FXUS63 KOAX 240348
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
948 PM CST TUE NOV 23 2010
.UPDATE...
UPDATED TO EXPAND THE FREEZING RAIN ADVISORY AND TO UPDATE
TEMPERATURES.
&&
.DISCUSSION...
00Z UPPR AIR ANLYS INDCD DEEP ARCTIC LO OVR THE GREAT BASIC
ASSOCIATED WITH 110 M H5 HEIGHT FALLS. AT H85...ATMOSPHERE OVR THE
CNTRL AND NRN PLAINS REMAINS FAIRLY DRY. DECENT QUALITY LO LVL
MOISTURE WAS SEEN OVER THE SRN PLAINS OF TX/LA WITH DEW POINTS OF
+10 C UP TO FWD. THIS IS PROGGED TO QUICKLY LIFT N/NE THRU THE
NIGHT INTO THE CNTRL AND ERN CWA BY MRNG.
LATEST MODELS ARE IN FAIRLY GOOD AGREEMENT IN STG LO LVL WAA
INCREASING OVER NIGHT. LATEST POINT FORECAST SOUNDINGS AND RH
PROGGS INDC THIS SATURATION WILL LIKELY NOT OCCUR UNTIL AT OR
AFTER 12Z ALNG THE MO RIVER AND AFTER ABOUT 10Z W OF HIGH WAY 81.
THUS HAVE BACKED OFF THE TIMING OF THE FZRA ADVRY OVER THE E UNTIL
AT 12Z. MODEL TMP FORECASTS SO FAR HAVE NOT VERIFIED ALL THAT WELL
DUE TO THE CLR SKIES EARLIER THIS EVNG ALLOWING FOR MORE COOLING
THAN PROGGED...BUT ERRORS ARE EXPECTED TO LESSON OVERNIGHT AS CLDS
INCREASE. GFS/EC/GEM ARE WAY TO WARM ON TMPS OVERNIGHT AND INTO
THE DAY ON WED...BUT THE NAM MAY BE A TOUCH COLD...BUT FEEL IT HAS
A BETTER HANDLE ON THE SITUATION GIVEN SUPPORT FOR THE WRF-ARW
/WRF-NNM AND HRRR. THUS HAVE COOLED SOME OF THE HOURLY TMPS THRU
TMRW AND NOW HAVE THE NW CWA NOT GETTING ABOVE FREEZING AT ALL.
THUS HAVE EXTENDED THE ADVRY INTO THE AFTN HOURS THERE. NOT SURE
HOW MUCH PRECIP IS REALLY GOING TO FALL OVER THE W WITH THIS
SYSTEM GIVEN THE MARGINAL DEPTH OF THE MOISTURE PROFILE AND THE
SWRLY LO LVL WINDS ABOVE THE SFC...BUT GIVEN THE DEEP TROPOSPHERIC
LIFT...FEEL SOME LIGHT FZDZ IS LIKELY AND IT DOESN'T TAKE MUCH TO
CAUSE PROBLEMS.
ONLY OTHER CONCERN WAS THAT THERE MAY BE SOME LIGHT FZDZ MOVG IN
BEHIND SUCH A STG ARCTIC CDFNT TMRW AFTN AND NR THE RUSH HOUR IN
THE OMA METRO AND HAVE ADDED TO THE GRIDS. NOT EXPECTED MUCH...BUT
IF ANY FALLS WITH SHARP ARCTIC BOUNDARY MOVG THRU...CLD MAKE RUSH
HOUR A LITTLE TOUGHER. OVERNIGHT SHIFT WL HAVE TO LOOK AT THIS
CLOSER. OTHERWISE HAVE LOWERED GOING HIGHS OVR MOST AREAS TMRW
GIVEN THE LATEST GUIDANCE.
NEW ZFP/GRIDS AND WSW WL BE OUT BY 1015.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 329 PM CST TUE NOV 23 2010/
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT.
