Jan 31 - Feb 1 Event - STORM MODE THREAD

[stormtracker]

Everyone is starting to get punchy 'round here.   And this is what it has come to.  Relax.  If it snows 4 inches or 14, it's snow.  If you are disappointed, ok.  Fair.  But no need to shit up entire threads about it.

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-NO WARNINGS, JUST STRAIGHT UP FORUM JAIL FOR AT LEAST 24 HOURS

- GIVE ME $5

 

[MD Snow]

ICON appears to be slightly south and tucked in with LPC from it's 6z through 81 hrs. Precip shield further north and west. 

[Eskimo Joe]

Morning AFD from LWX.

Quote

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
719 AM EST FRI JAN 29 2021

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVERHEAD TODAY THROUGH SATURDAY. LOW 
PRESSURE WILL APPROACH FROM THE WEST SUNDAY AND TRANSFER OFF 
THE COAST ON MONDAY. HIGH PRESSURE WILL BUILD BACK IN BY THE 
MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
HIGH PRESSURE CENTERED OVER THE CORN BELT EARLY THIS MORNING
WILL ONLY SLOWLY BUILD EAST TODAY THROUGH SATURDAY, WITH THE
PRESSURE RIDGE ACTUALLY NOT PASSING OVERHEAD TIL SATURDAY NIGHT.
THUS, WINDS WILL REMAIN GUSTY TODAY, THOUGH PROBABLY NOT QUITE
AS STRONG, WITH A SLOW DIMINISHING TREND THEREAFTER THROUGH
SATURDAY AFTERNOON. TEMPERATURES WILL REMAIN COLD, WITH HIGHS IN
THE 30S FOR MUCH OF THE AREA BOTH TODAY AND SATURDAY, BUT WITH
LESS WIND SATURDAY, WIND CHILLS WILL BE LOWEST TODAY, WITH
READINGS AGAIN STAYING IN THE TEENS AND 20S ALL DAY LONG. WITH
WINDS DIMINISHING A BIT TONIGHT COMPARED TO THE THIS MORNING,
EXPECT LOWS TO DROP A BIT MORE, BUT IT LOOKS LIKE ENOUGH WIND
LINGERS TO KEEP US FROM GETTING TRULY RADIATIONAL TONIGHT. THAT
SAID, WIDESPREAD TEENS TO LOW 20S LOOK LIKELY, PROBABLY THE
COLDEST NIGHT OF THE SEASON, THOUGH STILL WELL ABOVE WHAT SHOULD
BE THE COLDEST NIGHT OF WINTER (COMPARED TO A NORMAL COLDEST
NIGHT OF WINTER, ANYWAY).

