FXUS63 KOAX 250927
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
327 AM CST SAT DEC 25 2010
.DISCUSSION...
DIFFICULT FORECAST OVER THE NEXT TWO DAYS AS MODELS ARE NOT
HANDLING THE CURRENT CLOUD DECK WELL. INITIALIZATION OF THE
NAM/GFS/RUC COMPARED TO THE 00Z SOUNDINGS AT OMA/ABR/BIS INDICATE
THE MODELS ARE TO DRY IN THE STRATUS LAYER. THIS CREATES PROBLEMS
FOR HIGHS AND LOWS THROUGH THE DAY ON SUN. GIVEN THE LOW SUN
ANGLE...EXTEND THE CURRENT STRATUS DECK INTO SRN CANADA...AND THE
MODELS OVER-FORECASTING OF THE DRYING TONIGHT...WILL GO WITH A
PESSIMISTIC APPROACH THROUGH THE DAY ON SUN. THUS WILL MAINTAIN
CLDS IN ALL BUT THE FAR S AND SW CWA TODAY...THEN BACK THE CLDS
WWD TONIGHT TO COVER THE ENTIRE CWA AND ERODE FM SW TO NE DURING
THE DAY ON SUN. POINT FORECAST SOUNDINGS FM THE MODELS WERE NOT
HELPFUL...BUT ANALYSIS OF THE INDIVIDUAL MEMBERS OF THE SREF
INDICD 6 OF THE 21 MEMBERS /NNM-BMJ SCHEMES/ DID HANDLE THE
CURRENT CLDS WELL AND SHOWED THEY WOULD PERSIST THROUGH THE DAY ON
SUN IN ALL BUT THE SW.
MODELS ARE ALSO SIGNIFICANTLY STRUGGLING WITH CURRENT TMPS. SFC
TMPS WELL INTO ND ARE IN THE 10 TO 15 ABOVE RANGE WHERE IT IS
PROGGED TO BE NEAR ZERO. THE NAM/GFS INDC THIS COLD DRY AIR WILL
MOV INTO OUR FA THIS AFTN WHICH DOES NOT SEEM LIKELY WHEN COMPARED
TO CURRENT CONDITIONS. THUS WE HAVE KEPT CURRENT TMPS FOR HIGHS
TODAY WHICH...IS CLOSE TO THE 950 MB ISOTHERMAL TMPS...EXCEPT IN
THE SW WHERE TMPS WL LIKELY INCREASE A COUPLE OF DEGREES THIS
AFTN. WE HAVE MADE SIGNIFICANT CHANGES TO THE LOWS TONIGHT WITH
THE THINKING IT WILL REMAIN CLOUDY. WE HAVE GONE A GOOD 10 TO 12 F
ABOVE THE GUIDANCE ENVELOPE...BUT ANY BREAK IN THE CLDS...EVEN FOR
A SHORT TIME...CLD ALLOW FOR TMPS TO DROP SO THIS WILL NEED TO BE
WATCHED CLOSELY. OTHERWISE UPPR LVL RIDGE OVR THE WRN US SHLD
START TO ADVANCE EWD AND ALLOW FOR SRLY FLOW TO INCREASE ON SUN
NIGHT AND THROUGH THE DAY ON MON. THIS WILL ALLOW FOR CLDS TO
CLEAR AND TMPS TO WARM. CURRENT FORECAST HANDLES THE WARM-UP INTO
MID WEEK WELL AND NO CHANGES WERE MADE TO THESE PERIODS. THE
MODELS ARE IN GOOD AGREEMENT IN A SYSTEM TO MOVE THROUGH THE AREA
ON MON NIGHT INTO THE DAY ON TUES PROVIDING SOME LARGE-SCALE
SUPPORT FOR ASCENT...BUT IT CURRENT LOOKS LIKE A FAIRLY DRY
SYSTEM. FORCING IS PRETTY STRONG THOUGH...SO THIS WILL HAVE TO BE
WATCHED FOR SOME POPS AS THE SYSTEM NEARS.
BOUSTEAD
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
MVFR TO IFR CIGS WILL PERSIST THROUGH THE TAF CYCLE AS LOW-LEVEL
MOISTURE PERSISTS. MAY ALSO SEE VIS DROPPING TO MVFR RANGE AT TAF
SITES...ESPECIALLY AFTER 00Z WHEN WINDS WEAKEN TO LIGHT AND VARIABLE
AS HIGH PRESSURE MOVES THROUGH. MODELS HAVE NOT HANDLED STRATUS
WELL...BUT STRATUS DECK LOOKS LIKE IT COULD PERSIST WELL BEYOND THE
END OF THE TAF CYCLE...PARTICULARLY AT KOMA.
MAYES
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$