Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
853 PM EDT Friday Oct 24 2014
high pressure will build overhead through Saturday. A reinforcing
cold front will pass through the region late Saturday night into
Sunday before high pressure returns for Monday. The high will move
off the coast during the middle portion of next week.
Near term /through Saturday/...
shortwave digging across Appalachia this evening. The 500 mb trough axis
providing a place for cirrus to congregate-- these clouds have mvd little
since lt afternoon. Guidance suggesting nearly satd upper levels will shift eastward
between 06-12z. Have adjusted skycover and will make appropriate
adjustments to temperatures too.
High pressure will move further into the middle-Atlantic Saturday
while the shortwave trough moves off the SC/Georgia coast. Mostly
sunny conditions are expected Saturday with west-SW winds around 10
miles per hour. A dry cold front will approach the Allegheny Front Saturday
afternoon and overcast condtions are expected in upslope locations.
Forecast maximum temperatures will be slightly warmer than today...Friday...mid
to upper 60s expected. Have made an addtl upwd bump of a degf or two
based on Friday observation and 18z guidance.
Short term /Saturday night through Monday/...
vertically stacked low pressure will travel across southern Quebec
Saturday night...with a trailing cold front crossing the local area.
This front will be very weak in nature as the moisture and forcing
with this system will be well to our north. Conditions may be
favorable for upslope showers or sprinkles...but given the shallow
nature of the moisture...would expect any amounts to be very light.
Any precipitation that does fall should be in liquid form as
overnight lows will be near 40 in the higher elevations. Much in the
way of cloud cover may be difficult to come by with the frontal
passage east of the mountains with lows in the upper 40s to low 50s.
Pressure gradient from system to the northeast will result in a
breezy Sunday with good mixing. Minimal thermal differences behind
the front...plentiful sun and a downslope flow will result in high
temperatures similar to Saturday across most of the area...near or
slightly above seasonal norms. High pressure will build into the
central Appalachians Sunday night and with a dry atmosphere...
favorable radiational cooling conditions will develop. Have
middle-upper 30s west of the metros but feel these areas could sneak a
few degrees cooler. Mention of patchy frost has been maintained in
these areas. Middle 40s can be expected in the metros. The high will
slide toward the Carolina coast on Monday with middle/upper level
ridging expanding toward the East Coast. Many locations will see
highs near or above 70.
Long term /Monday night through Friday/...
European model (ecmwf) indicates that a shortwave from northern plains crossing Great
Lakes by late Tuesday. 500mb trough and weak positive vorticity advection crossing County Warning Area
Wednesday. Next shortwave to Cross County warning area Friday through Saturday.
Surface front from west will cross the County Warning Area Tuesday night into
Thursday morning. Another front from the west will affect the County Warning Area
from late Thursday into Friday afternoon. Certainty remains low this
far out in the forecast period. Although European model (ecmwf) timing seems to track
fairly well with HPC ensemble HPC indicates that pattern will
produce less precipitation than European model (ecmwf).
Aviation /01z Saturday through Wednesday/...
cirrus deck crossing the terminals this evening. Winds subsiding...and have
actually dcpld at several sites. VFR conditions expected tonight and
Saturday as high pressure moves over the region.
Clouds will increase from the northwest Sat night into Sunday. VFR
conditions expected. Gusty northwest winds are expected Sunday.
winds have subsided across the entire marine area. Allowed the Small Craft Advisory for
most of the waters to expire at 6pm...and have cancelled the rest.
High pressure moves near the waters tonight and Saturday. West-northwest
winds are expected but will stay below Small Craft Advisory criteria.
A dry cold front will move over the waters by Sunday and northwest winds
will increase across the waters. A Small Craft Advisory is likely Sunday and Sunday
High pressure will build overhead late Sunday night into Monday
before moving off the coast later Monday through the middle
portion of next week. A southerly flow will increase during this
time. A Small Craft Advisory may be needed for portions of the
waters Tuesday and Wednesday.
District of Columbia...none.