Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 252046 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 346 PM CDT Mon Sep 25 2017 .SHORT TERM...
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(Tonight through Thursday) Issued at 330 PM CDT Mon Sep 25 2017 ...A Wet Start to the Week, but Cooler/Drier the Next Several Days... Forecast concerns in the short term will primarily be the ending of the showers and thunderstorms, then cooler temperatures for the rest of the week. Rainfall amounts varied from zero for parts of southeast Nebraska and parts of southwest Iowa to 2.76" at the NWS Omaha/Valley office through 7am. A 2" plus band extended through parts of Gage/Lancaster/Saunders/western Douglas/Washington/Burt/Thurston counties. Toward Nebraska City and southeast of there...very little rain prior to 7am. The latest subjective surface analysis highlighted a cold front over southeast Nebraska and southwest Iowa at Noon. Surface temperatures were in the 80s at noon at Falls City and Clarinda with calm winds. Meanwhile, to the north, the winds were from the north and mostly in the 50s and 60s with abundant cloudcover/precipitation. By 3pm...the surface front had pushed southeast...but had not made it to St. Joseph yet. Showers covered much of the forecast area and were generally post- frontal at Noon...however the focus by 3pm had shifted closer the the front from northeast Kansas and southeast Nebraska into southwest to central Iowa. 20Z SPC Mesoanalysis shows surface based CAPE of 1000-2000J/kg near the front over southeast Nebraska and southwest Iowa southeastward with steep mid-layer lapse rates/PWAT of 1.5-1.7 inches just behind the surface front (ahead of the h85 front) in a zone of h85 warm air advection/mid level omega. Water vapor satellite imagery/the H50 pattern depict a closed low pressure system over southeast Montana with troughing extending southwestward toward southern California. Impulses moving through the flow with broad lift and deep moisture (axis of PWAT in excess of 1.5") with convection from the Southern Plains into the Missouri Valley. The short range models are in good agreement with the closed low opening up tonight as it shifts east into the Dakotas...meanwhile...energy remains trailing to the southwest eventually closing off over Nevada by 18Z Tuesday. h85 warm advection continues this evening...however is not as robust in our area after 06Z. Will maintain moderate to high pops this evening with decent forcing and deep moisture of 10-15 deg C h85 dewpoints...however precipitation coverage focuses farther east as the flow veers and the axis of high PWAT air shifts east. Patches of showers and isolated thunder continue overnight with mid and upper level support...and better pops will be in southeast Nebraska and southwest Iowa into Kansas and Missouri Tuesday. Dewpoints in the 40s will work in from the northwest with 50s/60s farther southeast. With light winds overnight and wet ground should see some areas of fog. With the clouds...most models are not hinting at vsbys less than a mile save for some patches in western Iowa. Decreasing clouds later Tuesday as the soundings dry out from a PWAT of 1.6" at 00Z today to 0.8" by 18Z Tuesday at Omaha. With surface high pressure over the area...will need to assess fog again Wednesday morning. Drier weather for Wednesday and Thursday. Cooler highs closer to normal in the upper 60s to mid 70s each day .LONG TERM...(Thursday night through Monday) Issued at 330 PM CDT Mon Sep 25 2017 The closed low pressure system over the southwest U.S. lifts north later this week and by Friday night and Saturday a few showers or thunderstorms may try to sneak into the area. There is a better chance for showers and thunderstorms later Sunday into Monday. Highs remain in the 60s and 70s.
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&& .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1150 AM CDT Mon Sep 25 2017 Expect mainly IFR conditions at all three sites, with some TEMPO MVFR conditions. SHRA with some embedded TSRA will make for a messy TAF forecast the next few cycles. Conditions should improve at KOFK toward 18Z Tuesday, but probably closer to 00Z Wednesday for KOMA and KLNK. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Zapotocny AVIATION...Miller

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