Not much of an update is really needed, but I did want to mention the chance of moderate to heavy snow potential Friday afternoon until sometime Friday night/early Saturday morning. GFS Bufkit is showing a dry layer at around 850. The GFS may be having a difficult time handling diabatic cooling due to evaporation. Therefore, I believe an isothermal layer may exist during the evening hours. I think it may be a situation in which light precip will fall as rain (less evap cooling) and more heavier precip (more evap cooling) will fall as snow up until a certain point during the night. Significant snowfall during rush hour is not out of the question. The timing may need to be updated tomorrow on the exact timing of the changeover to rain. I believe that any changeover to ZR will be brief due to latent heat release caused by freezing. Temps will be borderline for ZR to begin with so expect the ZR itself to lead to enough of a temp increase to change the precip to rain over night. Also, most of the precip should end early Saturday morning with some light freezing drizzle and flurries possible through the afternoon.
Will need to really look into the Christmas eve storm as well. Could be anything from all rain to mostly snow to a historic ice storm.... stay tuned. Starting to gain some confidence though that someone will say a major Christmas eve/Christmas storm.
New Forecast:
Friday afternoon: Snow, possibly mixed with the light rain. The snow could be moderate to heavy at times in the afernoon. High 36
Friday night: Snow changing to sleet and ZR between 10 PM and 1AM and then all rain after 1. The snow could be heavy during the evening. Low 30
Saturday: A chance of freezing drizzle and flurries. High 35
Thursday, December 17, 2009
Wednesday, December 16, 2009
12/16 - Weekend Winter Storm Forecast for the Triangle:
Synopsis: A low pressure will form along the gulf coast and move northeast off the North Carolina coast this weekend. Cold air will be in place as the low pressure nears the region which will likely bring wintery precip to the triangle. Forecast confidence is very low.
Discussion: A Miller A low will move up the North Carolina coast increasing moisture flux from the Atlantic into the triangle by Friday afternoon. This low will exit the area slowly first bringing in a round of precip due to overrunning warm advection over a fairly strong cold pool at the surface. A 2nd round of precip affiliated with the deformation band will occur later in the weekend. The GFS and ECMWF are in decently good agreement on the general location and timing of the low pressure. I am looking at GFS Bufkit soundings to determine first guess precip type. Forecast confidence is very low due to precip type remaining near the mixed bag region of the nomogram. Diabatic processes could play a large part in the precip type especially Friday afternoon as the precip begins. Also, this is a cold air damming scenario with cold air filtering in between a fairly weak high to the Northwest and a Low to the northeast. NWS RAH mentioned that this storm compares generally well with a storm in 05 in which very little wintery precip fell in the region. With that in mind this is a completely different storm. GFS and every other model for that matter tends to warm temps too much during a CAD event. This fact makes me want to go with an icier/snowier scenario for the triangle as the GFS already predicting a decent amount of ice and snow, especially in the deformation. Climatology however does not support this type of system as a major winter event however, which is why my confidence is so low. On top of that there will be a tight gradient between the rain/mix/snow lines. Also, diabatic processes will turn borderline temps for freezing rain into temps for rain. Right now it's too far out to truly pinpoint the exact location of the low and the strength of the cold air.
But I will forecast what I see as of now... This is likely to change!
Friday afternoon: A 60% chance of snow possibly mixed with rain
Friday night: 70% chance of snow mixing with freezing rain/rain and sleet by 8PM and then changing to all rain/freezing rain/sleet mix.
Saturday: Rain quickly changing over to freezing rain/drizzle before ending.
Discussion: A Miller A low will move up the North Carolina coast increasing moisture flux from the Atlantic into the triangle by Friday afternoon. This low will exit the area slowly first bringing in a round of precip due to overrunning warm advection over a fairly strong cold pool at the surface. A 2nd round of precip affiliated with the deformation band will occur later in the weekend. The GFS and ECMWF are in decently good agreement on the general location and timing of the low pressure. I am looking at GFS Bufkit soundings to determine first guess precip type. Forecast confidence is very low due to precip type remaining near the mixed bag region of the nomogram. Diabatic processes could play a large part in the precip type especially Friday afternoon as the precip begins. Also, this is a cold air damming scenario with cold air filtering in between a fairly weak high to the Northwest and a Low to the northeast. NWS RAH mentioned that this storm compares generally well with a storm in 05 in which very little wintery precip fell in the region. With that in mind this is a completely different storm. GFS and every other model for that matter tends to warm temps too much during a CAD event. This fact makes me want to go with an icier/snowier scenario for the triangle as the GFS already predicting a decent amount of ice and snow, especially in the deformation. Climatology however does not support this type of system as a major winter event however, which is why my confidence is so low. On top of that there will be a tight gradient between the rain/mix/snow lines. Also, diabatic processes will turn borderline temps for freezing rain into temps for rain. Right now it's too far out to truly pinpoint the exact location of the low and the strength of the cold air.