SIMILAR SCENARIO FROM COUPLE NIGHTS AGO SETTING STAGE FOR POSSIBLE
FREEZING DRIZZLE OVER THE NRN CWA TONIGHT. TIME SECTIONS SHOWING
MOIST LYR GENERALLY LOWEST 5KFT. SFC LOW DEEPENING IN ERN CO IN
RESPONSE TO DPVA ASSOCIATED WITH NRN ROCKIES CLOSED LOW TRACKING EWD
INTO THE PLAINS. STOUT UPGLIDE AHEAD OF SFC LOW COUPLE WITH
GOOD UPPER SUPPORT PROVIDING AMPLE FORCING. HOWEVER...SHALLOW
MOIST LYR PER BUFKIT SOUNDINGS PRETTY MUCH LIMITING PCPN TO DRIZZLE
OVER THE CWA. BIG PROBLEM IS WHERE TO DELINEATE FZDZ/DZ. APPEARS
THAT WAA AHEAD OF SFC LOW WILL KEEP THE SRN AND MOST OF THE ERN CWA
ABOVE THE FREEZING MARK...THUS WILL CONCENTRATE ADV HEADLINE LATE
TONIGHT INTO WED MORNING OVER THE NRN CWA WHERE CAA WILL BE MOST
INFLUENTIAL. BY WED AFTN...BOTH NAM/GFS DEPICT BEST LIFT SORT OF
ARCING AROUND THE CWA FROM THE DAKOTAS INTO MN THEN SWD INTO IA.
PTYPE SHOULD BE AN ISSUE BY THEN AND WILL FOCUS HIGHER POPS MAINLY
NORTHEAST. CLOSED OFF SYSTEM QUICKLY SHIFTS EAST TAKING BEST LIFT
AND MOISTURE WITH IT...THUS DRY AND CHILLIER CONDITIONS THEN HEADING
INTO THIS WEEKEND.
LONG TERM...FRIDAY THROUGH MONDAY.
GFS/ECM/CMC ALL AGREEING LONGWAVE PATTERN WILL BE QUITE PROGRESSIVE
THRU THE PD WITH LOW AMPLITUDE UPPER RIDGE OVER THE CNTRL CONUS
GETTING KICKED EWD BY AMPLIFYING WEST COAST LONGWAVE TROF. HEADING
INTO NEXT WEEKEND...ABOVE NORMAL TEMPS EXPECTED SAT AND SUN BEFORE
NOTICEABLE CHANGE BEGINS THE EARLY PART OF NEXT WEEK. LATE SUNDAY
NIGHT ECM/GFS ADVERTISING CAA QUICKLY SWEEPING SWD THRU THE DAKOTAS
AND INTO THE CNTRL PLAINS EARLY MONDAY MORNING. GFS SOLUTION ABOUT
6 HRS FASTER THAN ECM WITH FROPA INTO CWA. BOTH MODELS DO SHOW
DECENT LLVL MOIST ADVECTION INTO THE REGION...AND THEREFORE FEEL IT
IS REASONABLE TO GO WITH SMALL POPS SUNDAY NIGHT/MONDAY MORNING.
TIMING CAA/PTYPE WILL BE TRICKY GIVEN GFS/ECM DISAGREEMENT...HAVE
OPTED TO USE A SOLUTION COMPROMISE WITH -RA/SN MIX NORTH...-RA
CHANGING TO SN SOUTH.
AVIATION...
18Z TAFS
VFR CONDITIONS WILL CONTINUE THROUGH 06Z...THEN DETERIORATE TOWARD
08-09Z AND ONWARD AS LOW STRATUS OVERSPREADS THE SITES FROM WEST TO
EAST. DRIZZLE AND FREEZING DRIZZLE ARE POSSIBLE TOWARD THE 09-15Z
TIME WINDOW...BUT WILL HOLD MENTION OUT FOR NOW /WITH JUST A REDUCED
VIS MENTION/ AND LET NEXT TAF CYCLE REFINE TIMING. SOUTHEASTERLY
WINDS WILL STRENGTHEN AT THE SURFACE OVERNIGHT...BUT VERY STRONG
SOUTHWEST WINDS AROUND 800-1000FT AND UP WILL CREATE WIND SHEAR
CONCERNS OVERNIGHT.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...FREEZING RAIN ADVISORY FROM 6 AM TO NOON CST WEDNESDAY FOR
NEZ012-015-018-032>034-043-044.
FREEZING RAIN ADVISORY FROM 3 AM TO 3 PM CST WEDNESDAY FOR
NEZ011-016-017-030-031-042.
IA...FREEZING RAIN ADVISORY FROM 6 AM TO NOON CST WEDNESDAY FOR
IAZ043.
&&
$$