Heavy Snow/Icing Discussion from HPC at 10:33 pm

[Stormsfury]

Potential for NW NC to pick up 4"-8" of sleet per HPC Heavy Snow/Icing Discussion

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1028 PM EST SAT FEB 15 2003

12HR HEAVY SNOW AND ICING FCST VT FEB 16/0600 UTC THRU FEB 16/1800
UTC
REFERENCE AWIPS GRAPHICS UNDER...HEAVY SNOW FCST

MID ATL....

THE 1800 AND 0000 UTC ETA AND GFS HAVE COME INTO MUCH BETTER
AGRMNT THAN IN PAST RUNS WITH THE DETAILS OF THE MAJOR WINTER
STORM EXPECTED ACRS LARGE SECTION OF THE MID ATL. EVENING SFC
ANALYSIS SHOWS CLASSIC SET UP FOR MAJOR WINTER EVENT WITH
STRONG ARCTIC HIGH OVR SRN CAN NOSING SWD IN THE LEE OF THE
APPALACHIANS. THIS COLD AIR MASS WL CONT TO BE OVERRUN BY THE
AMPLIFYING MID LEVEL TROF UPSTREAM OVR THE MS VALLEY. STRONG
ISENTROPIC LIFT OVR THIS COLD DOME WL BRING WIDESPREAD HVY PCPN
FROM THE UPR OH VALLEY EWD INTO THE MID ATL. A WIDE VARIETY OF
PTYPE LIKELY WITH THIS SYSTEM. HVY SNOW IN THE 6-12"+ RANGE
EXPECTED FROM ERN WV ACRS NRN VA INTO MD AND DE. TO THE
SOUTH...PTYPE ALGORITHMS CONT TO SHOW MAJOR SLEET
ACCUMULATIONS ACRS SRN VA INTO NWRN NC WITH SLEET
ACCUMULATIONS OVER 4" HERE POSSIBLE. INTO WRN NC SWD INTO
UPSTATE SC...SGFNT ICE ACCUMULATIONS POSSIBLE TO THE EAST OF THE
APPALACHIANS. WITH THE LOW LEVEL COLD AIR SO WELL
ENTRENCHED...THE FCST OF SGFNT ICING IS COMPLICATED BY POTENTIAL
OF FZRAIN CHANGING OVR TO SLEET AS LOW LEVEL COLD LAYER BECOME
DEEPER. SUBSEQUENTLY...ONLY A LOW TO MDT PROBABILITY OF .25"+
ICING DEPICTED INVOF DAN SWWD TO GSP.

FAR SRN IN...FAR SRN OH...NRN KY....

SGFNT ICING ALSO POSSIBLE TO THE WEST OF THE APPALACHIANS THIS
PERIOD AS BELOW FREEZING BNDRY LAYER AIR EXPECTED TO BE
MAINTAINED ACRS THIS REGION AND OVERRUN BY THE MS VALLEY UPR
TROF. QPF AMTS ABOVE .50" THIS PERIOD WARRANT A MDT TO HIGH
PROBABILITY OF .25"+ ICING ACRS THESE REGIONS.

SIERRA...

HT FALLS EXPECTED TO PUSH INLAND INTO NRN CA EARLY SUN AND PUSH
QUICKLY INTO THE NRN GTBASIN. STRONG SWLY UPSLOPE FLOW INTO THE
SIERRA WL PRODUCE HVY PCPN IN THE 1-2" RANGE THRU THE SIERRA.
SNOW LEVELS LIKELY TO FALL TO NEAR 4000 FT...WITH A HIGH PROBABILITY
OF 12"+ SNOWS DEPICTED.

12HR HEAVY SNOW AND ICING FCST VT FEB 16/1800 UTC THRU FEB 17/0600
UTC
REFERENCE AWIPS GRAPHICS UNDER...HEAVY SNOW FCST

MID ATL....

