Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 191127
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
627 AM CDT FRI SEP 19 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 320 AM CDT FRI SEP 19 2014

...CONVECTIVE CHANCES TONIGHT ARE THE MAIN FORECAST CONCERN IN THE
SHORT TERM...

EARLY MORNING WATER VAPOR IMAGERY INDICATED A POSITIVELY TILTED
UPPER LEVEL TROUGH EXTENDING FROM SASK SOUTHWEST TO NV. THIS
TROUGH WILL MOVE INTO THE NORTHERN PLAINS TODAY AND ALLOW FOR THE
COLD FRONT /CURRENTLY EXTNDG FROM CNTRL ND INTO WRN SD/ TO ADVANCE
TO NEAR THE SD/NEB BORDER BY LATE THIS AFTERNOON. AHEAD OF THE
FRONT WE WILL SEE THE LOW CLOUDS/FOG EXIT TO THE E BY MID MORNING
WITH A GOOD DEAL OF SUN AND DRY WEATHER EXPECTED TODAY.
TEMPERATURES AT 850 MB ARE PRETTY WARM FOR THIS TIME OF YEAR...AND
WITH DEEP MIXING JUST AHEAD OF THE FRONT WE MAY SEE SOME PRETTY
HOT TEMPERATURES WITHIN THE 850 MB THERMAL AXIS ACROSS NORTHERN
NEB. WE HAVE INCREASE HIGHS INTO THE LOWER TO MID 90S FOR PARTS OF
THE EXTREME NORTHWEST CWA...BUT MOST LOCATIONS WILL SEE MID TO
UPPER 80S OVER ERN NEB AND LOWER TO MID 80S OVER WRN IA. THE 00Z
UPPER AIR ANALYSIS INDCD SEASONABLY RICH MOISTURE HAD ADVECTED
NORTH THROUGH THE PLAINS WITH MIXING RATIOS OF +10 G/KG AT LEAST
TO KTOP. AS THE TROUGH NEARS TODAY AND THE MID AND UPPER LEVEL
FLOW INCREASES FROM THE WEST WE SHOULD SEE A WELL-DEVELOPED EML
OVERSPREAD THIS MOISTURE AND LEAD TO A MODERATELY UNSTABLE
ATMOSPHERE OVER THE CWA BY LATE AFTN WITH MLCAPE VALUES OF
2000-3000 J/KG. THE LACK OF LARGE-SCALE HEIGHT FALLS OR ANY
DVPA...AS WELL AS THE STRONG EML...WILL KEEP THE FA CAPPED THROUGH
THE DAY TODAY. MODELS DO INDICATE THIS WILL LIKELY CHANGE THIS
EVENING THOUGH AS HEIGHT FALLS MOV INTO ERN NEB/SD ALLOWING FOR A
WEAKENING OF THE EML AND THIS...ALONG WITH THE INCOMING
FRONT...WILL LIKELY ALLOW FOR CI. CURRENT THINKING IS THAT THIS
WILL BE JUST BEHIND THE SFC BOUNDARY IN THE 01-03Z TIME FRAME
FROM AROUND NELIGH TO WAYNE AREA. STORMS WILL LIKELY INCREASE IN
COVERAGE AS THEY WORK SOUTHEAST OVERNIGHT WITH REMNANT OF ANY WEAK
MCS REACHING THE IA/MO BORDER AROUND 12Z SAT. WIDESPREAD SEVERE
WEATHER IS NOT EXPECTED DUE TO SLIGHTLY ELEVATED NATURE OF THE
CONVECTION THIS EVENING...BUT GIVEN THE INSTABILITY AND 25 TO 30
KT OF EFFECTIVE SHEAR WE COULD SEE A STORM OR TWO APPROACH SEVERE
LIMITS WITH HAIL BEING THE MAIN THREAT FOR AN HOUR OR TWO AFTER
INITIATION.

THE FRONT WILL STILL BE MOVING THROUGH THE SOUTHERN CWA DURING THE
DAY ON SAT...BUT IT APPEARS THAT MOST OF REDEVELOPMENT OF
CONVECTION LATE SAT AFTERNOON WILL BE ACROSS ERN KS/MO. WITH THE
SLOWER MOVEMENT OF THE FRONT WE DID INCREASE HIGHS A TOUCH SAT
AFTERNOON INTO THE SOUTHERN CWA. THE REST OF THE SHORT-TERM
FORECAST LOOKS FAIRLY QUIET WITH HIGH PRESSURE DEVELOPING THROUGH
THE CWA ON SAT NIGHT/SUN WITH HIGHS/LOWS RETURNING TO NEAR NORMAL.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 320 AM CDT FRI SEP 19 2014

THE QUIET WEATHER THAT ENDS THE SHORT TERM PERIOD OF THE FORECAST
WILL CONTINUE INTO THE MON TIME FRAME OF THE EXTENDED PERIOD.
AFTER THAT GLOBAL MODELS INDICATE A TROUGH MOVING THROUGH THE
CNTRL PLAINS. THIS LOOKS TO BRING ANOTHER CHANCE OF SOME SHOWERS
TO THE REGION MAINLY ON TUE. THE CONFIDENCE ON THIS TROUGH IS
LIMITED THOUGH AS THE SYSTEM WILL GENERALLY BE CUT-OFF FROM THE
MAIN WESTERLIES THAT WILL BE RETREATING NWD INTO CANADA THROUGH
THE WEEK. THUS THE CONFIDENCE IN THE TIMING OF PRECIP AND COVERAGE
IS LIMITED AND WE WILL KEEP POPS IN THE CHC CATEGORY FOR NOW.
OTHERWISE WITH SOME CLOUDS AND POSSIBLE PRECIP TEMPS SHOULD
GENERALLY BE BACK INTO THE 70S FOR HIGHS AND 50S FOR LOWS.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 627 AM CDT FRI SEP 19 2014

THE PRIMARY AVIATION CONCERNS INCLUDE... MORNING STRATUS... GUSTY
SOUTH WINDS... THEN SHOWERS AND THUNDERSTORMS OVERNIGHT.

EXTENSIVE AREA OF IFR STRATUS COVERED MUCH OF EASTERN NEBRASKA
EARLY THIS MORNING...HOWEVER IT HAS BEEN QUICKLY ERODING SINCE 10Z
DUE TO SOUTH WINDS THAT HAVE BEEN SLOWLY INCREASING. AT THE
CURRENT RATE...MOST OF THE STRATUS SHOULD MOVE OUT OF EASTERN
NEBRASKA BY 17Z. THE INCREASING WIND SPEEDS ARE IN RESPONSE TO AN
APPROACHING TROUGH OF LOW PRESSURE. EXPECT WINDS TO GUST TO NEAR
25 KNOTS AT TIMES MAINLY DURING THE AFTERNOON.

AS DESCRIBED IN THE SHORT TERM SECTION ABOVE...WE DO EXPECT
SCATTERED SHOWERS AND THUNDERSTORMS TONIGHT. KOFK COULD BE
IMPACTED AS EARLY AS 03Z...WITH KOMA AND KLNK BETWEEN 06Z AND 09Z.

&&

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

$$

SHORT TERM...BOUSTEAD
LONG TERM...BOUSTEAD
AVIATION...NIETFELD



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