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Pattern Fab Feb

Official guidance from GSP

KEY MESSAGE 2: A BRIEF RETURN OF WINTER WEATHER WITH VERY GUSTY NW
WINDS, ACCUMULATING SNOW FOR PORTIONS OF THE MOUNTAINS AND BELOW
NORMAL TEMPERATURES SUNDAY THROUGH TUESDAY.

NORTHWEST FLOW REALLY RAMPS UP ACROSS THE FORECAST AREA ON
SUNDAY, AS A COASTAL LOW RAPIDLY DEEPENS IN THE MID-ATLANTIC
COASTAL WATERS. A TIGHT PRESSURE GRADIENT AND STRONG LOW-LEVEL
CAA WILL SUPPORT VERY GUSTY WINDS ACROSS THE AREA BY EARLY AFTN
AND CONTINUING INTO SUNDAY NIGHT. PEAK GUSTS OF 30-40 MPH CANNOT
BE RULED OUT ACROSS MOST OF THE FOOTHILLS AND PIEDMONT SUNDAY
AFTN, BUT PEAK GUSTS INTO ADVISORY-CRITERIA RANGE OF 45-60 MPH
WILL BE POSSIBLE ABOVE 3500 FT HEADING INTO SUNDAY NIGHT. WITH
THE STRONGEST WINDS BEING IN LATE IN THE 2ND PERIOD AND INTO 3RD
PERIOD, WILL HOLD OFF ON ISSUING A WIND ADVISORY.

THERE MAY BE A BRIEF LULL IN SNOW SHOWER ACTIVITY IN THE MOUNTAINS
LATE SUNDAY MORNING THRU ABOUT MIDDAY, BUT MOISTURE SHOULD INCREASE
AGAIN IN THE AFTN AND RAMP UP SNOW SHOWERS ALONG THE TN BORDER. SNOW
ACCUMS WILL BE HIGHLY ELEVATION-DEPENDENT FOR THE FIRST FEW HOURS
OF THE EVENT DUE TO WARMER VALLEY TEMPS. THERE MAY ALSO BE A BAND
OF RAIN DEVELOPING WITHIN A DEFORMATION ZONE ASSOCIATED WITH THE
COASTAL LOW THAT COULD SET UP JUST EAST OF I-77. THIS IS NOT
EXPECTED TO BE HEAVY AND SHOULD BE ALL RAIN. OTHERWISE, SKIES
CLEAR OUT AND TEMPS RETURN TO BELOW-NORMAL FOR HIGHS, MAINLY IN
THE 30 TO LOWER 40S IN THE MOUNTAINS AND UPPER 40S TO LOWER 50S
IN THE PIEDMONT.

THE NORTHWEST FLOW SNOW MACHINE WILL BE CRANKING UP SUNDAY EVENING,
AS A STRONG MID-LEVEL SPEED MAX DIGS FROM THE CORN BELT SUNDAY
EVENING TO THE SOUTH CAROLINA COAST BY MONDAY MORNING. IN RESPONSE,
THE DEPTH OF POST-FRONTAL MOISTURE COVERING THE TN VALLEY AND MUCH
OF THE SOUTHERN APPALACHIANS WILL INCREASE TO NEAR 700 MB...WITH
TEMPS AT THE TOP OF THE MOIST LAYER COOLING TO -16 TO -20C. WHILE
THE DEPTH OF THE MOIST LAYER IS FORECAST TO BECOME GRADUALLY MORE
SHALLOW LATE SUNDAY NIGHT THROUGH MONDAY, TEMPS AT THE TOP OF THE
MOIST LAYER REMAIN NO WARMER THAN -16 UNTIL TUE EVENING. THIS MEANS
A PROTRACTED PERIOD...30 HOURS OR MORE OF A HIGH PROBABILITY OF
DENDRITIC ICE CRYSTAL GROWTH AND EFFICIENT SNOW:LIQUID RATIOS...ALL
WITHIN PERSISTENT STRONG NW UPSLOPE FLOW. SOLID WINTER WX ADVISORY
CRITERIA SNOWFALL IS LIKELY FROM THE HIGHER ELEVATIONS OF THE
SMOKIES NORTHEAST ACROSS THE MOUNTAINS AND VALLEYS OF THE OTHER NC
COUNTIES BORDERING TN. CURRENT FORECAST STORM TOTALS ARE GENERALLY
IN THE 1-4" RANGE IN THE VALLEYS NORTH OF I-40, WITH ABOUT TWICE
THAT RANGE EXPECTED ABOVE 3500 FEET. ESPECIALLY FAVORED UPSLOPE/HIGH
ELEVATION AREAS ALONG THE STATE LINE WILL LIKELY SEE AROUND A FOOT
OR MORE. THIS IS ENOUGH TO WARRANT ISSUANCE OF A WINTER STORM
WARNING FOR AVERY COUNTY AS WELL AS THE HIGH ELEVATIONS OF MITCHELL
COUNTY, WHILE WINTER WEATHER ADVISORIES WILL BE ISSUED FOR YANCEY,
MADISON, HAYWOOD, AND THE HIGH ELEVATIONS OF SWAIN.