THE MAJOR WINTER STORM WL CONT TO PRODUCE VERY HVY SNOWFALL
THIS PERIOD WITH ADDITIONAL 6-12"+ AMTS FROM SRN PA...NRN WV...NRN
VA AND MOST OF MD AND DE....BRINGING STORM TOTALS THRU THE FIRST
AND SECOND FCST PERIODS TO THE 1-2 FOOT RANGE FROM ERN WV THRU
NRN VA LARGE SECTION OF MD...DE AND SRN PA. THE TRACK OF THE SFC
LOW ALONG THE MID ATL COAST HAS COME INTO BETTER AGRMNT IN THE
1800 UTC AND 0000 UTC ETA AND GFS. THE 2100 UTC SREF MSLP MEANS
FROM THE ETA AND RSM ARE ALSO LATCHING ONTO A COMMON SFC
TRACK...LEADING TO HIGHER CONFIDENCE IN THE MODEL DETAILS. THE
ETA AT 1800 AND 0000 UTC TRENDED EWD FROM ITS 1200 UTC RUN WHICH
BROUGHT THE SFC LOW INLAND INTO NERN NC AND SERN VA...WHILE THE
1800 UTC GFS TRENDED WWD. CONCERN FOR SNOW ACCUMULATIONS
ACRS THE MID ATL CONTS TO BE POTENTIAL FOR A BRIEF CHANGE OVR TO
SLEET TOWARD THE END OF THIS FCST PERIOD. THIS WL BE MORE LIKELY
ACRS THE DELMARVA...DECREASING IN LIKELIHOOD FARTHER TO THE WEST.

SIMILAR TO THE FIRST FCST PERIOD...SGFNT SLEET ACCUMULATIONS ARE
POSSIBLE FOR CNTRL TO SWRN PORTIONS OF VA. ADDITIONAL 4"+ SLEET
ACCUMULATION POSSIBLE HERE.

ON THE SRN EDGE OF THE PCPN SHIELD...THE LOW LEVEL COLD AIR TO THE
EAST OF THE APPALACHIANS WL CONT THREAT FOR SGFNT ICING FROM
INVOF GSP NEWD THRU CLT...GSO...RDU...DAN.

FAR SRN IN/NRN KY..FAR SRN OH...

BELOW FREEZING BNDRY LAYER AIR EXPECTED REMAIN ACRS THIS REGION
SUN AFTERNOON INTO SUN NIGHT. THIS SHOULD CONT TO PRODUCE
POTENTIAL FOR ADDITIONAL ICE ACCUMULATION.
HOWEVER...PROBABILITIES WERE LOWERED FROM FIRST PERIOD AS QPF
AMTS ARE EXPECTED TO BE LIGHTER.

ORAVEC
GRAPHICS AVAILABLE ON THE WEB AT http://WWW.HPC.NCEP.NOAA.GOV

[wx247]

4" of sleet? Wow...that is a lot.

Garrett

[JQ Public]

where is it?

[Stormsfury]

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
208 AM EST SUN FEB 16 2003

VALID 12Z SUN FEB 16 2003 - 00Z TUE FEB 18 2003

INGREDIENTS CONTINUE TO COME TOGETHER FOR A MAJOR WINTER
STORM THAT WILL HAMMER THE MID ATL OVER THE NEXT TWO DAYS. SFC
MAP SHOWS STRONG HIGH PRESSURE OVER SERN CANADA RIDGING S
ALONG THE LEE OF THE APPALACHIANS...SETTING UP A CLASSIC COLD AIR
DAMMING SCENARIO. TO THE S...LOW PRESSURE WILL CONTINUE TO
PRESS E ACROSS THE CTRL GULF COAST STATES TODAY AS AN MID/UPR
LVL TROF OVER THE CTRL/SRN PLAINS BEGINS TO LIFT OUT TOWARDS THE
MID ATL. H85 FLOW WILL DIRECT A COPIOUS AMT OF GULF MOISTURE OUT
AHEAD OF THE SFC SYSTEM ACROSS THE COLD DOME AT THE
SFC...SPREADING A GENEROUS SWATH OF SLEET/FREEZING RAIN TODAY
FROM THE VIRGINIA/CAROLINA PIEDMONT...BACK ACROSS THE CTRL
APPALACHIANS INTO THE SRN OH VLY. TO THE N...ACROSS THE NRN MID
ATL...WHERE PCPN WILL LIKELY BE ALL OR MOSTLY SNOW...HEALTHY
OMEGA VALUES WITH AMPLE MOISTURE THROUGHOUT THE
DAY...CONTINUING INTO TOMORROW...SUGGEST THE STRONG POSSIBILITY
FOR MDT TO HVY SNOWS. LATE TODAY INTO TOMORROW...A SECOND LOW
SPINS UP ALONG THE CAROLINA COAST AND BECOMES THE DOMINATE
FEATURE AS IT DEEPENS AND TRACKS OFF TO THE N. BY THIS TIME WINDS
WILL REALLY BE ON THE INCREASE ACROSS THE NRN MID ATL AS A SHARP
CONTRAST BETWEEN THE HIGH THEN OVER NRN NEW ENGLAND AND THE
LOW OFF THE COAST SETS UP AN IMPRESSIVE PRESSURE GRADIENT. THIS
STRONG EASTERLY FLOW TO THE N OF THE SFC LOW TRACK WILL BRING A
STRONG MOISTURE FLUX AND SNOW FURTHER N INTO THE SRN NEW
YORK/NEW ENGLAND ON MONDAY. REFER TO THE QPFHSD FOR FURTHER
INFO ON THE THREATS FOR HVY SNOW/ICING RESULTING FROM THIS
POWERFUL WINTER STORM. IN THE W...MID/UPR LVL TROF WITH
EMBEDDED SHRTWV ENERGY MAKES LANDFALL ONTO THE PAC NW COAST
TODAY. DEEP LAYERED SWLY FLOW WILL DIRECT PAC MOISTURE ACROSS
IN NRN/CTRL CALIFORNIA...AFFORDING LIGHT TO MDT RAINS ACROSS THE
VALLEYS WITH SNOWS OVER THE SIERRA. SHRTWV ENERGY SPILLS OVER
INTO THE NRN GREAT BASIN LATER TODAY...GENERATING SCT LIGHT PCPN
FOR THE REGION. THINGS PICK UP AGAIN FOR THE W COAST LATE IN THE
PERIOD AS SECOND SHRTWV MOVES ONTO THE PAC NW
COAST...TRIGGERING MDT PCPN FOR THE PAC NW AND NRN CA WITH
HEAVIER PCPN ACROSS THE FAVORED UPSLOPE REGIONS.

