FXUS63 KOAX 250809
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
309 AM CDT THU AUG 25 2011
.DISCUSSION...
HIGH PRESSURE AT THE SURFACE AND ALOFT DOMINATES THE REGION
THIS MORNING WITH A POCKET OF DRIER AIR IN PLACE OVER EASTERN
NEBRASKA AND SOUTHWEST IOWA. AS THE SURFACE HIGH PRESSURE SHIFTS
EAST TODAY AND TONIGHT BOUNDARY LAYER AND 850 MOISTURE WILL BEGIN
TO RETURN TO THE AREA IN ADVANCE OF A COLD FRONT APPROACHING FROM
THE NORTHERN PLAINS. THIS FRONT WILL MOVE INTO THE FORECAST AREA
ON FRIDAY WITH A CHANCE OF SHOWERS AND THUNDERSTORMS IN THE
VICINITY OF THE FRONT. BOTH NAM AND GFS SHOW FRONT SINKING SLOWLY
SOUTH FRIDAY NIGHT THEN WASHING IT OUT ON SATURDAY ACROSS KANSAS
AS ANOTHER AREA OF HIGH PRESSURE MOVES INTO THE UPPER MIDWEST.
UPPER FLOW BECOMES MORE AMPLIFIED SATURDAY AND SATURDAY NIGHT AS
SOUTHERN CANADA TROUGH DIGS INTO EASTERN CANADA AND PICKS UP
REMNANTS OF IRENE AS IT LIFTS ACROSS THE NORTHEAST TOWARD EASTERN
CANADA.
NO MAJOR CHANGES IN FORECAST TRENDS IN THE SHORT TERM BUT DID ADJUST
MAX TEMPERATURES UP A BIT IN THE EXTENDED PERIOD AS NEXT TROUGH
DIGS OFF NORTHWEST COAST WITH UPPER RIDGE BUILDING OVER THE
NORTHERN ROCKIES AND MOVING INTO THE NORTHERN PLAINS LATE IN THE
PERIOD.
&&
.AVIATION...
DEEP LAYER RIDGING WILL CONTINUE ACROSS THE REGION THROUGH THE
PERIOD. SUBSIDENT FLOW REGIME WITH VERY DRY PROFILES ABOVE THE BL
WILL SUPPORT VFR CONDITIONS AT MOST SITES THIS AM. ISOLATED AREAS OF
MVFR WILL BE POSSIBLE IN VALLEY LOCATIONS BEFORE DAWN. HAVE RETAINED
VFR CONDITIONS AT ALL TAF SITES GIVEN DRY PROFILES PER 06Z OAX RAOB
AND ISOLATED NATURE OF CURRENT VIS RESTRICTIONS. CLEAR SKIES WITH
DEVELOPING SE WINDS EXPECTED TODAY. OTHERWISE...VEERING LL WIND
PROFILES WITH AN APPROACHING MID LEVEL IMPULSE WILL SUPPORT THETA-E
RISES IN THE H925-H8 LAYER LATE IN THE PERIOD. STEEPENING MID LEVEL
LAPSE RATES PER AN ADVANCING EML COUPLED WITH LL MOISTURE ADVECTION
WILL SUPPORT INCREASING ELEVATED CONVECTION CHANCES OVER NORTHERN
NEBRASKA WITH POTENTIAL CONVECTION INTO THE NORTHERN FA AFTER 06Z
FRI. WILL DEFER ANY TS MENTION IN THE TAFS UNTIL A BETTER HANDLE ON
COVERAGE/TIMING IS ESTABLISHED.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
FOBERT/JC