WITH VERY WINDY (LIKELY WIND ADVISORY-LEVEL CONDITIONS OVER THE
MOUNTAINS) AND COLD ADVECTION CONTINUING INTO SUNDAY NIGHT,
WIDESPREAD WIND CHILL VALUES IN THE SINGLE DIGITS ARE EXPECTED
ACROSS THE MOUNTAINS, WITH SUB-ZERO READINGS LIKELY ABOVE 4000 FEET
OR SO. CURRENT INDICATIONS THAT THIS WILL BE "VERY CLOSE, BUT NOT
QUITE" IN TERMS OF REACHING COLD WEATHER ADVISORY CRITERIA, BUT
CAN'T RULE OUT THAT ONE WILL EVENTUALLY BE NEEDED FOR THE HIGHER
ELEVATIONS AND/OR THE NORTHERN NC MOUNTAINS. SNOW SHOWERS WILL
FINALLY STEADILY TAPER OFF MONDAY NIGHT, WITH DRY AND COOLER-THAN-
NORMAL CONDITIONS EXPECTED THROUGH TUESDAY. MOUNTAIN WIND CHILL
VALUES WILL AGAIN BE LOW MON NIGHT, BUT WITH WINDS STEADILY
DIMINISHING, THEY ARE EXPECTED TO BE A LITTLE HIGHER THAN ON SUNDAY
NIGHT.
 
1d7fa79a9cb3d0237f229b67565d9e14.gif

6z NAM 3km showing a changeover to snow for the NE 1/4 of NC later this evening.


Sent from my iPhone using Tapatalk
 
Downeastnc said:
NWS has actually introduced a chance of accumulation here though only a half inch. They do mention a 10-20% chance we exceed a inch.
Click to expand...

c456276028eff615b9561ac41c17a137.jpg

Yeah it’ll be nice to get a small morsel of the big cake they’ll be having further north.


Sent from my iPhone using Tapatalk
 
KEY MESSAGE 1: A BRIEF RETURN OF WINTER WEATHER WITH VERY GUSTY NW
WINDS, ACCUMULATING SNOW FOR PORTIONS OF THE MOUNTAINS, AND BELOW
NORMAL TEMPERATURES SUNDAY THROUGH TUESDAY.

NW FLOW SIGNIFICANTLY RAMPS UP ACROSS THE FCST AREA TODAY, AS A
COASTAL LOW RAPIDLY DEEPENS OVER THE MID-ATLANTIC COASTAL WATERS. A
TIGHT PRESSURE GRADIENT AND STRONG LOW-LEVEL CAA WILL SUPPORT VERY
GUSTY WINDS ACROSS OUR AREA BY THE EARLY AFTERNOON AND CON-TINUING
INTO TONIGHT. PEAK GUSTS OF 30 TO 40 MPH WILL BE POSSIBLE ACROSS
MOST OF THE FOOTHILLS AND PIEDMONT THIS AFTERNOON, WITH PEAK GUSTS
INTO ADVISORY-CRITERIA RANGE OF 45 TO 60 MPH POSSIBLE ABOVE 3500 FT
HEADING INTO TONIGHT.

