Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 030546
SWODY2
SPC AC 030545

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT FRI JUL 03 2015

VALID 041200Z - 051200Z

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

...THERE IS A MRGL RISK OF SVR TSTMS LATE SATURDAY AFTERNOON AND
EVENING ACROSS PARTS OF THE CENTRAL PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS SATURDAY AFTERNOON AND EVENING
ACROSS PARTS OF THE GREAT BASIN...

...THERE IS A MRGL RISK OF SVR TSTMS SATURDAY EVENING INTO SATURDAY
NIGHT ACROSS PARTS OF NORTHERN MONTANA AND NORTH DAKOTA...

...SUMMARY...
SCATTERED STRONG STORMS MAY POSE SOME RISK FOR SEVERE WIND GUSTS AND
HAIL ON SATURDAY...THE 4TH OF JULY...ACROSS PARTS OF THE LOWER
MISSISSIPPI VALLEY...THE CENTRAL PLAINS...THE GREAT BASIN...AND
ACROSS NORTHERN PORTIONS OF MONTANA AND NORTH DAKOTA.

...SYNOPSIS...
EAST OF THE ROCKIES...THE MID-LATITUDE WESTERLIES MAY RETREAT A BIT
BACK TO THE NORTH...AT LEAST INTO THE NORTHEASTERN U.S....DURING
THIS PERIOD.  BUT SUBTROPICAL RIDGING APPEARS LIKELY TO REMAIN
SUPPRESSED...WITH BROAD WEAK UPPER TROUGHING LINGERING ALONG ITS
NORTHERN PERIPHERY...FROM THE SOUTHERN PLAINS INTO THE SOUTHEAST.
AT THE SAME TIME...A SIGNIFICANT SHORT WAVE TROUGH WITHIN THE
WESTERLIES IS FORECAST TO GRADUALLY TURN EASTWARD ACROSS THE
CANADIAN PRAIRIES...AND EAST SOUTH EAST OF THE CANADIAN ROCKIES.
AND WHILE A WEAK CLOSED LOW...EMERGING FROM THE SUBTROPICAL EASTERN
PACIFIC...SLOWLY SHIFTS NORTHWARD TO THE WEST OF THE CALIFORNIA
COAST...AT LEAST ONE SUBSTANTIVE IMPULSE MAY MIGRATE NORTHEAST OF
THE SOUTHERN SIERRA NEVADA...AROUND THE PERIPHERY OF A SUBTROPICAL
HIGH CENTERED OVER SOUTHERN NEW MEXICO.

ASSOCIATED WITH THIS REGIME...STEEP LOWER/MID TROPOSPHERIC LAPSE
RATES ARE EXPECTED TO BE GENERALLY CONFINED TO THE GREAT BASIN/
ROCKIES AND ADJACENT AREAS OF THE PLAINS.  SEASONABLY STRONG SHEAR
WILL LIKELY BE CONFINED TO NORTHERN PORTIONS OF MONTANA AND NORTH
DAKOTA...AS THE BASE OF THE WESTERN CANADIAN TROUGH APPROACHES LATE
IN THE PERIOD...AND BENEATH MODEST NORTHWESTERLY MID-LEVEL FLOW
DURING THE AFTERNOON AND EVENING ACROSS PARTS OF THE CENTRAL HIGH
PLAINS.  A MID-LEVEL SPEED MAXIMUM WITHIN LINGERING CYCLONIC FLOW
ACROSS THE SOUTHERN TIER STATES COULD ALSO CONTRIBUTE TO MODEST
SHEAR ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY.

...LOWER MISSISSIPPI VALLEY...
A SOUTHWARD/SOUTH SOUTHWESTWARD ADVANCING CONVECTIVE OUTFLOW
BOUNDARY MAY PROVIDE THE FOCUS FOR VIGOROUS THUNDERSTORM
DEVELOPMENT...AS EARLY AS MID DAY SATURDAY...INTO SATURDAY EVENING.
STRONG BOUNDARY LAYER HEATING ALONG AND TO THE SOUTHWEST OF THIS
FEATURE MAY CONTRIBUTE TO MODERATELY LARGE CAPE IN THE PRESENCE OF
SEASONABLY HIGH MOISTURE CONTENT.  PERHAPS AIDED BY FORCING AND
AFOREMENTIONED MODEST SHEAR ASSOCIATED WITH A DIGGING UPPER
IMPULSE...ONE OR TWO CLUSTERS OF STORMS MAY EVOLVE.  THESE COULD BE
ACCOMPANIED BY THE RISK FOR LOCALIZED POTENTIALLY DAMAGING WIND
GUSTS.

...CENTRAL HIGH PLAINS...
MID/UPPER FORCING FOR CONVECTIVE DEVELOPMENT REMAINS UNCLEAR... BUT
WIDELY SCATTERED TO SCATTERED THUNDERSTORM ACTIVITY APPEARS POSSIBLE
NEAR THE LEE SURFACE TROUGH...AS HEATING WEAKENS INHIBITION AND
CONTRIBUTES TO MIXED LAYER CAPE ON THE ORDER OF 2000 J/KG BY LATE
SATURDAY AFTERNOON.  IN THE PRESENCE OF STRONG DEEP LAYER VERTICAL
SHEAR BENEATH MODEST NORTHWESTERLY MID-LEVEL FLOW...CONVECTION THAT
DOES DEVELOP WILL DO SO IN AN ENVIRONMENT CONDUCIVE TO ORGANIZED
SEVERE STORMS...INCLUDING SUPERCELLS.

...GREAT BASIN...
CONSIDERABLE THUNDERSTORM DEVELOPMENT APPEARS POSSIBLE SATURDAY
AFTERNOON INTO SATURDAY EVENING...AIDED BY FORCING FOR LARGE-SCALE
ASCENT ASSOCIATED WITH THE UPPER IMPULSE...AS THE BOUNDARY LAYER
BECOMES STRONGLY HEATED...DEEPLY MIXED...AND CHARACTERIZED BY WEAK
TO MODERATE CAPE.  THIS ENVIRONMENT PROBABLY WILL BE CONDUCIVE TO AT
LEAST A FEW LOCALIZED STRONG DOWNBURSTS BEFORE STORMS WEAKEN
SATURDAY NIGHT.

...NORTHERN MONTANA INTO NORTHERN DAKOTA...
TIMING OF BOUNDARY LAYER MOISTENING ASSOCIATED WITH A SOUTHWARD
ADVANCING FRONT...AND STRENGTHENING VERTICAL SHEAR...DOES NOT APPEAR
OPTIMAL...AS IT MAY BE MOSTLY AFTER SUNSET SATURDAY EVENING.
HOWEVER...AIDED BY LARGE-SCALE FORCING ASSOCIATED WITH THE
APPROACHING UPPER TROUGH...VIGOROUS STORM DEVELOPMENT THAT COULD
POSE A RISK FOR SEVERE HAIL AND WIND DOES NOT APPEAR OUT OF THE
QUESTION BY LATE SATURDAY EVENING INTO SATURDAY NIGHT.

..KERR.. 07/03/2015



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