Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 133, NWS State College, PA

August 18, 2009Adams County, Cumberland County, York County, Pennsylvania

NWS State College, PA issued this severe thunderstorm warning at Aug 18, 2009, 4:18 PM EDT for Adams County, Cumberland County, York County, Pennsylvania. It was in force for 57 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 18, 2009, 4:18 PM EDT (20:18 UTC)
Expired
Aug 18, 2009, 5:15 PM EDT
In force
57 min
Issued by
NWS State College, PA
Area
Storm-based polygon

Counties Adams County, PA, Cumberland County, PA, York County, PA

The radar

The Sterling radar (KLWX), 118 km from the middle of the area, began a volume at 20:20 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 8.3 hours before the alert went out and 101 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Phillips Aaf/Abe, MD at 12:00Z on 2009-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 810 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Phillips Aaf/Abe, MD at 12:00Z on 2009-08-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 14 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
810 J/kg
Mixed-layer CIN
-78 J/kg
Mixed-layer LCL
1015 m above ground
0-6 km bulk shear
10 kt
0-1 km storm-relative helicity
14 m²/s²
0-3 km storm-relative helicity
20 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS State College, PA wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 18, 4:00 PM EDT, 18 minutes earlier.

Area forecast discussion, Aug 18, 4:00 PM EDT, 18 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
400 PM EDT TUE AUG 18 2009

.SYNOPSIS...
AN UPPER LEVEL RIDGE OVER THE EASTERN US AND WESTERN ATLANTIC
WILL DOMINATE OUR WEATHER FOR THE NEXT FEW DAYS. THE FIRST IN
SERIES OF FRONTS WORKING TO WEAKEN THE RIDGE WILL TRIGGER
THUNDERSTORMS THIS AFTERNOON. A STRONGER TROUGH TO OUR NORTHWEST
SHOULD PUSH A STRONGER FRONT INTO THE REGION LATER THIS WEEK AND
EARLY THIS WEEKEND TRIGGERING MORE SHOWERS. IT WILL ALSO KEEP THE
TROPICAL ACTIVITY TO OUR EAST. SUNDAY THROUGH PERHAPS TUESDAY
SHOULD BE COOLER AND DRIER.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A LINE OF THUNDERSTORMS HAS DEVELOPED ALONG THE LAKE BREEZE AND
SHOULD MOVE STEADILY WESTWARD INTO WARREN COUNTY THIS AFTERNOON.
UPPED POPS AND QPF IN NW PA TO ACCOUNT FOR THIS. THIS LINE SHOULD
MOVE EASTWARD SPREADING STORMS INTO NORTH-CENTRAL AREAS THIS
AFTERNOON AND POSSIBLY INTO THE EARLY EVENING HOURS.

TO THE SOUTHWEST THE S/W ON WAVER VAPOR HAS TRIGGERED A LINE OF
THUNDERSTORMS IN SW PA. THIS LINE IS MOVING ACROSS SOMERSET COUNTY
AND SHOULD MOVE EAST-NORTHEAST UPPED POPS IN SW TO 90 PERCENT AND
TAPERED OFF TO ENE. LOOKS LIKE MOST AREAS OF WESTERN PA HAVE A
GOOD SHOT FOR THUNDER THIS AFTERNOON AND EARLY EVENING AS THIS
SYSTEM TRACKS TO THE EAST.

EVEN A FEW STORMS IN THE LOWER SUSQUEHANNA VALLEY WHERE SOME
STATIONS...MOSTLY SECONDARY STATIONS...ARE IN THE LOWER 90S. MOST
AIRPORTS ARE STILL ONLY IN THE UPPER 80S. BUT DEW POINTS ARE IN
THE 70S. ANY SHOWERS DOWN IN THE SOUTH/SOUTHEAST CAN PRODUCE SOME
LOCALLY HEAVY RAINFALL.

