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November 15 Snow/Ice Chance

showmethesnow

By showmethesnow,
in Mid Atlantic

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Ji

Ji

Posted
Posted
1 minute ago, LP08 said:

Digging through soundings on the 3k show the area around DCA popping to 33 with some shallow warm layers on the way through the column.  It's very close throughout. 

if there is half a degree model error aloft..it could be Nov 87 again lol

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Eskimo Joe

Eskimo Joe

Posted
Posted
Quote 

.NEAR TERM /THROUGH TONIGHT/...
LATEST SURFACE ANALYSIS DEPICTS A STALLED FRONT ALONG THE
SOUTHEAST COAST AND HIGH PRESSURE EXTENDING FROM THE GREAT LAKES
TO TEXAS. THE 12Z IAD SOUNDING MEASURED A PRECIPITABLE WATER
VALUE OF ONLY 0.17 INCHES. UPPER JET DYNAMICS CONTINUE TO BRING
RATHER DENSE CIRRUS OVER THE REGION, ALTHOUGH THERE ARE SOME 
THIN SPOTS TO ALLOW SOME FILTERED SUN. OVERALL, THE THEME OF THE
DAY WILL BE CLOUDIER VERSUS SUNNIER. THE CLOUDS MIGHT KEEP 
TEMPERATURES FROM REACHING MAXIMUM POTENTIAL, BUT LITTLE CHANGE 
WAS NEEDED TO THE HIGH TEMPERATURE FORECAST IN THE UPPER 30S TO 
MID 40S. A NORTHWEST BREEZE WILL KEEP IT FEELING CHILLY. WILL BE
EVALUATING 12Z COMPUTER MODEL GUIDANCE BEFORE MAKING ANY CALLS
ON WINTER WEATHER HEADLINES FOR TONIGHT AND TOMORROW.

TONIGHT, DEVELOPING UPPER LOW TO THE SOUTHWEST AND SURFACE LOW
NEAR THE SOUTHEAST COAST WILL START SPREADING MOISTURE RAPIDLY
NORTHEASTWARD. CLOUDS WILL THICKEN THIS EVENING, WITH
PRECIPITATION SPREADING ACROSS THE REGION OVERNIGHT. THERMAL
PROFILES ARE HIGHLY QUESTIONABLE BETWEEN THE DIFFERENT MODELS,
WITH A SIGNIFICANT RANGE OF POSSIBILITIES ACROSS THE REGION.
MANY AREAS ARE DEPICTED WITH MULTIPLE P-TYPES LATE TONIGHT
DEPENDING ON THE MODEL ONE IS LOOKING AT, WITH THE NAM BEING AT
THE COLDER END AND THE GFS TOWARDS THE WARM SIDE. THE EC IS
OVERALL COLDER TOO, THOUGH AVAILABLE RESOLUTION MAY NOT BE
DEPICTING SMALL WARM LAYERS ACCURATELY. THUS, ALLOW FOR SLEET
AND RAIN ALONG AND EAST OF I-95 LATE TONIGHT, WITH MAINLY SLEET,
FREEZING RAIN AND SNOW FURTHER WEST. SOME AREAS COULD SEE A
QUICK THUMP OF SNOW WITH SEVERAL INCHES, EVEN ALONG I-95, IF THE
COLDER SOLUTIONS ARE CORRECT, WHILE THE WARMER MODELS SUGGEST
LITTLE SNOW WILL FALL ANYWHERE IN THE FORECAST AREA. HOWEVER, WE
ARE CONFIDENT THAT TEMPS WILL SETTLE BELOW FREEZING WEST OF I-95
THANKS TO COLD AIR DAMMING FROM THE HIGH BUILDING ACROSS
SOUTHEAST CANADA, WITH SLIGHTLY WARMER TEMPS LIKELY CLOSER TO
THE TIDAL WATERS. WINDS WILL BECOME NORTH TO NORTHEAST AS THE
COLD AIR DRAINS SOUTH.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
STRENGTHENING LOW PRESSURE RAPIDLY MOVES NORTHEAST UP THE COAST
ON THURSDAY AND THURSDAY NIGHT AS UPPER LOW PUSHES NORTHEAST
TOWARD US FROM THE SOUTH-CENTRAL US. COLD HIGH PRESSURE WILL
KEEP DAMMING GOING OVER THE WESTERN PORTIONS OF THE FORECAST
AREA, WHILE SOME COLD AIR EROSION LOOKS LIKELY EAST OF THE BLUE
RIDGE. THUS, HAVE SLEET/RAIN ALONG AND EAST OF I-95
TRANSITIONING TO PLAIN RAIN THROUGH THE DAY, WITH
SNOW/SLEET/FREEZING RAIN BETWEEN THE BLUE RIDGE AND I-95
CHANGING TO SLEET/FREEZING RAIN AND THEN RAIN VERY LATE. FROM
THE BLUE RIDGE WEST, COLD AIR LIKELY GETS STUCK, SO KEEP TEMPS
AT OR BELOW FREEZING ALL DAY WITH SNOW/SLEET/FREEZING RAIN
TRANSITIONING MAINLY TO SLEET/FREEZING RAIN. POTENTIAL FOR
SIGNIFICANT SNOW AND ICE EXISTS, BUT AS NOTED EARLIER, FORECAST
SOUNDINGS DIFFER SIGNIFICANTLY AMONG THE GUIDANCE. STRONG WARM
ADVECTION IS PARTLY AT PLAY HERE, WHICH MAY MEAN THE WARM LAYER
IS MORE POTENT THAN MODELED BY THE COLDER GUIDANCE, THOUGH HEAVY
PRECIP MAY TEND TO ERODE THE WARM LAYER MORE EFFICIENTLY THAN 
THE WARM GUIDANCE DEPICTS. BOTTOM LINE IS THAT IN AREAS WHICH
STAY NEAR OR BELOW FREEZING, THE WEATHER IS LIKELY TO REMAIN
HAZARDOUS THROUGH THE DAY, BUT EXACTLY WHAT HAZARD WILL BE THE
WORST IS STILL A BIT UNCERTAIN. 

