Area Forecast Discussion
Issued by NWS Oklahoma City, OK
Issued by NWS Oklahoma City, OK
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842 FXUS64 KOUN 012334 AFDOUN Area Forecast Discussion National Weather Service Norman OK 634 PM CDT Wed May 1 2024 ...New AVIATION... .SHORT TERM... (This afternoon through Thursday night) Issued at 129 PM CDT Wed May 1 2024 ***This Afternoon into Tonight*** As a wise man once said: It`s gonna be May. We`re ringing in the traditional most active month of the year with a highly complex forecast for both severe and flooding potential this evening. This morning`s convection has left a rather substantial cold pool with theta-E perturbations on the order of 4-10 Kelvin across central Oklahoma. Recovery is uncertain within our area, but West Texas Mesonet observations show a narrow plume of upper-60s dewpoints gradually advancing northwestward across the eastern Texas panhandle. Currently, the dryline is retreating westward, but with increased diurnal heating it will likely advance back into the eastern panhandle. The third boundary of note in our forecast is what appears to be the synoptic-scale warm front, which meets the dryline at a triple point low near Perryton and extends east-northeast from there toward Medford. Convection initiation appears probable in spite of the intrusion of the cold pool into central Oklahoma. The two likeliest zones for CI are: -Along the outflow boundary in the southeastern TX panhandle -Near the triple point in the northeastern TX panhandle Outflow boundary region: The presence of near-70 dewpoints and 3,000 J/Kg of MLCAPE will encourage thunderstorm development likely by mid afternoon. The initial mode will favor supercells capable of very large hail. Over time, CAMs show a tendency to weaken the 500 mb winds while increasing the LLJ. This will probably encourage supercells to grow upscale into an eastward-propagating squall line. Given the depth of boundary-layer winds and drying in the mid-levels to raise DCAPE to 1,400 J/kg, damaging wind gusts will become a threat toward sunset with a potential in southwest Oklahoma and western north Texas for significant (70+ mph) wind gusts. The tornado threat is conditional, and may be most focused in the spatiotemporal window where the LLJ is increasing directly along the remnant OFB. After sunset, this cluster will continue eastward toward south central Oklahoma, likely weakening over time. A second threat will occur overnight with this cluster - flooding. One-hour flash flood guidance sits as low as 1.6- 2 inches of rain across much of southwest Oklahoma and as low as 1 inch in the Arbuckles. Even a small residence time of storms in this area overnight could trigger recurrence of flooding. Triple point region: Storm coverage is more uncertain here as ongoing stratus/need for further moisture advection cast doubt on reaching convective temperatures. However, CAM guidance (notably the HRRR and MPAS) has become much more bullish in the late morning hours on depicting the development of scattered supercells by late afternoon. The longevity of these storms will be dependent on sufficient theta-E advection to overcome the development of a modest capping inversion after sunset. However, shear profiles will be sufficient for supercellular structures with the potential for large to very large hail. The frontal boundary may also become a focus for tornado potential toward sunset as the LLJ enlarges. CAM guidance is less bullish on the potential for an overnight MCS across north central Oklahoma; thus, it is anticipated that this activity will weaken after sunset. Meister ***Thursday into Thursday Night**** By tomorrow (Thursday) afternoon, a slowly-advancing cold front will be located somewhere in close proximity of I-44. The location of this cold front will likely be affected by tonight`s convection with some spread among guidance. In addition, a dryline will be located in the eastern Texas panhandle or western north Texas. Both of these surface boundaries will be likely focus for convective during the afternoon and evening hours as convective inhibition weakens with daytime heating. Effective bulk shear will be weak to modest at only ~30 knots, so transient supercell structures are possible. Even so, significant hail is possible given the modest cloud layer shear (~50 knots), weak low-level shear, and significant instability (MLCAPE >3000 J/kg). In addition, large downdraft CAPE (>1000 J/kg) may result in damaging wind gusts. The tornado risk is generally low, but if a supercell could constructively interact with the cold front or an outflow boundary, the tornado potential would be higher (especially given the magnitude of instability). Thunderstorms may grow upscale into clusters and move to the southeast late evening into the overnight hours. Flooding will become a hazard, especially for locations that have had recent heavy rainfall. Mahale && .LONG TERM... (Thursday night through next Tuesday) Issued at 300 PM CDT Wed May 1 2024 An active pattern will continue into early next week with periods of showers and thunderstorms as shortwave troughs lift northeast within the west to southwest flow. Currently, it appears the greatest risk of severe weather during this period will be on Monday. Heavy rainfall/flooding will be the primary hazard on the other days. Here are the specific details: Friday: Isolated to scattered daytime thunderstorms are possible as a subtle shortwave trough/PV anomaly moves through in a weakly capped environment. Friday Night into Saturday: A complex of thunderstorms associated with a cold front is expected to move through the area. Heavy rainfall and flooding will be the primary hazard. Sunday: Another shortwave trough is progged to lift into the Southern Plains with a threat for heavy rainfall and flooding. Monday: A negatively-tilted trough is progged to lift into the Plains. Currently, it appears the strongest synoptic-scale ascent and associated surface low will develop across the northern Plains. However, a trailing dryline will likely be located somewhere in the Southern Plains with a moist, unstable air mass with sufficient shear for supercells and severe weather. This is the next potential for significant severe weather if the ingredients come together. Mahale && .AVIATION... (00Z TAFS) Issued at 630 PM CDT Wed May 1 2024 Overall, much of the forecast period tonight and tomorrow morning expected to be MVFR most terminals. Gusty southerly winds will continue through the night. TSRA chances will be highest across southwest Oklahoma and northwest Texas tonight, with possibility for activity to progress eastward across the southern half of Oklahoma overnight into tomorrow morning. Cold front will move into northern Oklahoma toward and after 12Z, with slow progress southward during the day tomorrow. TSRA will be possible along the front late in the forecast period, but will leave out for now due to timing and possibility that cloudiness during the day will limit coverage. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 64 78 60 77 / 50 70 50 30 Hobart OK 61 79 57 76 / 60 40 40 30 Wichita Falls TX 64 82 61 80 / 70 20 40 20 Gage OK 57 76 50 76 / 30 30 20 30 Ponca City OK 64 76 56 75 / 50 80 40 20 Durant OK 66 79 64 81 / 70 70 60 30 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Flood Watch through Thursday morning for OKZ035>041-044>046-050. TX...Flood Watch through Thursday morning for TXZ084>090. && $$ SHORT TERM...04 LONG TERM....10 AVIATION...11