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January 12-14, 2019 Storm Discussion STORM MODE


WxUSAF
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Just now, jayyy said:

Bob...

id actually prefer the WAA thump over relying on a coastal when the flow is so progressive. Right?  That coastal has swing and a miss written all over it. 

In the mid atlantic you take whatever you can get. 0z suite seems to have reached consensus on everything. One more day and it's chips fall mode

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17 minutes ago, stormtracker said:

Whoa..6z NAM.   Just a tad better....compare to 0z

What did I tell you yesterday? Once it started relaxing the ns that we would see a stronger low with better moisture flow. Knowing the nam we will now get some namings as it starts overamping the low.

Eta: actually it's a little stronger with the ns. Improvements are probably due the adjustments to the trough.

Hate trying to read these maps on my phone.

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WSWs up to the SW and S of DC.

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
337 AM EST Fri Jan 11 2019

MDZ017-VAZ036>040-050-051-056-057-111645-
/O.NEW.KLWX.WS.A.0002.190112T1700Z-190113T1700Z/
St. Marys-Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-
Culpeper-Spotsylvania-King George-
337 AM EST Fri Jan 11 2019

...WINTER STORM WATCH IN EFFECT FROM SATURDAY AFTERNOON THROUGH
SUNDAY MORNING...

* WHAT...Significant snow possible. Snowfall accumulations of 5 or
  more inches possible.

* WHERE...Portions of central Virginia, the Virginia Piedmont and
  extreme southern Maryland.

* WHEN...From Saturday afternoon through Sunday morning. The
  steadiest snow is most likely late Saturday afternoon into
  Sunday morning.

* ADDITIONAL DETAILS...Travel may be difficult due to snow covered
  and slippery roads.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is potential for significant
snow, sleet or ice accumulations that may impact travel. Continue
to monitor the latest forecasts.

&&

$$

URGENT - WINTER WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
337 AM EST Fri Jan 11 2019

VAZ025>027-029-030-503-504-507-508-WVZ055-505-506-111645-
/O.NEW.KLWX.WS.A.0002.190112T1500Z-190113T1700Z/
Augusta-Rockingham-Shenandoah-Page-Warren-Western Highland-
Eastern Highland-Northern Virginia Blue Ridge-
Central Virginia Blue Ridge-Hardy-Western Pendleton-
Eastern Pendleton-
337 AM EST Fri Jan 11 2019

...WINTER STORM WATCH IN EFFECT FROM SATURDAY MORNING THROUGH
SUNDAY MORNING...

* WHAT...Significant snow possible. Snowfall accumulations of 5 or
  more inches possible.

* WHERE...Portions of the Potomac Highlands in eastern West
  Virginia and Virginia as well as the central Shenandoah Valley.

* WHEN...From Saturday morning through Sunday morning. The
  steadiest snow is most likely Saturday afternoon through Sunday
  morning.

* ADDITIONAL DETAILS...Travel may be difficult due to snow covered
  and slippery roads.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is potential for significant
snow, sleet or ice accumulations that may impact travel. Continue
to monitor the latest forecasts.

 

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And the latest AFD from LWX.

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Low pressure will track through the Gulf Coast States Saturday
into Saturday evening before transferring its energy to a
coastal low off the North and South Carolina Coast by Sunday
morning. The low will move off the Mid-Atlantic Coast Sunday and
high pressure will return for Sunday night. The closed upper-
level low associated with this system will get sheared apart as
it runs into a strong confluence zone, with shortwave energy and
jet maxes passing through Saturday into Sunday.

For Saturday...High pressure will remain over New England while
the surface ridge axis extends down through the Mid-Atlantic.
The low and mid-level flow will back to the southwest, causing
relatively warmer and more moist air to overrun the surface cold
air in plac. At the same time, shortwave energy well ahead of
the upper-level low will pass through the area. The overrunning
and shortwave energy should be enough to cause snow to break out
over much of the area, first across the Potomac Highlands and
Shenanodah Valley Saturday morning and across the rest of the
area Saturday afternoon. Temperatures will remain below freezing
or drop below freezing after precipitation begins, so
accumulating snow is likely.

The same pattern will persist for Saturday night with low
pressure transferring its energy to a coastal low as it passes
by to the south. Overrunning and shortwave energy will continue
to bring snow across the area with accumulation likely. The coastal low will will move out to sea Sunday and high pressure will wedge down from the north. This will cause snow to gradually end from north to south. Details are still a little uncertain at this time. Latest 00z guidance shows that the best chance for additional snow accumulation will be south of Interstate 66 and US 50. High pressure will continue to wedge into the area Sunday night. Most areas across the northern and central CWA should turn out
dry, but a little light snow or flurries cannot be ruled out
across central Virginia into southern Maryland where leftover
moisture will be tough to scour out.

As for accumulations, it does appear that snowfall rates will be
on the light to perhaps occasionally moderate side. This is
because the primary forcing mechanism appears to be overrunning.
Strong frontogentical forcing appears that it will remain to our
south, closer to the low. Therefore, latest thinking for most
likely snow amounts are around 2-4 inches near the Washington
and Baltimore Metropolitan areas into northern and central
Maryland as well as northern Virginia. Farther south and west, 4
to 8 inches are most likely at this time.
The reason for the
higher amounts is that moisture will be a bit deeper closer to
the low and farther from the drier air associated with the high.
A Winter Storm Watch is in effect for these areas (Potomac
Highlands into central Virginia and extreme southern Maryland).
Most likely forecast do have amounts below temporal criteria for
a warning, (5" in 12 hours and 7" in 24 hours), but still
several inches of snow are likely at this point. Also, there is
still some uncertainty with the low track Sunday morning. Some
outlying guidance suggest that heavier snow is still possible
across these areas. Therefore, a Watch has been issued.

 

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1 minute ago, Ji said:

6z fv3 best case

Not going to lie Ji, I’m sure you liked the 6z suite. Between the NAM, ICON, FV3, and even the GFS, every model moved the qpf max north and also beefed it up quite a bit. 

Were not seeing models deteriorate the precip shield into oblivion thanks to the shred factory. A little better look up top and better flow to keep the snow over us. Have noticed some fronto so that could give us some bands to work with as some have mentioned. 

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17 minutes ago, leesburg 04 said:

As models begin to converge and then fine tune as we are on the doorstep it sure does scream how we should view model runs a week out...

That said it's pretty awesome how the models can see that an event may happen from so far out. 

I just went back and look at last weekends runs of the GFS. A bunch came pretty close to nailing it. Especially the 18z from Sunday

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