But I will forecast what I see as of now... This is likely to change!
Friday afternoon: A 60% chance of snow possibly mixed with rain
Friday night: 70% chance of snow mixing with freezing rain/rain and sleet by 8PM and then changing to all rain/freezing rain/sleet mix.
Saturday: Rain quickly changing over to freezing rain/drizzle before ending.
Tuesday, November 10, 2009
Evening update
Not much to change. Will go with 4-6 inch storm fall totals for the triangle. Look for a bulls eye of precip well above three inches in the extreme southeast. The upslope regions may see a bit more as well. I don't see much of a break in the precip from beginning to end now due to the quick enhancement of the coastal low. It will almost be an immediate handoff from the 2 quasi seperate features mentioned earlier. Look for the precip to begin to wind down Thursday afternoon. Heaviest precip should be late tonight through tomorrow morning.
We're off to a pretty decent start already.. maybe moreso than the models were predicting so I wouldn't be shocked to see us in the 6+ range when all is said and done.
We're off to a pretty decent start already.. maybe moreso than the models were predicting so I wouldn't be shocked to see us in the 6+ range when all is said and done.
update on upcoming storm:
NAM now coming in even more bullish than the 6z GFS on precip amounts. So far it seems like a good call to go with the GFS yesterday. Despite the fact that this is an unusual storm, am now feeling extremely confident that we will see a historic storm in the triangle. Will post a quick update once the 12z GFS comes in.
November 09 heavy rain event
Potential historic rainfall event beginning this afternoon and lasting through mid week. Upwards of 5-7 inches could around and east of the triangle.
Moderate to heavy rain will begin later this afternoon into this evening as isentropic lift increases. Radar trends show showers already near the region. Expect these showers to increase in coverage and intensity as the right entrance region of an upper jet moves over the triangle region later this afternoon and through the night. The potential exists for one to two inches overnight as this feature moves through. Very slight lull in the heavy and widespread precip looks to occur tomorrow morning however, the rain will reintinsify Wednesday afternoon and through the night. In fact it appears that this has the potential to be the heaviest period of rain potentially dropping up to to 2 inches in a single 6 hour period Wednesday evening. This is due to a strong 500 mb vort max along with the emergence of the coastal low. This coastal low will continue to deepen due to strong diabatic influences and could deepen more than models are predicting. GFS predicts the precip to stick around through the day on Thursday despite the advance of cool dry air from the NW. It will be a figurative battle in regards to which air mass wins out... either the dry continental air or the moist tropical air. NAM finally starting to come into agreement with the GFS.
Now looking at statewide 3 inch storm total with 6-8 inches possible along the coastal plain. Will go ahead and call 4-5 inches storm total in the triangle region.
Wind also could be a major factor on Wednesday and Thursday as the Coastal low and Great Lakes High create an area of enhanced isobaric flow.
HPC is in genera agreement with a sharp cutoff in the western part of the state. I still think low level low will lead to enhanced precip due to orographic lift. RAH is less bullish on rainfall totals... but that may change later today.
Will try and update later today.
Moderate to heavy rain will begin later this afternoon into this evening as isentropic lift increases. Radar trends show showers already near the region. Expect these showers to increase in coverage and intensity as the right entrance region of an upper jet moves over the triangle region later this afternoon and through the night. The potential exists for one to two inches overnight as this feature moves through. Very slight lull in the heavy and widespread precip looks to occur tomorrow morning however, the rain will reintinsify Wednesday afternoon and through the night. In fact it appears that this has the potential to be the heaviest period of rain potentially dropping up to to 2 inches in a single 6 hour period Wednesday evening. This is due to a strong 500 mb vort max along with the emergence of the coastal low. This coastal low will continue to deepen due to strong diabatic influences and could deepen more than models are predicting. GFS predicts the precip to stick around through the day on Thursday despite the advance of cool dry air from the NW. It will be a figurative battle in regards to which air mass wins out... either the dry continental air or the moist tropical air. NAM finally starting to come into agreement with the GFS.
Now looking at statewide 3 inch storm total with 6-8 inches possible along the coastal plain. Will go ahead and call 4-5 inches storm total in the triangle region.
Wind also could be a major factor on Wednesday and Thursday as the Coastal low and Great Lakes High create an area of enhanced isobaric flow.
HPC is in genera agreement with a sharp cutoff in the western part of the state. I still think low level low will lead to enhanced precip due to orographic lift. RAH is less bullish on rainfall totals... but that may change later today.
Will try and update later today.
Monday, November 9, 2009
11/10-11/11 rainfal event
GFS and NAM both depict tropical storm Ida to come ashore late tonight/early tomorrow and interact with a strengthening short wave. A cold air damming high will move into the Great Lakes region as the storm slowly moves east along the Florida Peninsula. This sets up the potential for a significant overrunning event. Latest GFS Isentropic analysis supports this setup.