GIVEN THE HEAVY PRECIP EXPECTED, SNOW COULD PILE UP QUICKLY, AND
FREEZING RAIN ACCUMULATION IS ALSO POSSIBLY SIGNIFICANT. THERE
COULD EVEN BE AN INCH OR TWO OF PURE SLEET. THUS, EXPANDED
WINTER STORM WATCH A BIT FURTHER NORTH AND EAST. CONSIDERED
ADDING A TIER OF ADVISORIES EAST OF THE WATCH WITH THIS PACKAGE,
BUT GIVEN THE HIGHLY UNCERTAIN PROGGED TEMPS BOTH AT AND ABOVE
GROUND, IT SEEMED PRUDENT TO WAIT ONE MORE SHIFT.

EVEN WHERE PRECIP IS MAINLY RAIN, THE HAZARD OF HEAVY RAIN AND
POTENTIAL FLOODING WILL EXIST. SEE THE HYDRO SECTION BELOW FOR
MORE DETAILS.

THE SURFACE LOW QUICKLY LIFTS NORTHEAST OF THE REGION LATER
THURSDAY NIGHT INTO EARLY FRIDAY, BUT WITH SOME WRAPAROUND
MOISTURE ASSOCIATED WITH THE PASSING UPPER LOW, RAIN COULD
BRIEFLY CHANGE BACK TO SNOW/SLEET BEFORE ENDING. TEMPS WILL
LIKELY BE FAIRLY STEADY THURSDAY NIGHT.

FRIDAY INTO FRIDAY NIGHT, THE SYSTEM HEADS FURTHER AWAY AND WE
HAVE A COMPARATIVELY MILD WESTERLY FLOW SETTLING ACROSS THE
REGION. TEMPS WILL ACTUALLY BE NOTICEABLY MILDER ON FRIDAY AFTER
THE CLOUDS BREAK, WITH TEMPS MAKING A RUN AT 50. LOWS FRIDAY
NIGHT WILL BE CHILLY AGAIN, WITH TEMPS NEAR OR BELOW FREEZING -
HOWEVER, WITH HIGH PRESSURE IN NOMINAL CONTROL, IT SHOULD BE
DRY.

