SPC AC 250727
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 AM CDT TUE MAY 25 2010
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU ACROSS PARTS OF THE
NORTHEAST...
...THERE IS A SLGT RISK OF SVR TSTMS THU AFTN AND EVE ACROSS PARTS
OF THE NORTHERN ROCKIES/NORTHERN HIGH PLAINS...
...SYNOPSIS...
MODELS INDICATE THAT MID-LEVEL HEIGHTS WILL CONTINUE TO FALL ACROSS
THE NORTHEASTERN U.S. DURING THIS FORECAST PERIOD. THIS IS EXPECTED
TO OCCUR AS AT LEAST ONE SIGNIFICANT SHORT WAVE IMPULSE PIVOTS
AROUND THE WESTERN PERIPHERY OF A BROAD DEEP CLOSED LOW...THE CENTER
OF WHICH IS PROGGED TO SHIFT SOUTH/SOUTHEAST OF THE CANADIAN
MARITIMES. OTHERWISE LITTLE CHANGE TO THE LARGE SCALE PATTERN IS
EXPECTED ACROSS THE REST OF THE NATION. UPPER RIDGING APPEARS
LIKELY TO CONTINUE TO BUILD ACROSS THE PLAINS...DOWNSTREAM OF
ANOTHER BROAD CLOSED LOW VERY SLOWLY MIGRATING EASTWARD ACROSS THE
WESTERN STATES...TO THE SOUTH OF A BLOCKING HIGH CENTER OVER
NORTHWEST CANADA. ONE SHORT WAVE IMPULSE EMBEDDED WITHIN THE
CYCLONIC FLOW IS PROGGED TO LIFT ACROSS THE NORTHERN ROCKIES...AS A
STRONGER IMPULSE PROGRESSES INLAND ACROSS THE CALIFORNIA COAST.
...NORTHEAST...
GUIDANCE IS SUGGESTIVE THAT MODERATE INSTABILITY WILL DEVELOP WITHIN
A PRE-FRONTAL CORRIDOR EXTENDING SOUTHEASTWARD OUT OF
QUEBEC/SOUTHERN ONTARIO THROUGH NORTHERN NEW YORK STATE AND THE
CHAMPLAIN VALLEY INTO SOUTHERN NEW ENGLAND EARLY THURSDAY MORNING.
THERMODYNAMIC PROFILES ARE EXPECTED TO BECOME CHARACTERIZED BY
RELATIVELY STEEP LAPSE RATES...AND CAPE OF 1000-2000 J/KG WITH
DAYTIME HEATING...WHICH WILL SUPPORT POTENTIAL FOR STRONG/SEVERE
STORM ACTIVITY. THE FRONT WILL LIKELY PROVIDE THE FORCING AND FOCUS
FOR CONVECTIVE DEVELOPMENT...WHICH COULD BECOME ENHANCED BY
FAVORABLE SHEAR BENEATH AT LEAST MODEST NORTHWESTERLY MID-LEVEL
FLOW. DAMAGING WIND GUSTS AND LARGE HAIL APPEAR POSSIBLE IN THE
MOST VIGOROUS ACTIVITY FROM MIDDAY THURSDAY INTO THURSDAY
EVENING...AS THE FRONT ADVANCES WEST/SOUTHWESTWARD.
...NORTHERN PLAINS...
DESTABILIZATION IS EXPECTED TO CONTINUE THURSDAY ACROSS THE NORTHERN
ROCKIES AND NORTHERN HIGH PLAINS...AS LOW-LEVEL MOISTURE INCREASES
ON STRENGTHENING SOUTHEASTERLY LOW-LEVEL FLOW...IN THE PRESENCE OF
STEEP LAPSE RATES. MODERATELY STRONG CAPE AS HIGH AS 2000+ J/KG
APPEARS PROBABLE BY THURSDAY AFTERNOON ACROSS PARTS OF NORTHEAST
WYOMING AND THE WESTERN DAKOTAS INTO EASTERN MONTANA...WHERE WARM
ELEVATED MIXED LAYER AIR MAY INHIBIT CONVECTIVE DEVELOPMENT. BUT
INSTABILITY AND FORCING ACROSS THE MOUNTAINS OF WEST CENTRAL/SOUTH
CENTRAL MONTANA ARE EXPECTED TO BE SUFFICIENT TO SUPPORT THE
INITIATION OF STORMS...WHICH SHOULD DEVELOP NORTHEASTWARD OFF THE
HIGHER TERRAIN IN THE PRESENCE OF STRONG DEEP LAYER AND LOW-LEVEL
SHEAR FAVORABLE FOR SUPERCELLS. CONSOLIDATION OF ACTIVITY INTO AN
ORGANIZED SEVERE MESOSCALE CONVECTIVE SYSTEM APPEARS POSSIBLE
THURSDAY EVENING...WITHIN A ZONE OF ENHANCED LOWER/MID TROPOSPHERIC
WARM ADVECTION ACROSS EAST CENTRAL/NORTHEAST MONTANA.
..KERR.. 05/25/2010
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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