FXUS63 KOAX 172003
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
303 PM CDT TUE MAY 17 2011
.SHORT TERM...TONIGHT
WV IMAGERY THIS AFTN SHOWING FETCH OF MOISTURE ROTATING NWD THRU
THE ROCKIES ON FRONT END OF SLOW MOVING LARGE UPPER CLOSED LOW.
ASSOCIATED SFC CYCLOGENESIS RELATED TO THIS SYSTEM WAS OCCURRING
WITH MOST PREVALENT 3HR PRESSURE FALLS LOCATED IN SERN CO. MSAS
SHOWING SE FLOW BEGINNING TO ADVECT BNDRY LYR THETA-E AIRMASS INTO
THE WRN HIGHS PLAINS. AT THIS POINT EXPECT PCPN ACTIVITY TO MATURE
OVER THE WRN DAKOTAS/NEB PANHANDLE...THEN SLOWLY TREK EAST AND
APPROACH THE CWA WRN PERIPHERY AROUND 12Z. LAST COUPLE GFS RUNS
HAVE BEEN A BIT FASTER THAN THE NAM...AND NOW LATEST CMC IS
COMPLIMENTING GFS QPF PROGS. THEREFORE THINK IT IS REASONABLE TO
INTRODUCE SLGT POPS AFTER MID OVER THE WRN CWA.
DEE
.LONG TERM...WEDNESDAY THROUGH TUESDAY
CHANCES FOR PRECIPITATION THROUGH THE WEEK AND WEEKEND ARE THE
PRIMARY FORECAST CONCERNS. LOOKS LIKE A FAIRLY WET PERIOD WITH
SEVERAL CHANCES FOR SHOWERS OR STORMS.
OMEGA BLOCK PATTERN OVER THE CONUS WILL BREAK DOWN THIS WEEK AS
UPPER LOW IN THE WESTERN STATES SLOWLY TRANSLATES EAST INTO THE
PLAINS. MODELS ARE SIMILAR IN MOVING CENTER OF UPPER LOW INTO THE
CENTRAL ROCKIES OR HIGH PLAINS ON THURSDAY...BUT DIFFER THEREAFTER
IN REGARDS TO HOW MUCH ENERGY MOVES INTO THE PLAINS. THE GFS AND A
MAJORITY OF ITS ENSEMBLE MEMBERS PUSH THE UPPER LOW EAST THROUGH
SOUTH DAKOTA...WHICH WOULD YIELD A COOLER AND WETTER FORECAST FOR
OUR AREA. THE 00Z ECMWF AND EXTRAPOLATION OF 12Z NAM AND UKMET TAKE
BRUNT OF UPPER LOW ENERGY NORTH INTO SOUTHERN CANADA...YIELDING A
DRIER AND WARMER PATTERN FOR EASTERN NEBRASKA AND WESTERN IOWA. THE
CANADIAN MODEL TENDS TO SIDE WITH ECMWF AS WELL. NOW THE 12Z ECMWF
HAS TRENDED TOWARD THE GFS SOLUTION IN BRINGING THE UPPER LOW INTO
THE PLAINS...BUT IS MUCH FARTHER NORTH ACROSS NORTH DAKOTA RATHER
THAN SOUTH DAKOTA. GOT TO FIGURE FINAL OUTCOME WILL BE SOMEWHAT
SIMILAR TO A ECMWF/GFS BLEND...SO HAVE PLAYED THE FORECAST SOMEWHAT
DRIER AND WARMER THAN GFS.
AS UPPER LOW BEGINS TO PUSH EAST TOWARD THE FOUR CORNERS REGION
WEDNESDAY...WING OF MID LEVEL WARM ADVECTION WILL SPREAD CLOUDS AND
A CHANCE FOR PRECIPITATION INTO THE PLAINS. DIFFLUENT FLOW REGIME
SUGGESTS BULK OF THIS PRECIPITATION WILL MOVE WEST AND SOUTH OF OUR
CWA. BUT THERE IS STILL A CHANCE FOR SHOWERS/STORMS MUCH OF THE
DAY...ESPECIALLY IN OUR WEST.