 

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Ji

Ji

Posted
Posted
Just now, mappy said:

just giving you a hard time. i hope it snows for all too. 

i mean i am sure were not going to get Nov 87 but even i wouldnt complain about 5 inches of sleet on Nov 14 lol. Now if it was Dec 14, i would be having a full meltdown. Sleet is awful to shovel....so i hope you get alot of it:)

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mappy

mappy

Posted
Posted
3 minutes ago, Ji said:

i mean i am sure were not going to get Nov 87 but even i wouldnt complain about 5 inches of sleet on Nov 14 lol. Now if it was Dec 14, i would be having a full meltdown. Sleet is awful to shovel....so i hope you get alot of it:)

pffft, ill let the rain wash it all away ;) 

3 minutes ago, WxWatcher007 said:

:lol: 

As Founder & CEO of The Panic Room, I am ashamed of my last post asking for sanity. 

Carry on my brothers and sisters, carry on. 

May chaos reign as we track our earliest winter wx event in at least half a decade. 

giphy.gif?cid=3640f6095bec376b5969376249

Ground too warm. All snow melts on contact. 

yeah that post was really out of character for you. asking for sanity. 

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snowmagnet

snowmagnet

Posted
Posted
9 minutes ago, WxWatcher007 said:

:lol: 

As Founder & CEO of The Panic Room, I am ashamed of my last post asking for sanity. 

Carry on my brothers and sisters, carry on. 

May chaos reign as we track our earliest winter wx event in at least half a decade. 

giphy.gif?cid=3640f6095bec376b5969376249

Ground too warm. All snow melts on contact. 

That's what they said in 1987. https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/11/10/weathermen-recall-the-record-veterans-day-snowstorm-that-totally-fooled-them-30-years-ago/?noredirect=on&utm_term=.c60940691e8a

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psuhoffman

psuhoffman

Posted
Posted
49 minutes ago, high risk said:

I really have a hard time accepting the GFS having most of the DC and Baltimore metro areas in the mid 30s tomorrow at 12z.     I think we've seen plenty of winter precipitation cases in which the GFS has failed to properly model evaporative cooling and then eroded low-level cold air too quickly.    While the NAMs can hold on to low-level cold air a little too long, their track record in this kind of setup is superior.      I'm not calling for an OMG snow here in the I-95 corridor, but a few hours of snow and then sleet (and perhaps a longer period for the next tier of counties north and west) is still very much on the table, IMO.

I'm still holding out some hope for that. As I told showmethesnow I can remember several examples the last couple years where the current gfs ran a couple degrees warm in these kinds of marginal situations because it didn't accurately depict evaporation cooling. Doesn't mean it will again this time but it's been a bit too warm enough times (think that feb storm last year) to still think things could break our way here. Breaking our way to me means 1-2" of snow/sleet before the flip around the cities.   

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mappy

mappy

Posted
Posted
1 minute ago, WxWatcher007 said:

Yeah, I should know better lol. 

But last year was a catastrophe on the board, and if we get close to that again I won't be posting. Period. 

Let's have fun and be crazy. Hard pass on miserable posters, attention seeking meltdowns, and lazy analysis. 

This is probably better for banter, sorry guys. Moving on. 

Yeah, I was kidding about the warm ground. :) 

sadly it takes everyone to keep their weenie-isms in check in order for it not to become a disaster. 

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MillvilleWx

MillvilleWx

Posted
Posted

I posted my thoughts briefly in the banter thread yesterday after I commented on something else. The trends for snow have back-peddled since I posted, but the threat of majority frozen is still in play for areas NW of 95 and out to I-81. Front end thump will need to arrive a little sooner than currently modeled, which is certainly possible with the WAA regime being forecast, but will ultimately not be able to overcome the warm nose bulging into the region in wake of the screaming H85 southeasterly winds aloft. Isothermal environment may hold firm a little longer for places along and west of the Blue Ridge, leading to a little longer chance of snow, but even they will see a flip to sleet and ZR as the warm nose pushes out to the Allegheny Front. This is a scenario where someone like Losetoa could hang on to snow the longest while most flip to sleet/zr due to his farther north and west location. 

After the flip, the question becomes, how firmly entrenched is the sub-freezing airmass at the surface? It does look like sleet signature gets eroded toward the late morning with most of the area switching to rain by noon, but the typical spots prone to longer period of CAD will be susceptible to maintaining an icy period into the PM before any transition takes shape. Most notably, areas along the Mason Dixon and the 81 corridor into the WV Panhandle will be the targets for that outcome. 

If I had to do a totals outlook, 1.5-4" out toward the 81 corridor and up into the Mason Dixon by Northern Carroll before a full flip to IP/ZR. This area may also never fully transition to rain, which would still argue for a Warning issued, or at least an Advisory with opportunity for an upgrade. Northern MoCo, Western Howard, South-Central Carroll, Hereford Zone in Baltimore, and Frederick County could see 1" before the flip with majority precip falling as IP/ZR before a full transition to rain by the PM. Around 95 and the major cities, a short period of snowfall will quickly transition to IP/ZR before a flip to straight rain before noon tomorrow, especially inside the beltway. 

Regardless of what happens, it's mid-November and the signal for a storm is pretty phenomenal for this time of year. The fact we can talk about frozen precip early is pretty rare, so enjoy the slop while you can. I'll be living vicariously by you guys as I enjoy my 55 and sun out here in West Texas. 

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MDstorm

MDstorm

Posted
Posted
12 minutes ago, MillvilleWx said:

I posted my thoughts briefly in the banter thread yesterday after I commented on something else. The trends for snow have back-peddled since I posted, but the threat of majority frozen is still in play for areas NW of 95 and out to I-81. Front end thump will need to arrive a little sooner than currently modeled, which is certainly possible with the WAA regime being forecast, but will ultimately not be able to overcome the warm nose bulging into the region in wake of the screaming H85 southeasterly winds aloft. Isothermal environment may hold firm a little longer for places along and west of the Blue Ridge, leading to a little longer chance of snow, but even they will see a flip to sleet and ZR as the warm nose pushes out to the Allegheny Front. This is a scenario where someone like Losetoa could hang on to snow the longest while most flip to sleet/zr due to his farther north and west location. 

After the flip, the question becomes, how firmly entrenched is the sub-freezing airmass at the surface? It does look like sleet signature gets eroded toward the late morning with most of the area switching to rain by noon, but the typical spots prone to longer period of CAD will be susceptible to maintaining an icy period into the PM before any transition takes shape. Most notably, areas along the Mason Dixon and the 81 corridor into the WV Panhandle will be the targets for that outcome. 

If I had to do a totals outlook, 1.5-4" out toward the 81 corridor and up into the Mason Dixon by Northern Carroll before a full flip to IP/ZR. This area may also never fully transition to rain, which would still argue for a Warning issued, or at least an Advisory with opportunity for an upgrade. Northern MoCo, Western Howard, South-Central Carroll, Hereford Zone in Baltimore, and Frederick County could see 1" before the flip with majority precip falling as IP/ZR before a full transition to rain by the PM. Around 95 and the major cities, a short period of snowfall will quickly transition to IP/ZR before a flip to straight rain before noon tomorrow, especially inside the beltway. 

Regardless of what happens, it's mid-November and the signal for a storm is pretty phenomenal for this time of year. The fact we can talk about frozen precip early is pretty rare, so enjoy the slop while you can. I'll be living vicariously by you guys as I enjoy my 55 and sun out here in West Texas. 

Appreciate your input.  Hope to hear from you frequently during this active (hopefully) winter.

 

MDstorm

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