Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 232004
SWODY1
SPC AC 232003

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0303 PM CDT SAT JUL 23 2016

VALID 232000Z - 241200Z

...THERE IS AN ENH RISK OF SVR TSTMS FROM SOUTHEAST ND/NORTHEAST SD
ACROSS CENTRAL MN AND NORTHWEST WI...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK OVER
THE UPPER MS VALLEY REGION...

...THERE IS A SLGT RISK OF SVR TSTMS OVER EASTERN NY INTO NORTHERN
NEW ENGLAND...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE UPPER MIDWEST INTO THE
CENTRAL PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM EASTERN NY INTO NEW
ENGLAND...

...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF THE MID ATLANTIC
REGION...

...THERE IS A MRGL RISK OF SVR TSTMS OVER PART OF THE LOWER MS
VALLEY...

...SUMMARY...
SCATTERED SEVERE STORMS WILL BE POSSIBLE ACROSS THE UPPER MIDWEST
TODAY INTO THIS EVENING.  DAMAGING WIND AND LARGE HAIL WILL BE THE
MAIN THREATS.  OTHER STRONG TO SEVERE STORMS WITH A THREAT FOR
MAINLY DAMAGING WINDS ARE EXPECTED TODAY FROM EASTERN NEW YORK INTO
NEW ENGLAND...AND FROM SOUTHERN PENNSYLVANIA AND NORTHERN WEST
VIRGINIA INTO THE DELMARVA REGION.  ISOLATED STRONG TO SEVERE STORMS
WILL BE POSSIBLE INTO EARLY EVENING ACROSS PART OF THE LOWER
MISSISSIPPI VALLEY.

...UPPER MS VALLEY AREA...
THE EXPANSIVE AREA OF MORNING TO EARLY AFTERNOON
PRECIPITATION/CLOUDINESS AND EMBEDDED THUNDERSTORMS CONTINUES TO
ADVANCE TO THE EAST/NORTHEAST ACROSS EAST-CENTRAL MN THROUGH WESTERN
AND SOUTHERN WI.  GREATEST DESTABILIZATION HAS BEEN OCCURRING TO THE
WEST THROUGH SOUTH OF THIS CLOUD SHIELD WITH RECENT UPTICKS IN NEW
TSTM DEVELOPMENT.  PLEASE REFER TO SPC MESOSCALE DISCUSSIONS 1373
AND 1374 FOR SHORT TERM MESOSCALE DETAILS IN PARTS OF THE EASTERN
DAKOTAS/WESTERN MN AND PARTS OF EASTERN IA/SOUTHWEST WI/NORTHWEST
IL...RESPECTIVELY.  NO CHANGES ARE NEEDED WITH THE PORTION OF THE
OUTLOOK IN THE EASTERN DAKOTAS TO MN.

FOR NORTHEAST/EASTERN IA TO SOUTHERN WI/NORTHERN IL...RECENT TRENDS
IN MOSAIC RADAR IMAGERY AND THE VERY STRONG INSTABILITY /MLCAPE
2500-4000 J PER KG/ NEAR AND SOUTH OF THE ONGOING STORMS IN
NORTHEAST IA TO SOUTHERN WI...AND THE APPROACH OF AN MCV FROM
NORTH-CENTRAL IA HAVE INCREASED CONFIDENCE FOR THE SOUTHWARD
EXPANSION OF SEVERE PROBABILITIES/CATEGORICAL SLIGHT RISK AREA IN
THIS REGION.  AN INCREASING THREAT FOR GREATER COVERAGE OF ORGANIZED
SEVERE STORMS IS SUGGESTED BY THE 18Z PARALLEL HRRR FROM NORTHEAST
INTO EAST-CENTRAL IA THROUGH SOUTHERN WI AND NORTHERN IL.

...PARTS OF AR INTO CENTRAL MS...
AN INCREASING POTENTIAL EXISTS FOR ISOLATED STRONG TO SEVERE STORMS
THIS AFTERNOON ACROSS THIS AREA.  REFER TO SPC MESOSCALE DISCUSSION
1375 FOR SHORT TERM MESOSCALE DETAILS.

...ELSEWHERE...
THE SLIGHT AND MARGINAL RISK AREA IN NEW ENGLAND...AND THE MARGINAL
RISK AREA IN SOUTHERN PA TO NORTHERN VA TO THE DELMARVA REGION
REQUIRE NO CHANGES WITH THIS OUTLOOK ISSUANCE.  REFER TO SEVERE TSTM
WATCH 411 AND MESOSCALE DISCUSSION 1372...RESPECTIVELY FOR SHORT
TERM DETAILS IN THESE TWO AREAS.

