Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 221750
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1250 PM CDT FRI AUG 22 2014

.UPDATE...
ISSUED AT 1236 PM CDT FRI AUG 22 2014

SCATTERED THUNDERSTORMS CONTINUE TO DEVELOP IN NORTHEAST KANSAS
AND DRIFT INTO SOUTHEAST NEBRASKA THIS EARLY AFTERNOON IN WEAK MID
LEVEL WARM ADVECTION REGIME. THESE WILL CONTINUE TO MEANDER
THROUGH THE AREA BUT EXPECT COVERAGE TO GRADUALLY DIMINISH THROUGH
THE AFTERNOON AS UPPER RIDGING NOSES SLIGHTLY NORTH AND WARMS MID
LEVEL TEMPERATURES. FARTHER NORTH WHERE PLENTY OF SUNSHINE HAS
BEEN SEEN...BROKEN CU FIELD HAS DEVELOPED JUST NORTHWEST OF
INTERSTATE 80 NEAR STATIONARY FRONT DELINEATED BY LIGHT NORTHEAST
WINDS IN NORTHEAST NEBRASKA AND SOUTHEAST WINDS TO THE SOUTH.
LAST FEW RAP FORECASTS SUGGEST SOME CONVECTION COULD FIRE LATER
THIS AFTERNOON CLOSE TO THIS BOUNDARY...LIKELY FROM THE OMAHA
METRO AND WEST...IN AREA WHERE MLCAPES HAVE INCREASED TO NEAR 3500
J/KG. SHEAR IS WEAK HERE...BUT HIGH INSTABILITY COULD LEAD TO
STRONG STORMS IF THINGS DO FIRE. OTHERWISE WE ARE STILL EXPECTING
INCREASING CHANCES FOR STORMS AS THE EVENING PROGRESSES WITH
APPROACH OF STRONG SHORTWAVE ENTERING THE HIGH PLAINS.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 341 AM CDT FRI AUG 22 2014

CONVECTIVE ACTIVITY HAS DEVELOPED OVER SWRN IA AND SERN NEB THIS
MORNING ALONG A SFC TROF EXTENDING FROM NRN IA TO WRN KS. SIMILAR
TO THE LAST SEVERAL NIGHTS...ENVIRONMENT IS QUITE UNSTABLE WITH
MUCAPES AROUND 3000 J/KG WITH A STRONG LLVL MOISTURE FEED INTO THE
PLAINS. EXPECT ACTIVITY WILL GRADUALLY DIMINISH OVER THE NEXT
SEVERAL HOURS AND BE OUT OF THE CWA BY SUNRISE.

MOST PRESSING ISSUE FOR THIS FCST PACKAGE IS POTENTIAL SVR
TSTMS ALONG WITH HEFTY RAINFALL ANTICIPATED LATER TONIGHT.

MODELS HAVE BEEN CONSISTENT LAST SEVERAL RUNS FOCUSING IN ON THE
NRN CWA WITH RESPECT TO HIGH POTENTIAL FOR HEAVY NOCTURNAL PCPN
LATER TONIGHT. AN OPEN GULF WITH PERSISTENT MOISTURE ADV THRU
TODAY WILL ENSURE A MOISTURE RICH ENVIRONMENT WILL BE IN PLACE
DURING THE OVERNIGHT HOURS.

TODAY...MODELS PROG A POTENT LITTLE VORT MAX EJECTING OUT OF THE
BASE OF A DEEP UPPER TROF SITUATED OVER THE WRN CONUS WITH DPVA
INDUCING LEESIDE CYCLOGENESIS INVOF THE CNTRL HIGH PLAINS. MODELS
AGREE SFC LOW WILL RAPIDLY LIFT TWD THE DAKOTAS THIS AFTN ALONG
WITH ATTENDANT WARM FRONT PUSHING INTO THE CWA LATE THIS AFTN.
COMBINATION OF STOUT INSTABILITY/EFF SHEAR AND ADEQUATE DEEP LYR
SHEAR WITH PROVIDE A FAVORABLE ENVIRONMENT FOR LATE AFTN/EARLY
EVENING SUPERCELL DEVELOPMENT. IN ADDITION...VERY HEAVY
RAINFALL...MAINLY OVER THE NRN CWA...LOOKS VERY PROBABLE TONIGHT
GIVEN COMBINATION OF WARM CLOUD DEPTH AROUND 4500 METERS/SYNOPTIC
SCALE MAX OMEGA WILL BE IN PHASE WITH PWS GREATER THAN 2". BEST
MOISTURE/FORCING THEN QUICKLY LIFTS NORTH OF THE CWA EARLY SAT
MORNING.

SAT NIGHT AND SUN...MODELS PROG A SOMEWHAT STRONG COLD FRONT
APPROACHING THE CWA. NOT ALL THAT IMPRESSED WITH PCPN POTENTIAL SO
WILL OPT FOR TOKEN 20S DURING THOSE PDS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 341 AM CDT FRI AUG 22 2014

COMPARED TO 21/00Z RUN...LATEST ECM IS NOW TRYING TO COME BACK IN
LINE WITH GFS/CMC SOLUTIONS SWEEPING A CANADIAN AIR MASS INTO THE
NRN/CNTRL PLAINS LATER NEXT WEEK WITH PCPN CHANCES FOCUSED ON
FRONTAL BNDRY PASSAGE. GOING POPS LOOK REASONABLE THUS NO MAJOR
CHANGES PLANNED.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1236 PM CDT FRI AUG 22 2014

AREA OF CUMULUS CLOUDS HAD DEVELOPED AT TAF ISSUANCE TIME AND
WILL AFFECT ALL TAF SITES THIS AFTERNOON. BROKEN CLOUDS WILL
LIKELY REMAIN VFR...BUT SOME FL020 CIGS COULD OCCUR NEAR KOFK FOR
A TIME EARLY IN THE AFTERNOON. THEN THE CHANCE FOR SCATTERED
CONVECTION WILL INCREASE LATE THIS AFTERNOON...AND ESPECIALLY
BY LATE EVENING...AS A STRONG SHORTWAVE LIFTS INTO THE PLAINS.
STORMS COULD FIRE AT ANY TIME AFTER 22Z BUT LATEST TRENDS SUGGEST
KOMA WILL BE MOST LIKELY SITE TO SEE AFTERNOON AND EARLY EVENING
ACTIVITY. OTHERWISE EXPECT CHANCES AND AREAL COVERAGE TO INCREASE
BY 05Z AT ALL SITES WITH KOFK THE MOST LIKELY TO SEE OVERNIGHT
CONVECTION. ATTENDANT MVFR/IFR CONDITIONS WILL PREVAIL IN ANY
STORMS. THUNDERSTORMS SHOULD BE MOVING NORTH OF ALL TAF SITES BY
14Z WITH VFR CONDITIONS AND SOUTHEAST WINDS NEAR 10KT PREVAILING.

&&

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

$$

UPDATE...DERGAN
SHORT TERM...DEE
LONG TERM...DEE
AVIATION...DERGAN


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