Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
241 am EDT Sat Mar 28 2015
a potent upper level disturbance will track across the area this
morning. In the wake of the disturbance...dry high pressure will
build into the region from the northwest tonight and settle over
the Carolinas on Sunday.
Near term /today/...
as of 240 am Saturday...
Morning: strong DPVA /height falls/ attendant a powerful upper
level trough progressing across the region early this morning will
result in shallow convective showers between 06-10z this
morning... primarily east and northeast of the Triangle. Despite
steep low- level lapse rates...thermal profiles will remain nearly
saturated with little evap cooling potential (06z surface observation indicate
dewpoint depressions of only 0-3f in the coastal plain). And the
freezing level is prognosticated to fall no lower than 1-2 kft above ground level by 12z
(currently 3 kft per 06z Storm Prediction Center mesoanalysis)...a formidable melting
layer to overcome...particularly in the absence of significant
evap cooling and/or heavy precipitation. With the above in mind...
have opted to remove mention of a rain/snow mix early this
morning...with precipitation exiting before thermal profiles
become supportive of a mixed ptype.
Afternoon: despite full sun /late March insolation/...an
anomalously cold airmass deposited by strong cold advection this
morning will result in well below normal highs ranging from the
middle 40s north/northwest to lower 50s S/se. -Vincent
Short term /tonight and Sunday/...
as of 240 am Saturday...
..freeze watch upgraded to a freeze warning...
Tonight: Canadian high pressure will build into the region from
the northwest this evening into tonight...settling over central
and western NC by sunrise Sun morning. Based on observations of
the upstream airmass advecting into the region and the latest
model guidance...confidence is high that temperatures will fall
below freezing by 06z sun and bottom out in the low/middle 20s
across the north/northwest Piedmont and middle/upper 20s along and south of
Highway 64...coldest in the western Piedmont and warmest in the far southeast
Sunday: the strongest synoptic subsidence will shift offshore on
Sunday in concert with the progressive upper trough...with the
attendant low-level ridge shifting offshore the Carolina/southeast coast
by 00z Monday. A southwest flow /warm advection/ will develop across
the western Piedmont by middle/late afternoon...though a neutral
advection pattern is expected over eastern portions of the area.
Accounting for airmass modification via late March insolation...and
marginal warm advection in the west...expect highs ranging from
the upper 40s NE coastal plain to lower 50s SW Piedmont. -Vincent
Long term /Sunday night through Friday/...
as of 240 am Saturday...
Sunday night and Monday...a middle level short wave and associated surface cold
front will approach from the northwest and move across the Carolinas early
Monday. Given antecedent dry air and lack of signif moisture return
ahead of the front...this system should move through with little
precipitation...although guidance suggests at least low-end chance probability of precipitation are
warranted for Monday morning...but as noted...quantitative precipitation forecast values are low.
Lows Monday morning in the upper 30s and highs on Monday reaching
the lower 60s...thanks to Post-frontal westerly flow and sunshine
returning by mid-day.
Monday night through Tuesday...look for quiet weather as dry northwest flow
persists over the region while a transient surface high moves across the
Carolinas. Seasonable temperatures...lows Monday night around 40 and highs
on Tuesday in the middle-upper 60s.
Tuesday night and Wednesday...a backdoor cold front will drift south
across our state...stalling near the SC border by late Wednesday.
Once again...moisture appears to be limited...so not expecting much
if any precipitation associated with this front. Lows in the middle 40s and highs
Thursday through Friday...a southern stream short wave is prognosticated to
move across our region on Thursday...followed by a northern stream
short wave passing across our area late Friday. As such...look for
the aforementioned backdoor cold front to lift to our north as a
warm front on Thursday...bringing at least slight chance probability of precipitation during
the daytime Thursday. A better chance for rain will come Friday
along and ahead of the cold front associated with the northern stream
short wave. Highs around 70 and lows in the 50s.
Aviation /06z Saturday through Wednesday/...
as of 200 am Saturday...
24-hour taf period: aside from a brief potential for MVFR ceilings
and rain showers at the rwi terminal between 06-10z this
morning...VFR conditions and clear skies will rule at all central
NC terminals through the taf period. A northwest breeze at 10-15
knots with gusts up to 20 knots is expected during the day...weakening
to ~5 knots by sunset and becoming calm by the end of the taf period
as Canadian high pressure builds over central and western portions
of the Carolinas.
Looking ahead: VFR conditions will rule Sunday as high pressure
builds into the region from the west/NW. The next potential for
adverse conditions (mvfr ceilings and light rain) will be Monday
afternoon as an upper level disturbance tracks across the region.
Otherwise...expect VFR conditions to prevail through the middle of
next week. -Vincent
record low temperatures for March 29th are listed below.
Record minimum temperature
freeze warning from 2 am to 10 am EDT Sunday for ncz028-042-