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Jan 22-23 East Coast Storm Discussion


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KGSP Afternoon Discussion is Out.

 

266
FXUS62 KGSP 202006
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
306 PM EST WED JAN 20 2016

...A SIGNIFICANT WINTER STORM IS EXPECTED LATE THURSDAY THROUGH
SATURDAY...

.SYNOPSIS...
A MOIST UPPER LEVEL DISTURBANCE WILL CROSS EAST OF THE CAROLINAS AND
NORTHEAST GEORGIA THIS EVENING. A STRONG LOW PRESSURE SYSTEM WILL
SPREAD WINTRY PRECIPITATION ACROSS THE AREA THURSDAY NIGHT INTO
SATURDAY...BEFORE DRY HIGH PRESSURE BUILDS IN ON SUNDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 235 PM EST...THE BEST DEEP MOISTURE AND FORCING BAND IS MOVING
EAST OF THE MOUNTAINS THIS AFTERNOON...AND WILL TRAVERSE THE
PIEDMONT THROUGH LATE AFTERNOON. THE IMPROVED PRECIPITATION RATES
HAVE WET BULBED SOUNDINGS BACK DOWN TO SUPPORT MAINLY SNOW...WITH
SOME SLEET MIXING IN AT TIMES. RATES SHOULD SLOWLY DIMINISH ACROSS
THE MOUNTAINS THROUGH 5 PM...WHILE PICKING UP ACROSS THE PIEDMONT
DURING THAT TIME. THE CURRENT SETUP OF THERMAL PROFILES...AND SFC
TEMPS RANGING FROM BELOW FREEZING IN NW SECTIONS TO MID TO UPPER 30S
SOUTHEAST...MAKES THE CURRENT HAZARD PRODUCTS APPEAR WELL PLACED. NO
FURTHER ADJUSTMENT TO THE ONGOING EVENT IS EXPECTED. STILL
ANTICIPATE MID LEVEL DRYING TO WRAP IN FROM THE WEST THROUGH EARLY
EVENING AND TRANSITION ANY LINGERING PRECIPITATION IN THE WESTERLY
FLOW TO LIGHT FREEZING RAIN OR FREEZING DRIZZLE. LIGHT ICE
ACCUMULATIONS WOULD IMPACT MAINLY WRN MOUNTAIN SECTIONS.

OTHERWISE...THE PHASING H5 VORT LOBE WILL MOVE EAST OF THE REGION
AFTER 00Z. BROAD BUT FLAT H5 RIDGING WILL DEVELOP OVERNIGHT THROUGH
THU AS HEIGHTS FALL SHARPLY FROM THE PLAINS TO THE TX GULF COAST.
MEANWHILE...SPRAWLING SFC HIGH PRESSURE WILL STRETCH FROM THE
MIDWEST TO THE MID ATLANTIC TO REINFORCE COLD AIR OVER THE REGION
THROUGH THURSDAY. DEEPER MOISTURE WILL BE KNOCKING ON THE DOOR FROM
THE SOUTH BY LATE THURSDAY AHEAD OF THE NEXT SYSTEM AS LOW LEVEL
UPGLIDE BEGINS ON THE BACKING SRLY FLOW. TEMPERATURES SHOULD WARM
INTO THE 40S MOST AREAS ON THU TO PERMIT MELTING OF ANY LIGHT ACCUMS
FROM TODAY/S EVENT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 300 PM WEDNESDAY...MODELS CONTINUE TO BE IN GOOD
AGREEMENT...WITH SUBTLE DIFFERENCES IN EXACT DETAILS IN THIS
UPCOMING MAJOR STORM.

THE STORM STILL LOOKS MILLER-B-LIKE...WITH A SFC LOW DEVELOPING OVER
THE LWR MISSISSIPPI VALLEY THURSDAY...THEN A SECONDARY LOW WILL
BECOME DOMINANT ALONG THE CAROLINA COAST BY FRIDAY EVENING. THE LOW
WILL DEEPEN AS A STRONG NOR/EASTER ON SATURDAY...AND LIFT OUT THE
SEA ON SUNDAY. THE STRONGEST FORCING WILL BE FROM ABOUT 12Z FRIDAY
TO 12Z SATURDAY...AS A NEUTRAL-TILTED SLOW-MOVING CLOSED UPPER LOW
CROSSES THE AREA. AS THE LOW CROSSES...A SELY LLJ OF AROUND 50 KTS
WILL PRODUCE STRONG LLVL LIFT ATOP A STRONG COLD AIR DAMMING (CAD)
WEDGE.

