Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 220557
SWODY1
SPC AC 220555

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT FRI MAY 22 2015

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS MAINLY THIS EVENING THROUGH
TONIGHT ACROSS SOUTHWEST AND WEST TX AND EASTERN NM...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK AREA
ACROSS THE SOUTHERN HIGH PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
ACROSS NORTHEAST CO...

...SUMMARY...
ISOLATED SEVERE STORMS ARE POSSIBLE LATE THIS AFTERNOON ACROSS
SOUTHWEST TEXAS...WITH STORM COVERAGE AND THE SEVERE THREAT
INCREASING THROUGH TONIGHT ACROSS EASTERN NEW MEXICO AND SOUTHWEST
TO WEST TEXAS. LARGE HAIL...STRONG WIND GUSTS...AND A TORNADO THREAT
WILL ALL BE POSSIBLE.  ISOLATED STRONG OR SEVERE STORMS WILL BE
POSSIBLE ACROSS NORTHEAST COLORADO DURING THE AFTERNOON AND EARLY
EVENING.  STORMS WITH A THREAT FOR SMALL HAIL WILL BE POSSIBLE
ACROSS MAINE THIS AFTERNOON.

...SYNOPSIS...
A LEAD SHORTWAVE TROUGH SHOULD WEAKEN TODAY AS IT MOVES NWD FROM ERN
CO INTO AN UPPER RIDGE POSITIONED OVER THE NRN PLAINS...WHILE THE
NEXT UPSTREAM /AND MORE AMPLIFIED/ TROUGH TRACKS FROM SRN CA TO THE
FOUR CORNERS REGION AND NWRN MEXICO.  MEANWHILE...A QUITE COLD...
CLOSED LOW WILL SHIFT ESE ACROSS SRN QUEBEC TOWARD NRN MAINE AND NEW
BRUNSWICK...WITH THE ATTENDANT TROUGH MOVING ACROSS THE NORTHEAST
STATES.

...SOUTHERN HIGH PLAINS /LATE THIS AFTERNOON THROUGH TONIGHT/...
A LEE SURFACE TROUGH IS EXPECTED TO BECOME ESTABLISHED ACROSS THE
SRN HIGH PLAINS THIS FORECAST PERIOD...PRIMARILY ACROSS ERN NM INTO
FAR WEST/SOUTHWEST TX.  LOW-LEVEL S/SELY WINDS WILL PROMOTE
BOUNDARY-LAYER MOISTENING TODAY...WITH POLEWARD MOISTURE RETURN
PERSISTING THIS EVENING INTO EARLY SATURDAY MORNING...AS A SLY LLJ
STRENGTHENS ACROSS THIS REGION IN RESPONSE TO HEIGHT FALLS.  THIS
MOISTURE COUPLED WITH DIABATIC WARMING WILL SUPPORT MODERATE
INSTABILITY ACROSS FAR WEST/SOUTHWEST TX THIS AFTERNOON.
MEANWHILE...STEEPENING MIDLEVEL LAPSE RATES SPREADING ACROSS THE SRN
HIGH PLAINS AFTER 23/00Z ATOP FURTHER LOW-LEVEL MOISTENING WILL
RESULT IN THE DEVELOPMENT OF MODERATE INSTABILITY FROM S-N THROUGH
TONIGHT/EARLY SATURDAY.

SLIGHT HEIGHT RISES ACROSS THE SRN HIGH PLAINS TODAY SHOULD INHIBIT
TSTM DEVELOPMENT ACROSS MUCH OF THIS REGION...EXCEPT FOR OVER THE
HIGHER TERRAIN OF FAR WEST/SOUTHWEST TX.  STORMS THAT DEVELOP AND
MOVE OFF THE HIGHER TERRAIN WILL POSE A THREAT FOR MAINLY LARGE HAIL
AND STRONG WIND GUSTS.  AS THE LLJ STRENGTHENS THIS EVENING THROUGH
LATE TONIGHT AND FORCING FOR ASCENT SPREADS INTO ERN NM/WEST
TX...TSTM DEVELOPMENT IS EXPECTED TO INCREASE IN COVERAGE WITH
STRONG TO SEVERE STORMS LIKELY.  FORECAST SOUNDINGS SUGGEST THE
LOW-LEVEL MOISTENING AND WAA WILL MINIMIZE THE INCREASE IN
SURFACE-BASED INHIBITION WILL ALL SEVERE HAZARDS POSSIBLE THROUGH
TONIGHT.

...NERN CO /THIS AFTERNOON AND EVENING/...
SURFACE HEATING WILL OCCUR OVER ERN CO BENEATH RELATIVELY COOL
TEMPERATURES ALOFT /-14 TO -16 C AT 500 MB/ NORTH OF STRENGTHENING
MID- TO UPPER-LEVEL WINDS INTO THE CENTRAL HIGH PLAINS.
MEANWHILE...SELY SURFACE WINDS NORTH OF A DEVELOPING AREA OF LOW
PRESSURE IN SERN CO WILL RESULT IN UPSLOPE FLOW AND AN INCREASE IN
CONVERGENCE ENHANCING LIFT...MAINLY NORTH OF THE PALMER DIVIDE.
STORMS THAT DEVELOP IN THIS MARGINALLY UNSTABLE ENVIRONMENT WITH
SURFACE DEW POINTS ONLY IN THE 40S F AND AN INCREASE IN BULK SHEAR
COULD PRODUCE MARGINALLY SEVERE HAIL. A STORM OR TWO COULD ACHIEVE
SUPERCELL STRUCTURE GIVEN VERTICALLY VEERING WINDS WITH RELATIVELY
STRAIGHT HODOGRAPHS SUGGESTING THE POTENTIAL FOR SPLITTING STORMS.
STORMS COULD PERSIST INTO THE EVENING...PERHAPS APPROACHING THE KS
BORDER...AS WAA INCREASES ALONG A STRENGTHENING SLY LOW-LEVEL JET.

...MAINE /THIS AFTERNOON/...
A COLD FRONT WILL ADVANCE EASTWARD ACROSS NEW ENGLAND TODAY...WHILE
HEIGHT FALLS AND DPVA ATTENDANT TO EMBEDDED VORTICITY LOBES WITH THE
QUEBEC TROUGH SPREAD ACROSS THIS REGION.  DIABATIC WARMING AHEAD OF
THE BOUNDARY ACROSS MAINE AND COOLING MIDLEVEL TEMPERATURES WILL
RESULT IN STEEPENING LAPSE RATES.  MEAGER BOUNDARY LAYER MOISTURE
/SURFACE DEW POINTS IN THE LOW-MID 40S/ SHOULD MINIMIZE INSTABILITY
WITH MUCAPE OF 200-300 J/KG.  FORECAST SOUNDINGS SUGGEST LOW-TOPPED
STORMS WILL BE POSSIBLE ALONG THE COLD FRONT WITH SMALL HAIL AND
LOCALLY STRONGER WIND GUSTS POSSIBLE THIS AFTERNOON.

..PETERS/PICCA.. 05/22/2015




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