FXUS63 KOAX 162115
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
315 PM CST TUE NOV 16 2010
.SHORT TERM...TONIGHT THROUGH FRIDAY.
TRACK OF CLIPPER-TYPE SYSTEM TONIGHT/WEDNESDAY MAIN FORECAST
CHALLENGE IN SHORT TERM AS MODELS HAVE SHIFTED TRACK FARTHER SW
THAN YDA. AFTERNOON STLT IMAGERY SHOWED THIS SYSTEM DROPPING
FAIRLY QUICKLY SEWD WITH CLOUD AND PCPN SHIELD OVER MUCH OF WY AND
MT WITH EVEN AN OCNL LTG STRIKE SCNTRL WY. MORNING UA SHOWED A
30DM HGT FALL AT H300 AT SPOKANE WITH BROADER AREA OF MODEST/STG
FALLS SVRL HUNDRED MILES EITHER SIDE. SYSTEM WILL HAVE A
RELATIVELY BRIEF PD OF DECENT FORCING WITH IT WITH AMPLE MOISTURE
FOR PCPN. HOWEVER...USING A BLENDED TRACK 0F H7 LOW BETWEEN
GFS/ECMWF AND NAM WOULD PUT HIGHEST CHC OF PCPN ACROSS SWRN CWA
LATE TNGT THROUGH MIDDAY WED AND MADE RATHER MODERATELY LARGE
CHANGES TO FORECAST TO REFLECT LESS CHC OF PCPN AND LITTLE SNOW
ACROSS NRN ZONES AND UPPED POPS ACROSS SW. NAM/GFS FORECAST
SOUNDINGS INDICATED EITHER NO PCPN OR RAIN...BUT LEFT IN A MIX OF
RAIN/SNOW OR SNOW DOWN TOWARD KS/MO BORDERS AS DYNAMICS OF SYSTEM
MAY PROVIDE ENOUGH COOLING. HOWEVER...WITH BLYR TEMPS REMAINING A
LTL WARMER ACROSS SOUTHERN CWA...FELL MOST SNOW AMOUNTS WL BE
UNDER AN INCH. ADJUSTED HOURLY TEMPS TNGT TO ACCOUNT FOR A NON-
DIURNAL TEMP TREND WITH MOST LOWS PROBABLY LATE THIS EVENING
BEFORE CLOUDS THICKEN FOR GOOD WITH APPROACHING SYSTEM. ALSO WITH
SYSTEM DROPPING FAR ENOUGH S BY MID AFTN FELT MOST AREAS WILL HAVE
SOME TEMP RECOVERY.
STILL LOOKS QUITE COOL WEDNESDAY NIGHT AS HIGH SETTLES ACROSS MO
RIVER VALLEY BHND SYSTEM WITH COOLER MAV PROBABLY THE BETTER MOS
GUIDANCE. WITH MODEST RECOVERY EXPECTED ON THU...SPCLY W/NAM AND
ECMWF...BOOSTED TEMPS TO MET NUMBERS. DRY FROPA EXPECTED ON FRIDAY
WITH DECENT AGREEMENT BETWEEN 12Z GFS/NAM/ECMWF...BUT MOST OF THE
SIGNIFICANT COOLING REMAINS TO OUR NORTH YET.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY.
FAIRLY LOW CONFIDENCE REMAINS IN EXTENDED PERIOD AS A POSITIVELY
TILTED UPPER TROUGH IS STILL FORECAST TO SET UP FROM THE CA COAST
INTO SOUTH CENTRAL/NERN CANADA BRINGING A SWRLY UPPER FLOW TO
FORECAST AREA. WITH THE AIRMASS SPILLING INTO THE NORTHERN PLAINS
QUITE COLD DUE TO A MORE NRLY UPPER FLOW IN CANADA...THE AMOUNT OF
COLD AIR THAT SLIPS UNDER THIS SWRLY UPPER FLOW MAKES FOR A
DIFFICULT AND PROBABLE CHANGEABLE TEMPERATURE FORECAST. MODEL
CONTINUITY...INCLUDING ECMWF...HAS BEEN LACKING WITH DIFFERING
RUNS SUGGESTING STRONGER WAVES OR TIMING OF THEM DIFFERENT ENOUGH
SO THAT BOTH TEMPS AND WINDS DIFFER BY A CATEGORY OR TWO. GFS
ENSEMBLE MEAN BASICALLY KEEPS BOUNDARY N OF SRN ZONES TILL MONDAY
AND ALTHOUGH OPERATIONAL RUNS OF 12Z GFS/00Z ECMWF WERE CLOSE IN
THE LARGER PICTURE...NARROWING IT DOWN TO CWA SCALE CAUSES THESE
PROBLEMS. FOR NOW ALLOWED FOR ONLY MODEST COOLING WITH ANY FRONTAL
PASSAGE IN SAT/SUN PD AND THEN A COOLING TREND MON AND TUE AS
UPPER TROUGH AXIS COLLAPSES A BIT SE ALLOWING MORE A PUSH OF
COLDER AIR. WITH SWRLY UPPER FLOW...PCPN CHCS ARE NOT ZERO BUT
APPEAR LOW. DUE TO UNCERTAINTY LEFT IN SMALL POPS IN SUN NGT/MON
PD AS COLDER AIR POSSIBLY BEGINS SLIPPING INTO CWA AND ADDED SMALL
POPS SUNDAY AS BOTH 12Z GFS/00Z ECMWF HAD A MODESTLY STRONG WAVE
EJECT ACROSS DAKOTAS.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
THE BACK EDGE OF A LARGE DECK OF MVFR CIGS CONTINUES TO SKIRT NERN
NEB WITH LATEST SATELLITE IMAGES SHOWING SOME FILLING IN OF THE
STRATUS FURTHER WEST AROUND KOFK. THIS WL CONTINUE TO BE WATCHED
CAREFULLY BOTH AT KOMA AND KOFK. OTHERWISE...AN OVERCAST DECK OF MID
CLOUDS WILL ADVECT EWD THRU THE TAF PD AHEAD OF INCOMING PCPN. MOST
PCPN LOOKS TO FALL ACROSS KLNK WITH A FEW SHOWERS POSSIBLE AT KOFK
AND KOMA. MOST OF THE PCPN SHOULD REMAIN -RA. VFR TO MVFR CONDITIONS
EXPECTED WITH THE PCPN.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
CHERMOK/KERN