THE PROFILES AND THICKNESS NOMOGRAMS ALL SHOW A SIMILAR THEME...WITH
CAD STRENGTHENING AS THE LOW PRES SYSTEM APPROACHES FROM THE WEST. I
USED A 2:1 BLEND OF NAM/GFS FOR PROFILES AND A TOP-DOWN APPROACH FOR
THE WX GRIDS AND ESTABLISH THE P-TYPE EVOLUTION. THIS RESULTS IN
MOSTLY SNOW AND SLEET ACRS MOST OF THE MTNS WITHIN THE WEDGE...AND
ACRS THE NC FOOTHILLS AND NC PIEDMONT. TO THE SOUTH AND TOWARD THE
EDGES OF THE WEDGE IS WHERE P-TYPES GET COMPLICATED. OVERALL...FCST
SNDGS SHOW POTENTIAL FOR SEVERAL HOURS OF FREEZING RAIN ACRS THE
PIEDMONT. BLENDING IN THE RAW MODEL TEMPS FOR FRIDAY INTO FRIDAY
NIGHT...I GET A SWATH OF ICE ACRS THE NORTHERN UPSTATE AND ALONG
I-85 TOWARD THE TRIAD. USING THE WPC QPF AND STICKING CLOSE TO THEIR
SNOW-LIQUID RATIOS...I GET STORM TOTAL SNOW OF 8-12 INCHES ACRS THE
MTNS...TAPERING OFF AS USE GO SOUTH AND EAST. FOR ICE...THE CONCERN
IS FOR A QUARTER TO HALF INCH (0.25-0.50") OF ACCUMS FOR PORTIONS OF
THE PIEDMONT. THE DETAILS WILL LIKELY CHANGE WITH NEW GUIDANCE
TONIGHT AND TOMORROW. BUT CONFIDENCE IS HIGH ENUF TO WARRANT A
WINTER STORM WATCH. THE MTN SECTION OF THE WATCH IS FOR MOSTLY SNOW
AND SLEET AND ALSO ENCOMPASSES THE WRAP-AROUND/NWFS ACCUMS SATURDAY
NIGHT. THE PIEDMONT SECTION WILL HIGHLIGHT THE FREEZING RAIN AND
WINTRY MIX...AND WILL END A LITTLE EARLIER (00Z SUNDAY).

&&

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Snippet from KCAE 3PM discussion:

 

 

 

THIS LOOKS TO BE A POTENTIALLY SIGNIFICANT QPF EVENT WITH LIQUID
ACCUMULATIONS OF A 0.50-1.00 INCH WITH ACCUMULATING FREEZING RAIN
ACROSS PARTS OF THE NORTHERN MIDLANDS COUNTIES. WILL INCLUDE SOME
LIGHT ICE ACCUMULATION ACROSS THE NORTHERN MIDLANDS WITH THIS
FORECAST ISSUANCE BUT WILL HOLD OFF ON ANY HEADLINES AND ALLOW
LATER SHIFTS TO VIEW NEW DATA AND ISSUE A WATCH FOR
LANCASTER/CHESTERFIELD IF NEEDED.
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KGSP Afternoon Discussion is Out.

 

266

FXUS62 KGSP 202006

AFDGSP

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC

306 PM EST WED JAN 20 2016

...A SIGNIFICANT WINTER STORM IS EXPECTED LATE THURSDAY THROUGH

SATURDAY...

.SYNOPSIS...

A MOIST UPPER LEVEL DISTURBANCE WILL CROSS EAST OF THE CAROLINAS AND

NORTHEAST GEORGIA THIS EVENING. A STRONG LOW PRESSURE SYSTEM WILL

SPREAD WINTRY PRECIPITATION ACROSS THE AREA THURSDAY NIGHT INTO

SATURDAY...BEFORE DRY HIGH PRESSURE BUILDS IN ON SUNDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...

