Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 011723
SWODY2
SPC AC 011723

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CDT SAT OCT 01 2016

VALID 021200Z - 031200Z

...THERE IS A MRGL RISK OF SVR TSTMS SUNDAY AFTERNOON INTO SUNDAY
NIGHT ACROSS PARTS OF THE EASTERN GREAT BASIN AND ADJACENT NORTHERN
ROCKIES...

...SUMMARY...
THUNDERSTORM ACTIVITY MAY BE ACCOMPANIED BY AT LEAST SOME SEVERE
WEATHER RISK ACROSS PARTS OF THE EASTERN GREAT BASIN SUNDAY
AFTERNOON INTO SUNDAY NIGHT.

...SYNOPSIS...
LARGE-SCALE TROUGHING WITHIN THE MID-LATITUDE WESTERLIES APPEARS
LIKELY TO FINALLY DEVELOP INLAND OF THE PACIFIC COAST DURING THIS
PERIOD.  ONE SIGNIFICANT EMBEDDED SHORT WAVE IMPULSE HAS ALREADY
PROGRESSED INLAND ACROSS THE PACIFIC NORTHWEST...AND IS FORECAST TO
TURN NORTHEASTWARD ACROSS THE NORTHERN U.S. ROCKIES INTO THE WESTERN
CANADIAN PRAIRIES LATER TODAY AND TONIGHT...AS ANOTHER DIGS INTO THE
PACIFIC NORTHWEST COAST.  MODELS INDICATE THAT THE LATTER IMPULSE
WILL THEN PIVOT INLAND ACROSS THE SOUTHERN CASCADES AND SIERRA
NEVADA INTO THE GREAT BASIN SUNDAY THROUGH SUNDAY NIGHT.  AS IT
DOES...LARGE-SCALE TROUGHING APPEARS LIKELY TO TAKE ON MORE OF A
NEUTRAL TO NEGATIVE TILT ACROSS THE GREAT BASIN AND NORTHERN ROCKIES
BY 12Z MONDAY.  THIS PROBABLY WILL BE ACCOMPANIED BY A DEEPENING
SURFACE LOW ACROSS THE NORTHERN GREAT BASIN...ALONG A FRONT EXPECTED
TO SURGE THROUGH MUCH OF THE INTERMOUNTAIN WEST...BEFORE A BIT MORE
PROMINENT SURFACE CYCLOGENESIS COMMENCES TO THE LEE OF THE NORTHERN
ROCKIES.

DOWNSTREAM...A MID/UPPER CLOSED LOW...WHICH HAS BEEN CUT OFF FROM
THE STRONGER WESTERLIES THE PAST FEW DAYS ACROSS THE LOWER OHIO
VALLEY...IS ALREADY BEGINNING TO MIGRATE NORTHWARD TOWARD THE GREAT
LAKES REGION.  IN RESPONSE TO UPSTREAM DEVELOPMENTS...AND ANOTHER
SIGNIFICANT SHORT WAVE IMPULSE FORECAST TO DIG ACROSS NORTHERN
QUEBEC...TOWARD THE CANADIAN MARITIMES...MODELS SUGGEST THAT IT WILL
BE FORCED EASTWARD ACROSS THE LOWER GREAT LAKES REGION AND UNDERGO
CONSIDERABLE DEFORMATION SUNDAY/SUNDAY NIGHT.

WHILE A COLD FRONT WHICH HAS ADVANCED INTO/THROUGH MUCH OF THE SOUTH
ATLANTIC/GULF COAST REGION MAY CONTINUE TO SLOWLY WEAKEN...LITTLE
SUBSTANTIVE LOW-LEVEL MOISTURE RETURN TO THE PLAINS APPEARS LIKELY
THROUGH AT LEAST THIS PERIOD...DESPITE DEEPENING OF SURFACE
TROUGHING TO THE LEE OF THE ROCKIES.  ACROSS THE INTERMOUNTAIN
WEST...MODELS SUGGEST SOME DRYING OF LOW/MID-LEVELS MAY OCCUR IN THE
WAKE OF THE INITIAL SHORT WAVE IMPULSE PROGRESSING INTO WESTERN
CANADA.  HOWEVER...BASED ON LATEST OBSERVATIONAL DATA...IT SEEMS
POSSIBLE THAT THIS MAY BE A BIT OVERDONE...PARTICULARLY ACROSS PARTS
OF THE EASTERN GREAT BASIN.

...EASTERN GREAT BASIN...
WITHIN THE WARM SECTOR OF THE DEVELOPING SURFACE LOW...RESIDUAL
MOISTURE ACROSS THE GREAT SALT LAKE DESERT/WASATCH
REGION...NORTHWARD INTO THE UPPER SNAKE RIVER VALLEY AND MOUNTAINS
OF WESTERN WYOMING...MAY REMAIN SUFFICIENT TO CONTRIBUTE TO WEAK TO
LOCALLY MODEST BOUNDARY LAYER DESTABILIZATION BY LATE SUNDAY
AFTERNOON AND EVENING.  THIS LIKELY WILL BE AIDED BY STRENGTHENING
FORCING FOR ASCENT AND MID-LEVEL COOLING ASSOCIATED WITH THE
APPROACHING SHORT WAVE TROUGH...WHICH MAY CONTRIBUTE TO CONSIDERABLE
STEEPENING OF MID-LEVEL LAPSE RATES.  IN THE PRESENCE OF
STRENGTHENING SOUTHWESTERLY LOWER/MID TROPOSPHERIC WIND
FIELDS...INCLUDING TO AROUND 40-50+ KT AT 500 MB...THE ENVIRONMENT
SEEMS LIKELY TO BECOME AT LEAST MARGINALLY CONDUCIVE TO ORGANIZED
VIGOROUS THUNDERSTORM DEVELOPMENT.  THIS MAY INCLUDE SUPERCELL
STRUCTURES ACCOMPANIED BY POTENTIAL FOR SEVERE HAIL...IN ADDITION TO
STRONG SURFACE GUSTS.

..KERR.. 10/01/2016

$$


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