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1/13, 1/14 - Freezing rain threat


packfan98

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RAH

 

PHASING OF THE PRECIPITATION AND FREEZING TEMPERATURE FORECASTS SHOWS THAT THE MOST LIKELY AREA TO HAVE ANY IMPACTS IN REGARDS TO FREEZING RAIN WOULD BE THE SOUTHEASTERN COUNTIES WITH A POTENTIAL SWEET SPOT FOR THE MOST ACCUMULATION OF ICE OCCURRING ROUGHLY ALONG THE I-95 CORRIDOR BETWEEN FAYETTEVILLE AND ROCKY MOUNT. WITH WEAK RAIN RATES AND LIMITED TIME BELOW FREEZING...ICE ACCRUAL VALUES SHOULD BE AT MOST A FEW HUNDREDTHS OF AN INCH WITH CLOSER TO 0.05 INCHES IN THE AFOREMENTIONED SWEET SPOT.HOW CONFIDENT IS THE FORECAST? WITH MODELS TRENDING COLDER...THERE IS INCREASING CONFIDENCE THAT WE WILL GET TEMPERATURES LOW ENOUGH TO SUPPORT FREEZING RAIN. THAT BEING SAID...THE PRECIPIATION FORECAST REMAINS THE LARGEST VARIABLE. A SHIFT IN TRACK OF THE OFFSHORE LOW COULD RESULT IN A CHANGE IN QPF VALUES ONE WAY OR THE OTHER AS WELL AS THE DISTRIBUTION OF PRECIPIATION. ALSO A CHANGE IN THE AMOUNT OF TIME THAT FREEZING TEMPERATURE AND PRECIPIATION COMBINE WOULD ALSO AFFECT ICE ACCRUAL VALUES AND ULTIMATELY IMPACTS. FURTHER DETAILS WILL BEGIN TO EMERGE AS SOME OF THE HIGHER RESOLUTION MODELS BEGIN TO PICK UP THE SYSTEM. 
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Freezing rain and icy roads are possible Tuesday night and early Wednesday across portions of central NC. Based on today's data, the I-95 corridor may have the best chance to see travel impacts Wednesday morning. Be sure to check back for updates, as precip amounts are uncertain this forecast may still change.

10929146_583579011743462_121071504134255
 
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18z NAM-12km was pretty nasty with 0.5 inches liquid QPF NE piedmont/coastal plains all freezing rain. NAM-4km though curiously was lighter.


 



NAM-4km with only 0.1 to 0.25 in same areas. NAM-12 likely overdone, trend worth monitoring comparing NAM-12 vs NAM-4.


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Temp portion of this setup is fairly impressive for Raleigh > Greensboro area.  GFS has Raleigh temp at 26 with dewpoint of 20 Wed morning at 7AM.  NAM is 28 / 24 at same time.

 

Just have to see how the precip shakes out.  Could be the NAM over doing the precip as usual and it ends up being very light...or maybe the other models will tick up over the next 24 hours.

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Temp portion of this setup is fairly impressive for Raleigh > Greensboro area.  GFS has Raleigh temp at 26 with dewpoint of 20 Wed morning at 7AM.  NAM is 28 / 24 at same time.

 

Just have to see how the precip shakes out.  Could be the NAM over doing the precip as usual and it ends up being very light...or maybe the other models will tick up over the next 24 hours.

 

The Euro already went up some last run.

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Temp portion of this setup is fairly impressive for Raleigh > Greensboro area.  GFS has Raleigh temp at 26 with dewpoint of 20 Wed morning at 7AM.  NAM is 28 / 24 at same time.

 

Just have to see how the precip shakes out.  Could be the NAM over doing the precip as usual and it ends up being very light...or maybe the other models will tick up over the next 24 hours.

We have to assume that the NAM-12km is on crack at this point. The NAM-4 is probably more realistic. Still if temps get to 26, and we get .1 of freezing rain that will cause problems.

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We have to assume that the NAM-12km is on crack at this point. The NAM-4 is probably more realistic. Still if temps get to 26, and we get .1 of freezing rain that will cause problems.

 

Yeah, NAM is on it's own but here is what it shows for RDU, mainly sleet with some frzn.

post-2311-0-77028700-1421099054_thumb.pn

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well here is the 15 UTC SREF 

 

Probability of freeing rain at 9 UTC Wed

SREF_prob_zr_precip_01__f042.gif

 

Here is the 12 hours QPF ending at 9UTC wed. 

 

SREF_prob_totpcpn_0.25_12hr__f042.gif

 

1/4 of a inch is freezing rain advisory criteria. Id give a 30% of coastal plain counties getting a advisory. Probability of warning criteria is around 10%. Models keep featuring a piece of vorticity that shoots up the Piedmont, someone should cash in from that if that happens. 

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I've never been too big on the NAM since its upgrade a few years ago, but since we're model hugging and this may be all we have to track for a while lol, here's a run down of the 18z bufkit sounding for RDU. The winds shift NE early Tuesday morning and temps fall slowly through the day to below freezing by 9pm. Most of the day Tuesday will be drizzle w/ low clouds. The one thing we have going for us is the column remains pretty much saturated from 750mb down the entire time, which means the only time lost to evap cooling will be saturating the area from 750mb up to 600mb. The depth of the warm layer is pretty deep aloft from 750mb down to 950mb ( around 5k ft deep). The layer of cold air at the sfc is probably deep enough to produce ip for a few hours early morning Wednesday (when the screenshot is taken). That said the majority would be zr. The lowest temp is  b/n -2c to -3c near the sfc early Wednesday.  Looks like over .5 total is zr/ip.

post-233-0-78733200-1421103545_thumb.png

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