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Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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153 FXUS63 KOAX 150858 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 358 AM CDT Mon Jul 15 2024 .KEY MESSAGES... - Dangerous heat continues into Monday, with heat index readings of 100 to 110+ degrees likely. - Widespread storm chances (20-40%) this afternoon and linger through Wednesday. Best chances for severe storms will be across southwest Iowa 3 to 10 PM with wind being the primary threat. - An extended stretch of cooler-than-average temperatures will carry us into the weekend, with chances for widespread rain increasing into next week. && .DISCUSSION... Issued at 355 AM CDT Mon Jul 15 2024 Today and Tomorrow: Water vapor imagery this morning features broad ridging over the western half of the CONUS with increasingly northwesterly flow in the mid/upper levels locally and a pair of storm clusters traveling across ND/MN and IL/IN/MI. A recent surface map places a surface trough or warm front extending northeastward from a surface low in north-central Kansas stretching into western and central Iowa, with notably increased surface moisture and temperatures along and just to the south of it. Areas of fog also exist near this boundary where weak winds and more efficient radiational cooling have been in full force. Expect this front to dissolve by mid-morning with temperatures quickly rebounding alongside increasing dewpoints to create dangerous heat for much of eastern Nebraska and southwest Iowa ahead of a front and cooler airmass moving in from the north. Heat indices for southeastern Nebraska including Lincoln and Omaha/CB are expected to reach the 105-110+ degree range, aided by the soon-to- depart low-level thermal ridge, compressional heating, and the increased evapotranspiration. Despite leaning towards a more conservative temperature and moisture forecast, cloud cover to the west of the area and a thin veil of smoke could serve as potential failure mechanisms and could keep us cooler than forecast. In addition to the heat, 4500+ J/kg of surface-based CAPE will be in place in western/central Iowa where they are joined by healthy lapse rates to result in strong to severe storm chances in that area decreasing to the west. Damaging wind will lead the way hazard-wise driven by high DCAPE values, while damaging hail and a brief tornado can`t be ruled out due to the high instability and ambient surface vorticity from the leftover AM front. Chances go from the late afternoon and generally wrap up by 10 PM as the remaining storm clusters move east and south of the area. Activity from western Nebraska will carry additional light rain chances into Tuesday morning, before what could be another round of storms in northeast Nebraska after 3 PM (by which we`ll be enjoying noticeably cooler high temperatures in the mid 80s. Wednesday and Beyond: By Wednesday, we`ll find ourselves starting a cooler than average stretch as the northwesterly mid/upper jet shifts directly overhead with ridging staying bottled up out west. The name of the game during this part of the forecast period will be monitoring subtle shortwaves as they get lobbed towards the forecast area, with the most potent of which seems to come late Friday into Saturday. Based on the main deterministic models, the upper ridge over the western CONUS only becomes more pronounced with time and we could see ourselves seeing this cool period linger into next week with increasing rain chances. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1124 PM CDT Sun Jul 14 2024 VFR conditions are expected to prevail throughout the forecast period. Calm southerly winds will persist overnight. A low chance of scattered light rain showers will move across KOFK in the 06-10Z timeframe. Patchy fog capable of MVFR visibilities will be possible overnight, primarily for KOFK and KOMA. Due to low confidence in the coverage, have opted to not include in the TAFs at this time. A front moving through the area from north to south through the day Monday will shift winds clockwise from southerly to northeasterly. A chance of scattered showers and thunderstorms will move into KOMA and KLNK in the 23-02Z timeframe. There is low confidence in the coverage of these storms and it therefore has been left out of this TAF issuance. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory from noon today to 8 PM CDT this evening for NEZ015-033-034-042>045-050-065-078-088. Excessive Heat Warning until 8 PM CDT this evening for NEZ051>053-066>068-089>093. IA...Heat Advisory from noon today to 8 PM CDT this evening for IAZ043-055-056. Excessive Heat Warning until 8 PM CDT this evening for IAZ069- 079-080-090-091. && $$ DISCUSSION...Petersen AVIATION...Wood