Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 020019 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 719 PM CDT TUE SEP 1 2015 .SHORT TERM...(TONIGHT THROUGH FRIDAY) ISSUED AT 247 PM CDT TUE SEP 1 2015 WARM...HUMID...AND SLIGHTLY UNSETTLED WEATHER WILL CONTINUE THROUGH THE WORK WEEK. SUBJECTIVE 12Z UPPER AIR ANALYSIS INDICATES BROAD WEST-SOUTHWESTERLY UPPER-LEVEL FLOW...WITH A DEVELOPING UPPER LOW IN WESTERN CANADA...AND INCREASING RIDGE OVER THE EASTERN US. WEAK UPPER LOWS WERE NOTED OVER IN AND OVER EASTERN TX/EASTERN OK...AS WELL AS A SHORTWAVE TROUGH IN EASTERN CO/WESTERN NEB. HIGH AT 850MB WAS PARKED OVER THE SOUTHEAST US...WITH LOW TO THE NORTHWEST...AND SOUTHERLY FLOW ACROSS THE PLAINS DRAWING SOME GULF MOISTURE NORTHWARD. WESTERN EDGE OF 850MB MOISTURE /8C+/ WAS FROM AROUND EASTERN SD TO CENTRAL NE TO UT/AZ. SURFACE LOW AT 19Z WAS CENTERED IN WESTERN SD...WITH MAINLY SOUTHERLY WINDS ACROSS THE CWA...ALONG WITH SOME HIGH CLOUDS. MAIN FORECAST CONCERN IS PERSISTENT POTENTIAL FOR SHOWERS/A FEW STORMS THROUGHOUT THE PERIOD...WITH SOUTHWEST UPPER-LEVEL FLOW DEVELOPING. WESTERN US TROUGH AND EASTERN US RIDGE PATTERN WILL PERSIST ESSENTIALLY THROUGHOUT THE FORECAST PERIOD...EXCEPT FOR POSSIBLY FLATTENING FOR A DAY OR TWO AROUND SUNDAY/MONDAY WITH A STRONGER SHORTWAVE PASSAGE. CWA IS ON THE EASTERN FRINGE OF THE SOUTHWESTERLY FLOW...AND THUS WILL BE IN A BIT OF A BATTLEGROUND BETWEEN THE INFLUENCES OF THE RIDGE AND THE TRANSIENT SHORTWAVES THROUGH THE UPPER-LEVEL SOUTHWESTERLIES. RESULT WILL BE LOW POPS ON JUST ABOUT EVERY DAY...BUT VERY LOW CONFIDENCE OF PRECIPITATION MATERIALIZING ON ANY GIVEN DAY THROUGH THE WORK WEEK. A FEW SHOWERS/STORMS MAY DEVELOP IN NORTHEAST TO CENTRAL NEB LATER THIS AFTERNOON INTO THIS EVENING...ON THE NOSE OF THE 850MB WARM/MOIST AIR ADVECTION AND TIED TO A PASSING SHORTWAVE TROUGH /MAINLY CLOSER TO NORTHWEST IA/. CAMS ARE MUCH LESS ROBUST THAN DETERMINISTIC MODELS WITH SHOWERS/STORMS TONIGHT INTO WEDNESDAY...AND HAVE SHAVED POPS DOWN IN EXTENT AS WELL AS SLIGHTLY LOWERING THEM DUE TO COVERAGE CONCERNS...BUT THINK THERE IS ENOUGH POTENTIAL TO LEAVE THEM IN THROUGH THE MORNING. ANY LINGERING SHOWERS SHOULD BE CLEAR BY AROUND MIDDAY...LEAVING FAIR WEATHER IN THE AFTERNOON AND EVENING. SHOWERS/STORMS AGAIN ARE POSSIBLE ON WEDNESDAY NIGHT...CLOSER TO DAYBREAK...ON THE NOSE OF THE LOW-LEVEL JET...BUT WITHOUT A SHORTWAVE TO AID FORCING...THINK POTENTIAL IS QUITE LOW. HAVE SCALED BACK TO JUST A SLIGHT CHANCE MENTION IN SOUTHEAST NEB. WARM...MOIST...AND MURKY SOUTHWEST FLOW ALOFT/SOUTHERLY