Data health

Storm Mode / Tracked area

Winter: Maryland

Wall mode

4 warnings total · 0 tornado warnings · 5 alerts including watches and advisories

Current alert feed · checked

Change time or forecast product

Replay uses retained source bytes. Recording begins with activation; missing history is not clear weather.

Live sources keep independent clocks.

Replay coverage and interpretation

Rolling target: 24 hours; cells: six hours. Radar: NOAA MRMS national overview, 8-minute tolerance. Satellite: original GOES GeoColor day/night picture, hourly sampling, 75-minute tolerance. No interpolation or latest-image fallback. Warning and source checks retain their own clocks. “Recorded by” is collector acquisition evidence, not exact browser publication history.

Current GLM density, velocity and specialist layers are hidden during replay. Snow uses retained footprint metadata with unverified pixel time. Forecast uses one pinned issuance/run and exact valid time.

No observed replay frame displayed.

Open the complete replay reader (works without scripting or WebGL)

Warnings in area

5 of 5 alerts
  1. Freeze WarningWashington; Frederick; Carroll; Northern Baltimore; Extreme Western Allegany; Central and Eastern Allegany; Northwest Harford; Western Garrett; Eastern Garrett; Augusta; Rockingham; Shenandoah; Frederick; Page; Warren; Clarke; Western Highland; Eastern Highland; Western Loudoun; Northern Virginia Blue Ridge; Central Virginia Blue Ridge; Hampshire; Morgan; Berkeley; Jefferson; Hardy; Western Grant; Eastern Grant; Western Mineral; Eastern Mineral; Western Pendleton; Eastern PendletonNWS Baltimore MD/Washington DC · until warning · alerts checked
  2. Freeze WarningWarren; Potter; Elk; Cameron; Northern Clinton; Clearfield; Northern Centre; Southern Centre; Cambria; Blair; Huntingdon; Mifflin; Juniata; Somerset; Bedford; Fulton; Franklin; Tioga; Northern Lycoming; Sullivan; Southern Clinton; Southern Lycoming; Union; Snyder; Montour; Northumberland; Columbia; Perry; Dauphin; Schuylkill; Lebanon; Cumberland; Adams; York; LancasterNWS State College PA · until warning · alerts checked
  3. Freeze WarningTuscarawas; Carroll; Columbiana; Coshocton; Harrison; Jefferson; Muskingum; Guernsey; Belmont; Noble; Monroe; Mercer; Venango; Forest; Lawrence; Butler; Clarion; Jefferson; Beaver; Allegheny; Armstrong; Washington; Greene; Westmoreland; Westmoreland Ridges; Fayette; Fayette Ridges; Indiana; Higher Elevations of Indiana; Hancock; Brooke; Ohio; Marshall; Wetzel; Marion; Monongalia; Ridges of Eastern Monongalia and Northwestern Preston; Preston; Eastern Preston; Western Tucker; Eastern TuckerNWS Pittsburgh PA · until warning · alerts checked
  4. Freeze WarningSussex; Carbon; Monroe; Warren; Morris; Hunterdon; Berks; Lehigh; Northampton; Western Chester; Western Montgomery; Upper BucksNWS Mount Holly NJ · until warning · alerts checked
  5. Frost AdvisoryNorthwest Montgomery; Northwest Howard; Nelson; Albemarle; Greene; Madison; Rappahannock; Orange; Culpeper; Northern Fauquier; Southern Fauquier; Eastern Loudoun; Northwest Prince WilliamNWS Baltimore MD/Washington DC · until advisory · radar-alerts checked

Watched places

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Layers

Map

  • Freeze Warning 4
  • Frost Advisory 1

NWS’s polygons as issued, or the zones a zone-issued alert names; SPC’s watches by their counties. Checked . Data: NOAA/NWS, NOAA/SPC.

Agency warning geometry · no observed imagery displayed
North ↑

Interactive imagery loads separately. Missing radar does not remove warnings or imply clear weather.

