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February 17-18 Threat Discussion


The Iceman

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Another thing is dews are currently in the teens. That is a very good thing. We LL see a solid temp drop when precip starts. That's a plus. Latest nam plus the hrrr both look solid still. I'm staying positive I really think this plays out better than most are expecting. Nws most likely map is still 3-6" for all of se pa last I checked. So while there are definitely things to be concerned about, I just still have a feeling about this storm. I've also been on board all week, feels wrong jumping ship now :lol: I'm calling the Philly special here...

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Very interesting disco from mt Holly posted below. I really trust their judgement when they say they don't see a blatant warm layer outside of s and e areas. Also say they are leaning on the nams thermals. Gorse is killing it this storm with the disco's. His thoughts are so clear and relays the difficulty of the forecast but I really like how he goes into depth of why they feel the way they do. Learned a few new things to look for in borderline events going forward. We really have one of the best nws offices in the world.

 

 I feel this one has a few surprises in store especially with the great forcing over our area. There will be some real good periods of near whiteout conditions.

Quote

other Nature looks to put on a show tonight as a quick moving storm
affects our region. As mentioned in the near term section, a potent
short wave will move across the Northeast tonight with height falls
to its southeast. This will help sustain a surface low off the Mid-
Atlantic coast as it quickly tracks northeastward and away from our
area overnight.

The model guidance overall is in good agreement with a widespread
precipitation event occurring mainly through the first half of
tonight. The large scale ascent will be augmented within a right
entrance region of a potent 250 mb jet. In addition, lower to mid
level frontogenetic forcing will enhance the precipitation
especially through about 06z. Some of the high resolution guidance
hints at some banding potential, however the quick movement of the
system may result in any heavier embedded bands to be transient.
Where this occurs is a tough call at this time, however somewhere in
the I-95 corridor may be the zone where this may try and become more
focused. It is here where the better transition takes place with the
thermal fields, resulting in stronger forcing associated with
frontogenetic mechanisms. It is within this enhanced forcing where
snowfall rates of up to an inch per hour is very possible. The
entire system and lift however are on the move with the associated
lift moving out of the area after midnight. As a result, a 3-6 hour
window of enhanced precipitation rates along with embedded heavier
elements look to occur.

The snowfall forecast is still challenging as the heavier rates will
help overcome any lingering warmth close to the ground, although
this is occurring at night. It is during the heavier snowfall rates
where road conditions will deteriorate quickly especially where air
temperatures hover right near freezing. The liquid to snow ratios
will also be lower as one goes southeastward across our region. This
will result in a zone of larger wet snowflakes especially during the
time frame of enhanced lift where accumulations may end up being the
most efficient. Given the extent of the dry air in place initially,
wet bulbing should be a factor in allowing temperatures to drop a
bit more. We therefore blended closer to the cooler guidance such as
the NAM. The snow accumulations are mostly from the I-295/NJ
Turnpike corridor westward, with amounts dropping off quite a bit to
the south and east. The far southeastern areas and southern Delaware
into portions of northeast Maryland should see little to no snow.
The forecast soundings still look to not have a pronounced warm
layer aloft, at least enough to produce much sleet therefore we did
not factor this into the forecast all that much. Looks like rain,
snow, rain/snow mix. Some mixing may get northwestward into
Philadelphia before the precipitation ends.

Given the forecast snow amounts and less confidence on where some
banding may enhance local accumulations, we went with a Winter
Weather Advisory for the Watch area and added a tier to the south
and east. It is near and west of I-95 where the greatest snow
accumulations are forecast, however the I-95 corridor needs to be
monitored as a period of enhance lift, higher QPF and increased
snowfall rates may result in a zone of higher amounts of wet snow.
If 2-4 inches of wet snow falls and sticks efficiently in a short
period of time, there could be some power outages. This potential
impact is less certain.

The storm quickly moves away overnight with precipitation ending
quickly, and clouds should start to thin some from the west toward
daybreak.

 

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4 minutes ago, Rtd208 said:

Temp has gone up pretty quickly here this morning, currently 35 here.

Really our high temp doesn't have too much effect for tonight.. Dew points are more important to keep an eye on. As long as they stay in the teens or low 20s we LL be fine even if highs get a little above forecast.

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34 minutes ago, The Iceman said:

Really our high temp doesn't have too much effect for tonight.. Dew points are more important to keep an eye on. As long as they stay in the teens or low 20s we LL be fine even if highs get a little above forecast.

20F DP here right now but damn it doesn't feel like snow out there. (bright sun and not cold in the sun) Birds chirping don't help...lol.

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34F/19DP. Yeah, feels/looks like a spring day out there. If it wasn't for the mud, I'd get out and do a little yard work ...lol!

I haven't had much enthusiasm for this event, maybe because whatever falls will be gone by tomorrow. But great job by Iceman staying on top of this one...bring it home for us!

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20 minutes ago, JTA66 said:

34F/19DP. Yeah, feels/looks like a spring day out there. If it wasn't for the mud, I'd get out and do a little yard work ...lol!

I haven't had much enthusiasm for this event, maybe because whatever falls will be gone by tomorrow. But great job by Iceman staying on top of this one...bring it home for us!

Funny you said that. Landscaping crew cutting down a large tree down the road...like it's April/May without a worry in the world.

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2 hours ago, RedSky said:

12z RGEM looks good a general 4-4.5" event. Paints a 7-8" bullseye just west of Kamu's squirrel country! Hrrr  keeps loving the high counties but has gone up for the lower each run.

Expectations set at 4" locally.

 

I saw that, lol. Still lots of variation in modeled snowfall, tracking this event has been a little crazy. Should be interesting, hopefully in a good way for all of us. Going to blow some leaves in a few spots this afternoon, followed by a kettle fire. This will be a first, waiting down there by the fire for snow, checking radar. Lots of anticipation! Just starting to cloud up here now, temp at 41F, DP 25F. Hoping for cold air aloft to hang in there, not so worried about the surface. We've had a few events in the last few years here where we accumulated decent snow with the surface temp only getting down to 33F. Expectations here are 2" to 3", more would be a bonus. Could go either way, keeping fingers and toes crossed!

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Temp here is 41F w/dp 25F.  Starting to cloud up although looks like I'm getting some more stratusey low clouds.  Going to a niece's birthday party tomorrow and am trying to decide whether to throw a cover over my windshield to reduce the SUV clean-off time tomorrow or let 'er ride and hope it all melts by noon.

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