Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
1051 PM EDT Tuesday Jul 28 2015
Synopsis...a series of perturbations aloft interacting with a moist
and unstable air mass will trigger isolated to scattered
thunderstorms...mainly during the afternoon and evening hours...
through the remainder of the work week.
Near term /through tonight/...
as of 1050 PM Tuesday...
The 00z Wednesday upper air analyses continue to show the upper
level ridge centered to the west-southwest...with generally northwest flow
aloft over central NC. Aside from a few lingering showers in Virginia...
the convection from early this evening has ended. A few of the hi-
res cams try to generate some additional shower activity in the northwest
overnight. Although confidence is not terribly high at this
time...will forecast a slight chance for showers in the northwest tonight.
Otherwise...expect lows in the low to middle 70s overnight.
Short term /Wednesday and Wednesday night/...
as of 335 PM Tuesday...
Upper ridge centered over the Southern Plains temporarily
amplifies/extends eastward into the Carolinas Wednesday in response
to a short wave traversing the northern plains. This building of heights
aloft will induce a middle level cap on the atmosphere...inhibiting
convective development over most of the area. The exception will be
the far west and north sections of the County Warning Area where the persistent
leeside trough and a stalled weak surface boundary will provide a focus
for is attributed to patchy fog and/or low clouds. This occurrence
appears more likely at krwi and possibly kfay.Olated-scattered
convection int eh afternoon-early evening.
Maximum temperatures wedneday should be comparable to high temperatures recorded today
(near 90-lower 90s). Potential to see a spot or two in the southern
Piedmont/sandhills flirt with middle 90s. Min temperatures near 70-lower 70s.
Long term /Thursday through Monday/...
as of 300 PM Tuesday...
The main feature for our area during the long term period will be
the deepening long wave trough over the east. It will begin late
Thursday as the trough begins deepening over the Ohio Valley and middle
Atlantic region...and in doing so will push a cold front across our
area Thursday night. Will have to begin ramping probability of precipitation up across our
western zones during the afternoon Thursday...but most of daytime
Thursday should remain dry. The best chance for rain will be
Thursday night into Friday morning...then rain chances ending from west-
east during the afternoon Friday. Temperatures during this time near normal.
Fair weather then appears to be in store for central NC over the
weekend with high pressure building to our north and much drier air
over our region. The prognosticated low level airmass still appears to
support highs as warm as the low 90s...so little if any relief
temperature-wise despite high pressure building to our north.
Probability of precipitation expected to rebound closer to daily climatology values as we head
through early next week and precipitable water slowly recovers. However...
coverage should be isolated at best given the better synoptic features
remaining both to our north and to our south.
It's Worth noting that given the lingering boundary and low pressure
to our south during this time...any slight northward shift in the
pattern could mean higher rain chances for US during the weekend and
early next week...especially across our southern zones. So given our
proximity to these features...our confidence in this part of the
forecast isn't particularly high.
Aviation /00z Wednesday through Sunday/...
as of 755 PM Tuesday...
Scatterattributed to patchy fog and/or low clouds. This occurrence
appears more likely at krwi and possibly kfay.Ed convection across
the western and central Piedmont continues to wane...and should
gradually diminish with continued loss of heating. There may be a
brief period of IFR conditions in fog/stratus Wednesday morning...at
fog prone krwi and in the west where rainfall has been heaviest.
Otherwise...central NC will remain in a typical Summer pattern with
VFR conditions interrupted by brief instances of afternoon-evening
MVFR due to convection...and early morning IFR conditions due to
patchy fog and low clouds. Afternoon coverage may be enhanced Friday
as a surface front drifts southward across the region.