PEREIRA
GRAPHICS AVAILABLE AT http://WWW.HPC.NCEP.NOAA.GOV

[Stormsfury]

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
323 AM EST SUN FEB 16 2003

12HR HEAVY SNOW AND ICING VT FEB 16/1200 UTC THRU FEB 17/0000 UTC
REFERENCE AWIPS GRAPHICS UNDER...HEAVY SNOW FCST

MID ATL....

THE LATEST 0000 UTC MODEL GUIDANCE FROM THE ETA AND GFS HAVE
COME INTO MUCH BETTER AGRMNT WITH THE DETAILS OF THE MAJOR
WINTER STORM EXPECTED ACRS LARGE SECTION OF THE MID ATL. SFC
ANALYSIS SHOWS CLASSIC SET UP FOR MAJOR WINTER EVENT WITH
STRONG ARCTIC HIGH OVR SRN CAN NOSING SWD IN THE LEE OF THE
APPALACHIANS. THIS COLD AIR MASS WL CONT TO BE OVERRUN BY THE
AMPLIFYING MID LEVEL TROF UPSTREAM OVR THE MS VALLEY..WITH A VERY
ANOMALOUS ELY TO SELY LOW LEVEL JET (4-5 STD DEPARTURE FROM
CLIMATOLOGY) PRODUCING STRONG ISENTROPIC LIFT OVR THIS COLD
DOME AND BRINGING WIDESPREAD HVY PCPN FROM THE UPR OH VALLEY
EWD INTO THE MID ATL. THIS SET UP IS VERY SIMILAR TO THE FIRST
PRESIDENT'S DAY STORM IN 1979. A WIDE VARIETY OF PTYPE LIKELY WITH
THIS SYSTEM. HVY SNOW IN THE 6-12"+ RANGE EXPECTED FROM ERN WV
ACRS THE DC METRO AREA OF NRN VA/ MD AND INTO DE. TO THE
SOUTH...PTYPE ALGORITHMS CONT TO SHOW MAJOR SLEET
ACCUMULATIONS ACRS SRN VA INTO NWRN NC WITH SLEET
ACCUMULATIONS OVER 4" HERE POSSIBLE. INTO WRN NC SWD INTO
UPSTATE SC...SGFNT ICE ACCUMULATIONS POSSIBLE TO THE EAST OF THE
APPALACHIANS. MAX ICING THREAT APPEARS TO BE DURG THIS PERIOD
OVR WRN NC AS MAIN AREA OF PCPN IS FCST TO BE AWAY FROM BEST LOW
LEVEL COLD AIR BEYOND THIS PERIOD. PTYPE ALGORITHMS SUGGEST
BEST ICING WL BE FROM INVOF AND/GSP NEWD TO GSO....WITH ICING AMTS
OF .50"+ POSSIBLE. A MDT TO HIGH PROBABILITY OF SGFNT ICING DEPICTED
ACRS EXTREME NERN GA...INTO UPSTATE SC AND WRN NC TO THE EAST OF
THE APPALACHIANS.