Alert outlines: NOAA/NWS; cell points/observed segments: IEM/NEXRAD. A warning polygon is not a tornado footprint.

Lightning activity — GOES GLM

Total lightning, including in-cloud activity. Not ground-strike locations or a safe-to-go-outside signal.

Cached lightning observations have not loaded. An empty map is not zero lightning.

Cached lightning source details and text readings

Snow analysis — NOHRSC

Source-rendered snow depth and snow water equivalent for the lower 48. History changes this snow picture only; warnings and radar keep their own clocks.

Stored snow depth · footprint valid 2026-10-17 00:00:00 UTC, picture retrieved 2026-10-17 06:08:57.387 UTC.

No NOHRSC picture displayed on the interactive map.

  • 0 - 0.39 in
  • 0.39 - 2.0 in
  • 2.0 - 3.9 in
  • 3.9 - 9.8 in
  • 9.8 - 20 in
  • 20 - 39 in
  • 39 - 59 in
  • 59 - 98 in
  • 98 - 197 in
  • 197 - 295 in
  • 295 - 394 in
  • 394 - 787 in
NOHRSC snow analysis for the lower 48; see the adjacent source legend and time qualification
NOAA/NWS/NOHRSC’s original picture and legend. No station or address value is inferred.

NOHRSC footprint times are metadata; pixel analysis time is not independently verified. Snow-depth pixels have previously differed from the footprint time. This is modeled/assimilated snow analysis, not a measurement at a place. Unshaded and no-data areas do not establish zero snow.

Snow pictures, retained history and source provenance

Radar-derived cells (0) · unavailable

Collector checked not reported; feed generated not reported. Zero cells does not establish coverage or clear weather. Observations from different radars are not merged.

    Station and river observations (25)

    Surface source current; observed water-level source current. Each reading keeps its own time. Map markers show at most 500 stations and 500 gauges; the complete source directory is paginated.

    Circle: surface station; square: water-level gauge. Filled: current reading and source; hollow: stale, unconfirmed or missing observation. Marker color is not a hazard category. Enable “Stations and gauges” in Layers to inspect them on the map.

    Showing 25 of 25 listed sources. All surface stations and retained trends · All supported gauges and forecasts

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    Water-level gauge APAM2

    unavailable · No observation in the latest cached source list. Retained readings below are historical; an absent gauge may have fallen below action stage or stopped reporting.

    Tide gauge (coastal water level) · Annapolis (IN MLLW) · Severn River · -76.48, 38.983056. Units ft; datum not supplied.

    Source checked 2026-10-17 08:55:04.416Z · current.

    Stage in this gauge’s units, not a regional flood depth. Tide/lake gauges remain water levels; datum is not supplied by this feed. Historical observations and the latest forecast keep separate times.

    Retained observations: 0; target 24 hours, at most 96 reports per station. Recording began 2026-10-17 06:15:05.234Z; oldest available reading none.

    No retained observations yet. Reload after the existing scheduled source pass runs.

    NWS forecast · current

    Highest listed forecast: 2.5 ft at 2026-10-19 04:00:00 UTC; issued 2026-10-16 18:30:00 UTC. Action stage.

    Impacts and the full forecast are read for gauges in flood; this one is at action stage.

    Gauge thresholds: action 2 ft; minor 2.6 ft; moderate 3.3 ft; major 5 ft.

    Observed reports as a table (0)
    Observed (UTC)Stage / unitsSource category / water
    No retained observations.
    Capture times, quality and provenance

    Each report keeps its observation time, first capture of this version, and the SHA-256 of the source bulk body. Corrections at the same observation time replace that point and are marked; unrelated bulk-file changes do not freshen a report.

      Only observed gauge records enter this history. Forecast maxima and forecast hydrograph points never become observations. A missing datum or unsupported flow value remains unknown.

