Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1024 am EDT Friday Jul 3 2015
a stationary front over North Carolina will drift north as low
pressure moves east along the front and crosses the central middle-
Atlantic late tonight into Saturday. High pressure builds Sunday.
An upper level disturbance lingers over the southern middle-Atlantic
Monday and Tuesday before a cold front enters the area Wednesday.
Near term /through Saturday/...
as of 13z...stationary front remains in place over North Carolina
with high pressure to the north over the Great Lakes. Fog is
dissipating at this time so thoughts of an advisory no longer
Today...weak low pressure drifts east along the Ohio River...lifting
the stationary front north as a warm front. Eastern extent of prefrontal
rain currently over far western Virginia will shift NE into southwestern zones later
this morning. Rain coverage increases this afternoon with embedded
isolated thunderstorms roughly kcho and short wave. Maximum temperatures limited by increasing
high clouds and afternoon cumulus field (as well as rain in southwestern half of
cwa). Latest guidance has slowed the advance of precipitation into the
metropolitan...so nudged highs up a smidge and cut the mention of
showers out until this evening. Also...given Morning
Sun...decreased sky cover for the next several hours until late
arriving system finally results in a broad increase later this
Tonight...warm front lifts into the area as weak low center drifts
east across the County Warning Area. Exact track will determine instability/thunderstorm
threat as well as be the axis of heaviest rainfall. Nudged probability of precipitation up
again with categorical into the metropolitan. Quantitative precipitation forecast generally a quarter
inch to an inch.
Fourth of July...weak low shifts east to the Bay in the morning with
trailing front drifting south as a cold front. Plenty of frontal
forcing to cause rain...so likelies as back in the forecast.
Widespread cloud cover should limit instability with best thunder
chances south of the front in the warm sector. Northwesterly flow begins in
the afternoon with precipitation generally tapering off from northwest to southeast.
Clouds look to persist however...so nudged temperatures down a
bit...with 70s common.
Short term /Saturday night/...
by 00z sun...surface lp prognosticated to be moving away from our area.
Models continue to trend away from any precipitation after 0z...so nudged
probability of precipitation down a bit more...with precipitation taken out of the forecast
after about 1z in the metropolitan. Any isolated thunder should be
early. With some clearing possible later Saturday night...will
need to monitor possibility of fog.
Once rain pulls away...expecting a gradual clearing trend through
the day sun...ahead of the next system approaching from the SW.
Temperatures expected to be in l80s with light winds.
Long term /Sunday through Thursday/...
fairly weak flow pattern at middle and upper levels through the
extended...with waves of energy moving through the flow near our
area. First wave approaches late sun or early Monday...bringing with it
a chance for showers and thunderstorms as surface low tracks near our area. Next wave
and associated cf approach the area around Wednesday and is more
progressive/compact. While thunderstorms are forecast nearly each
day...activity will be mainly diurnally driven...and with weak middle
level flow...atmosphere not expecting convective activity to be very
Quasi-zonal flow by middle-week will help to keep temperatures near
climatology norms. There is a hint of middle/upper level ridging trying to
build in towards the end of the week...which could lead to temperatures
slowly increasing to at or above climatology norms. Humidity will also be
tolerable with dewpoints generally remaining at or below 70f.
Aviation /15z Friday through Tuesday/...
stationary front over NC this morning. Fog earlier this morning is
dissipating. High clouds overspreading the area at this time. The
front drifts north through tonight as low pressure rides east from
the Ohio Valley. The low moves east of the District of Columbia metros Saturday
afternoon. Generally MVFR conds in likely rain across the
terminals with possible IFR late tonight and early Saturday. Best
thunderstorm chances south of District of Columbia metros Saturday. Will need to watch
potential fog development late Saturday night.
Conds expected to improve through the day Sunday...with light winds
and little chances for precipitation at the terminals. Next aviation concerns
possible late sun through Monday as next system approaches and brings
chances for shwrs/tstms. Sub-VFR conditions possible near thunderstorms...with
onshore flow today north of a stationary front over NC. Small Craft Advisory for
southern Maryland waters tonight and Saturday morning as weak low pressure
crosses with southerly flow gusting up to 20 knots. Isolated gusty
thunderstorms late tonight through Saturday as low pressure
Winds are expected to remain below Small Craft Advisory levels through the extended
period under light and variable flow. However...mariners are advised
to monitor for thunderstorms...as isolated thunderstorms are possible nearly each
day...with the best chances Monday and Wednesday.
District of Columbia...none.
Marine...Small Craft Advisory from 6 PM this evening to 6 am EDT
Saturday for anz534-536-537-543.