARTHER SOUHTHWEST AS MOISTURE PULLS AWAY TO THE NORTHEAST. THERMAL PROFILES STILL ONLY SUPPORT A RAIN OR RAIN/SNOW MIX THROUGH THE DAY WEDNESAY...EXCEPT IN THE FAR NORTHWEST WHERE WHAT DOES FALL SHOULD BE SNOW. HOWEVER...ANOTHER SURGE OF COLDER AIR...DEEPER RH...AND SOME UPPER LEVEL FORCING WED NIGHT AND THURSDAY MORNING WILL YIELD A DECENT CHANCE FOR LIGHT SNOW ACROSS MAINLY THE NORTHEAST THIRD OF THE AREA...BUT COULD SEE FLAKES JUST ABOUT ANYWHERE. THANKSGIVING DAY LOOKS TO BE COLD AND BREEZY WITH SCATTERED SNOW SHOWERS OR FLURRIES...AT LEAST EARLY IN THE DAY. THINKING THAT AT WORST...1 TO 2 INCHES OF SNOW IS POSSIBLE NORTHEAST OF A LINE FROM ESTHERVILLE TO MARSHALLTOWN BY THANKSGIVING MORNING...WITH POSSIBLY A DUSTING FARTHER SOUTH. NO CHANGES TO THE FORECAST MADE BEYOND FRIDAY. AN UPPER LEVEL RIDGE BUILDS ACROSS THE UPPER MIDWEST FRIDAY INTO SATURDAY...BUT GIVES WAY TO THE NEXT LONGWAVE TROUGH PRESSING ACROSS THE ROCKIES SUNDAY. && .AVIATION... 23/12Z...PCPN AREAS LIFTING NWD OVR ERN IA AND EXPECT TO SEE THE RAIN END BY 15Z. CLOUDS WILL REMAIN ABV 030 TDA WITH MVFR CLOUDS MOVG INTO THE KFOD AREA LATER THIS AFTN. BR WILL BE AN ISSUE THROUGH 16Z...BUT WILL LIFT TO VFR CONDS AT ALL TAF SITES EXCEPT KMCW...WHERE IT WILL LKLY REMAIN MVFR THRU THE DAY. AS NEXT SYS MOVS INTO THE AREA IFR CONDS WITH SPTY LIFR CONDS WILL OVR SPREAD THE TAF SITES BY AROUND 06Z +/- A COUPLE HRS. ISOLD TSRA WILL SPRD OVR THE SW THIRD OF IA AND HAVE PUT A CB REMARK IN THE KDSM TAF FOR THAT REASON. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...MS NOV 09 LONG TERM...MOYER AVIATION...MS NOV 09
