SWODY2
SPC AC 271714
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1214 PM CDT FRI APR 27 2007
VALID 281200Z - 291200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
AMPLIFICATION IN THE LARGE-SCALE UPPER FLOW NOW UNDERWAY ACROSS THE
U.S. WILL PERSIST INTO SATURDAY. BUT...MODELS INDICATE THAT THE
PATTERN WILL REMAIN GENERALLY PROGRESSIVE. EASTERN UPPER TROUGH IS
PROGGED TO BEGIN ADVANCING OFF ATLANTIC COASTAL AREAS BY LATE
SATURDAY NIGHT...AS UPSTREAM RIDGE SHIFTS EAST OF THE INTERMOUNTAIN
WEST. SOME SUPPRESSION/BROADENING OF THE UPPER RIDGE IS FORECAST TO
OCCUR IN RESPONSE TO IMPULSES MIGRATING AROUND ITS NORTHERN
PERIPHERY...INCLUDING ONE TOPPING AND DIGGING TO THE LEE OF ITS
CREST...ACROSS THE CENTRAL CANADIAN PROVINCES...AND ANOTHER LIFTING
INTO PACIFIC COASTAL AREAS BY 12Z SUNDAY. MORE UNCERTAINTY EXISTS
CONCERNING CUT-LOW...NOW DEVELOPING INTO AREAS NEAR/EAST OF THE BAJA
SPUR. BUT...LATEST GFS/ECMWF AND NAM ALL SUGGEST THAT A
NORTHEASTWARD ACCELERATION ACROSS THE NORTHWESTERN MEXICAN PLATEAU
COULD OCCUR LATE IN THE PERIOD.
..INTERMOUNTAIN WEST/ROCKIES/HIGH PLAINS...
IN THE WAKE OF THE EASTERN UPPER TROUGH...LOW-LEVEL RIDGING WILL
MINIMIZE CONVECTIVE POTENTIAL ACROSS MOST AREAS EAST OF THE ROCKIES.
HOWEVER...LINGERING MOISTURE IN THE LOWER RIO GRANDE VALLEY WILL
ADVECT UPSLOPE AROUND THE SOUTHWESTERN PERIPHERY OF THE RIDGE...INTO
HIGHER TERRAIN OF THE MEXICAN PLATEAU/SOUTHWEST TEXAS AND THE
SOUTHERN ROCKIES. LOW/MID-LEVEL MOISTURE WILL BE MORE LIMITED
NORTHWARD THROUGH THE ROCKIES INTO THE NORTHERN INTERMOUNTAIN
REGION. BUT...STRONG HEATING ACROSS THE HIGHER TERRAIN BENEATH
UPPER RIDGE IS EXPECTED TO BE SUPPORTIVE OF SUFFICIENT
DESTABILIZATION FOR AT LEAST WEAK SCATTERED AFTERNOON/EVENING
THUNDERSTORM ACTIVITY.
LARGE-SCALE ISENTROPIC ASCENT ON NORTHERN FRINGE OF THE UPPER RIDGE
MAY ENHANCE CONVECTIVE DEVELOPMENT LATE SATURDAY AFTERNOON/EVENING
ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN REGION/ROCKIES...WITH
HIGH-BASED/ELEVATED ACTIVITY PERHAPS SPREADING EASTWARD INTO PARTS
OF THE NORTHERN PLAINS SATURDAY NIGHT. FARTHER SOUTH...STRONGER
DESTABILIZATION AND FORCING ASSOCIATED WITH THE CUT-OFF LOW SEEMS TO
FAVOR THE MEXICAN PLATEAU FOR STRONGEST/MOST NUMEROUS
STORMS...UNLESS SYSTEM LIFTS OUT MORE RAPIDLY THAN ANTICIPATED.
HOWEVER...AT LEAST ISOLATED VIGOROUS STORMS ARE POSSIBLE ACROSS THE
MOUNTAINS OF SOUTHWEST TEXAS...WHERE MODELS INDICATE MODERATE FLOW
FIELDS VEERING STRONGLY WITH HEIGHT...CONTRIBUTING TO SUFFICIENT
SHEAR FOR AT LEAST BRIEF UPDRAFT ROTATION.
..FLORIDA PENINSULA...
LOW-LEVEL CONVERGENCE MAY BECOME FOCUSED SATURDAY AHEAD OF COLD
FRONT...ALONG SEA BREEZES ACROSS SOUTHEAST COASTAL AREAS. THIS MAY
BECOME SUFFICIENT FOR ISOLATED THUNDERSTORM ACTIVITY IN MOIST
..POTENTIALLY UNSTABLE ENVIRONMENT. BUT...MODEL FORECAST SOUNDINGS
SUGGEST THAT MID-LEVEL INHIBITION WILL BE CONSIDERABLE ...PROBABLY
MINIMIZING CONVECTIVE POTENTIAL.
.KERR.. 04/27/2007
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