MOST ACTIVITY SHOULD TAIL OFF SHORTLY AFTER SUNSET ESPECIALLY IN
THE WEST.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
THE FRONT TO OUR WEST IS FORECAST TO DRY IT OUT IN WEST AND SAG
SOUTHWARD. THUS AN EAST-WEST BOUNDARY IS FORECAST TO BE STALLED
OVER SOUTHERN PA/MD REGION WEDNESDAY. THIS COULD SERVE AS BOUNDARY
FOR SHOWERS AND STORMS ON WEDNESDAY AFTERNOON. THE SREF/SUPER
ENSEMBLE SHOW HIGHER POPS IN SOUTH. MADE GRIDS REFLECT THIS WITH
LOWER POPS AS ONE MOVE SOUTH TO NORTH. FARTHER NORTH IN PA
TOMORROW THE BETTER. IT SHOULD BE COOLER AND DRIER WEDNESDAY OVER
MOST REGIONS. CHANGED GRIDS TO REFLECT THIS.

THE BOUNDARY IS FORECAST TO SURGE BACK TO THE NORTH AND BRING AN
INCREASE IN HUMIDITY OVERNIGHT WED INTO THURSDAY. SHOWERS AND
THUNDERSTORMS ARE POTENTIALLY A PROBLEM ON THURSDAY. WITH ABOVE
NORMAL PW VALUES...SOME LOCALLY HEAVY RAINS ARE POSSIBLE WITH
THESE STORMS.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
EXTENDED PORTION OF THE FORECAST STARTS OFF ACTIVE AND VERY MILD
BEFORE TURNING DRIER AND COOLER OVER THE WEEKEND.

A STRONG TROUGH TO OUR NORTHWEST WILL PUSH A STRONG FRONT ACROSS
THE REGION FRI INTO SAT...TRIGGERING MORE SHOWERS/THUNDERSTORMS.
IT WILL ALSO KEEP THE TROPICAL ACTIVITY OFF TO OUR EAST AND
OFFSHORE. WITH PLENTY OF MOISTURE REMAINING ACROSS PA AHEAD OF THE
FRONT AND INCREASING DYNAMICS ASSOCIATED WITH THE APPROACH OF THE
COLD FRONT...ANTICIPATE THAT THE STORMS ON FRI MAY BE STRONG TO
POTENTIALLY SEVERE...AND WILL HAVE TO MONITOR FOR POTENTIAL FOR
HEAVIER RAINFALL...ALTHOUGH FRONT LOOKS TO REMAIN FAIRLY
PROGRESSIVE.

ONCE THE FRONT PASSES THROUGH TO THE EAST...SURFACE HIGH WILL
BUILD IN AND SAT NIGHT THROUGH TUESDAY SHOULD BE COOLER AND DRIER
WITH HIGH TEMPS 5-10F COOLER AND NIGHTTIME LOWS 10-15F COOLER.

MODEL DIFFERENCES BETWEEN GFS AND ECMFW COME INTO PLAY BY MIDWEEK
AS THEY HANDLE PROGRESSION OF NEXT TROUGH DIFFERENTLY...WITH THE
GFS FASTER. FOR NOW HANDLED WITH LOW CHANCE POPS ACROSS THE NORTH.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
NMRS SHRA/TSRA HAVE DEVELOPED IN THE PAST FEW HOURS ACROSS THE
CWA. HENCE EXPECT WIDELY VARYING FLYING CONDITIONS THIS
AFTERNOON...WITH VFR CONDITIONS TURNING TO MVFR/IFR IN THESE
STORMS.

SHRA/TSRA WILL TAPER THIS EVENING AS CONVECTION SHUTS DOWN...AND A
RETURN TO WIDESPREAD VFR IS EXPECTED. THERE IS ONCE AGAIN A CHANCE
FOR FOG DEVELOPMENT...ALTHOUGH IT APPEARS THE WINDS MAY BE STRONG
ENOUGH...ESPECIALLY ACROSS THE LAUEL HIGHLANDS...TO PREVENT FOG
FROM SETTLING IN.