MID ATL....

THE PRESIDENT'S DAY STORM PART II WILL CONT IN EARNEST LATE SUN
INTO MON WITH OPERATIONAL AND SREF MODELS IN GOOD AGRMNT WITH
THE SFC CYCLOGENESIS PHASE OF THE STORM ALONG THE CAROLINA
COAST. THE ANOMALOUS LOW LEVEL ELY JET EXPECTED TO STRENGTHEN
TO GREATER THAN 5 STD FROM CLIMATOLOGY IN RESPONSE TO THIS
DEEPENING LOW. THIS WL CONT TO SUPPORT STRONG ISENTROPIC LIFT
OVER THE LOW LEVEL COLD DOME EXPECTED TO REMAIN ENTRENCHED TO
THE EAST OF THE APPALACHIANS. ADDITIONAL SNOW TOTALS IN THE 6 INCH
TO FOOT PLUS RANGE POSSIBLE FROM PANHANDLE OF WV EWD ACRS NRN
VA...MOST OF MD......NRN DE...SRN PA AND INTO SRN-CNTRL NJ. THIS WL
BRING STORM TOTALS THRU THE DAY 1 PERIOD IN THE 1-2' RANGE FOR THE
MID ATL. WITH STRONG LOW LEVEL ELY FLOW...THERE WL LIKELY BE A
PERIOD OF SLEET MIXING IN FOR PORTIONS OF THE MID ATL FROM THE I-95
CORRIDOR EWD. THE ICING POTENTIAL THIS PERIOD DOES NOT APPEAR
TO BE AS GREAT ACRS NC AS PREV PERIOD AS BULK OF PCPN WL BE TO THE
NORTHEAST OF THE STATE. STILL POTENTIAL FOR PROLONGED FREEZING
DRIZZLE IN THE LOW LEVEL COLD WEDGE...BUT PROBABILITIES OF .25"+
ICING KEPT AT LOW GIVEN EXPECTED MARGINAL QPF AMTS.

DAY2 HEAVY SNOW AND ICING FCST VT FEB 17/1200 UTC THRU FEB 18/1200
UTC
REFERENCE AWIPS GRAPHICS UNDER...HEAVY SNOW FCST

NRN MID ATL/DOWNSTATE NY/SRN NEW ENGLAND....

THE PRESIDENT'S DAY STORM PART II EXPECTED TO PRESS NEWD INTO THE
NRN MID ATL...NYC METRO AREA...DOWNSTATE NY AND INTO SRN NEW
ENGLAND DURG DAY 2. ANOMALOUS LOW LEVEL ELY FLOW (GREATER
THAN 4 STD ABOVE CLIMATOLOGY) EXPECTED TO CONT AHEAD OF THIS LOW
PROVIDING STRONG ISENTROPIC LIFT ACRS THE NRN MID ATL NEWD INTO
SRN NEW ENGLAND. THE ETA AND GFS BEGIN TO SHOW SOME DIFFS BY THE
END OF THE PERIOD WHICH AFFECTS HOW FAR TO THE NORTH HEAVY
SNOW SPREADS. THE GFS IS STRONGER AND FARTHER TO THE NW THAN
THE ETA BY END OF DAY 2...AS IS THE CANADIAN. ATTM...WE ARE LEANING
TOWARD THE STRONGER FARTHER NWD SOLN. HVY SNOWS IN EXCESS OF
A FOOT LIKELY FROM ERN PA INTO SRN NY AND ACRS MOST OF SRN NEW
ENGLAND FROM MA SWD. THE TRACK OF THE LOW SUGGESTS THAT MOST
AREAS WL BE ALL SNOW DURG DAY 2 ACRS THE ABOVE MENTIONED
REGIONS. SOME MIX TO SLEET POSSIBLE ACRS FAR SERN NEW ENGLAND
INVOF CAPE COD AND THE ISLANDS.

OR CASCADES...

ADDITIONAL NERN PAC HT FALLS EXPECTED TO PUSH INLAND INTO THE PAC
NW DURG DAY 2. SNOW LEVELS EXPECTED TO BE FAIRLY LOW IN THE 3000-
4000 FT RANGE. QPF AMTS IN THE .50-1" RANGE IN THE UPSLOPE AREAS OF
THE OR CASCADES SHOULD SUPPORT AT LEAST A LOW PROBABILITY OF
18"+ SNOWS.

GRAPHICS AVAILABLE ON THE WEB AT http://WWW.HPC.NCEP.NOAA.GOV


ORAVEC