Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 021124
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
624 AM CDT SAT MAY 2 2015

.SHORT TERM...(TODAY)
ISSUED AT 334 AM CDT SAT MAY 2 2015

PRIMARY FORECAST CONCERNS FOR TODAY ARE PCPN CHANCES/COVERAGE AND
HIGH TEMPERATURES. SCATTERED TO ISOLATED SHOWERS/THUNDERSTORMS WILL
CONTINUE TO LIFT EAST/NORTHEAST ACROSS THE AREA THIS MORNING...AND
MAY LINGER THIS AFTERNOON.

MAIN FORCING MECHANISMS THIS MORNING ARE WARM/MOIST LOW/MID LEVEL
ADVECTION WITH ISENTROPIC UPGLIDE IN THE 300-305K LAYER. THERE IS
ALSO A LOW LEVEL JET OF AROUND 40 KNOTS AT 1 KM AGL THAT EXTENDS
FROM THE TX PANHANDLE UP INTO SERN NE. THIS SHOULD GRADUALLY MOVE
NORTHEAST AND WEAKEN LATER TODAY. HIGHS IN ERN NE ARE EXPECTED TO
REACH THE UPPER 70S AND LOWER 80S...WITH HIGHS MAINLY 75 TO 80 IN
SWRN IA. HIGHS IN IOWA COULD BE SLIGHTLY LOWER IF CLOUDS DO NOT
DECREASE AS EXPECTED.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 334 AM CDT SAT MAY 2 2015

BEHIND EASTWARD DRIFTING AFTERNOON CONVECTION...ATTENTION THEN TURNS
TO COLD FRONT APPROACHING OUR AREA SUNDAY AFTERNOON AND EVENING.
SOUTHWEST LOW LEVEL JET SHOULD KEEP LAYER MOISTURE RELATIVELY DRY
OVERNIGHT BEFORE INCREASING DURING THE DAY SUNDAY. THUS WILL KEEP A
DRY FORECAST GOING THROUGH SUNDAY MORNING. PERSISTENT SOUTHERLY
SURFACE FLOW WILL DRIVE DEW POINTS INTO THE MIDDLE 50S AHEAD OF
FRONT...AND COMPRESSIONAL WARMING SHOULD PUSH HIGHS WELL INTO THE
80S. THIS COMBINATION WILL YIELD SURFACE-BASED CAPE VALUES
APPROACHING 2000 J/KG AS PER GFS...BUT RELATIVELY WARM MID LEVEL
TEMPS MAY HOLD CONVECTION OFF UNTIL CLOSER TO EVENING. FRONTAL
BOUNDARY SHOULD BE INTO NORTHEAST NEBRASKA BY 00Z...SO WILL INITIATE
THUNDERSTORM CHANCES THERE LATE SUNDAY AFTERNOON...WITH
INCREASING CHANCES IN THE EVENING AS THE FRONT SETTLES SOUTH AND
MID LEVELS COOL. BULK SHEAR VALUES ARE HIGHEST BEHIND FRONTAL
ZONE...SO ORGANIZED STORMS ALONG AND AHEAD OF FRONT LOOK TO BE
WIDELY SCATTERED. HOWEVER STILL COULD SEE HAIL AND WINDS WITH THE
STRONGEST.

CONTINUED DEVELOPMENT OF CONVECTION IS EXPECTED OVERNIGHT AS FRONT
SETTLES INTO SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. LOW LEVEL JET IS
NOT STRONG AND PARALLELS FRONT...SO SEVERE RISK SHOULD DIMINISH BUT
OCCASIONAL RAIN/THUNDER WILL PERSIST. COULD SEE SOME LOCALLY
HEAVY RAINS WHERE TRAINING OF STORMS OCCURS.

ON MONDAY...A MAJORITY OF SYNOPTIC SCALE MODELS INDICATE A SHORTWAVE
WILL EJECT INTO THE PLAINS...DRAWING MOISTURE/INSTABILITY OVER TOP
OF STALLED FRONT ALONG THE KANSAS BORDER. VARYING DEGREES OF THIS
MOISTURE RETURN ARE NOTED...BUT ALL KEEP FAIRLY HIGH RAIN CHANCES IN
PLACE DURING THE DAY. WE COULD SEE A LULL IN ACTIVITY MONDAY MORNING
BEFORE SHOWERS/STORMS INCREASE FROM WEST TO EAST THROUGH THE
MORNING. WHILE SEVERE THREAT IS MINIMAL...STORMS NEAR THE KANSAS
BORDER NEARER FRONTAL BOUNDARY AND HIGHER INSTABILITY COULD BE
STRONG.

THE SEVERE POTENTIAL WILL INCREASE SOMEWHAT MONDAY NIGHT WHEN MID
LEVEL FLOW TURNS MORE SOUTHWESTERLY AS TROUGH SWINGS INTO THE
SOUTHERN ROCKIES. FRONT ALONG KANSAS BORDER WILL LIFT NORTH
OVERNIGHT AS DIFFLUENT FLOW ALOFT IN AREA OF COUPLED JET STRUCTURE
INDUCES INCREASE IN LOW LEVEL JET AND THUS STRONG THETA-E ADVECTION.
THIS REGIME WILL CONTINUE LIFTING NORTHEAST TUESDAY MORNING...AND
WOULD EXPECT A LULL IN CONVECTION ACROSS ALL OF THE CWA TUESDAY
AFTERNOON AND EVENING BEFORE MID LEVEL TROUGH ENTERS THE PLAINS
LATER TUESDAY NIGHT AND WEDNESDAY.

WILL SEE OFF AND ON THUNDERSTORM CHANCES WEDNESDAY AND THURSDAY AS
THAT TROUGH LIFTS THROUGH THE PLAINS. EXACT LOCATION/TIMING OF
STRONGEST STORMS WILL HAVE TO BE WORKED OUT WITH TIME...BUT MUCH OF
OUR AREA WILL BE IN FAVORABLE SHEAR AND INSTABILITY PROFILES
WEDNESDAY AFTERNOON THROUGH THURSDAY EVENING FOR POTENTIALLY SEVERE
STORMS. SHOULD SEE A LOWER POTENTIAL FOR STORMS ON FRIDAY WITH
INITIAL TROUGH EXITING TO OUR NORTHEAST.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 625 AM CDT SAT MAY 2 2015

EXPECT MAINLY VFR CEILINGS AT THE TAF SITES THE NEXT 24 HOURS.
THERE WILL BE SOME SPOTTY MVFR CEILINGS AND SOME VSBYS LESS THAN
3 MILES IN THE HEAVIER SHRA/TSRA BUT CHANCES SEEM TOO LOW TO
MENTION IN THE TAFS AT THIS POINT. WILL AMEND AS NEEDED. SOUTHERLY
WINDS WILL INCREASE LATER TODAY WITH SOME GUSTS MAINLY IN THE
AFTERNOON. WINDS WILL DECREASE BY EARLY EVENING.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...MILLER
LONG TERM...DERGAN
AVIATION...MILLER



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