WITH LOW MOVING CLOSER WEDNESDAY NIGHT...UPPER FLOW STRENGTHENS JUST
TO OUR WEST WITH STRONGLY DIFFLUENT FLOW ALOFT. COINCIDENT INCREASE
IN LOW LEVEL JET TO 40KTS WILL DRIVE HIGHER THETA-E AIR OVER
TIGHTENING 850 BAROCLINIC ZONE NEAR THE KANSAS BORDER. WILL LIKELY
SEE ELEVATED STORMS DEVELOP IN THIS REGIME AS JET STRENGTHENS
OVERNIGHT.
COULD SEE A BREAK IN THE ACTIVITY THURSDAY MORNING BEFORE A STRONG
SHORTWAVE ROTATES NORTHEAST INTO THE PLAINS THURSDAY AFTERNOON.
ECMWF EXPLODES PRECIPITATION OVER EASTERN NEBRASKA NEAR 00Z...AGAIN
IN AREA OF STRONG LOW LEVEL JET AND UPPER DIFFLUENCE. SIMILAR
SCENARIO LOOKS LIKELY ON FRIDAY WITH MORNING STORMS MOVING AWAY AND
A GOOD CHANCE FOR AFTERNOON/EVENING CONVECTION. THURSDAY AND
ESPECIALLY FRIDAY AFTERNOON BOTH LOOK POTENTIALLY SEVERE GIVEN
STRONG FLOW AND COOL TEMPERATURES ALOFT. HOWEVER SURFACE BOUNDARIES
ARE NOT AS CLEAR CUT SO DEFINING LOCATION OF THREAT THIS FAR OUT IS
AT BEST MARGINAL.
MORNING CONVECTION SATURDAY SHOULD MOVE OFF TO THE NORTHEAST RATHER
QUICKLY...WITH MOST OF SATURDAY BEING DRY AS UPPER LOW SHIFTS INTO
THE NORTHERN PLAINS. THE ECMWF SHOWS ANOTHER SHORTWAVE ROTATING
THROUGH THE PLAINS SATURDAY AFTERNOON...SO SOME THREAT FOR
CONVECTION WILL EXIST THEN. A COLD FRONT WILL SETTLE INTO THE REGION
BEHIND THIS SHORTWAVE ON SUNDAY...THEN SAG SOUTH OF OUR AREA ON
MONDAY. HOWEVER WEST TO SOUTHWEST FLOW ALOFT RIDING OVER THAT
BOUNDARY WILL CONTINUE TO BRING OFF AND ON PRECIP CHANCES TO OUR
AREA MONDAY AND TUESDAY.
TEMPERATURES THROUGH THE PERIOD WILL AVERAGE IN THE 60S AND 70S WITH
LOWS MAINLY IN THE 50S AND 60S. NO REAL COOL PUSH EXPECTED...BUT A
LITTLE WARMER HIGHS COULD BE REALIZED FRIDAY THROUGH SUNDAY IF
CLOUDS/PRECIP EXIT TO OUR NORTHEAST FOR AFTERNOON WARMING.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
SFC WIND GUSTS AROUND 20KT OVER ERN NEB SHOULD BEGIN TO RELAX LATE
THIS AFTN AND REMAIN OUT OF THE SE 5-10KT THE REST OF THE FCST PD.
BY 18/12Z...EXPECT LINE OF PCPN ASSOCIATED WITH A FEW UPPER
DISTURBANCES PASSING THRU TO BE APPROACHING ERN NEB WITH ORIENTATION
NW-SE. UNSURE AT THIS POINT WHETHER PCPN WILL MAKE IT TO ANY OF THE
TAF SITES...THUS HAVE OPTED TO NOT INCLUDE ANY PROB30 GROUPS AND
ANTICIPATE ONLY VFR CIGS 18/12Z-18Z AROUND FL100 AGL TO CONTEND
WITH.
DEE
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$