THERE COULD BE A BRIEF LULL IN SNOW SHOWER ACTIVITY OVER THE MTNS
LATER THIS MORNING THRU ABOUT MIDDAY, BUT MOISTURE SHOULD INCREASE
AGAIN THIS AFTERNOON WITH SNOW SHOWERS RAMPING UP ALONG THE NC/TN
BORDER. SNOW ACCUMS WILL BE HIGHLY ELEVATION-DEPENDENT FOR THE FIRST
FEW HRS OF THE EVENT DUE TO WARMER VALLEY TEMPS. THERE MAY ALSO BE A
BAND OF RAIN DEVELOPING WITHIN A DEFORMATION ZONE ASSOCIATED WITH
THE COASTAL LOW THAT COULD SET UP JUST EAST OF I-77. ANY QPF FROM
THIS WOULD BE MINIMAL. OTHERWISE, SKIES CLEAR OUT AND TEMPS REMAIN
BELOW NORMAL TODAY.

THE NW FLOW SNOW MACHINE WILL BE CRANKING UP THIS EVENING, AS A
STRONG MID-LEVEL SPEED MAX DIGS FROM THE CORN BELT TO THE SC COAST
BY MONDAY MORNING. IN RESPONSE, THE DEPTH OF POST-FRONTAL MOISTURE
COVERING THE TN VALLEY AND MUCH OF THE SOUTHERN APPALACHIANS WILL
INCREASE TO NEAR 700 MB, WITH TEMPERATURES AT THE TOP OF THE MOIST
LAYER COOLING TO -16 TO -20C. THIS WILL ALLOW FOR A PROTRACTED
PERIOD (AT LEAST 24 TO 30 HRS) OF OPTIMIZED DENDRITIC ICE CRYSTAL
GROWTH AND ABOVE-AVERAGE SNOW TO LIQUID RATIOS, ALL WITHIN
PERSISTENT NW UPSLOPE FLOW. SOLID WINTER WX ADVISORY CRITERIA
SNOWFALL IS LIKELY FROM THE HIGHER ELEVATIONS OF THE SMOKIES
NORTHEAST ACROSS THE MTNS AND VALLEYS OF THE OTHER NC COUNTIES
BORDERING TN. CURRENT FCST STORM TOTALS ARE GENERALLY IN THE 1 TO 4
INCH RANGE IN THE VALLEYS NORTH OF I-40, AND ABOUT TWICE THAT RANGE
EXPECTED ABOVE 3500 FEET. ESPECIALLY FAVORED UPSLOPE/HIGH ELEVATION
AREAS ALONG THE STATE LINE WILL LIKELY SEE A FOOT OR MORE. THUS, A
WINTER STORM WARNING IS IN EFFECT FOR AVERY COUNTY AS WELL AS THE
HIGH ELEVATIONS OF MITCHELL COUNTY. A WINTER WEATHER ADVISORY IS IN
EFFECT FOR YANCEY, MADISON, HAYWOOD, AND THE HIGH ELEVATIONS OF
SWAIN.

WITH VERY WINDY AND COLD ADVECTION CONTINUING THRU SUNDAY NIGHT,
WIDESPREAD WIND CHILL VALUES IN THE SINGLE DIGITS ARE EXPECTED
ACROSS THE NC MTNS, WITH SUB-ZERO READINGS LIKELY ABOVE ROUGHLY 4000
FEET. AT PRESENT, THOSE AREAS DON'T QUITE REACH COLD WEATHER
ADVISORY CRITERIA, BUT IF THEY TREND ANY COLDER AN ADVISORY MAY BE
NEEDED FOR THE HIGHER ELEVATIONS AND/OR THE NORTHERN NC MTNS. SNOW
SHOWERS WILL FINALLY TAPER OFF MONDAY NIGHT, WITH DRY AND BELOW
NORMAL TEMPERATURES EXPECTED THRU TUESDAY. MOUNTAIN WIND CHILL
VALUES WILL BE LOW AGAIN MONDAY NIGHT, BUT WITH WINDS STEADILY
WEAKENING WIND CHILLS SHOULDN'T BE AS COLD AS SUNDAY NIGHT/EARLY
MONDAY.
 
