FXUS63 KOAX 242005
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CDT SUN APR 24 2011
.DISCUSSION...
FORECAST CHALLENGE IS HOW QUICKLY WILL PRECIPITATION SPREAD ACROSS
THE FORECAST AREA ON MONDAY...HOW LONG WILL IT LINGER...AND THEN
CLOUDS/PRECIPITATION AFFECT ON TEMPERATURES.
AFTER A RARE GLIMPSE OF SUNSHINE ACROSS A GOOD PART OF THE
FORECAST AREA SUNDAY AFTERNOON...A RETURN TO A CONSIDERABLE AMOUNT
OF CLOUDS AND A CONTINUATION OF MUCH BELOW NORMAL TEMPERATURES IS
IN STORE...PROBABLY AT LEAST THROUGH TUESDAY.
MORNING/EARLY AFTERNOON UPPER AIR/SATELLITE IMAGERY SHOWED A BROAD
NEGATIVELY TILTED UPPER TROUGH FROM NEW MEXICO TO PACIFIC NW. A
LARGE PIECE OF THIS ENERGY AT H5 IS FORECAST TO MOVE ACROSS MID
MISSOURI VALLEY AND CLOSE-OFF BY TUESDAY NEAR SD/IA/MN COMMON BORDER.
DECENT QG FORCING SPREADS OVER THE AREA BY MONDAY AFTERNOON AS
SHARPER UPPER TROUGH APPROACHES...PLUS SLIGHTLY STEEPER H7-H5
LAPSE RATES AND NEGATIVE H85-H5 LIFTED INDICES MOVE INTO SERN
ZONES BY MONDAY MORNING. THUS IT APPEARS PRECIPITATION WILL SPREAD
FAIRLY QUICKLY ACROSS THE CWA ON MONDAY WITH CHANCES SOMEWHAT
LOWER AND DELAYED MORE TILL AFTERNOON FAR NW ZONES. BULK OF PRECIP
PROBABLY CENTERED ON LATE MORNING THROUGH EARLY EVENING TIME
PERIOD. ISOLATED THUNDERSTORM CHANCES SEEM POSSIBLE SERN ZONES AS
EARLY AS MONDAY MORNING...AND PERSIST THROUGH THE AFTERNOON IF
SLIGHTLY MORE UNSTABLE GFS WOULD VERIFY. HIGHER PRECIP CHANCES
SHOULD BE SHIFTING INTO NERN ZONES AND PERHAPS EVEN NE OF THERE
LATE MONDAY NIGHT AS UPPER LOW CLOSES OFF...ALTHOUGH A MESSY BROAD
TROUGHINESS PERSISTS BEHIND MAIN SYSTEM INTO WEDNESDAY.
HOWEVER...SINCE UPPER LOW COULD BE SLOWER TO DEPARTS AS IT CLOSES
OFF...BUMPED POPS UP TO CHANCE CATEGORY TUESDAY FAR NERN ZONES.
ALTHOUGH LITTLE CHANGES WERE MADE TO LOWS MONDAY NIGHT AND
TUESDAY NIGHT...AFTER GETTING BURNED BY LOWS THIS MORNING...COOLER
THAN EXPECTED...WILL LOWER LOWS NRN ZONES TONIGHT WHERE THICKER
CLOUDS COULD ARRIVE LATEST. WILL ERROR ON COOLER SIDE. BECAUSE OF
EXPECTED WIDESPREAD CLOUDS BOTH MONDAY AND TUESDAY AND PRECIP ON
MONDAY...TIGHTENED DIURNAL TEMPERATURE RANGE...MAINLY BY LOWERING
MAX TEMPS.
KEPT TUESDAY NIGHT/WEDNESDAY PERIOD DRY FOR THE TIME BEING
SINCE IT APPEARS MOST OF THE ENERGY WITH THE TRAILING TROUGH WILL
BE DIGGING SE OF AREA AND MAIN UPPER LOW/TROUGH WILL BE FARTHER
REMOVED FROM NERN ZONES. HOWEVER...KEPT TEMPERATURES A LITTLE BELOW
GUIDANCE YET ON WEDNESDAY AS NORTHERLY UPPER FLOW PERSISTS AND
UPPER THERMAL TROUGH REMAINS OVER THE AREA. PROBABLY A LOT OF
LINGERING CLOUDS EVEN IF NO PRECIP.
MODERATING TEMPERATURES STILL APPEAR ON TRACK FOR THURSDAY AND
FRIDAY. LEFT IN SMALL SHOWER CHANCE ON THURSDAY AS WARM ADVECTION
COMBINES WITH WEAK TRAILING WAVE MOVING ACROSS SD/NERN NEBR VCNTY
AND BOTH 12Z GFS/ECMWF GENERATED A LITTLE QPF IN OR NEAR ERN
ZONES. BOTH OF THOSE MODELS ALSO INCREASED CHANCES OF WARMER
TEMPERATURES THURSDAY AND FRIDAY AS H85 TEMPS WARM TO 8 TO 11
DEGREES C ON THU AND AT LEAST SEVERAL DEGREES WARMER THAN THAT ON
FRIDAY. RAISED MAX TEMPS BOTH THURSDAY AND FRIDAY. IN FACT IF 12Z
ECMWF WOULD VERIFY SOME 80S COULD FINALLY RETURN TO THE FORECAST
AREA. THUNDERSTORM CHANCES STILL VALID FRIDAY NIGHT AS COLD FRONT
CROSSES AREA. ALTHOUGH POST-FRONTAL READINGS LIKELY COOLER ON
SATURDAY...WITH NEXT UPPER LOW TO OUR N/NW YET BY THAT
TIME...COOLEST AIR ALOFT WILL BE LAGGING BACK. THUS DECENT WNW
COMPONENT TO WINDS COULD ALLOW FOR HIGHS WARMER THAN WHAT WILL BE
CARRIED IN FORECAST...GENERALLY LOWER 60S N TO UPPER 60S S.
COOLING TREND SHOULD CONTINUE INTO SUNDAY AS UPPER LOW MOVES NE OF
AREA PULLING DOWN COOLER AIR AND MORE NRLY COMPONENT TO WINDS OVER
A DEEPER PART OF THE SOUNDING. ADDED SMALL POPS TO SATURDAY AS
AFTN HEATING AND SECONDARY COLD FRONT POSSIBLE...AND LEFT SUNDAY
DRY AS UPPER LOW DEPARTS TO OUR NE.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE TAF CYCLE...WITH
LIGHT WINDS MAINLY VARIABLE THROUGH THE PERIOD BEFORE BECOMING
NORTHEASTERLY. RAIN WILL OVERSPREAD THE AREA BETWEEN 12-18Z
MONDAY...AND HAVE DEGRADED VISIBILITY TO MVFR WITH THE ONSET OF RAIN AT
EACH SITE.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
CHERMOK/MAYES