..PETERS.. 07/23/2016

.PREV DISCUSSION... /ISSUED 1129 AM CDT SAT JUL 23 2016/

...UPPER MS VALLEY AREA...
A COMPLEX CONVECTIVE SCENARIO IS UNFOLDING TODAY AS MULTIPLE ONGOING
CONVECTIVE CLUSTERS/BANDS ARE PROGRESSING EWD AND NEWD OVER ND AND
ACROSS EAST CENTRAL MN INTO WEST CENTRAL/SWRN WI AND NERN IA.  THIS
ACTIVITY IS LIKELY TO PERSIST INTO THE AFTERNOON...WILL MODIFY THE
THERMODYNAMIC ENVIRONMENT IN THE WAKE OF CONVECTION AND MODULATE
POTENTIAL FOR POSSIBLE REDEVELOPMENT.

AT THE MID-UPPER LEVELS...A WELL-DEFINED SHORT WAVE TROUGH OVER SRN
SASKATCHEWAN INTO ERN MT IS FORECAST TO TRANSLATE EWD ACROSS THE
CANADIAN PRAIRIE PROVINCES AND ND DURING THE PERIOD WITH MID-LEVEL
HEIGHT FALLS SPREADING EWD ACROSS THE REGION.  THE STRONG CONVECTION
CURRENTLY OVER SERN ND IS ON THE NOSE OF DRYING ALOFT AND LIKELY
INDICATES THE LEADING EDGE OF STRONGER LARGE SCALE ASCENT IN ADVANCE
OF THE TROUGH.  THESE STORMS ARE EXPECTED TO MOVE EWD WITH TIME AND
SPREAD INTO AN AREA FROM SERN ND/NERN SD INTO WEST CENTRAL MN WHERE
VISIBLE IMAGERY INDICATES FILTERED SUNLIGHT/STRONGER DIABATIC
HEATING WILL OCCUR.  THE DOWNSTREAM ENVIRONMENT IS CHARACTERIZED BY
AMPLE MOISTURE INSTABILITY ALONG/SOUTH OF THE MODIFIED WARM
FRONT...AND THERE IS POTENTIAL FOR THE STORMS TO BUILD SWD TOWARD
NERN SD THIS AFTERNOON IN ADVANCE OF THE SURFACE COLD FRONT.  THIS
ACTIVITY IS EXPECTED TO MOVE EWD THROUGH THE EVENING HOURS WITH A
THREAT FOR DAMAGING WINDS AND LARGE HAIL.

OTHER STRONG TO LOCALLY SEVERE STORMS ARE ALIGNED IN SEVERAL BANDS
FROM CENTRAL MN INTO NERN IA/SWRN WI.  THIS ACTIVITY IS LOCATED
CLOSE TO THE COMPOSITE SURFACE WARM FRONT LOCATION...AND HAS BEEN
SLIGHTLY ELEVATED DURING THE MORNING.  THE DOWNSTREAM CIRRUS PLUME
WILL TEMPER DIABATIC HEATING IMMEDIATELY IN ADVANCE OF THE
STORMS...BUT 12Z MPX SOUNDING EXHIBITED LARGE ANTECEDENT MUCAPE AND
STEEP MID-LEVEL LAPSE RATES.  THIS ACTIVITY IS EXPECTED TO PERSIST
INTO THE EARLY AFTERNOON...AND DESPITE MODEST VERTICAL SHEAR...IT
MAY INTENSIFY AS IT MOVES NEWD WITH A THREAT FOR DAMAGING WIND GUSTS
AND HAIL.

...ERN NY INTO NEW ENGLAND...
CONVECTION IS INCREASING OVER SRN QUEBEC IN ASSOCIATION WITH A SHORT
WAVE TROUGH MOVING SEWD TOWARD THE ST LAWRENCE VALLEY AND NEW
ENGLAND.  DOWNSTREAM CUMULUS CLOUDS ARE ALSO INCREASING FROM PARTS
OF ERN NY INTO NRN NEW ENGLAND. AS DIABATIC HEATING
CONTINUES/STEEPENS LOW-LEVEL LAPSE RATES...SUFFICIENT INSTABILITY
WILL BE PRESENT TO SUPPORT A FEW STRONG TO SEVERE STORMS WITH A
THREAT FOR MAINLY STRONG WIND GUSTS.  SEE MCD 1369 FOR MORE DETAILS.

...SRN PA AND NRN WV ACROSS THE DELMARVA REGION...
A VERY WARM/MOIST LOW-LEVEL AIR MASS IS PRESENT WITH SURFACE
TEMPERATURES EXPECTED INTO THE 90S WITH DEW POINT VALUES IN THE
UPPER 60S TO LOWER 70S.  12Z RAOBS AT PIT AND IAD EXHIBIT LARGE
DCAPE PROFILES SUGGESTING POTENTIAL FOR STRONG DOWNBURST WINDS TO
DEVELOP WITH ANY SUSTAINED STORMS THAT DEVELOP.  ALTHOUGH COVERAGE
OF DEEP CONVECTION IS UNCERTAIN AT THIS TIME...A MARGINAL SEVERE
RISK /5% WIND PROBABILITY/ HAS BEEN INTRODUCED TO ACCOUNT FOR THIS
SCENARIO.

$$



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