FXUS63 KOAX 202005
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CDT WED JUL 20 2011
.DISCUSSION...
STRONG UPPER SHORTWAVE TROUGH THAT WAS LIFTING ACROSS
MANITOBA/SASKATCHEWAN WAS SENDING A COLD FRONT TOWARD FAR NWRN
PART OF THE FORECAST AREA...AND AT 19Z IT WAS ESTIMATED NEAR ONL.
MID LEVEL TEMPERATURES REMAIN QUITE WARM ACROSS FORECAST
AREA...+15 TO +17 AT H7...AND THIS WILL REMAIN A WILD CARD IN
COVERAGE OF ACTIVITY TONIGHT. ANOTHER QUESTION MARK IS THE FACT
THAT MUCH OF THE UPPER SUPPORT WAS LIFTING SO FAR N OF THE AREA.
WILL LEAVE IN SMALL POPS NEAR AND NW OF FRONT THROUGH 06Z...BUT
FEEL MAIN ACTIVITY MAY NOT START UNTIL STRENGTHENING LOW LEVEL
JET IMPINGES ON AND NORTH OF FRONT AROUND AND AFTER 06Z.
THUS...MAIN CHANGES WITH POPS TONIGHT WAS TO LOWER OR DROP THEM
SERN ZONES BEFORE 06Z AND THEN TO INCREASE IN WEST CENTRAL THROUGH
CENTRAL ZONES LATER TONIGHT. CONTINUED LIKELY POPS ON THURSDAY
ALONG AND JUST NORTH OF I80 CORRIDOR MATCHING UP WITH 09Z
SREF...AND WHICH HAD SUPPORT OF 12Z OPERATIONAL RUNS OF NAM/GFS
AND 00Z ECMWF. FORECAST SOUNDINGS SHOWED ACTIVITY FAIRLY HIGH
BASED INTO THURSDAY WITH CAPE SHRINKING INTO THURSDAY AFTERNOON.
THUS...SOME WIND POSSIBLE WITH INITIAL STORMS BUT SEVERE THREAT
PROBABLY LIMITED THROUGH THURSDAY LATE AFTERNOON/EVENING...IF
EVEN THEN. PRECIPITABLE WATER REMAINS HIGH AND POTENTIAL EXISTS FOR
ISOLATED HEAVY RAIN AMOUNTS. HOWEVER...EVEN THOUGH QPF AMOUNTS
WERE BOOSTED TONIGHT/THURSDAY...STILL KEPT THEM WELL BELOW BULLISH
GFS DUE TO WARM MID LEVEL TEMPERATURES MAKING COVERAGE
QUESTIONABLE. ALSO NOTICED 4KM WRF REALLY DOWNPLAYED ACTIVITY ON
THURSDAY BASICALLY DISSIPATING SHOWERS BY 15Z WITH LATE AFTERNOON
REDEVELOPMENT TAKING PLACE IN NERN KS. WITH TEMPERATURES REMAINING
QUITE WARM OFF THE SURFACE...CLOUDS/SHOWERS OR LACK OF THEM COULD
POTENTIALLY ALLOW A 20+ DEGREE RANGE IN TEMPERATURES ACROSS
FORECAST AREA THURSDAY. BUT EVEN IF SHOWERS WOULD MANAGE TO KEEP
READINGS DOWN INTO EARLY AFTERNOON...BREAKS LATER WOULD ALLOW THEM
TO JUMP...THUS KEPT READINGS IN MID 80S ALONG/N OF PLATTE
RIVER/HIGHWAY 30 AND MID 90S ACROSS SOUTHERN ZONES.
STRENGTHENING LOW LEVEL JET COULD FEED ANY ACTIVITY THAT DEVELOPS
LATE IN THE AFTERNOON AIDED BY DIFFERENTIAL HEATING. UPPER
RIDGE/WARMTH COULD TEND TO SUPPRESS SOUTHERN EXTENT...HOWEVER...SO
KEPT HIGHER POPS ACROSS NERN ZONES. HOWEVER...A SOLUTION OF 12Z
GFS NOT ENTIRELY OUT OF THE QUESTION AND POP FIELD MAY NEED
ADJUSTING LATER. ALSO WITH MOIST PLUME REMAINING IN PLAY...IF
CONVECTION BECOMES WIDESPREAD BY LATE AFTN/EARLY EVENING...QPF AMOUNTS
WOULD LIKELY BE MUCH HIGHER THAN THE 0.25-0.40 FORECAST.
WARMER AIR RETURNING FRIDAY/FRIDAY NIGHT COULD TOUCH OFF
ADDITIONAL THUNDERSTORM DEVELOPMENT...ESPECIALLY IF IT WOULD
MANAGE TO COINCIDE WITH ANY WAVE THAT WOULD EJECT AHEAD OF NEXT
STRONGER NRN ROCKIES/PLAINS TROUGH. FOR NOW LEFT FRIDAY DRY BUT
ADDED SLIGHT CHANCE NORTHERN ZONES FRIDAY NIGHT WHICH COULD CATCH
ANY HIGH PLAINS ACTIVITY THAT DEVELOPS AHEAD OF NEXT FRONT OR
ALONG NWD RETREATING WARM FRONT.
BOOSTED TEMPERATURES AHEAD OF THIS NEXT FRONT ON SATURDAY AND WITH
WARM MID LEVELS REMAINING/RETURNING...FEEL ANY CONVECTION MAY BE
MORE POST FRONTAL UNTIL SAT NIGHT AND THUS CUT BACK OR DROPPED
POPS SE OF LNK/OMA SINCE GFS AND ECMWF KEPT FRONT NORTHWEST OF
THERE THROUGH 00Z SUN. HOWEVER...AN INCREASED PRECIP CHANCE SAT
NIGHT STILL LOOKED OK.
LITTLE CHANGES WERE MADE BEYOND SATURDAY...THE MAIN ONE WAS TO ADD
PRECIP CHANCES SUNDAY NIGHT AS WARMER AIR/FRONT LIFTS BACK NORTH.
RESIDUAL CLOUDS COULD LINGER ON MONDAY PERHAPS LIMITING MAX
TEMPS...BUT DID NOT INCLUDE PRECIP CHANCES AT THIS TIME.
TEMPERATURES APPEAR TO WARM BACK UP AFTER THAT...AND IF ECMWF
VERIFIES COULD WARRANT MORE HEAT HEADLINES.
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
MAIN AVIATION CONCERN IS CHANCES FOR THUNDERSTORMS WITH APPROACHING
COLD FRONT...AS WELL AS THE WIND SHIFT. APPEARS THAT PRECIPITATION
WILL BE EITHER ALONG OR JUST BEHIND THE FRONT...AND THEREFORE HAVE
PROB30 GROUPS TIMED STARTING AT 05Z IN KOFK AND HELD OFF UNTIL 10Z
FOR KOMA AND KLNK. AT LEAST INITIALLY...EXPECT CLOUD BASES TO
REMAIN RELATIVELY HIGH UNTIL RAINS CAN SATURATE LOWER LEVELS.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...EXCESSIVE HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR NEZ011-
012-015>018-030>034-042>045-050>053-065>068-078-088>093.
IA...EXCESSIVE HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR IAZ043-
055-056-069-079-080-090-091.
&&
$$
CHERMOK/NIETFELD