FXUS63 KOAX 292010
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
310 PM CDT FRI JUL 29 2011
.SHORT TERM...TONIGHT.
MONSOONAL MOISTURE IS STILL STREAMING FROM THE SOUTHWEST U.S. INTO
THE CENTRAL PLAINS AND LOWER GREAT LAKES/OHIO VALLEY...HOWEVER
FORCING MECHANISMS WEAK...THUS RISK IS MAINLY FOR ISOLATED SHOWERS
AND THUNDERSTORMS TONIGHT.
TEMPERATURES HEATED UP IN NORTHEAST NEBRASKA AND CLOUD COVER OVER THE
REST OF THE AREA PROVIDING A GOOD THERMAL CONTRAST. SOME ISOLATED
STORMS FROM ALBION TOWARD OMAHA INTO SOUTHWEST IOWA WHERE THE
INSTABILITY IS GREATEST AND OTHER SHOWERS SCATTERED AROUND DUE TO
WEAK H50 SHORTWAVE PASSING THRU THE AREA. AT 19Z...THE SURFACE
BOUNDARY STRETCHED FROM KANSAS INTO MISSOURI. THE WEAK H85 BOUNDARY
HAS BECOME LESS DEFINED AS THE FLOW VEERS AND THE WEAK H7 WAVE WAS
LESS NOTABLE AS WELL. EVENING SHOWER AND THUNDERSTORM ACTIVITY
SHOULD WEAKEN DIURNALLY. AS THE LOW LEVEL JET OVER KANSAS AND
STRENGTHENS...ADDITIONAL SHOWER AND THUNDERSTORMS MAY FORM
OVERNIGHT...KEPT POPS ISOLATED TO SCATTERED AND HIGHEST POPS IN THE
SOUTH CLOSER TO THE SURFACE BOUNDARY. DID MENTION SOME PATCHY FOG
WITH WEAK SURFACE FLOW AND MOIST LOW LEVELS. LOWS STILL ABOVE
NORMAL IN THE UPPER 60S TO LOWER 70S.
.LONG TERM...SATURDAY THROUGH FRIDAY.
LIKE YESTERDAY...THE PRIMARY FORECAST CONCERNS ARE THUNDERSTORMS
CHANCES AND HEAT. IT DOES APPEAR THAT WE MAY NEED SOME HEADLINES
FOR HEAT AT SOME POINT...PROBABLY FROM SUNDAY INTO TUESDAY. BUT
THERE IS ENOUGH UNCERTAINTY TO DELAY ISSUANCE.
STRONG 500 MB RIDGE STRETCHING FROM THE SOUTHEASTERN UNITED STATES
BACK INTO THE SOUTHWEST IS STILL EXPECTED TO RETROGRADE AND BUILD
OVER THE CENTRAL AND SOUTHERN PLAINS OVER THE WEEKEND. UNLIKE THE
PAST HEAT EVENT WE HAD...THE MODELS KEEP THE MAXIMUM HEIGHT VALUE
AT THE CENTER OF THE 500 MB RIDGE UNDER 5990 METERS. MONSOONAL
MOISTURE CONTINUES TO FEED UP FROM MEXICO INTO THE CENTRAL ROCKIES
AND THEN EAST INTO THE PLAINS. WILL KEEP THUNDERSTORM CHANCES
GOING ON SATURDAY...ESPECIALLY FOR SOUTHEAST NEBRASKA AND
SOUTHWEST IOWA. THIS IS WHERE OVERALL MODEL CONSENSUS POINTS TO
HIGHEST MID LEVEL MOISTURE VALUES. 12Z NAM MIGHT BE A BIT OVERDONE
WITH ITS RAINFALL AMOUNT FORECAST. THE LARGE SCALE FORCING
(LOOKING AT 500-300 MB Q VECTORS) APPEARS TO BE MUCH WEAKER THAN
TODAY. WILL ALSO CARRY A SLIGHT CHANCE OF THUNDERSTORMS ACROSS OUR
SOUTHERN COUNTIES INTO SUNDAY.
PRECIPITATION CHANCES SEEM LOW ENOUGH (14 PERCENT OR LESS) SUNDAY
NIGHT INTO MONDAY NIGHT WITH MID TROPOSPHERIC RIDGE IN PLACE AND
BEST FORCING TO OUR WEST AND NORTH. THE RIDGE WILL START TO
FLATTEN TUESDAY...ALLOWING A COLD FRONT TO PUSH EASTWARD ACROSS
THE NORTHERN AND CENTRAL PLAINS TUESDAY INTO TUESDAY NIGHT. THE
12Z ECMWF IS GENERALLY FASTER WITH THE COLD FRONT THAN THE 12Z
GFS. FOR NOW...USED A BLEND OF THOSE FOR FRONTAL TIMING. AS THE
MID LEVEL RIDGE CONTINUES TO FLATTEN LATER IN THE WEEK...
12 HOUR THUNDERSTORM CHANCES WILL PROBABLY REMAIN IN THE 20-30
PERCENT RANGE BUT THE TIMING SPECIFIC EVENTS WILL BE TOUGH THIS
FAR OUT.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE INTO THE
EVENING HOURS WITH HEATING THIS AFTERNOON AND AN UNCAPPED MOIST...
UNSTABLE ATMOSPHERE. THE HIGHER INSTABILITY IS IN AN AREA NEAR
ALBION TOWARD OMAHA INTO SOUTHWEST IOWA. STORMS THAT FORM SHOULD
WEAKEN AFT 01Z. CIGS SHOULD MAINLY BE VFR HOWEVER MVFR CIGS ARE
POSSIBLE WHERE THERE IS CONVECTION. LATER TONIGHT THE LOW LEVEL
JET WILL INCREASE IN KANSAS WITH WEAK H85 THETA-E ADVECTION INTO
EASTERN NEBRASKA ...THUS ADDITIONAL SHOWERS COULD DEVELOP. DID
INCLUDE A MENTION AT KLNK AFT 10Z. TONIGHT...WEAK FLOW AND A MOIST
LOW LEVEL ENVIRONMENT WILL PROMOTE FOG AND SOME MVFR/IFR CIGS
BETWEEN 10Z AND 14Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
SHORT TERM...ZAPOTOCNY
LONG TERM...MILLER