The week at a glance

Most of Central Appalachia gets a pleasant Labor Day before heat and humidity return. Wednesday will be the hottest day, with afternoon temperatures reaching the upper 80s and lower 90s in many valleys and lower elevations.

A cold front will bring thunderstorms into eastern Ohio and western Pennsylvania Wednesday evening or night. Storms should spread through northern West Virginia and western Maryland by Thursday. A few could produce damaging wind, but the forecast still depends heavily on when the front arrives and how many storms develop.

Cooler, less humid weather should follow Friday. Temperatures begin climbing again over the weekend.

The practical takeaway: enjoy Monday and Tuesday, use some heat caution Wednesday, and keep an eye on the forecast before Wednesday evening and Thursday plans.

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Full technical briefing

Seven-day forecast for Central Appalachia

This outlook covers western Pennsylvania, eastern Ohio, northern West Virginia, western Maryland and nearby portions of Central Appalachia.

Day	Expected pattern	Main concern	What CAWA should do
Monday, Sept. 7	Dry and comfortable	Patchy early valley fog	Routine monitoring is enough
Tuesday, Sept. 8	Sunny, warmer	No organized hazard expected	Watch the developing heat trend
Wednesday, Sept. 9	Hot and increasingly humid	Heat; storms arriving northwest late	Update heat messaging and monitor storms approaching Ohio
Thursday, Sept. 10	Cold front with showers and storms	Isolated damaging wind; locally heavy rain	Be ready for active coverage if storms organize
Friday, Sept. 11	Front departing	Lingering early showers, mainly southeast	Check southern and eastern counties before scaling back
Saturday, Sept. 12	Dry and warmer	No significant hazard expected	Routine monitoring is enough
Sunday, Sept. 13	Warm with increasing humidity	Heat trend; forecast confidence lower	Watch whether the next warmup becomes more impactful

Monday: A quiet Labor Day

High pressure will keep Monday dry, with afternoon temperatures generally in the upper 70s and lower 80s. Humidity remains manageable.

Patchy river-valley fog may briefly reduce visibility around sunrise, especially in sheltered portions of West Virginia and western Pennsylvania. It should dissipate quickly. No weather alerts were in effect for the Pittsburgh, Cleveland or Charleston forecast areas Sunday afternoon.

Routine monitoring is enough. If CAWA publishes a morning forecast, mention fog only where it is actually observed.

Sources: NWS Pittsburgh forecast discussion, NWS Charleston forecast discussion

Tuesday: Warmer, but still quiet

Southerly flow develops as high pressure moves east. Afternoon temperatures should reach the lower and middle 80s, with a few warmer readings in the valleys. Humidity will begin creeping upward, but dangerous heat is not currently expected.

Use Tuesday to prepare Wednesday heat graphics and review staffing for the midweek frontal passage.

Source: NWS Cleveland forecast discussion

Wednesday: The hottest day, then storms approach

Wednesday should bring the week’s highest temperatures. Most lower elevations will reach the upper 80s or lower 90s. NWS Cleveland expects heat indices in the lower to middle 90s, while NWS Charleston forecasts lower 90s in parts of the Ohio–West Virginia–Kentucky Tri-State area.

This is a meaningful heat day, although current forecasts do not suggest a widespread high-end heat episode. People working or practicing outdoors should still take breaks and drink water.

A cold front will approach during the evening. NWS Cleveland expects moderate to strong instability ahead of it and says organized thunderstorms may develop across northern Ohio Wednesday evening or night. Damaging wind would be the main concern if a substantial line or cluster forms.

Confidence is moderate that thunderstorms reach eastern Ohio and northwestern Pennsylvania, but lower on their coverage and arrival time. This is an official local NWS forecast signal—not a claim by CAWA that a categorical SPC risk covers the region.

Update heat messaging Wednesday morning. By afternoon, watch radar and upstream observations across northern and central Ohio rather than assuming storms will wait until Thursday.

Sources: NWS Cleveland forecast discussion, NWS Pittsburgh forecast discussion

Thursday: The main storm day for much of the region

Showers and thunderstorms should accompany the front through western Pennsylvania, eastern Ohio, northern West Virginia and western Maryland.

