Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 202004
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0304 PM CDT MON JUL 20 2015
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID
MS/LOWER OH VALLEY AREA...
...THERE IS A MRGL RISK OF SVR TSTMS FROM SRN NEW ENGLAND AND THE
MID-ATLANTIC REGION WWD TO THE SRN HIGH PLAINS...
...SUMMARY...
STRONG TO SEVERE THUNDERSTORMS WITH ISOLATED DAMAGING WIND GUSTS AND
HAIL REMAIN POSSIBLE FROM PARTS OF THE SOUTHERN HIGH PLAINS THROUGH
THE MID-MISSISSIPPI AND LOWER OHIO VALLEYS TO THE MID-ATLANTIC
COAST.
...DISCUSSION...
ASIDE FROM MINOR TWEAKS TO THE OUTLOOK LINES...FORECAST
REASONING/EXPECTATIONS REMAIN VALID ATTM. SEVERE RISK ACROSS THE
MID MS/LOWER OH VALLEYS -- I.E. WITHIN THE SLIGHT RISK AREA --
APPEARS A BIT LESS CERTAIN GIVEN EXTENSIVE CLOUDINESS STILL
LINGERING INVOF THE REMNANT MCV. STILL...A COUPLE OF SEVERE STORMS
REMAIN POSSIBLE HERE -- AND ACROSS THE BROADER MARGINAL RISK AREA.
..GOSS.. 07/20/2015
.PREV DISCUSSION... /ISSUED 1130 AM CDT MON JUL 20 2015/
...SYNOPTIC SETUP...
ERN HALF OF ELONGATED RIDGE ACROSS THE S CNTRL AND SERN U.S. WILL BE
SUPPRESSED SLIGHTLY S THIS PERIOD AS BROAD TROUGH SOMEWHAT AMPLIFIES
ACROSS ONT/WRN QUE. WITHIN THE BELT OF ENHANCED FLOW ON S SIDE OF
THIS TROUGH...SHORTWAVE IMPULSE NOW OVER IA SHOULD CONTINUE ESE TO
THE IL-IND BORDER THIS EVE...BEFORE CONTINUING E INTO WRN PA/WV
EARLY TUE. A BIT FARTHER S...CONVECTIVELY-ENHANCED DISTURBANCE/MCV
NOW NEAR STL SHOULD TRACK ESE INTO SW IND BY THIS EVE...AND MAY
REACH ERN TN EARLY TUE. WEAK SPLIT FLOW WILL PERSIST OVER THE
WEST...WITH ANOMALOUS MOISTURE CONTINUING OVER SRN CA AND THE LWR CO
VLY.
AT LWR LVLS...COLD FRONT ASSOCIATED WITH AMPLIFYING TROUGH IN ONT
WILL ADVANCE SE ACROSS THE UPR GRT LKS...UPR MS VLY...AND CNTRL PLNS
TODAY...WHILE WEAKER...SIMILARLY-ORIENTED BOUNDARY TO ITS SE FURTHER
DISSIPATES OVER THE OH VLY/LWR GRT LKS. STILL FARTHER S AND
E...COMPOSITE OUTFLOW BOUNDARY ATTM EXTENDING FROM THE SRN HIGH PLNS
ENE THROUGH SRN MO INTO THE TN VLY WILL REMAIN ESSENTIALLY QSTNRY.
THIS FEATURE...AND LEE TROUGH E OF THE CNTRL APPALACHIANS...SHOULD
FOCUS THE STRONGEST TSTM DEVELOPMENT THIS PERIOD.
...SE MO TO LWR OH/LWR TN VLYS AFTN/EVE...
HEATING OF VERY MOIST AIR /PW AROUND 2.00 INCHES/ AHEAD OF STL AREA
MCV SHOULD BOOST AFTN MLCAPE TO AOA 2500 J PER KG. THIS SHOULD
PROMOTE A SUFFICIENT INCREASE IN ASSOCIATED STORM COVERAGE/STRENGTH
TO YIELD A RISK FOR LOCALLY DMGG WIND GUSTS OVER SE MO...SRN
IL...WRN KY...SW IND... AND PERHAPS NW TN...DESPITE WARM MID-LVL
TEMPERATURES AND MODEST /20-25 KT/ WLY DEEP SHEAR. EWD DEVELOPMENT
OF STORMS MAY BE ENCOURAGED BY LOW-LVL UPLIFT ALONG REMNANT BOUNDARY
ORIENTED ROUGHLY W-E NEAR OWB IN NW KY. THE CONVECTION MAY
PERSIST/CONSOLIDATE TOWARD THE MCV CENTER TNGT/EARLY TUE OVER SRN
IL/KY.
...MID-OH VLY TO MID-ATLANTIC CST AFTN/EVE...
E OF THE AREA INFLUENCED BY THE MCV...STRONG SFC HEATING...TERRAIN
CIRCULATIONS...AND UPLIFT ALONG WEAKENING SFC FRONT AND LEE TROUGH
EXPECTED TO PROMOTE STRONG AFTN STORMS OVER ERN KY AND WV...AND FROM
ERN NC ACROSS ERN MD INTO NJ. THESE STORMS COULD YIELD ISOLD LOCALLY
DMGG GUSTS...DESPITE MODEST LAPSE RATES/SHEAR.
...SRN HIGH PLNS AFTN/EVE...
W OF MO MCV...VERY STRONG HEATING WILL RESULT IN A FAIRLY DEEP YET
RELATIVELY MOIST BOUNDARY LAYER FROM NE NM ENE INTO SRN KS AND
NRN/CNTRL OK...ALONG AND N OF WEAK FRONT STALLED OVER REGION. WARM
MID-LVL TEMPERATURES WILL TEMPER DEEP-LAYER BUOYANCY. BUT WITH
MOISTURE RANGING FROM AOA 1.00 INCH IN NM TO 2.00 INCHES IN
KS/OK...AND WITH WEAK UPSLOPE FLOW TO PROMOTE DEVELOPMENT IN
NM...ISOLD DMGG GUSTS AND AND PERHAPS MARGINALLY SVR HAIL FROM
SLOWLY-MOVING PULSE STORMS MAY OCCUR. THE ACTIVITY SHOULD MERGE INTO
A SSE-MOVING CLUSTER OR TWO...ESPECIALLY OVER ERN NM/W TX...THIS
EVE.
...MID-MO/MID-MS VLYS LATE AFTN/EVE...
A FEW STRONG TO PERHAPS BRIEFLY SVR STORMS MAY ARISE LATE THIS AFTN
ALONG COLD FRONT OVER PARTS OF ERN NEB/IA/WI...AS REGION IS GLANCED
BY SRN FRINGE OF AMPLIFYING CANADIAN IMPULSE. CLOUDS WILL SOMEWHAT
LIMIT LOW-LVL DESTABILIZATION. BUT COUPLED WITH 30+ KT WNWLY DEEP
SHEAR AND COMPARATIVELY STEEP MID-LVL LAPSE RATES...A CONDITIONAL
RISK FOR MARGINALLY SVR HAIL/LOCALLY DMGG WIND WILL EXIST WITH ANY
SUSTAINED STORMS THAT DO FORM.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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