      Observation source page · Cached readings as JSON · Official source

      Recent source changes

      Recording coverage and limits
      • warnings: retained from 2026-10-16T08:58:14.885Z through 2026-10-17T08:58:03.139Z
      • outlooks: retained from 2026-10-16T08:58:14.885Z through 2026-10-17T08:55:04.944Z
      • hydro: retained from 2026-10-16T08:58:14.885Z through 2026-10-17T08:55:04.744Z
      • analysis: retained from 2026-10-16T08:58:14.885Z through 2026-10-17T08:45:06.623Z
      • winter: retained from 2026-10-16T08:58:14.885Z through 2026-10-17T08:53:04.766Z

      Source-message history is not recorded imagery replay. Recorded radar/satellite imagery is not available in this view.

      Auto-updating checks this site’s cache every minute; each source keeps its own clock.

      Spotlight: Winter Storm Severity Index

      1 of 7

      Winter Storm Severity Index

      WPC: “WSSI does not depict official warnings and should always be used in context with official NWS forecasts and warnings.”

      • Winter Weather Area
      • Minor Impacts
      • Moderate Impacts
      • Major Impacts
      • Extreme Impacts

      Highest in this area, by day and by cause

      Day 1
      nothing drawn
      Day 2
      nothing drawn
      Day 3
      nothing drawn
      Snow amount, Days 1–3
      nothing drawn
      Snow load, Days 1–3
      nothing drawn
      Ice, Days 1–3
      nothing drawn
      Blowing snow, Days 1–3
      nothing drawn

      Each day and cause on the Winter tab, with its own issue time

      WPC’s WSSI, overall impact, Days 1–3, valid to , issued . WPC issues each day and cause on its own clock. Not a warning, and not a chance. Data: NOAA/NWS/WPC.

      Chance of Moderate impacts or worse, Day 1

      WPC: “WSSI does not depict official warnings and should always be used in context with official NWS forecasts and warnings.”

      • 5–10%
      • 10–20%
      • 20–30%
      • 30–40%
      • 40–50%
      • 50–60%
      • 60–70%
      • 70–80%
      • 80–90%
      • 90–95%
      • 95% or more

      Each level and day on the Winter tab

      WPC’s WSSI-P, the 24 hours to , WPC’s forecast from . Each band runs to the next. Data: NOAA/NWS/WPC.

      Chance of at least 4 inches of snow, Day 1

      WPC gives no chance of 4 inches of snow or more in this area over the next three days, so Day 1’s 4 inches is shown.

      • Slight: at least 10%
      • Moderate: at least 40%
      • High: at least 70%

      Every day and amount on the Winter tab

      WPC’s Probabilistic Winter Precipitation Forecast, to , issued . Outlines, as WPC draws them. Data: NOAA/NWS/WPC.

      Winter watches, warnings and advisories

      • Freeze Warning 4 4 not yet in effect · until · NWS Baltimore MD/Washington DC, NWS Mount Holly NJ, NWS Pittsburgh PA, NWS State College PA
      • Frost Advisory 1 1 not yet in effect · until · NWS Baltimore MD/Washington DC

      NWS’s winter and cold alerts in force in the area, by event as issued, each counted once, with the offices that issued them and the latest end. Data: NOAA/NWS.

      Snow on the ground

      NOHRSC snow depth and snow water equivalent use the source’s original pictures and legends, with qualified footprint times. Open the cached source page for availability and retained history. This wall has no snow picture to rotate; missing imagery does not mean no snow.

      NOHRSC snow analysis and retained pictures

      Data: NOAA/NWS/NOHRSC. Snow analysis, not a measurement at a place.

      WPC’s heavy snow and icing discussion

      The whole discussion

      Issued , for to . WPC’s words, as written. Data: NOAA/NWS/WPC.

      Radar, winter preset

      The Radar page’s winter preset over the area: HRDPS forecast snow with NWS’s warnings on top, loaded by your browser. A forecast, labelled as one there.