FLOW IN THE LOWER LEVELS CONTINUES THURSDAY AND FRIDAY. MODELS DO INDICATE A SHORTWAVE TRAVERSING THE NORTHWESTERLY FLOW ON THURSDAY EVENING/NIGHT...AND FOR THE MOST PART...THEY KEEP CONVECTION WEST OF THE CWA IN WESTERN TO CENTRAL NEB. WILL TIP IN THAT DIRECTION AS WELL...CLOSER TO THE SHORTWAVE...AND KEEP PRECIP MENTION OUT OF THE AREA ON THURSDAY NIGHT. DID KEEP SMALL POPS IN THE NORTHERN CWA ON FRIDAY...BUT ALSO HAVE LOW CONFIDENCE ON THESE MATERIALIZING...AS CWA WILL BE FAIRLY WELL EAST OF THE DEVELOPING SURFACE LOW DURING THE DAY AND LIKELY WILL BE CAPPED. DID KEEP TEMPERATURES ON THE WARM SIDE THROUGH FRIDAY...AND KEPT DEWPOINTS ON THE HIGH SIDE AS WELL...AS WARM AND MOIST SOUTHERLY FLOW IN THE LOWER LEVELS WILL LIKELY PUSH TEMPS UP. CONFIDENCE WOULD BE OFFSET BY ANY SHOWER/STORM ACTIVITY THAT DOES MATERIALIZE AND PROVIDE CLOUDINESS DURING THE DAY. .LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY) ISSUED AT 247 PM CDT TUE SEP 1 2015 WITH VARYING INTENSITY AND SOUTHWARD PUSH...MODELS DO BRING AN UPPER- LEVEL LOW ACROSS THE NORTHERN US...DRAWING THE SURFACE LOW EASTWARD AND PUSHING COOLER AND DRIER AIR INTO THE MISSOURI RIVER VALLEY. WEAK CHANCES OF SHOWERS/STORMS CONTINUE ON SATURDAY...MUCH LIKE EARLIER IN THE WEEK. FRONTAL PASSAGE SEEMS MOST LIKELY ON SUNDAY/SUNDAY NIGHT...WITH 12Z ECMWF TRENDING TOWARD A STRONGER/COOLER/DRIER PUSH LIKE THE 12Z GFS. RESULT WOULD BE TO STABILIZE THE AIRMASS OVER THE CWA...AND DRIVE THE CHANCES FOR PRECIP SOUTH INTO KS/MO. HAVE BACKED OFF POPS MONDAY NIGHT/TUESDAY CONSIDERABLY...AND OFF OF MONDAY POPS SOMEWHAT TOO. TEMPERATURES WOULD TREND TOWARD BELOW-NORMAL READINGS TO START THE NEXT WORK WEEK. && .AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 659 PM CDT TUE SEP 1 2015 VFR CONDITIONS ARE EXPECTED TO PREVAIL AT KOMA...KOFK...AND KLNK THROUGH THE FORECAST PERIOD. A WEAK UPPER LEVEL SHORTWAVE TROUGH WILL MOVE ACROSS THE DAKOTAS INTO THE MID AND UPPER MISSISSIPPI VALLEY TONIGHT AND WEDNESDAY. SOME MID LEVEL CLOUDS AROUND 10000 FEET ARE POSSIBLE AT KOMA AND KLNK AFTER. WIDELY SCATTERED SHOWERS AND THUNDERSTORMS MAY DEVELOP AFTER AFTER 06Z AS LOW LEVEL JET INCREASES. MUCH OF THE PRECIPITATION MAY BECOME BETTER ORGANIZED IN WESTERN IOWA. AT THIS TIME...HAVE INCLUED VCSH AT KOMA BETWEEN 04Z AND 14Z. BECAUSE OF THE STRENGTHENING LOW LEVEL JET...LOW LEVEL WIND SHEAR IS LIKELY AT 2000 FEET AFTER 04Z AT KOFK...KOMA...AND KLNK. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...MAYES LONG TERM...MAYES AVIATION...SMITH

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