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SPC Sep 21, 2024 1300 UTC Day 1 Convective Outlook

9 months 4 weeks ago

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Sat Sep 21 2024 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe storms capable of all hazards are possible this afternoon and evening across portions of the southern High Plains. ...Southern High Plains... Water-vapor imagery this morning shows a potent mid- to upper-level low and associated trough moving east across AZ. An associated 70-kt 500-mb speed max will round the base of the trough and move into central NM by early evening before weakening overnight as it moves into the TX Panhandle. Southerly low-level flow will maintain a fetch of seasonably rich moisture across the region today (reference 12 UTC Del Rio, TX and Midland, TX raobs; 18.3 and 14.9 g/kg lowest 100-mb mean mixing ratios, respectively). Early morning surface analysis places a cold front pushing southward over the central High Plains and this boundary will reach northeast NM and parts of the Panhandles late this afternoon/early evening. Some continuation of ongoing shower/thunderstorm activity may continue through the morning across eastern NM into the TX Panhandle, lending some uncertainty in airmass destabilization/recovery in wake of this convection. 06z model guidance (particularly the NAM) seemed to reasonably depict the low-level moisture plume emanating from the Rio Grande Valley/Edwards Plateau northwestward into the southern High Plains. Steep 700-500 mb lapse rates (7.5 to 8.0 deg C/km) sampled this morning from Albuquerque and Midland will combine with daytime heating to yield a moderately unstable airmass by afternoon across eastern NM into west TX. Increasing large-scale deep-layer ascent approaching from the west and frontal/orographic lift will likely contribute to scattered thunderstorms developing relatively early this afternoon. Forecast hodographs indicate supercells will evolve within this environment. The risk for large hail/severe gusts will likely accompany the stronger storms, and a threat for a few tornadoes may be realized later this afternoon/early evening from eastern NM into parts of adjacent west TX. ...Upper Midwest to Mid MO Valley... A northern-stream short-wave trough will continue to move eastward from southern MB/Dakotas into MN/northwest ON during the period. A surface cold front will advance into MN-western IA-southern NE by midday, before accelerating east into the Upper Great Lakes, while the trailing portion of the boundary pushes south-southeast into central KS by early to mid afternoon. This boundary will serve as the focus for potential convective development during the late afternoon, though surface heating is not expected to be particularly strong ahead of the wind shift. With the strongest forcing expected to spread across northwest ON, convection may be more isolated along the front trailing across the Upper Midwest. Even so, some hail/wind threat will exist with this activity which should peak in intensity during the early evening. ...Western PA into western VA... Weak short-wave trough will dig southeast across the upper OH Valley later this afternoon with modest mid-level northwesterly flow expected to extend across western PA/VA. This feature will encourage scattered convection later this afternoon along a frontal zone that will be draped across the Delmarva-western PA into western NY. Models suggest scattered storm coverage and forecast soundings would imply some of the stronger storms being capable of an isolated risk for wind damage (50-60 mph) and perhaps some hail. This activity will likely diminish by early evening coincident with nocturnal cooling. ..Smith/Broyles.. 09/21/2024 Read more

Eastern North Pacific Tropical Weather Outlook

National Hurricane Center (NHC) Pacific Map

9 months 4 weeks ago

000
ABPZ20 KNHC 211151
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Sep 21 2024

For the eastern North Pacific...east of 140 degrees west longitude:

Central Portion of the East Pacific:
An area of low pressure could form well to the southwest of the
southwestern coast of Mexico during the next couple of days.
Environmental conditions appear conducive for some slow development
of this system, and a tropical depression could form during the
early or middle part of next week while the system moves slowly
northward or northeastward.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...medium...50 percent.

$$
Forecaster Reinhart

NHC Webmaster