AS OF 235 PM EST...THE BEST DEEP MOISTURE AND FORCING BAND IS MOVING

EAST OF THE MOUNTAINS THIS AFTERNOON...AND WILL TRAVERSE THE

PIEDMONT THROUGH LATE AFTERNOON. THE IMPROVED PRECIPITATION RATES

HAVE WET BULBED SOUNDINGS BACK DOWN TO SUPPORT MAINLY SNOW...WITH

SOME SLEET MIXING IN AT TIMES. RATES SHOULD SLOWLY DIMINISH ACROSS

THE MOUNTAINS THROUGH 5 PM...WHILE PICKING UP ACROSS THE PIEDMONT

DURING THAT TIME. THE CURRENT SETUP OF THERMAL PROFILES...AND SFC

TEMPS RANGING FROM BELOW FREEZING IN NW SECTIONS TO MID TO UPPER 30S

SOUTHEAST...MAKES THE CURRENT HAZARD PRODUCTS APPEAR WELL PLACED. NO

FURTHER ADJUSTMENT TO THE ONGOING EVENT IS EXPECTED. STILL

ANTICIPATE MID LEVEL DRYING TO WRAP IN FROM THE WEST THROUGH EARLY

EVENING AND TRANSITION ANY LINGERING PRECIPITATION IN THE WESTERLY

FLOW TO LIGHT FREEZING RAIN OR FREEZING DRIZZLE. LIGHT ICE

ACCUMULATIONS WOULD IMPACT MAINLY WRN MOUNTAIN SECTIONS.

OTHERWISE...THE PHASING H5 VORT LOBE WILL MOVE EAST OF THE REGION

AFTER 00Z. BROAD BUT FLAT H5 RIDGING WILL DEVELOP OVERNIGHT THROUGH

THU AS HEIGHTS FALL SHARPLY FROM THE PLAINS TO THE TX GULF COAST.

MEANWHILE...SPRAWLING SFC HIGH PRESSURE WILL STRETCH FROM THE

MIDWEST TO THE MID ATLANTIC TO REINFORCE COLD AIR OVER THE REGION

THROUGH THURSDAY. DEEPER MOISTURE WILL BE KNOCKING ON THE DOOR FROM

THE SOUTH BY LATE THURSDAY AHEAD OF THE NEXT SYSTEM AS LOW LEVEL

UPGLIDE BEGINS ON THE BACKING SRLY FLOW. TEMPERATURES SHOULD WARM

INTO THE 40S MOST AREAS ON THU TO PERMIT MELTING OF ANY LIGHT ACCUMS

FROM TODAY/S EVENT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...

AS OF 300 PM WEDNESDAY...MODELS CONTINUE TO BE IN GOOD

AGREEMENT...WITH SUBTLE DIFFERENCES IN EXACT DETAILS IN THIS

UPCOMING MAJOR STORM.

THE STORM STILL LOOKS MILLER-B-LIKE...WITH A SFC LOW DEVELOPING OVER

THE LWR MISSISSIPPI VALLEY THURSDAY...THEN A SECONDARY LOW WILL

BECOME DOMINANT ALONG THE CAROLINA COAST BY FRIDAY EVENING. THE LOW

WILL DEEPEN AS A STRONG NOR/EASTER ON SATURDAY...AND LIFT OUT THE

SEA ON SUNDAY. THE STRONGEST FORCING WILL BE FROM ABOUT 12Z FRIDAY

TO 12Z SATURDAY...AS A NEUTRAL-TILTED SLOW-MOVING CLOSED UPPER LOW

CROSSES THE AREA. AS THE LOW CROSSES...A SELY LLJ OF AROUND 50 KTS

WILL PRODUCE STRONG LLVL LIFT ATOP A STRONG COLD AIR DAMMING (CAD)

WEDGE.

