FXUS63 KOAX 172037
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
337 PM CDT THU MAR 17 2011
.SHORT TERM...TONIGHT THROUGH SUNDAY
SURFACE COLD FRONT HAS MADE IT THROUGH THE FA THIS AFTERNOON...BUT
DEEP MIXING BEHIND THE BOUNDARY HAS ALLOWED FOR A MILD AFTERNOON.
WINDS WILL TEND TO DIMINISH THIS EVENING AND CLOUDS WILL INCREASE.
THE THERMAL GRADIENT OVER NORTHERN NEB WILL INCREASE TONIGHT AS
CONFLUENT MID-LEVEL FLOW ACTS TO INCREASE FRONTOGENESIS. 12Z KOAX
SOUNDING INDICATING STEEP MID-LEVEL LAPSE RATES. THIS WEAK STATIC
STABILITY WILL ALLOW FOR THE FRONTAL CIRCULATION TO PROVIDE LIFT
OVER THE NORTHWEST FA AFTER 09Z. DRY SURFACE HIGH PRESSURE
BUILDING SOUTHWARD THOUGH WILL TEND TO LIMIT THE AMOUNT OF PRECIP
THAT WOULD REACH THE SURFACE. THIS ALONG WITH FAIRLY NEUTRAL TO
WEAK FORCING FOR ASCENT ON THE LARGE-SCALE LIMITS THE POPS TO THE
MID CHANCE CATEGORY. SOME SLIGHT CHANCE OF SHOWERS WILL SPREAD
SOUTHEAST THROUGH THE AREA ON FRIDAY ALONG WITH A GOOD DEAL OF
CLOUDS AS THE FRONTAL CIRCULATION SHIFTS SOUTHWARD. DRY LOW-LEVEL
AIR THOUGH WILL CONTINUE TO LIMIT ACCUMULATIONS AND THUS JUST MAY
SEE SOME SPRINKLES.
QUIET WEATHER THEN SETS IN FOR FRIDAY NIGHT WITH CLEARING SKIES
AND LIGHT WINDS. RETURN FLOW SHOULD GET GOING ON LATE FRIDAY NIGHT
AND INCREASE ON SATURDAY. WE BELIEVE THAT THE GFS AND ECMWF ARE TO
FAST IN RETURNING PRECIP TO THE AREA...AND WE WILL START POPS OFF
IN THE AFTERNOON. ISENTROPIC LIFT REALLY INCREASES ON SATURDAY
NIGHT ALONG WITH A BETTER QUALITY OF AIR MASS MOISTURE
/CHARACTERIZED BY 850 MB DEW POINTS OF +10/ OVER SOUTHEAST NEB
AND SW IA. MAY SEE SOME ISOLATED THUNDER AT THIS TIME...BUT
OTHERWISE A GOOD CHANCE OF SHOWERS INTO SUNDAY MORNING BEFORE THE
LIFT AND MOISTURE SHIFTS EASTWARD AND DRY WEATHER BRIEFLY RETURNS.
BOTH SATURDAY AND SUNDAY SHOULD BE FAIRLY COOL WITH A GOOD DEAL OF
CLOUDS AND SOUTHEAST WINDS.
BOUSTEAD
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
FORECAST CONFIDENCE IN THE EXTENDED PERIOD WILL BE ON THE LOW
SIDE...ESPECIALLY WITH REGARD TO POPS. MAIN UNCERTAINTY WILL BE WITH
MOISTURE AVAILABILITY AS BOTH THE GFS AND ECMWF PLACE A STRONG RIDGE
OF HIGH PRESSURE ACROSS THE GULF OF MEXICO AT THE BEGINNING OF THE
PERIOD AND MAINTAIN THIS RIDGE UNTIL LATE IN THE PERIOD WHEN
CANADIAN HIGH PRESSURE BUILDS SOUTH INTO THE GULF. TIMING OF SHORT
WAVE ENERGY COMING OUT OF THE WESTERN TROUGH ALSO WILL PRESENT A
PROBLEM DURING THE PERIOD. MAIN WAVE LIFTS INTO THE NORTHERN PLAINS
AROUND TUESDAY WITH BEST CHANCE FOR RAIN DURING THIS TIME. HAVE
TRENDED FORECAST TODAY TOWARD THE 12Z HPC GUIDANCE WHICH FAVORED
ECMWF ENSEMBLE MEAN.
FOBERT
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
12Z TAFS
VFR CONDITIONS ARE EXPECTED THIS TAF PD. A COLD FRONT HAD MOVED THRU
THIS AFTERNOON. GUSTY NORTHWEST SFC WINDS WILL CONTINUE THRU THE
EVENING HOURS AND SHOULD BEGIN TO DIE DOWN BY 06Z. MID CLOUDS ARE
EXPECTED TO INCREASE OVERNIGHT AND A FEW SPRINKLES ARE POSSIBLE AT
KOFK AFTER 12Z SO HAVE ADDED A TEMPO GROUP FOR THIS.
BK
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$