169 
fxus61 kmhx 210831 
afdmhx 


Area forecast discussion 
National Weather Service Newport/Morehead City NC 
430 am EDT sun Mar 21 2010 


Synopsis... 
high pressure will continue to drift offshore today. A wet cold 
front will approach eastern North Carolina late tonight and cross 
the region on Monday. An upper low pressure area and secondary 
surface cold front will move across the area Tuesday. High 
pressure will build back into the area middle week. 


&& 


Near term /until 6 PM this evening/... 
cloud shield assctd with upper level system over Southern Plains will spread 
in from SW today...keeping inland temperatures 3-5 degrees cooler than on Sat. 
More sun near the coast but highs still mainly 65-70 due to sea 
breeze influence. Model guidance supports precipitation holding off until tonight 
so kept dry forecast. 


&& 


Short term /6 PM this evening through Tuesday night/... 
models remain consistent with complex surface system affecting area 
tonight and Monday assctd with upper moving in from SW. Main precipitation period 
expected to be 06z tonight through 18z Monday. Some model differences 
on how widespread precipitation will be and kept probability of precipitation in likely range for now. 
With low level jet developing across area late tonight...some concern 
for gusty winds with any stronger convection but concur with Storm Prediction Center day 
1 and 2 outlooks that instability will be limited at severe threat 
isolated at best. Dry slot will rotate in behind main precipitation band Monday 
afternoon and dropped probability of precipitation then for SW 2/3 of area. Kept 20 probability of precipitation all zone 
Monday night with upper low moving across...but limited to northern sections 
on Tuesday as westerly low level flow will keep most of area dry. 


Raised min temperatures a few degrees tonight with warm air advection...and also raised highs 
over SW on Monday with some clearing expected. MOS blend rest of 
period. 


&& 


Long term /Wednesday through Saturday/... 
no changes to previous forecast. Ridging surface and aloft expected Wednesday-Thursday 
with latest models indicating weak backdoor front stalling over area 
early Thursday. Next system will affect area Fri-Sat. Latest models have 
weakening trend with this system but still enough support to keep 
chance probability of precipitation. 


&& 


Aviation /08z Sunday through Thursday/... 
as of 245am sun...VFR/skc continues early this morning with the area 
still under the influence of vertically stacked ridging. Return flow 
pattern has allowed low level moisture to increase...though think there is 
still enough dewpoint depression and southerly flow in the boundary layer 
to prevent widespread fog formation. Patchy MVFR visibilities will be possible 
through 13z though. Upstream Sat pics and forecast soundings suggest 
we will see increasing high cloudiness today...with possible scu also 
developing in the afternoon with diurnal effects and continued moisture increase 
with southerly flow. Expect VFR to persist through this evening with cloud 
bases gradually lowering to more of a middle level deck...though think 
precipitation will hold off until after 22/6z. A band of showers with 
embedded thunderstorms is expected to accompany a frontal system moving through 
the region between 6-18z Monday...with associated MVFR/isolated IFR. 
Improving conds expected Monday afternoon as deepest moisture pushes offshore. 
Will also need to watch for low level wind shear late tonight into 
early Monday morning as 35-45kt low level jet translates through the region just 
above the surface. 


Low probabilities for -shra/MVFR Monday night into Tuesday as upper low 
moves through the region...and otherwise VFR in extended. 


&& 


Marine... 
as of 330am Sunday...1022 mb high pressure just east of the obx this 
morning will continue pushing offshore through the day...allowing 
light southerly winds with seas at or below 3ft to persist most of the day. Low 
pressure will organize over the Tennessee River valley tonight and move slowly 
NE through Monday. Associated initial surface boundary expected to approach 
from the SW late tonight and move through the waters Monday morning and 
afternoon. Models continue to agree that S/southeast flow will gradually 
increase tonight ahead of this feature to Small Craft Advisory 
levels by early Monday morning most waters except for the albamarle 
sound. Some concern of how strong winds will be with poor mixing 
environment given warm southerly flow over chilly shelf waters....so was 
hesitant to put any winds over 25kt despite a few sporadic 30kt 
barbs showing up in the 00z guidance suite. Winds shift SW Monday 
afternoon/night behind surface boundary and expected to be mainly 15-20kt. 
Low end Small Craft Advisory range SW to west winds (20-25kt) expected again Tuesday and Tuesday 
night as low pressure strengthens north of the area while interacting with 
high pressure skirting east across the Gulf Coast. The strongest winds on 
Tuesday are expected over the central and southern waters. Diminishing westerly 
winds expected Wednesday as low pressure to our north moves east and high pressure 
builds in from the south. 


Uncertainty arises for the Wednesday night/Thursday timeframe as medium range 
guidance is disagreeing with a cold front to impact the area. The 
GFS has been consistent with pushing the feature south of the area 
with a surge of northerly winds for early Thursday...while the European model (ecmwf) stalls the 
boundary out near our northern waters on Thursday and then returns north Thursday 
night. Given the uncertainty decided to make no changes to previous 
forecast this time frame which keeps mainly light westerly flow over the 
area Wednesday night/early Thursday before veering southerly into Thursday night. 


Generally followed Swan in the short term except did not build or 
decay the short period southerly wave system as quickly as its solution 
tonight/Monday since this is systematic problem. Expecting an area 
of near 10ft seas to transition north through the waters late 
tonight and especially Monday. Small craft seas to linger for central and 
southern waters through early Wednesday morning...and end sooner (mon nite) for 
northern waters with less exposure to this fetch. Seas come down 
Wednesday...but if the Wednesday night/early Thursday front pans out could see 
building northerly wind waves for northern waters on Thursday. Did not use ww3 this 
time frame in order to be consistent with our wind grids. 


&& 


Mhx watches/warnings/advisories... 
NC...none. 
Marine...Small Craft Advisory from 5 am to 5 PM EDT Monday for 
amz135. Small Craft Advisory from midnight tonight to 5 am 
EDT Wednesday for amz152-154-156-158. 
Small Craft Advisory from 7 am Monday to 2 am EDT Tuesday for 
amz150. 


&& 


$$ 
Synopsis...jbm 
near term...jbm 
short term...jbm 
long term...jbm 
aviation...mw 
marine...mw 

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