Friday through Wednesday...
Not much change in the forecast thinking during this period either,
with the latest global model suites still building very strong
ridging into the region from the SE as the upper trof along the
West Coast weakens and moves off to the NE. Models are still pushing
500mb heights upward to near, or even slightly above 600dm, with
850mb temperatures rising into the 33-37C range during the Sun-Tues
time period. These values, if they verify, would be at historic
levels (99th or Max percentile) rivaling the June 1990 heat wave.
After highs in the 104-107F range on Friday and the 107-111F range
on Saturday, it still appears very likely the highs will rise into
the very dangerous 115-120F range from Sunday into next Tuesday.
These extreme temperatures, combined with a slight increase of the
dewpoint temperatures will keep overnight lows very warm as well
with the warmest lower desert locations struggling to fall below
90F. Although temperatures will likely cool a bit next Wednesday as
the ridging finally begins to weaken, lower desert highs will likely
still approach Excessive Heat criteria, especially if the warmer GFS
verifies.

&&

.CLIMATE...

Record high temperatures late this week through early next week:

Date Phoenix Yuma
---- ------- ----
June 18 115 in 2015 116 in 2015
June 19 115 in 1968 115 in 1960
June 20 115 in 1968 116 in 2008
June 21 115 in 2008 116 in 1968
June 22 116 in 1988 115 in 1960

Top 5 hottest temperatures all-time:

Rank Phoenix Yuma
---- ------- ----
1) 122 on June 26 1990 124 on July 28 1995
2) 121 on July 28 1995 123 on Sept 1 1950
3) 120 on June 25 1990 122 on June 26 1990
4) 119 on June 29 2013 120 on Aug 27 1981
5) 118 on several days 120 on June 24 1957

SPC AC 111710

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1210 PM CDT TUE MAR 11 2014

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR PORTIONS OF THE MIDDLE
ATLANTIC...

...SYNOPSIS...
WATER VAPOR LOOPS IMPLY A MID-LEVEL DISTURBANCE CURRENTLY EMERGING
OVER THE CNTRL PLAINS...AND THIS FEATURE IS FORECAST TO SHIFT EWD
AND REACH THE MID MS VALLEY BY THE BEGINNING OF D2/WED. AS IT DOES
SO...IT WILL PHASE WITH A NRN-STREAM SHORTWAVE IMPULSE DIGGING SSEWD
FROM ONTARIO AND MANITOBA. THE RESULTING PERTURBATION WILL BE A
POTENT...HIGH-AMPLITUDE SHORTWAVE TROUGH THAT WILL ADVANCE EWD
ACROSS THE ERN UNITED STATES. HIGH-MAGNITUDE...LARGE-SCALE UPWARD
MOTION PRECEDING THIS TROUGH WILL BE AUGMENTED BY STRONG UPPER
DIVERGENCE ATTENDANT TO A COUPLED UPPER JET STRUCTURE AND
INTENSIFYING LLJ OVER THE MID ATLANTIC AND NORTHEAST. THIS WILL
SUPPORT THE ENEWD/NEWD DEVELOPMENT AND INTENSIFICATION OF A FRONTAL
CYCLONE FROM THE UPPER OHIO VALLEY TO THE ATLANTIC WATERS OFF THE
SRN NEW ENGLAND COAST. A STRONG COLD FRONT TRAILING SSW OF THE
CYCLONE WILL SWEEP EWD ACROSS THE SERN STATES AND MID
ATLANTIC...WHILE STRONG POLEWARD MASS FLUXES PRECEDING THE CYCLONE
ALLOW A WARM SECTOR TO EXTEND INTO PORTIONS OF ERN PA AND NJ.

...THE MIDDLE ATLANTIC...
THE AIR MASS IN ADVANCE OF THE STRONG COLD FRONT WILL BECOME
MARGINALLY UNSTABLE -- E.G. MLCAPE AROUND 300-600 J/KG -- DURING THE
AFTERNOON. THIS WILL BE IN RESPONSE TO THE COMBINATION OF /1/ AT
LEAST PARTIAL INSOLATION IN SOME AREAS IN THE WAKE OF
EARLY-DAY...WARM-ADVECTION-ENCOURAGED CLOUDS/SHOWERS ASSOCIATED WITH
THE STRENGTHENING LLJ...AND /2/ STRONG NWD FLUXES OF RELATIVELY
HIGHER THETA-E AIR IN THE BOUNDARY LAYER WITH SFC DEWPOINTS IN THE
MIDDLE 50S. THE NRN EXTENT OF THE WARM/BUOYANT SECTOR WILL BE
MODULATED TO SOME EXTENT BY DOWNWARD-DIRECTED SENSIBLE HEAT FLUXES
WITHIN THE SFC LAYER ATOP THE ONGOING SNOW PACK IN NRN PA AND NRN
NJ. REGARDLESS...DIURNALLY ENHANCED BUOYANCY SHOULD ALLOW
THUNDERSTORMS TO INCREASE IN NUMBER AND INTENSITY ALONG THE COLD
FRONT AS IT ADVANCES FROM SERN OHIO/ERN KY INTO WRN WV AND WRN PA BY
MID-DAY...WITH THIS ACTIVITY QUICKLY SPREADING EWD/NEWD THROUGH THE
AFTERNOON.

WITH THE EXIT REGION OF A 70-90-KT H5 JET CORE OVERSPREADING THE
WARM SECTOR BUOYANCY ABOVE A SWLY LLJ INCREASING TO 50-60 KT...WIND
PROFILES WILL BE FAVORABLE FOR LOW-TOPPED...ORGANIZED CONVECTION.
THUNDERSTORMS ARE EXPECTED TO BECOME ORGANIZED INTO FAST MOVING
QUASI-LINEAR SEGMENTS WITH EMBEDDED LEWP STRUCTURES INVOF THE COLD
FRONT. STRONG CONVECTIVE MOMENTUM TRANSPORT WILL SUPPORT THE
POTENTIAL FOR DAMAGING WIND GUSTS...WITH THIS POTENTIAL BOLSTERED BY
THE STRONG CROSS-FRONTAL...SYNOPTIC PRESSURE RISE-FALL COUPLET.
STRONG LOW-LEVEL SHEAR -- E.G. AROUND 30-40 KT OF 0-1-KM BULK
SHEAR -- WILL SUPPORT SOME POTENTIAL FOR LINE-EMBEDDED MESOVORTICES
TO PRODUCE TORNADOES.

THE GREATEST SVR POTENTIAL WILL EXTEND ACROSS THE ERN PANHANDLE OF
WV INTO NRN VA...CNTRL/WRN MD...THE DISTRICT OF COLUMBIA...AND
S-CNTRL PA...WHICH MAY HAVE THE GREATEST OPPORTUNITY TO EXPERIENCE
PRE-FRONTAL INSOLATION. THERE WILL BE SOME POTENTIAL FOR A MORE
WIDESPREAD SVR-WIND EVENT TO TAKE PLACE IN THESE AREAS...POTENTIALLY
WARRANTING HIGHER SVR PROBABILITIES IN SUBSEQUENT OUTLOOKS.
HOWEVER...SUCH POTENTIAL WILL BE PREDICATED ON THE DEGREE OF
INSOLATION-ENHANCED STEEPENING OF LOW-LEVEL LAPSE RATES...FOR WHICH
SOME UNCERTAINTY EXISTS. STORMS ARE EXPECTED TO MOVE OFF THE COAST
AS THE FRONT MOVES OFFSHORE.

..COHEN.. 03/11/2014