      Open the radar

      Live tiles; the radar keeps no last-good copy.

      What changed, last 60 minutes

      since , when this server began watching this area
      1. WPC Winter Storm Severity Index issued

      The products’ own words and times, and what is no longer in force since the last read. Never written by AI.

      Monitoring area, legacy alert summary and selection rules
      Area
      Maryland (NWS states: MD)
      Hazards
      Winter warnings, watches and advisories, and the forecasts for them
      Window
      In force now, with the next days of SPC’s and WPC’s products
      Made by
      This address: anyone can make one, and nothing is stored. Change the area or hazards

      An area you chose, not a storm’s footprint: everything here is in force in this area, never “from this storm”.

      In force in this area 5

      1. Freeze Warning44 not yet in effect · until 18 Oct 13:00Z
      2. Frost Advisory11 not yet in effect · until 18 Oct 12:00Z
      Every alert in this area, most urgent first
      1. Freeze WarningWashington; Frederick; Carroll; Northern Baltimore; Extreme Western Allegany; Central and Eastern Allegany; Northwest Harford; Western Garrett; Eastern Garrett; Augusta; Rockingham; Shenandoah; Frederick; Page; Warren; Clarke; Western Highland; Eastern Highland; Western Loudoun; Northern Virginia Blue Ridge; Central Virginia Blue Ridge; Hampshire; Morgan; Berkeley; Jefferson; Hardy; Western Grant; Eastern Grant; Western Mineral; Eastern Mineral; Western Pendleton; Eastern PendletonFrom · until · NWS Baltimore MD/Washington DC
      2. Freeze WarningWarren; Potter; Elk; Cameron; Northern Clinton; Clearfield; Northern Centre; Southern Centre; Cambria; Blair; Huntingdon; Mifflin; Juniata; Somerset; Bedford; Fulton; Franklin; Tioga; Northern Lycoming; Sullivan; Southern Clinton; Southern Lycoming; Union; Snyder; Montour; Northumberland; Columbia; Perry; Dauphin; Schuylkill; Lebanon; Cumberland; Adams; York; LancasterFrom · until · NWS State College PA · drawn over this area
      3. Freeze WarningTuscarawas; Carroll; Columbiana; Coshocton; Harrison; Jefferson; Muskingum; Guernsey; Belmont; Noble; Monroe; Mercer; Venango; Forest; Lawrence; Butler; Clarion; Jefferson; Beaver; Allegheny; Armstrong; Washington; Greene; Westmoreland; Westmoreland Ridges; Fayette; Fayette Ridges; Indiana; Higher Elevations of Indiana; Hancock; Brooke; Ohio; Marshall; Wetzel; Marion; Monongalia; Ridges of Eastern Monongalia and Northwestern Preston; Preston; Eastern Preston; Western Tucker; Eastern TuckerFrom · until · NWS Pittsburgh PA · drawn over this area
      4. Freeze WarningSussex; Carbon; Monroe; Warren; Morris; Hunterdon; Berks; Lehigh; Northampton; Western Chester; Western Montgomery; Upper BucksFrom · until · NWS Mount Holly NJ · drawn over this area
      5. Frost AdvisoryNorthwest Montgomery; Northwest Howard; Nelson; Albemarle; Greene; Madison; Rappahannock; Orange; Culpeper; Northern Fauquier; Southern Fauquier; Eastern Loudoun; Northwest Prince WilliamFrom · until · NWS Baltimore MD/Washington DC

      Most urgent first, by the Briefing’s ranking. Checked .

      Sources

      Choose another storm or areaChange monitoring areaSource status

      Not an official warning service. Warnings and watches are the National Weather Service’s, outlooks and reports the Storm Prediction Center’s and the Weather Prediction Center’s (Data: NOAA/NWS, NOAA/SPC, NOAA/WPC). When a warning is issued for you, act on it, and use weather.gov or a NOAA Weather Radio for where you are.