The NAM has recently trended away from high precip amounts... but I really like this setup for a heavy rain event. Cold dry air will filter in from the north, but it will basically be confined to the surface with warm moist tropical air advecting in strongly from the east just above the surface. I have doubts that the cold dry air at the surface will effect the precip that much if at all. It just looks like a classic setup to me even with the northerly surface winds. Normally I would be concerned about the NAM showing little precip for North Carolina... but in this case I'm quite confident that the GFS is correct. But with that in mind... we are talking about weather forecasting. Now... there will be a sharp cut off in the precip depending up the height of the column of dry air and the "reach" of the moist air. This boundary should be well to our north.
Expect widespread 2-3 inch rainfall amounts w/ potentially higher amounts near the foothills due to additional orographic lifting.
HPC outlook review: Basically 2-3 inch totals statewide except for the far northwest. The have the intensity increasing from NW to SE. This depiction does make some sense, although I am concerned a bit more with orographic effects.
RAH AFD review: RAH in basic agreement, but they do a nice job of mentioning the upper level features associated with the heavy rainfall including two instances of favorable jet dynamics due to the settling of the quasi irregular troughiness (i.e. merging of the deepening northern trough with the weakening southern trough.). Also, they point out the dynamic effect of latent heat release leading to an enhanced PV anomaly off the coast. This is the kicker for the enhanced rainfall along the coast. Will really need to keep an eye on this for some unexpected very rapid deepening which could lead to enhanced rain even for the triangle. Although, dry air should be pretty well mixed in through high enough in the column to keep the moisture off the coast. But again these thermodynamic effects need to be watched.
Forgot to mention the high wind potential Wednesday as the coastal develops. Could see some pretty good gusts with the high over the lakes and a deeping cyclone off the coast. This should be a fun storm.
The NAM has recently trended away from high precip amounts... but I really like this setup for a heavy rain event. Cold dry air will filter in from the north, but it will basically be confined to the surface with warm moist tropical air advecting in strongly from the east just above the surface. I have doubts that the cold dry air at the surface will effect the precip that much if at all. It just looks like a classic setup to me even with the northerly surface winds. Normally I would be concerned about the NAM showing little precip for North Carolina... but in this case I'm quite confident that the GFS is correct. But with that in mind... we are talking about weather forecasting. Now... there will be a sharp cut off in the precip depending up the height of the column of dry air and the "reach" of the moist air. This boundary should be well to our north.
Expect widespread 2-3 inch rainfall amounts w/ potentially higher amounts near the foothills due to additional orographic lifting.
HPC outlook review: Basically 2-3 inch totals statewide except for the far northwest. The have the intensity increasing from NW to SE. This depiction does make some sense, although I am concerned a bit more with orographic effects.
RAH AFD review: RAH in basic agreement, but they do a nice job of mentioning the upper level features associated with the heavy rainfall including two instances of favorable jet dynamics due to the settling of the quasi irregular troughiness (i.e. merging of the deepening northern trough with the weakening southern trough.). Also, they point out the dynamic effect of latent heat release leading to an enhanced PV anomaly off the coast. This is the kicker for the enhanced rainfall along the coast. Will really need to keep an eye on this for some unexpected very rapid deepening which could lead to enhanced rain even for the triangle. Although, dry air should be pretty well mixed in through high enough in the column to keep the moisture off the coast. But again these thermodynamic effects need to be watched.
Forgot to mention the high wind potential Wednesday as the coastal develops. Could see some pretty good gusts with the high over the lakes and a deeping cyclone off the coast. This should be a fun storm.
Friday, September 25, 2009
Myrtle Beach Forecast
Saturday afternoon: A 40% chance of showers and storms. Precip less than .1 inches.
Saturday night: A 60% chance of showers and storms. Precip .25 - .5 inches.
Sunday: A 60% chance of showers and storms before noon, but mainly earlier in the morning. A 20% chance between noon and 2 PM with clouds decreasing after noon. High 84 but a bit lower on the beach.
Sunday night: Clearing skies
Monday: Partly cloudy with a 20% chance of late afternoon storms. Precip less than .1 inches High 86 but lower on the beach.
Monday night: Partly cloudy with a 20% chance of showers/storms in the evening. Precip less than .1 inches.
Tuesday: Clear and cooler with a high of 78.
Saturday night: A 60% chance of showers and storms. Precip .25 - .5 inches.
Sunday: A 60% chance of showers and storms before noon, but mainly earlier in the morning. A 20% chance between noon and 2 PM with clouds decreasing after noon. High 84 but a bit lower on the beach.
Sunday night: Clearing skies
Monday: Partly cloudy with a 20% chance of late afternoon storms. Precip less than .1 inches High 86 but lower on the beach.
Monday night: Partly cloudy with a 20% chance of showers/storms in the evening. Precip less than .1 inches.
Tuesday: Clear and cooler with a high of 78.
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