THE PROFILES AND THICKNESS NOMOGRAMS ALL SHOW A SIMILAR THEME...WITH

CAD STRENGTHENING AS THE LOW PRES SYSTEM APPROACHES FROM THE WEST. I

USED A 2:1 BLEND OF NAM/GFS FOR PROFILES AND A TOP-DOWN APPROACH FOR

THE WX GRIDS AND ESTABLISH THE P-TYPE EVOLUTION. THIS RESULTS IN

MOSTLY SNOW AND SLEET ACRS MOST OF THE MTNS WITHIN THE WEDGE...AND

ACRS THE NC FOOTHILLS AND NC PIEDMONT. TO THE SOUTH AND TOWARD THE

EDGES OF THE WEDGE IS WHERE P-TYPES GET COMPLICATED. OVERALL...FCST

SNDGS SHOW POTENTIAL FOR SEVERAL HOURS OF FREEZING RAIN ACRS THE

PIEDMONT. BLENDING IN THE RAW MODEL TEMPS FOR FRIDAY INTO FRIDAY

NIGHT...I GET A SWATH OF ICE ACRS THE NORTHERN UPSTATE AND ALONG

I-85 TOWARD THE TRIAD. USING THE WPC QPF AND STICKING CLOSE TO THEIR

SNOW-LIQUID RATIOS...I GET STORM TOTAL SNOW OF 8-12 INCHES ACRS THE

MTNS...TAPERING OFF AS USE GO SOUTH AND EAST. FOR ICE...THE CONCERN

IS FOR A QUARTER TO HALF INCH (0.25-0.50") OF ACCUMS FOR PORTIONS OF

THE PIEDMONT. THE DETAILS WILL LIKELY CHANGE WITH NEW GUIDANCE

TONIGHT AND TOMORROW. BUT CONFIDENCE IS HIGH ENUF TO WARRANT A

WINTER STORM WATCH. THE MTN SECTION OF THE WATCH IS FOR MOSTLY SNOW

AND SLEET AND ALSO ENCOMPASSES THE WRAP-AROUND/NWFS ACCUMS SATURDAY

NIGHT. THE PIEDMONT SECTION WILL HIGHLIGHT THE FREEZING RAIN AND

WINTRY MIX...AND WILL END A LITTLE EARLIER (00Z SUNDAY).

&&

 

 

Man, LOVE the GFS/NAM around here huh?  No Euro blend at all or a mention.  I'd love to get a rationale as to why? 

 

Also, I'm curious why the piedmont precip would end earlier in the piedmont than the mountains? NW flow snows?  You'd think the further east you are, the more you'd be under the western edge of the storm off the coast...

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Any reason why calls I'm reading in the media/NWS aren't matching model results for RDU I'm reading here...? 

Models are tools used to help make forecasts.  The weather doesn't always match what a model depicts two days prior.  Forecasters usually do not go for predicting extremes far in advanced.  This question gets asked every storm. 

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I'm just north of Raleigh, but Wakefield VA office just issued WSW for its area.

Have a place at the lake on NC/VA border so o get notifications for there on my phone.

NCZ012-VAZ084-086>090-092-210430-

/O.NEW.KAKQ.WS.A.0001.160122T1200Z-160124T1200Z/

NORTHAMPTON NC-GLOUCESTER-MATHEWS-GREENSVILLE-SUSSEX-SURRY-

JAMES CITY-SOUTHAMPTON-

INCLUDING THE CITIES OF...MARGARETTSVILLE...EMPORIA...WAKEFIELD...

WILLIAMSBURG...FRANKLIN

317 PM EST WED JAN 20 2016

...WINTER STORM WATCH IN EFFECT FROM FRIDAY MORNING THROUGH

SUNDAY MORNING...

THE NATIONAL WEATHER SERVICE IN WAKEFIELD HAS ISSUED A WINTER

STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY MORNING THROUGH

SUNDAY MORNING.

* AREAS AFFECTED: INTERIOR SOUTHEAST VIRGINIA AND NORTHAMPTON

COUNTY NORTH CAROLINA.

* HAZARDS: SNOW...MIXED WITH SLEET AND FREEZING RAIN...AND GUSTY

WINDS.

* ACCUMULATIONS: 3 INCHES OR GREATER SNOW. UP TO ONE TENTH OF AN

INCH OF ICE IS POSSIBLE...MAINLY IN WESTERN TIDEWATER AREAS

INTO SOUTH CENTRAL VIRGINIA AND FAR INTERIOR NORTHEAST NORTH

CAROLINA.

* TEMPERATURES: RISING INTO THE LOWER TO MID 30S LATE

FRIDAY...THEN INTO THE MID AND UPPER 30S FRIDAY NIGHT.

* WINDS: NORTHEAST WINDS 10 TO 20 MPH FRIDAY...BECOMING NORTH AND

INCREASING TO 15 TO 25 MPH AND GUSTY FRIDAY NIGHT AND SATURDAY.

* TIMING: SNOW WILL OVERSPREAD THE AREA FRIDAY MORNING AND

MIDDAY...GRADUALLY MIXING WITH SLEET AND FREEZING RAIN FRIDAY

AFTERNOON INTO THE EVENING. PERIODS OF FREEZING RAIN OR RAIN ARE

EXPECTED FRIDAY NIGHT INTO SATURDAY. A CHANGE BACK TO A PERIOD

OF SNOW IS POSSIBLE SATURDAY AFTERNOON.

* IMPACTS: ROADS WILL BECOME SNOW AND ICE COVERED AND HAZARDOUS.

TRAVEL WILL LIKELY BE SUBSTANTIALLY IMPACTED FRIDAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT

SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.

CONTINUE TO MONITOR THE LATEST FORECAST

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