ANOTHER ROUND OF MVFR SHOWERS IS EXPECTED WEDNESDAY AS A COLD
FRONT MOVES THROUGH.

OUTLOOK...

THUR-FRI...MAINLY MVFR IN SHRA/TSRA...FOG...AHD HZ.
SAT/SUN...MORNING FOG...THEN MAINLY VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

SYNOPSIS...GRUMM/RXR
NEAR TERM...GRUMM
SHORT TERM...GRUMM
LONG TERM...RXR
AVIATION...DICKEY
Hazardous weather outlook, Aug 18, 5:27 AM EDT, 10 hours 51 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
527 AM EDT TUE AUG 18 2009

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-190930-
WARREN-MCKEAN-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-LANCASTER-
527 AM EDT TUE AUG 18 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY AND TONIGHT.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

In the hours before

Special weather statement, Aug 18, 1:46 PM EDT, 2 hours 32 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
146 PM EDT TUE AUG 18 2009

PAZ065-181830-
YORK PA-
146 PM EDT TUE AUG 18 2009

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL YORK COUNTY...

AT 145 PM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER WEIGELSTOWN...
MOVING SOUTHEAST AT 10 MPH.

THIS STORM WILL BE NEAR SPRING GROVE AROUND 155 PM...NEW SALEM AROUND
210 PM...YORK AROUND 215 PM...SEVEN VALLEYS AROUND 225 PM AND SPRY
AROUND 230 PM.

THIS WILL IMPACT I-83 BETWEEN MILE MARKERS 6 AND 26.

THIS WILL ALSO IMPACT ROUTE 30.

LAT...LON 3992 7697 3995 7699 4010 7690 4000 7650
      3998 7649 3977 7661

EXPERIMENTAL

FORECASTER: GRUMM
Special weather statement, Aug 18, 2:22 PM EDT, 1 hour 56 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
222 PM EDT TUE AUG 18 2009

PAZ017-018-024>027-181900-
BLAIR PA-CAMBRIA PA-CLEARFIELD PA-HUNTINGDON PA-MIFFLIN PA-
NORTHERN CENTRE PA-
222 PM EDT TUE AUG 18 2009

...STRONG THUNDERSTORMS WILL AFFECT BLAIR...NORTHEASTERN CAMBRIA...
NORTHERN HUNTINGDON...SOUTHWESTERN CENTRE...SOUTHWESTERN CLEARFIELD
AND SOUTHWESTERN MIFFLIN COUNTIES...

AT 218 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 16 MILES
NORTH OF EBENSBURG TO 8 MILES NORTHEAST OF EBENSBURG TO 6 MILES SOUTH
OF HOLLIDAYSBURG...MOVING EAST AT 30 MPH.

WIND GUSTS TO 30 MPH AND SMALL HAIL ARE POSSIBLE WITH THESE STORMS.

THESE STORMS WILL BE NEAR PRINCE GALLITZIN STATE PARK...LAKEMONT...
AND HOLLIDAYSBURG AROUND 230 PM...WESTOVER...AND ALTOONA AROUND 235
PM...ROYER...CANOE CREEK STATE PARK...AND ENTRIKEN AROUND 240 PM...
IRVONA AND BELLWOOD AROUND 245 PM.

THIS WILL IMPACT I-99 BETWEEN MILE MARKERS 16 AND 55.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 22...ROUTE
22/522...ROUTE 219...ROUTE 220...ROUTE 522...STATE ROAD 350...STATE
ROAD 453.

LAT...LON 4055 7869 4065 7885 4072 7882 4078 7882
      4087 7829 4078 7816 4074 7822 4075 7814
      4073 7809 4067 7798 4037 7775 4036 7776
      4027 7835 4030 7843 4026 7845

EXPERIMENTAL

FORECASTER: GRUMM
Special weather statement, Aug 18, 2:44 PM EDT, 1 hour 34 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
244 PM EDT TUE AUG 18 2009

PAZ066-181915-
LANCASTER PA-
244 PM EDT TUE AUG 18 2009

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL LANCASTER COUNTY...

