Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
856 PM EDT Sat Mar 28 2015
an upper-level trough will move across the eastern United States
tonight. High pressure will build overhead on Sunday. A cold front
will drop through the area on Monday...with another cold front
arriving on Wednesday.
Near term /through Sunday/...
latest water vapor imagery showing vorticity maximum centered over south-
central PA...swinging through and offshore by 06z tonight. Despite
forcing aloft...with the loss of daytime
heating/instability...seeing snow showers dcrsng in coverage over
northeastern Maryland. Have mention of flurries still through 02z then dry
the remainder of the night.
In the wake of the vorticity...expect mean layer relative humidity to thin...which when
factored west/ loss of diurnal clouds and negative vorticity advection...clouds should rapidly
decrease. Still a decent p-gradient so winds should become less but will
still be a factor. Considering impact of cold air advection and current temperatures...
went on the cool side of MOS mean even west/o good dcplg. Thus min-T in
the teens commonplace blurdg westward.
Will be under transitory surface hipres Sunday west/ building heights aloft. That
should be a favorable combo...mosun skies and warmer temperatures. MOS mean not
far off from prvs forecast...so a blend was taken. Maxt may exceed 50f in
our Virginia counties...still more than 10 degf below average but 10+ degf warmer
than today. In addition...winds around 5 knots would mean not much of a wind
Short term /Sunday night through Tuesday/...
after yet another reminder winter hasn/T completely left...the
start of the work week will have more of a Spring-like rebound.
Lows Sun night into Monday morning will be cold...near freezing in
most areas briefly - and also starting off cloudy west/ an upper wave
passage. A brief period of upslope precipitation...and some light snow
and/or rain showers for portions of the southern fringe of the area.
Good guidance agreement that the Appalachians efficiently disperse much
of the precipitation as the upper wave and surface cold front quickly passes
overhead. Some weak low level jet dynamics and some limited the winds will
then kick-in shortly after sunrise...low level - but increasing -
moisture should also allow for some precipitation develop across our southern
fringe briefly early Monday. A light and brief rain/snow mix possible
over southern Maryland/Delaware-Maryland-Virginia before dawn...then this activity quickly
moves off the coast.
In its wake will be clearing skies over the area and a breezy westerly
wind that will keep the higher terrain cooler but the downsloping
effect in the valleys/lowlands will help high temperatures reach the M-u50s by
afternoon. Winds will gust in the 20-30kt range across the area...espec
along the Mason-Dixon line and across the higher terrain. Not
anticipating Wind Advisory conds but it could be warranted for
higher terrain. Monday night...temperatures will again drop toward the
freezing mark...even west/ a relatively higher dewpoint field across
As winds drop off from the Monday cold frontal passage...Tuesday will
start off much more calm but still cold. Temperatures will quickly climb
back through the 40s and 50s on the way to highs in near 60f before yet
another upper wave passage. Oddly the 12z versions of the Euro and
GFS traded solutions from their 06z runs. The latest GFS took the
minor upper wave elongated more latitudinally and made it the
further north compact low spreading directly over PA and touching
our northern fringe. The 12z Euro is the opposite. Their algorithms also
make a decent percentage of the model precipitation into snow...espec over
the northern reaches of the precipitation batch. The trouble west/ the stronger of
the solutions - which would be the potent and more compact system to
the north is that it would illicit a stronger warm air advection region out ahead
of the system. The warmer air entrained into the portion of the
system spreading across our region would have a lower potential for
frozen precipitation west/ highs reaching the 50s/l60s just ahead of the
system. Not an intense temperature plunge expected west/ this feature either
way...W/ temperatures dropping at an average pace into the u30s/l40s. The
advection pattern also not particularly strong according to these
same models...which keeps the surface winds fairly light throughout this
Long term /Tuesday night through Saturday/...
a few rain showers could linger along the Mason Dixon region Tuesday
night as a cold front works its way southward and high pressure
builds southeastward from the Great Lakes region. Low temperatures
will be mainly in the upper 30s to near 40...near normal for early
The high pressure will bring dry conditions and near normal
temperatures to the region Wednesday. Expect high temperatures to be
near 60 to the middle 60s.
As the high moves to the East Coast and offshore Wednesday night...a
southerly flow will develop and increase during the day Thursday
ahead of an approaching cold front. Low temperatures should reach
the middle 40s Wednesday night as highs are expected to approach 70
degrees across much of the region Thursday.
A cold front should push across the lower Great Lakes Thursday
before slowing down and dragging across the middle Atlantic region
Thursday night and Friday. This front will be the focal zone of
developing rain showers and perhaps a rumble of thunder or two
late Thursday through Friday. Temperatures should remain mild
Thursday night and Friday with highs reaching the middle 60s Friday.
By Friday night and possibly as late as Saturday afternoon...a
low pressure system is expected to develop along the cold front
and push across the region...bringing prolonged chances of rain
showers or even a thunderstorm. Timing is uncertain as to this
low's development and its location or progress...nonetheless...the
rain chances linger once again across the middle Atlantic.
Aviation /01z Sunday through Thursday/...
VFR conditions through sun. Northwest flow with gusts...ending 01-03z
everywhere except kbwi/kmtn. Might become more occasional in nature
overnight before ending by 12z. Light northwest flow will shift to west
midday...then SW for tomorrow evening.
Dcrsng clouds tonight...mainly middle level if any. Few high level clouds
possible during the day sun ahead of next low pressure system.
Incrsng middle level clouds Sun night as precipitation approaches from the
west. A fast-moving cold front will slide through early Monday morning...W/
little if any precipitation but a brief period of overcast middle clouds that
break up and move east quickly after sunrise. Low level winds 35-45
kts...with gusts 20-30 kts at the surface Monday.
VFR conditions...and light winds Monday night-Tue. MVFR conditions
possible at kmtn and kbwi terminals Tuesday night with lingering precipitation.
Otherwise...VFR conditions Tuesday night and Wednesday. Winds
light and variable Tuesday night becoming northwest and gusting to
15 knots Wednesday.
Small Craft Advisory remains in effect all waters with 00z observation showing gusts 20-25
kts. Small Craft Advisory is dropped upper tidal Potomac at midnight...upper
Chesapeake Bay midday Sunday...and the remaining areas Sun afternoon.
The Small Craft Advisory may end earlier for the southern portion of the
Bay...though will hold with timing for now.
Small Craft Advisory will likely be needed again later Sun night as a cold front
crosses over the area early Monday morning. Behind the front...west
winds will again pick up into solid Small Craft Advisory ranges and possible gales
for the daytime hours Monday. Winds will gradually subside overnight
into Tuesday. Another cold front will cross the region late Tuesday...W/ a
period of low-end Small Craft Advisory gusts possible.
No marine hazards expected Tuesday night and Wednesday. Winds may
gust to 15 knots Wednesday.
a late season shot of cold air is currently moving over the region.
If temperatures do not spike any higher this evening...Dulles
international Airport (iad) will be on track to break a record daily
low maximum temperature. The record daily low maximum temperature
for March 28th is 39 degrees which was set in 1996. So far today
they have reached 37 degrees...which was shortly after midnight
local Standard time last night.
Sunday morning (march 29th)...low temperatures may approach record
minimum values for the date.
Site...3/29 record min T...forecast min T...
District of Columbia...none.
Marine...Small Craft Advisory until noon EDT Sunday for anz530>532-
Small Craft Advisory until 4 PM EDT Sunday for anz533-534-541-
Small Craft Advisory until midnight EDT tonight for anz535-536.