Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 060547
SWODY2
SPC AC 060545

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT FRI MAY 06 2016

VALID 071200Z - 081200Z

...THERE IS A SLGT RISK OF SVR TSTMS SATURDAY AFTERNOON AND EVENING
ACROSS PARTS OF THE NORTH CENTRAL HIGH PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
CENTRAL AND SOUTHERN HIGH PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER OHIO
VALLEY...

...SUMMARY...
A FEW SEVERE STORMS ARE POSSIBLE SATURDAY ACROSS PARTS OF THE NORTH
CENTRAL HIGH PLAINS...WITH MUCH MORE WIDELY SCATTERED TO ISOLATED
STRONG STORMS POSSIBLE ACROSS THE REMAINDER OF THE CENTRAL AND
SOUTHERN HIGH PLAINS.  SCATTERED STRONG TO SEVERE STORMS ARE ALSO
POSSIBLE ACROSS PARTS OF THE LOWER OHIO VALLEY.

...SYNOPSIS...
THE SOUTHERN BRANCH OF SPLIT MID-LATITUDE WESTERLIES EMANATING FROM
THE MID-LATITUDE PACIFIC APPEAR LIKELY TO REMAIN RATHER AMPLIFIED
ACROSS THE U.S...WITH CLOSED LOWS STILL PROMINENT WITHIN A COUPLE OF
TROUGHS AT 12Z SATURDAY.  HOWEVER...MODELS SUGGEST THAT THE EASTERN
CLOSED LOW MAY UNDERGO CONSIDERABLE DEFORMATION DURING THIS
PERIOD...AND BEGIN TO ACCELERATE EASTWARD OFF THE ATLANTIC COAST IN
THE FORM OF AN OPEN-WAVE TROUGH...AS AN IMPULSE WITHIN THE MORE
PROGRESSIVE NORTHERN BRANCH DIGS SOUTH OF HUDSON BAY.

THIS LATTER FEATURE...CURRENTLY PROGRESSING ACROSS THE CANADIAN
NORTHWEST TERRITORIES...IS FORECAST TO EVOLVE INTO DEEP CLOSED
LOW...AND CONTRIBUTE TO THE SOUTHWARD ADVANCEMENT OF ANOTHER COLD
FRONT TO THE EAST OF THE ROCKIES.  GUIDANCE INDICATES THAT THE FRONT
MAY REACH THE UPPER GREAT LAKES/MIDWEST REGION AND NORTH CENTRAL
PLAINS BY 12Z SATURDAY...BEFORE CONTINUING INTO NEW ENGLAND AND MID
ATLANTIC COASTAL AREAS BY 12Z SUNDAY...WHILE STALLING ACROSS THE
LOWER OHIO/MIDDLE MISSISSIPPI VALLEYS INTO NORTH CENTRAL PLAINS.

IN THE WAKE OF AN ONGOING LOW-LEVEL COOLING/DRYING ACROSS THE GULF
OF MEXICO...APPRECIABLE MOISTENING OF THE BOUNDARY LAYER...ON
SOUTHERLY RETURN FLOW...MAY NOT COMMENCE ACROSS THE LOWER RIO GRANDE
VALLEY INTO THE SOUTHERN HIGH PLAINS UNTIL SOMETIME SATURDAY
EVENING.  OTHERWISE...SUBSTANTIVE MOISTENING OVER WHAT IS NOW
PRESENT APPEARS UNLIKELY...EXCEPT PERHAPS NEAR THE AFOREMENTIONED
FRONTAL ZONE...ASSOCIATED WITH SOME MOISTURE INFLUX OF PACIFIC
ORIGINS.  STILL...THIS MAY BE SUFFICIENT...COUPLED WITH STEEPENING
MID-LEVEL LAPSE RATES ASSOCIATED WITH ELEVATED MIXED LAYER AIR
EMERGING FROM THE ROCKIES/PLATEAU REGION...TO CONTRIBUTE TO
DESTABILIZATION SUPPORTIVE OF AREAS OF SCATTERED STRONG/SEVERE STORM
DEVELOPMENT.  THE MOST CERTAIN/CONCENTRATED AREA OF SEVERE STORM
POTENTIAL APPEARS TO BE ACROSS THE NORTH CENTRAL HIGH PLAINS.

...NORTH CENTRAL HIGH PLAINS...
FORCING FOR ASCENT ASSOCIATED WITH AN IMPULSE PIVOTING OUT OF THE
INTERMOUNTAIN WEST...AROUND THE EASTERN/NORTHEASTERN PERIPHERY OF
THE WESTERN CLOSED LOW...APPEARS LIKELY TO BECOME FAVORABLY TIMED
WITH PEAK LATE AFTERNOON BOUNDARY LAYER INSTABILITY...MAINLY NORTH
OF THE PALMER DIVIDE INTO THE CHEYENNE RIDGE AREA OF THE HIGH
PLAINS.  MOISTENING EASTERLY/EAST SOUTHEASTERLY UPSLOPE FLOW ACROSS
THIS REGION IS EXPECTED TO CONTRIBUTE TO MIXED LAYER CAPE IN EXCESS
OF 1000 J/KG.  THE PROXIMITY OF THE NOSE OF A 50-70 KT SOUTHWESTERLY
500 MB JET REMAINS A BIT UNCLEAR.  REGARDLESS...VERTICAL SHEAR
PROFILES SHOULD BECOME MORE THAN SUFFICIENT FOR SUPERCELL
STRUCTURES.  ACTIVITY COULD EVENTUALLY CONSOLIDATE INTO AN EASTWARD
PROPAGATING CONVECTIVE SYSTEM...WITH CONTINUING SEVERE WEATHER
POTENTIAL ACROSS AT LEAST PARTS OF SOUTHWESTERN NEBRASKA AND
NORTHWEST KANSAS BEFORE WEAKENING SATURDAY EVENING.

...LOWER OHIO VALLEY...
WEAK TO MODEST BOUNDARY LAYER DESTABILIZATION APPEARS POSSIBLE IN AT
LEAST A NARROW PRE-FRONTAL CORRIDOR BY LATE SATURDAY AFTERNOON.
THIS MAY BE FAVORABLY TIMED WITH INCREASING FORCING FOR ASCENT NEAR
THE BASE OF THE DIGGING NORTHERN BRANCH TROUGH...AND STRENGTHENING
OF WESTERLY LOWER/MID TROPOSPHERIC MEAN WIND FIELDS TO 30-50 KTS.
STRONG TO SEVERE STORM DEVELOPMENT WITH THE RISK FOR AT LEAST
MARGINALLY SEVERE WIND GUSTS AND HAIL APPEARS POSSIBLE...ACROSS
PARTS OF EASTERN ILLINOIS/CENTRAL INDIANA...TOWARD THE CENTRAL
APPALACHIANS THROUGH SATURDAY EVENING.

...SOUTHERN HIGH PLAINS...
DESTABILIZATION ASSOCIATED WITH LOW-LEVEL MOISTURE RETURN MAY BECOME
FAVORABLE FOR ISOLATED TO WIDELY SCATTERED SEVERE STORM DEVELOPMENT.
HOWEVER...THIS GENERALLY MAY NOT BE UNTIL MID TO LATE EVENING...AT
THE EARLIEST...AS FORCING FOR ASCENT BEGINS TO INCREASE DOWNSTREAM
OF THE NEXT IN A SERIES OF IMPULSES PIVOTING AROUND THE WESTERN
CLOSED LOW.

..KERR.. 05/06/2016

$$



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