AT 243 PM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER LEOLA...MOVING
EAST AT 25 MPH.

WIND GUSTS TO 30 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.

THIS STORM WILL BE NEAR LEOLA AROUND 250 PM...NEW HOLLAND AROUND 300
PM...TERRE HILL AROUND 305 PM AND CHURCHTOWN AROUND 315 PM.

THIS WILL IMPACT THE PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 286
AND 295.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 30...ROUTE
222...ROUTE 322...STATE ROAD 501.

LAT...LON 4013 7590 4011 7593 4005 7594 4002 7595
      4000 7632 4018 7636 4023 7601 4015 7589
      4014 7589

EXPERIMENTAL

FORECASTER: GRUMM
Special weather statement, Aug 18, 3:09 PM EDT, 1 hour 9 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
309 PM EDT TUE AUG 18 2009

PAZ026>028-035-036-056-063-181945-
CUMBERLAND PA-FRANKLIN PA-FULTON PA-HUNTINGDON PA-JUNIATA PA-
MIFFLIN PA-PERRY PA-
309 PM EDT TUE AUG 18 2009

...A CLUSTER OF THUNDERSTORMS WILL AFFECT NORTHEASTERN FULTON...
NORTHERN FRANKLIN...SOUTHERN HUNTINGDON...SOUTHWESTERN JUNIATA...
SOUTHWESTERN MIFFLIN...SOUTHWESTERN PERRY AND WESTERN CUMBERLAND
COUNTIES...

AT 308 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 14 MILES
SOUTH OF HUNTINGDON TO 17 MILES NORTHEAST OF BREEZEWOOD TO 10 MILES
EAST OF BREEZEWOOD...MOVING EAST AT 25 MPH.

WIND GUSTS TO 30 MPH ARE POSSIBLE WITH THESE STORMS.

THESE STORMS WILL BE NEAR CASSVILLE AROUND 315 PM...FORT LITTLETON
AROUND 320 PM...SHADE GAP...AND ORBISONIA AROUND 325 PM...MAPLETON...
AND SHIRLEYSBURG AROUND 330 PM...MOUNT UNION...AND FANNETTSBURG
AROUND 335 PM...NEWTON HAMILTON AND WILLOW HILL AROUND 340 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...THE
PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 168 AND 216...I-81 BETWEEN
MILE MARKERS 24 AND 34.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 11...ROUTE
22...ROUTE 22/522...ROUTE 30...ROUTE 522.

LAT...LON 4015 7811 4033 7824 4037 7820 4045 7748
      4024 7733 4002 7743 3993 7820

EXPERIMENTAL

FORECASTER: DEVOIR
Special weather statement, Aug 18, 3:39 PM EDT, 39 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
339 PM EDT TUE AUG 18 2009

PAZ012-017>019-026-027-045-049-050-182045-
CLEARFIELD PA-HUNTINGDON PA-MIFFLIN PA-NORTHERN CENTRE PA-
NORTHERN CLINTON PA-SNYDER PA-SOUTHERN CENTRE PA-SOUTHERN CLINTON PA-
UNION PA-
339 PM EDT TUE AUG 18 2009

...A LINE OF THUNDERSTORMS WILL AFFECT CENTRE...EAST CENTRAL
CLEARFIELD...NORTHEASTERN HUNTINGDON...NORTHERN MIFFLIN...
SOUTHEASTERN CLINTON...SOUTHWESTERN UNION AND WEST CENTRAL SNYDER
COUNTIES...

AT 338 PM EDT...THUNDERSTORMS WERE ALONG A LINE FROM 15 MILES
WEST OF BELLEFONTE TO STATE COLLEGE TO 9 MILES SOUTH OF STATE
COLLEGE...MOVING NORTHEAST AT 25 MPH.

WIND GUSTS TO 40 MPH ARE POSSIBLE WITH THESE STORMS.

