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Area Forecast Discussion
Issued by NWS Omaha/Valley, NE
Issued by NWS Omaha/Valley, NE
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406 FXUS63 KOAX 031114 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 614 AM CDT Wed Jul 3 2024 .KEY MESSAGES... - Multiple rounds of showers and thunderstorms could affect the region from this evening into Thursday afternoon. Some severe weather is possible with the primary hazards being isolated occurrences of large hail and/or damaging winds. Heavy-rain potential appears lower than recent events. - Pleasant weather is expected Thursday evening. - Thunderstorm potential increases again Saturday afternoon into Saturday night with some severe weather appearing possible. - Daytime temperatures to remain near or below seasonal normals. && .DISCUSSION... Issued at 419 AM CDT Wed Jul 3 2024 .Today and Tonight: The mid-level pattern will be characterized by broad, cyclonic flow from the northern Rockies through the Great Lakes with an embedded shortwave trough tracking from the lee of the Canadian Rockies into the northern Plains by Thursday morning. In the low levels, a weakening surface high will quickly build through the mid MO Valley early today ahead of an inverted trough/front that will advance through western portions of the Dakotas and Nebraska tonight. Clear skies and light winds associated with the surface high have resulted patchy fog development early this morning, and some expansion of the fog is possible through daybreak. Thereafter, weak warm advection on the backside of the high will contribute to an increase in clouds today with some models suggesting the potential for a few light showers across portions of southeast NE this afternoon. Highs today will be in the low to mid 80s. By late this afternoon into tonight, increasing height falls/forcing for ascent preceding the above-mentioned shortwave trough is forecast to contribute to the development of one or two thunderstorm complexes over western and central NE into southern/western SD. Latest CAM data suggest that the initial wave of thunderstorms could move into portions of northeast NE by as early as 5 or 6 PM amidst an environment supportive of isolated occurrences of large hail and/or locally strong wind gusts. Subsequent weakening of that initial thunderstorm complex is forecast as it continues east into the area during the overnight hours. By late tonight into Monday morning, a second thunderstorm complex could move into our area from the west with a similar potential for damaging winds and hail. In regard to heavy rainfall potential, the 03/00z HREF indicates really low probabilities (<10%) of >1" 6-hr rainfall in our area with other metrics such as probability-matched-mean fields indicating the better potential to our west. The HREF signal is in general agreement with other CAMs outside of that ensemble system and the parameterized-convection models. In short, the heavy-rain threat currently appears lower than the previous couple of events we`ve experienced. .Thursday and Thursday night: The above-mentioned shortwave trough is forecast to intensify over the northern Plains into upper MS Valley with a belt of unseasonably strong mid and high-level winds developing to the immediate south across the central Plains into mid MS Valley. At the surface, an area of low pressure will develop through eastern NE and western IA during the morning with a trailing cold front advancing east through our area during the late morning and afternoon hours. While renewed thunderstorm development is possible along the front, early-day clouds and lingering precipitation coupled with the early passage of the front through the area casts uncertainty on the extent of any severe weather threat owing to instability concerns. Clouds should begin to decrease from west-to-east Thursday afternoon with below-normal highs in the mid 70s to low 80s. By evening, pleasant conditions are expected for 4th of July activities with temperatures in the 60s to low 70s, partly to mostly clear skies, and northwest winds of generally less than 10 mph. .Friday: A deep-layer cyclone will move from the upper Midwest into the Great Lakes with breezy northwest winds (especially in the morning) expected on the backside of the system across our area. Highs will remain below normal; in the mid 70s to low 80s. An isolated shower or two possible, especially over portions of northeast NE into west-central IA. .This Weekend: The 03/00z global models are in reasonably good agreement in suggesting that a shortwave trough will progress through the northern and central Plains on Saturday into Saturday night, ahead of another disturbance following the same track on Sunday. The former system will interact with a moist and unstable air mass, supporting a chance of showers and thunderstorms Saturday afternoon into Saturday night. Some severe weather appears possible. Precipitation chances are more uncertain on Sunday in association with the second mid-level system. Highs are forecast to be in the 80s both days. .Early Next Week: The models maintain an amplified mid-level trough from Hudson Bay into the MS Valley early next week with the best precipitation chances residing to our east. Daytime highs are expected to remain in the 80s. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 603 AM CDT Wed Jul 3 2024 Weak southwesterly winds this morning will back and become southeasterly by 21Z. Winds are expected to largely remain under 10 knots at all TAF sites, though there may be an occasional gust or two near KOFK up to 15 knots. Scattered thunderstorms will be possible tonight across eastern Nebraska, primarily after 06Z. Have a -SHRA FM group at TAF sites during the most likely time to see these storms working in the general area of the terminal. A TEMPO group will likely be used in subsequent TAF issuances as the timing for these storms fall more in the TAF forecast period. A few storms in northeast Nebraska (KOFK) may have wind gusts up to 50 knots and hail up to quarter sized. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Mead AVIATION...Darrah