The environment may support damaging wind where storms encounter sufficient afternoon instability and wind shear. NWS Baltimore/Washington describes the severe threat as non-zero but emphasizes considerable uncertainty over the front’s timing and strength. A faster morning passage would limit instability; a slower arrival near peak heating would increase the chance of stronger storms.

Locally heavy rain is possible, especially if the front stalls over Ohio or storms repeatedly cross the same area. The available local discussions do not establish a widespread flash-flood threat, so CAWA should avoid leading with flooding unless later WPC guidance or rainfall trends support it.

Prepare for possible active coverage Thursday. Check the latest official SPC outlooks and WPC excessive-rainfall outlooks before publishing a more specific threat area.

Sources: NWS Baltimore/Washington forecast discussion, NWS Cleveland forecast discussion

Friday: Cooler air returns

The front should move south and east, allowing cooler and less humid air to spread across eastern Ohio and western Pennsylvania. Showers could linger early in West Virginia or western Maryland if the boundary moves more slowly than forecast.

Check southern and eastern counties Friday morning. If the front has cleared, routine coverage can resume.

Saturday and Sunday: Warmer again

Saturday looks mainly dry and comfortable. The upper-level ridge is expected to rebuild during the weekend, bringing warmer conditions by Sunday.

There is no clear organized hazard signal at this range. Confidence in the general warming trend is moderate; confidence in exact temperatures and humidity is lower.

Routine monitoring should cover Saturday. On Sunday, check whether the returning heat and humidity will carry into the following workweek.

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Operational meteorology and communication updates

NWS is considering making CAP its primary alert format

Status: Proposal open for comment through September 21, 2026

On September 1, the National Weather Service requested initial feedback on transitioning watch, warning and advisory dissemination to the Common Alerting Protocol, or CAP, as its primary format. The proposal could eventually discontinue traditional VTEC-formatted products, although CAP messages would retain event tracking, calls to action and impact-based warning information.

This could be a major change for any CAWA system that parses raw warning text or uses VTEC strings to identify events, updates and cancellations. CAP offers better support for structured and geospatial information, but a complete transition would require careful testing.

CAWA should inventory which tools read VTEC directly and which already consume CAP or the NWS API. Automated warning posts must continue recognizing corrections, extensions, upgrades and cancellations—not merely the initial alert.

No production workflow should change yet. This is an early proposal, not an announced implementation.

Source: NWS CAP transition proposal

NEXRAD Level II address changes September 15

Status: Scheduled implementation

NWS will discontinue the current NEXRAD Level II directory on NOMADS at 1200 UTC September 15. Identical files are already available from the replacement TGFTP location. Level III radar products are not affected.

Any CAWA downloader using the retiring NOMADS address will stop receiving Level II files unless its URL is changed. The format and filenames are staying the same, so this should be a straightforward migration.

Check radar scripts this week and add a freshness alarm if one is not already present. A feed that silently stops updating is more dangerous than one that fails visibly.

Source: NEXRAD Level II migration notice

RRFS and REFS testing should continue

Status: Operational implementation scheduled for October 6

NCEP still plans to introduce RRFS and REFS on October 6, alongside the retirement of NAM, SREF, HREF, HiresW and NAM MOS. Parallel RRFS and REFS data are available for testing.

The Wednesday-night and Thursday storm setup offers another useful comparison opportunity. CAWA can examine simulated reflectivity, updraft-helicity guidance and ensemble precipitation probabilities without treating the parallel system as established operational truth.

Continue auditing scripts, dashboards and graphics for dependencies on the retiring model families.

Source: RRFS and REFS implementation notice

WPC’s ERO comment period has ended

Status: Proposal awaiting a decision

Public comment closed September 5 on WPC’s proposal to add an Enhanced Risk category to the Excessive Rainfall Outlook, creating a five-level scale. No implementation decision is identified here.

CAWA should leave existing ERO graphics and category parsing unchanged until NWS publishes a formal decision and effective date.

Source: WPC Excessive Rainfall Outlook proposal

This briefing is planning guidance, not an official warning or substitute for current forecasts. Follow watches, warnings and advisories issued by the National Weather Service. This post was created with AI assistance.