Boston has a decent shot at a top 10 snowfall of all time, perhaps even top 5.

* WHAT...Blizzard conditions expected. Total snow accumulations
between 18 and 25 inches. Winds gusting as high as 75 mph.

* WHERE...Portions of eastern, northeastern, and southeastern
Massachusetts and northern and southern Rhode Island.

* WHEN...From 4 PM this afternoon to 7 AM EST Tuesday.
 
The wind here is putting on enough of a show for a wind advisory as the refreshing Canadian air continues to rush in with virtually cloudless skies. Winds have already gusted to as high as 44 mph at the airport! I’ve been needing to clear my roof of leaves/debris. Well, Mother Nature has done me a favor and already cleared a good portion of it today with the yard now a mess! It was ~64 at sunrise and it’s now 60.6. Looking forward to walking!

Expecting a slow fall the rest of the afternoon as we head for low 30s by morning. Cold wx advisory is out. Tomorrow’s high is forecasted to be only in the upper 40s, which compares to yesterday’s 86. There’s a near 100% chance of a freeze tomorrow night. I assume there will be freeze watches soon. N FL has them for tomorrow night.
 
Last edited:
SD said:
Solid precipitation week for a good part of the area, unfortunately not everyone though View attachment 194445
Click to expand...

I forgot to post my rainfall from last night through just after sunrise. I got 0.65”. That added to my 0.75” of Feb 15th gives me a beneficial 1.4” for the 7 day period covered by your posted map, which fits perfectly with the colors on it for my area.
 
  • Thank You
Reactions: SD
DEEP MOISTURE ASSOCIATED WITH THE UPPER LOW WILL CONTINUE TO BATTER
AGAINST THE MOUNTAINS, LEADING TO A PROLONGED PERIOD OF NW FLOW
SNOW. SOME DISAGREEMENT IN QPF AMONG OPERATIONAL AND ENSEMBLE
GUIDANCE, BUT CERTAINLY COULD SEE SOME HEFTY AMOUNTS GIVEN THE
EXTREMELY COLD TEMPS AND HIGH SNOW RATIOS. NBM ACCUMS WERE QUITE A
BIT HIGHER THAN LAST NIGHT WITH SOME AREAS IN THE SMOKIES AND NEAR
ROAN MTN APPROACHING 20". PULLED BACK ON THOSE AMOUNTS GIVEN THE
SHALLOW MOISTURE BUT CONSIDERING 50KT WINDS AT 850MB TONIGHT PLUS
MULTIPLE ROUNDS OF DPVA SPINNING AROUND THE LARGER VORT LOBE, WOULD
NOT BE SURPRISED IF SOME AREAS OUTPERFORM THE CURRENT FORECAST.
OPERATIONAL GFS KEEPS 700MB FAIRLY SATURATED THROUGH 15-18Z MONDAY
AT TEMPS -15 TO -12C, SO PLENTY OF DENDRITIC SNOW GROWTH POTENTIAL.
HIGHEST AMOUNTS WILL AS USUAL BE AT THE HIGHEST ELEVATIONS SO WILL
CONTINUE PRODUCTS AS THEY ARE (WSW FOR AVERY AND >3500FT MITCHELL,
WSY FOR MOST OF THE REST OF THE BORDER COUNTIES EXCEPT >3500FT
SWAIN). CERTAINLY EXPECT SOME SNOW SHOWERS AT THE LOWER ELEVATIONS
BUT MINIMAL IF ANY ACCUMULATIONS.
 
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