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Solak

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    November 2019 Observations

    in Southeastern States

    Posted

    Watching the sunrise and waiting on the "mainly after 4AM" rain.

    Then, the eyes will be squinting this evening, just in case... 

    I have some concerns that we`ll see a short
period of sufficiently high precip rates to switch us over to mostly
snow and sleet for a brief time, although likely no more than an
hour. While the ground should be warm enough to prevent accumulation
there (NC State Climate Office agnet stations confirm this), heavy
enough rates may produce a light coating on elevated surfaces.
Confidence in this scenario is not high enough to warrant any
mention of accumulation at this time. But this is certainly
something to be watched closely this morning.

    Mid to Long Term Discussion 2019

    in Southeastern States

    Posted

    RAH - For Thur/Fri 

    In terms of p-type Thursday night into 
Friday...right now it looks like there's simply not enough cold air 
involved with this system to warrant concern for anything other than 
rain, esp given that the coldest air and northern stream is detached 
and located well to our north while the aforementioned closed low is 
moving across the Carolinas.  However and as always...we'll continue 
to closely monitor trends in the guidance.

    Mid to Long Term Discussion 2019

    in Southeastern States

    Posted

    RAH --- model problems and forecasting for NC. 

    That Arctic front, analyzed at 20Z this afternoon from cntl WI swwd 
to srn IA, then wnwwd across srn and wrn NE and cntl WY, will be 
preceded by an increasingly closely-spaced but separate front 
analyzed from nern OH swwd across cntl IN/IL/MO, sern KS, and the OK 
and TX panhandles. A distinction between the two is critical for two 
related reasons regarding how quickly cold, particularly Arctic air, 
arrives in cntl NC: 1) the models tend to depict hypergradients 
about such closely-spaced fronts as one and 2) how the models (fail 
to accurately) resolve the Appalachian mountains yields a premature 
Arctic air surge in the lee of the mountains. Consider the past two 
early season Arctic frontal passages in cntl NC, for example, from 
Halloween night and last Thu/Nov 7. In both cases the models rushed 
the cold air east of the Appalachians prematurely relative to 
reality. 

These model failures are one of the chief reasons that a pattern 
such as the one described above, with "cold air chasing the 
moisture", fails to produce wintry precipitation in cntl NC. 
Nevermind that it's still Nov. And it provides an opportunity for 
failure of even the best of NWP ensemble systems that depict 
accumulating snow in cntl NC, and for a human to add forecast skill 
and value. With that in mind, a band of anafrontal rain, driven by 
the right entrance region of a strong (125-150 kt) swly upr jet 
streak from the cntl Appalachians to the Labrador Sea, behind the 
lead front described above, will edge ewd across cntl NC late Mon 
night and (particularly early) Tue - in a pattern very similar to 
the band of anafrontal rain that occurred last Thu/Nov 7. The Arctic 
boundary will then sweep sewd across cntl NC through early-mid 
afternoon Tue, with following much below average temperatures, 
including teens to low-mid 20s Wed morning, and highs only in the 
upr 30s to low-mid 40s on Wed.
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