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
GENERAL MODEL AGREEMENT EXISTS FOR SUNDAY'S SYSTEM, BUT REMAINS
SHAKY ON SOME OF THE DETAILS. WHAT WE ARE REASONABLY CONFIDENT 
OF IS THAT SATURDAY NIGHT WILL SEE INCREASING CLOUDS, WITH TEMPS
NOT ABLE TO DROP AS COLD AS FRIDAY NIGHT THANKS TO THE LOSS OF 
RADIATIONAL COOLING. LOWS LIKELY IN THE 20S. SNOW WILL MOVE IN 
FROM SOUTHWEST TO NORTHEAST LATE SATURDAY NIGHT AND EARLY SUNDAY
MORNING, WITH SNOW LIKELY WIDESPREAD BY MID-LATE MORNING 
SUNDAY. AFTER THAT, WE MAY START TO SEE SOME WARM AIR PUSHING 
NORTHWARD, ALLOWING SNOW TO MIX WITH SLEET AND FREEZING RAIN. A 
DRY SLOT THEN APPEARS MORE LIKELY TO MOVE OVERHEAD, RESULTING 
IN MORE SLEET AND FREEZING RAIN SUNDAY NIGHT, THOUGH AS PRECIP 
SHOULD BE FAIRLY LIGHT, WE ARE NOT EXPECTING A BIG ICE 
ACCUMULATION. TEMPERATURES PROBABLY STAY NEAR OR BELOW FREEZING 
FOR MUCH OF THE AREA SUNDAY WITH THE STEADY PRECIP AND 
NORTHEAST WIND DEVELOPING, AND DROP ONLY A LITTLE SUNDAY NIGHT. 
CURRENT EXPECTATIONS ARE ADVISORY TO LOW-END WARNING LEVEL 
SNOWFALL ALONG WITH SOME ADVISORY LEVEL ICING, BUT AS MENTIONED 
ABOVE, GUIDANCE REMAINS SHAKY ON THE DETAILS, SO WOULD NOT BE 
SURPRISED TO SEE A SIGNIFICANT UPWARD OR DOWNWARD ADJUSTMENT. 
THAT SAID, THINK ADVISORIES ARE A VERY GOOD BET AT THIS POINT, 
BUT NOT QUITE AS CONFIDENT IN WARNING-LEVEL SNOW JUST YET. THUS,
WILL HOLD OFF ON WATCHES FOR THE TIME BEING AND LET DAY SHIFT 
TAKE ONE MORE CRACK AT THINGS.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A POTENT UPPER LEVEL LOW WILL MOVE INTO THE MID-ATLANTIC REGION
MONDAY. THE DEVELOPMENT AND INTENSIFICATION OF A COASTAL LOW 
PRESSURE SYSTEM WILL BRING US A CONTINUED CHANCE OF ACCUMULATING
SNOWFALL MONDAY INTO MONDAY EVENING. SOME SLIGHTLY WARMER AIR 
MAY BE JUST ABOVE THE BOUNDARY LAYER MONDAY TO THROW A THREAT 
OF SLEET AND FREEZING RAIN OUR WAY, AS WELL.

THE MAIN LOW PRESSURE SYSTEM AT THE COAST SHOULD PULL AWAY LATE
MONDAY NIGHT AND TUESDAY. THUS, THIS MOVEMENT SHOULD TAPER ANY 
WINTRY PRECIPITATION AND COME TO AN END TUESDAY MORNING.

FROM MIDDAY TUESDAY THROUGH TUESDAY EVENING, AN UPSLOPE 
SNOWFALL COULD DEVELOP ALONG THE ALLEGHENY FRONT. OTHERWISE, WE 
WILL DRY OUT AND REMAIN CHILLY.

HIGH PRESSURE WILL BUILD IN QUICKLY BOTH AT THE SURFACE AND 
MID- LEVELS WEDNESDAY THROUGH EARLY THURSDAY. TRANQUIL 
CONDITIONS AND CHILLY TEMPERATURES ARE EXPECTED.

DURING THE DAY THURSDAY, HIGH PRESSURE WILL MOVE EAST AS A WARM
FRONT PUSHES IN FROM THE SOUTHWEST ACROSS OUR WESTERN ZONES. 
THIS FRONT COULD BRING SOME LIGHT SNOW AT HIGHER ELEVATIONS.

 

[Dabuckeyes]

12z runs so far:

 

NAM a little progressive with part 2

RGEM and ICON have the coastal stall with CCB

[nj2va]

ICON looks like it would be about 0.5” QPF as snow from the WAA before any mixing concerns in DC.  We then mix before the coastal takes over.  CCB initially pointed north of us but then rotates down into the region and snows itself out through Tuesday.  Looks great to me.

[MD Snow]

ICON literally sits off the coast of OC for 24 hrs from Monday morning through Tuesday morning. 

[MN Transplant]

Ok - big difference between the NAM and RGEM in the northeast which appears to impact the shape of the trough.  Given the choice, we clearly want the RGEM solution which allows the trough to more easily go neutral.

NAM top, RGEM bottom.

 

[AmericanWxFreak]

[Hyphnx]

From AKQ

 

Quote

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 415 AM EST Friday...

Clear and cold to start, with the sfc high pushing offshore
through the day. Quasi-zonal/downslope flow will actually allow
for a modest warm up on Saturday, and went a few degrees above
NBM inland. Highs in the upper 30s to around 40 at the coast,
low to some mid 40s inland on Saturday.

Clouds will quickly start filling in later Sat aftn/night, ahead
of next system digging from the mid-south across the Carolinas
Sat night. All eyes will turn to this feature Saturday night.
Lead shortwave shifts to the coast with initial slug of WAA-
induced overrunning moisture pushing across the mountains into
our area around and after midnight EST Sat night/early Sunday.
Models continue to point toward some light PCPN possible
earlier, but antecedent dry airmass will delay onset by a few
hours. In any case, model timing differences remain, with the
GFS trending toward the slower ECMWF, with the NAM/CMC in the
middle. Have nudged PoPs up into likely to categorical range
after midnight into Sunday morning toward that middle ground
solution, as it appears there will be sufficient moisture with
that initial WAA slug of moisture to bring some snow to much of
the area pre-dawn Sunday morning. Top-down tools yield snow/sleet
at the onset for most early Sun morning, w/wintry mix (IP/SN)
at onset even along the coast by daybreak Sunday with
wetbulbing.

Snow gradually goes over to a wintry mix (RA/SN/IP) as prominent
warm nose nudges in from the SW as the system approaches.
Exception appears as if it will be across far NW tier of zones,
where ECMWF/CMC and their member ensembles continue to show
high probs for Warning criteria snows, mainly along and N of a
FVX-RIC-XSA line. Nudged Storm Total Snow forecast to 4-6 inch
range north- northwest of the RIC metro area, with a maxima
along the Hwy 15 corridor in Louisa/Fluvanna counties. Lesser
totals for RIC /Tri-Cities area and points farther south, as
rain and sleet are likely to cut into totals considerably over
much of these areas (and especially points S/E). Accordingly,
also expect there will be a rather tight gradient as is typical
well inland. Regardless, this remains a tricky forecast with
rain likely over the southern portion of the area, snow over the
northern portion of the area, and mixed precip likely for much
of central and eastern VA (just inland from the coast). Bulk of
the precip is likely from 12Z Sunday to 00Z Monday.

Parent upper low crosses the area Sunday night into Monday,
with some additional light pcpn possible. Accumulating
precipitation will be largely over, but considerable clouds and
light rain/snow will be possible. Lows Sunday night in the mid
20s well inland to mid 30s SE.

 

[87storms]

1 minute ago, MN Transplant said:

Ok - big difference between the NAM and RGEM in the northeast which appears to impact the shape of the trough.  Given the choice, we clearly want the RGEM solution which allows the trough to more easily go neutral.

NAM top, RGEM bottom.

the latest nam is like most of the earlier gfs runs with the primary a nudge too far north.  that seems to be the big player.  i still think a coastal sidewinder is pretty unlikely given the trough setup (neutral/positive), but if h5 is just a little further south i would think that would result in a better latitude for the coastal to develop.  feb 10, 2010 did something similar and the capture occurred just in time.  still seems like that option is on the table for the dc/bmore/philly corridor, but maybe not hecs-like without a strong feed from the atlantic (trough going negative and a coastal forming off obx/va beach, for example).

[MillvilleWx]

Damnit @stormtracker, I had a post all set in the other thread and you closed it as I was submitting

Anywho, I was going to say the RGEM is much cleaner on the transfer, the 7H low passes cleanly underneath with a strengthening as it pivots south of the area. This allows for the 700mb jet to enhance and point into the region, leading to strong 7H frontogenic forcing placed along I-95 and points just southeast. 

[Scarlet Pimpernel]

Just now, MN Transplant said:

Ok - big difference between the NAM and RGEM in the northeast which appears to impact the shape of the trough.  Given the choice, we clearly want the RGEM solution which allows the trough to more easily go neutral.

NAM top, RGEM bottom.

 

Was that little "dip" over NY that the NAM displays also on the Euro?  I think I recall someone mentioning something about that (perhaps @Wentzadelphia)?

[stormtracker]

Just now, MillvilleWx said:

Damnit @stormtracker, I had a post all set in the other thread and you closed it as I was submitting

Anywho, I was going to say the RGEM is much cleaner on the transfer, the 7H low passes cleanly underneath with a strengthening as it pivots south of the area. This allows for the 700mb jet to enhance and point into the region, leading to strong 7H frontogenic forcing placed along I-95 and points just southeast. 

Apologies!  Hopefully other guidance matches the RGEM.

[MillvilleWx]

1 minute ago, stormtracker said:

Apologies!  Hopefully other guidance matches the RGEM.

All good! My timing is just impeccable. 

The RGEM and ICON certainly would calm the nerves of many in here. Pretty solid runs for both. The intricacy of these little vorts can cause mass chaos with setups like these. Need a clean transfer for this to work no matter what. I'm curious for the GFS and Euro and see where they have that vort over New England. 

[MN Transplant]

4 minutes ago, Always in Zugzwang said:

Was that little "dip" over NY that the NAM displays also on the Euro?  I think I recall someone mentioning something about that (perhaps @Wentzadelphia)?

Yes.  It is trailing energy from the low that is passing through New England right now.  On the 00z Euro it actually ends up merging with our storm over the northeast.

[frd]

14 minutes ago, MillvilleWx said:

Anywho, I was going to say the RGEM is much cleaner on the transfer, the 7H low passes cleanly underneath with a strengthening as it pivots south of the area. This allows for the 700mb jet to enhance and point into the region, leading to strong 7H frontogenic forcing placed along I-95 and points just southeast. 

From HM, lower part 

 

 

[frd]

 

Interesting observation from Jack regarding the Canadian versus the Euro. Keep this feature in mind in future model runs.  

 

 

[jewell2188]

One would think 4-8 would be a good starting point. Certainly room for up or down. 

[MD Snow]

Through 60...GFS is 1 mb weaker and smidge further south with the primary compared to it's 6z run. This results in a slightly colder surface for the WAA snow. 

[clskinsfan]

What a beautiful run from the ICON. Snow starts with all of us in the low to mid 20's. Surface stays below freezing through the entire event. DC does go to 33 for an hour or so before the low gets cranking. 

[MN Transplant]

1 minute ago, frd said:

 

Interesting observation from Jack regarding the Canadian versus the Euro. Keep this feature in mind in future model runs.  

 

 

Yes, the 00z Euro and 12z NAM are very similar with that feature, but the 12z RGEM continued to show a weaker and NE solution.  Go Canada!

[Ralph Wiggum]

19 minutes ago, Always in Zugzwang said:

Was that little "dip" over NY that the NAM displays also on the Euro?  I think I recall someone mentioning something about that (perhaps @Wentzadelphia)?

I mentioned yesterday afternoon that piece is what could keep confluence tighter and nudge everything S.

[LP08]

GFS colder than 12z.  Deform looks to hit DC and NE

[stormtracker]

16 minutes ago, MillvilleWx said:

All good! My timing is just impeccable. 

The RGEM and ICON certainly would calm the nerves of many in here. Pretty solid runs for both. The intricacy of these little vorts can cause mass chaos with setups like these. Need a clean transfer for this to work no matter what. I'm curious for the GFS and Euro and see where they have that vort over New England. 

Yeah, just saw the RGEM.  That would be a forum saver for sure.

[LP08]

GFS is a great hit.

[baltosquid]

No need for a super in depth response since that would be best left to its own thread, but do people more in the know think the huge issues with GFS thermals are to some extent brough about by certain overcorrections from its experimental days when the FV3 was cranking out nonsensical cold solutions storm after storm?

[Deck Pic]

GFS is pretty tasty....still some mixing east of I-95, but a more robust response from the coastal

[MN Transplant]

Just now, Ralph Wiggum said:

I mentioned yesterday afternoon that piece is what could keep confluence tighter and nudge everything S.

The good news is that the 12z GFS is more RGEM like with that piece.  The thermals remain a problem, but, GFS.

[frd]

1 minute ago, Deck Pic said:

GFS is pretty tasty....still some mixing east of I-95, but a more robust response from the coastal

 

 

 

 

[nj2va]

Just now, LP08 said:

GFS colder than 12z.  Deform looks to hit DC and NE

Adjust for GFS’ terrible ability at thermals (not saying we don’t mix at all) but I don’t think we mix to the extent GFS is showing in that deform.  Much better coastal for the area.