THESE STORMS WILL BE NEAR BOALSBURG...AND BELLEVILLE AROUND 345 PM...
SNOW SHOE...AND UNIONVILLE AROUND 350 PM...PLEASANT GAP...
MILESBURG...BELLEFONTE...AND REEDSVILLE AROUND 400 PM...POTTERS MILLS
AND CENTRE HALL AROUND 405 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...
I-80 BETWEEN MILE MARKERS 131 AND 185...I-99 BETWEEN MILE MARKERS 64
AND 85.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 220...
ALTERNATE ROUTE 220...ROUTE 322...STATE ROAD 26...STATE ROAD 45...
STATE ROAD 120.

LAT...LON 4127 7751 4104 7729 4080 7716 4054 7786
      4078 7799 4100 7821

EXPERIMENTAL

FORECASTER: DEVOIR
Special weather statement, Aug 18, 4:13 PM EDT, 5 minutes before
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The office that day

Everything else NWS State College, PA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 18, 1:46 PM EDTSpecial Weather StatementCTPYork44 min
Aug 18, 2:22 PM EDTSpecial Weather StatementCTPBlair, Huntingdon38 min
Aug 18, 2:44 PM EDTSpecial Weather StatementCTPLancaster31 min
Aug 18, 3:09 PM EDTSpecial Weather StatementCTPFranklin36 min
Aug 18, 3:39 PM EDTSpecial Weather StatementCTPCentre66 min
Aug 18, 3:44 PM EDTSevere Thunderstorm WarningCTPCentre, Clinton61 min
Aug 18, 3:52 PM EDTSevere Thunderstorm WarningCTPMcKean, Warren53 min
Aug 18, 4:01 PM EDTSevere Thunderstorm WarningCTPJuniata, Mifflin, Snyder59 min
Aug 18, 4:13 PM EDTSpecial Weather StatementCTPJuniata, Mifflin, Perry32 min
Aug 18, 4:23 PM EDTSevere Thunderstorm WarningCTPJuniata, Perry52 min
Aug 18, 4:26 PM EDTSpecial Weather StatementCTPMcKean79 min
Aug 18, 4:37 PM EDTSpecial Weather StatementCTPAdams53 min
Aug 18, 4:44 PM EDTSevere Thunderstorm WarningCTPClinton, Lycoming46 min
Aug 18, 4:49 PM EDTSevere Thunderstorm WarningCTPMcKean, Potter56 min
Aug 18, 4:50 PM EDTSevere Thunderstorm WarningCTPDauphin, Juniata, Northumberland, Perry, Snyder, Union55 min
Aug 18, 4:54 PM EDTSpecial Weather StatementCTPAdams36 min
Aug 18, 4:57 PM EDTSevere Thunderstorm WarningCTPCumberland, Dauphin, Lebanon, York78 min
Aug 18, 5:05 PM EDTSevere Thunderstorm WarningCTPAdams, York55 min
Aug 18, 5:19 PM EDTSpecial Weather StatementCTPDauphin56 min
Aug 18, 5:25 PM EDTSevere Thunderstorm WarningCTPColumbia, Lycoming, Montour, Sullivan80 min
Aug 18, 5:35 PM EDTSevere Thunderstorm WarningCTPColumbia, Dauphin, Lebanon, Northumberland, Schuylkill70 min
Aug 18, 5:45 PM EDTSpecial Weather StatementCTPTioga30 min
Aug 18, 5:46 PM EDTSpecial Weather StatementCTPTioga59 min
Aug 18, 5:54 PM EDTSevere Thunderstorm WarningCTPColumbia, Montour, Northumberland51 min
Aug 18, 6:02 PM EDTSevere Thunderstorm WarningCTPLancaster, York88 min
Aug 18, 6:26 PM EDTSpecial Weather StatementCTPTioga34 min
Aug 18, 6:30 PM EDTSpecial Weather StatementCTPWarren75 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2009Every severe thunderstorm warning in 2009

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.