SWOMCD
SPC MCD 290434
PAZ000-MDZ000-VAZ000-WVZ000-291030-
MESOSCALE DISCUSSION 2276
NWS STORM PREDICTION CENTER NORMAN OK
1134 PM CDT FRI OCT 28 2011
AREAS AFFECTED...NWRN VA...ERN WV...WRN/CNTRL MD...S-CNTRL PA
CONCERNING...HEAVY SNOW
VALID 290434Z - 291030Z
EARLY-SEASON HEAVY SNOW...WITH RATES OF 1 TO LOCALLY 2 IN/HR...WILL
DEVELOP AND SPREAD NNEWD AFTER 09Z...AND CONTINUE THROUGH SATURDAY
MORNING.
A STRONG MID-LEVEL IMPULSE ROUNDING THE BASE OF A LONGWAVE TROUGH
OVER THE CNTRL/ERN CONUS WILL PROGRESS ENEWD TOWARD THE MID ATLANTIC
TONIGHT. AS THIS OCCURS...INTENSE LOW/MID-LEVEL FRONTOGENESIS WILL
OCCUR BENEATH A POWERFUL UPPER-LEVEL SWLY JET MAX /CORE SPEEDS
REACHING 150 KT AT 250 MB AFTER 09Z/ OFFERING STRONG DCVA. THESE
ELEMENTS ARE BEING MANIFESTED IN THE BAROCLINIC LEAF STRUCTURE
ALREADY TAKING SHAPE OVER THE LOWER GREAT LAKES AND OHIO VALLEY PER
RECENT WATER VAPOR IMAGERY. THE LARGE-SCALE ASCENT WILL SUPPORT THE
DEVELOPMENT OF AN 850-MB WAVE...WHICH IS FORECAST TO RIDE NEWD ALONG
A BAROCLINIC ZONE STRETCHING FROM THE WRN CAROLINAS INTO THE
DELMARVA REGION. INCREASING ELY/SELY FLOW AHEAD OF THIS WAVE WILL
ENHANCE UPSLOPE FLOW INTO THE CNTRL APPALACHIANS. ALSO OF
NOTE...SUBSTANTIAL LOW/MID-LEVEL MOISTENING HAS ALREADY TAKEN PLACE
IN ASSOCIATION WITH THE EARLIER PASSAGE OF A LEAD WAVE /REF
BLACKSBURG AND STERLING VA 00Z RAOBS/. GIVEN THESE FACTORS...AN
INCREASE IN SNOWFALL RATES IS ANTICIPATED FROM SSW TO NNE AFTER
09Z...AS AFFIRMED BY RECENT RUNS OF THE EXPERIMENTAL HRRR AND
EXPERIMENTAL ENSEMBLE HIGH-RESOLUTION WRF GUIDANCE.
SNOWFALL RATES OF 1 IN/HR WILL BE LIKELY THROUGHOUT THE DISCUSSION
AREA. HOWEVER...THE MOST FAVORABLE JUXTAPOSITION OF THE
AFOREMENTIONED FORCING MECHANISMS COULD SUPPORT LOCALLY HIGHER RATES
/POSSIBLY UP TO 2 INCHES PER HOUR/ WITHIN 35 MILES EITHER SIDE OF A
LINE FROM STAUNTON VA TO HAGERSTOWN MD TO HARRISBURG PA. ALSO IN
THIS AREA...NAM/GFS CROSS SECTIONS OF THETA-E AND GEOSTROPHIC
MOMENTUM SUGGEST CONDITIONAL SYMMETRIC INSTABILITY DEVELOPING IN THE
MID LEVELS TOWARD 12Z...COINCIDENT WITH SLANTWISE CAPE INCREASING TO
150-200 J/KG PER EXPERIMENTAL NAM OUTPUT. THIS WILL FAVOR
WSW-ENE-ORIENTED HEAVY SNOW BANDS...AND AN ISOLATED LIGHTNING STRIKE
OR TWO CANNOT BE RULED OUT. THE HEAVY SNOW WILL LIKELY CONTINUE
THROUGH SATURDAY MORNING...WITH RATES TAPERING OFF FROM SSW TO NNE
AFTER 18Z. FOR LOCATIONS FARTHER EAST /INCLUDING AREAS FROM
BALTIMORE TO THE DISTRICT OF COLUMBIA/...FORECAST SOUNDINGS SUGGEST
THAT WARMER THERMODYNAMIC PROFILES WILL BE LESS CONDUCIVE FOR HEAVY
SNOW.
..COHEN.. 10/29/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...CTP...LWX...RNK...PBZ...RLX...
LAT...LON 37757909 37457967 37508016 37838050 38848036 39697979
40187921 40447854 40507743 40247664 39517678 38687774
38087850 37757909
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment