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December Discobs 2020

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5 minutes ago, losetoa6 said:

Nothing beats tracking coastals year around but especially in winter . We've had a bunch this fall and winter . Bodes well I'd think for JFMA .I've seen many snows at 35-38 degrees too:snowing:

Good practice for when the blocking gets real. :bike:

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double hmmm... from LWX morning disco

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The cold front will pass through the area Thursday, likely
bringing some showers with it, especially across the
Allegheny/Potomac Highlands, northern VA, the Balt/Wash Metro
areas, and central MD. This is where there may be some
anafrontal characteristics (precip on the cold side) due to the
right entrance of an upper-level jet and a shortwave passing
through). While temps should still be warm enough for the ptype
to be rain for most areas, the rain will likely end as a period
of snow near the Allegheny Front in Garret, extreme western
Allegany, and western Grant counties. Snow amounts (if any)
should be light for most areas, but localized amounts around an
inch or two are possible during the morning commute in Garrett
County where the colder air will work its way in a little
sooner. The change over to snow is most likely going to be
during the early morning hours Friday for these areas (5-7 am).

The cold front will drop to the south Thursday night. There may
be a lull in precipitation as colder and drier air work its way
in from the north in associated with high pressure building to
our north. However, a closed low in the southern stream both at
the surface and upper-levels will begin moving northeast. Some
light rain across central VA perhaps into southern MD will
spread northeast and become steadier late Thursday night through
Friday morning. Rain will continue through Friday afternoon as
the low moves into the Midwest, allowing for warm and moist air
from the Gulf and Atlantic to overrun colder air in place. With
the colder air in place, this causes a concern for freezing
rain, especially across our northern and western areas. Latest
guidance continues to suggest that there will be enough low-
level cold air for temps to be near or below freezing late
Thursday night through midday Friday across northern/central MD,
northern VA, eastern WV, the Blue Ridge Mountains, and the
Allegheny/Potomac Highlands. A prolonged period of ice is
possible across these areas for a couple reasons. First, the
high building to our north during this time will advect some
drier air into the area, causing evaporative cooling when the
precip does move in. Second, there may even be some radiational
cooling across our northern areas with possible breaks in the
clouds overnight Thursday. A Winter Storm Watch (for a possible
Ice Storm) may need to be considered later today or tonight for
locations near the Allegheny Front in western MD and eastern WV.

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@losetoa6 Perhaps a preview for Friday?  Low level cold taking longer to scour out here.  Currently 31 and guidance had me in the mid to upper 30s by now.  I am sure we’ll get into the upper 40s tonight before the front drops through the area overnight but models tend to want to rush the 2m warming in these setups.

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12z GFS trended a touch colder at the surface.  A lot of the higher res guidance is dropping dew points ahead of precip into the upper 20s and lower 30s along the 81 corridor.

Looks like western areas from west of Hagerstown to Cumberland may be in for a descent ice event.  Fairly good agreement on 0.25" - 0.5" falling as zr there for New Years Day.  Looks like winter storm watches will be needed there later today.

May get an advisory level event across central MD, into northern VA, and then west of the Blue Ridge to around Harrisonburg.

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54 minutes ago, nj2va said:

@losetoa6 Perhaps a preview for Friday?  Low level cold taking longer to scour out here.  Currently 31 and guidance had me in the mid to upper 30s by now.  I am sure we’ll get into the upper 40s tonight before the front drops through the area overnight but models tend to want to rush the 2m warming in these setups.

Yea. The trend is definitely cold hanging in  longer Friday but I've noticed precip onset is really been slowing especially in central Md . It was 12z yesterday.  Now its ticking close to 18z .

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1 hour ago, losetoa6 said:

Yea. The trend is definitely cold hanging in  longer Friday but I've noticed precip onset is really been slowing especially in central Md . It was 12z yesterday.  Now its ticking close to 18z .

A bit slower on 12z vs 6z for onset...now after 19z east of HGR on the Euro.

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LWX has watches up for the extreme western zones.

Quote
URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
143 PM EST Wed Dec 30 2020

MDZ001-501-WVZ503-311000-
/O.NEW.KLWX.WS.A.0004.210101T1200Z-210102T0600Z/
Garrett-Extreme Western Allegany-Western Mineral-
143 PM EST Wed Dec 30 2020

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

* WHAT...Significant icing possible. Total ice accumulations of
  up to one quarter of an inch possible.

* WHERE...In Maryland, Garrett and Extreme Western Allegany
  Counties. In West Virginia, Western Mineral County.

* WHEN...From Friday morning through late Friday night.

* IMPACTS...Power outages and tree damage are likely due to the
  ice. Travel could be nearly impossible. The hazardous
  conditions could impact the morning or evening commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the latest forecasts for updates on this situation.

&&

$$

 

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4 hours ago, thunderman said:

12z GFS trended a touch colder at the surface.  A lot of the higher res guidance is dropping dew points ahead of precip into the upper 20s and lower 30s along the 81 corridor.

Looks like western areas from west of Hagerstown to Cumberland may be in for a descent ice event.  Fairly good agreement on 0.25" - 0.5" falling as zr there for New Years Day.  Looks like winter storm watches will be needed there later today.

May get an advisory level event across central MD, into northern VA, and then west of the Blue Ridge to around Harrisonburg.

Hope the cold trend continues!! 

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3k coming in colder for early Friday no surprise.  Just one problem....no precip :lol:

Keeps getting delayed ...maybe some freezing drizzle early morning my guess . @CAPEs high of 50 is in real trouble though. 30s till at least midnight Saturday. 

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2 minutes ago, losetoa6 said:

3k coming in colder for early Friday no surprise.  Just one problem....no precip :lol:

Keeps getting delayed ...maybe some freezing drizzle early morning my guess . @CAPEs high of 50 is in real trouble though. 30s till at least midnight Saturday. 

CHO even gets in on the ice.

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24 minutes ago, thunderman said:

One thing I will point out.  Lower QPF isn't necessarily bad with borderline surface temps.  With borderline temps, light QPF will usually slick things up more than heavier QPF.

Yup. Less latent heat release and more time to accrete in cold surfaces.

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1 hour ago, nj2va said:

Guidance gets far western areas into the low 20s early Friday. Shaping up to be a legit event as it doesn’t look to get above freezing until late Friday night.  

Mid 20s here.  Hagerstown west definitely looking like legit atm .60 hours ago it was supposed to be a 3 day mini torch . Now we are down to just 1 day lol  ( Saturday) and Nam has been  hinting that might be in jeopardy . Long range 2m temps are a huge take with a grain of salt.  

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17 minutes ago, WinterWxLuvr said:

Per the NAM’s, not many freezing rain events start in the middle of the afternoon 

Onset getting delayed run after run but keep in mind dews are like 25-28 still around precip start.  I81 and west definitely favored for .25" ice amounts.  Up here my best guess is up to .10" . Earlier onset definitely. 25" would be in play . 

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