FXUS63 KOAX 160250
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
950 PM CDT MON AUG 15 2011
.UPDATE...SHORTWAVE IS NOW PUSHING EAST OUT OF NORTHEAST
COLORADO..AND ALONG THE NEBRASKA/KANSAS STATE LINE. SURFACE LOW IS
LOCATED ACROSS WEST CENTRAL KANSAS WITH VERY WARM AND MOIST
CONDITIONS BEING ADVECTED NORTHWARD AHEAD OF THIS FEATURE. THE LOW
LEVEL JET WILL STRENGTHEN CONSIDERABLY OVERNIGHT...WITH THE AXIS
POINTING NORTH INTO SOUTHEAST NEBRASKA. IF THE MODELS HAVE THE
CORRECT PLACEMENT...THIS WOULD ALLOW CONVECTION TO DEVELOP ACROSS
SOUTHEAST NEBRASKA OR NORTHERN KANSAS. THE QUESTION IS HOW FAR
NORTH THIS ACTIVITY WILL REACH. OPTED TO EXPAND LOW CHANCE POPS A
BIT FURTHER NORTH TO ACCOUNT FOR THIS UNCERTAINTY. WITH THE
MOISTURE BEING ADVECTED NORTHWARD...LOCALLY HEAVY RAINFALL CAN BE
EXPECTED UNDERNEATH THE DEVELOPING STORMS LATE TONIGHT. THE PRIME
AREA APPEARS TO BE FAR SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA AND
NORTHWEST MISSOURI. NO OTHER CHANGES WERE MADE TO ONGOING FORECAST.
KAS
&&
.PREV DISCUSSION... /ISSUED 411 PM CDT MON AUG 15 2011/
SHORT TERM...TONIGHT
A COUPLE OF IMPULSES SEEN MOVING EAST ALONG THE NEB/KS BORDER IN
WATER VAPOR IMAGERY. THESE IMPULSES ARE EXPECTED TO INTERACT WITH A
NOCTURNAL LOW LEVEL JET. MODELS IN GOOD AGREEMENT WITH CENTRAL KS
INTO EASTERN NEB TO BE THE STRONGEST JET AXIS. ISENTROPIC UPGLIDE
WITH LOWEST COND PRESS DEF OVER SE NEB AND SW IA...AND WILL HAVE THE
HIGHEST CHANCE POPS TO ACCOUNT. SOME QUESTION ON HOW FAR NORTH THE
SHOWERS WILL DEVELOP. CURRENT FORECAST IS CONSERVATIVE COMPARED TO
THE SHORT RANGE MODELS BASED MORE ON TRENDING THE IMPULSE FROM WATER
VAPOR. LATE TONIGHT...WITH DEW PTS IN THE 60S AND SOUTH WINDS
EXPECTED TO CONTINUE TO HOLD MOISTURE UP...PATCHY FOG AND/OR LOW
STRATUS IS FORECAST AS LOWS DIP INTO THE 60S. SHOWERS WILL STIR UP
THE BOUNDARY LAYER AND DID NOT MENTION WHERE POPS WERE THE HIGHEST.
LONG TERM...TUESDAY THROUGH MONDAY
PATCHY FOG WILL CONTINUE THROUGH MID MORNING. SOME PRECIPITATION
WILL LINGER IN SOUTHEAST NEBRASKA DURING THE MORNING HOURS. VIGOROUS
UPPER SHORTWAVE TROUGH WILL BE MOVING ACROSS THE NORTHERN PLAINS.
THIS WILL CAUSE A COLD FRONT TO DROP SOUTHEAST INTO NORTHEAST
NEBRASKA BY TUESDAY AFTERNOON AND THROUGH THE REST OF NEBRASKA BY
06Z WEDNESDAY. THUNDERSTORM ACTIVITY IS EXPECTED ALONG THE
FRONT...ESPECIALLY AFTER 00Z WHEN INSTABILITY IS EXPECTED TO BE
GREATEST. THERE IS ALSO A CHANCE OF SOME ISOLATED SEVERE STORMS.
EAST-WEST FRONT STALLS OUT OVER NORTHERN KANSAS WHILE SURFACE HIGH
MOVES INTO THE AREA ON WEDNESDAY. SOME THUNDERSTORMS MAY LINGER
DURING IN THE DAY OVER SOUTHEAST NEBRASKA SO SLIGHT POPS IN THE
EXTREME SOUTHEAST. AFTER A TRANQUIL DAY ON THURSDAY...BY THURSDAY
NIGHT ANOTHER WEAK SHORTWAVE TROUGH AND ISENTROPIC LIFT WILL CREATE
A CHANCE OF THUNDERSTORMS. ANOTHER COLD FRONT WILL MOVE THROUGH THE
AREA ON FRIDAY GIVING A CHANCE OF THUNDERSTORMS ACROSS THE AREA
FRIDAY. ANOTHER DISTURBANCE WILL PRODUCE A CHANCE OF STORMS ON
FRIDAY NIGHT INTO SATURDAY. SUNDAY LOOKS MOSTLY DRY AS HIGH PRESSURE
MOVES INTO THE PLAINS AND MID MISSISSIPPI VALLEY.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
00Z ISSUANCE.
TRICKY FORECAST OVERNIGHT AS WE WAIT THE ARRIVAL OF A SHORTWAVE
FROM THE WEST. CONVECTION WILL LIKELY BREAK OUT SOMEWHERE ACROSS
NORTHERN KANSAS OR SOUTHERN NEBRASKA AND TRACK EAST OR NORTHEAST
ACROSS AREAS SOUTH OF I-80. AT THIS POINT...THERE IS A BIT OF
UNCERTAINTY ON HOW FAR NORTH THIS CONVECTION WILL REACH. SO MUCH
UNCERTAINTY...THAT OPTING TO NOT PUT IN THE TAF FOR THE TIME
BEING. UPDATES MAY BE NEEDED IF THE CONVECTION FIRES FAR ENOUGH
NORTH. HOWEVER...BEING ON THE FENCE...OPTED TO BE MORE OPTIMISTIC.
CONVECTION WILL DEPART BY MIDDAY...LEAVING BEHIND VFR CONDITIONS.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$