Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
823 PM EDT Friday Mar 27 2015
an upper-level trough will slowly move across the eastern United
States tonight and Saturday morning. High pressure will build
overhead Sunday. Several weak fronts will cross the area next
Near term /through Saturday/...
Re: District of Columbia Cherry blossoms and average temperature.
For the past 30 yrs...looking at average temperatures for the period 2/1-3/26...for
District of Columbia 2015 is the 2nd coldest...only behind 1993. Nps web site still
does not show any Blossom activity as havg begun. In 1993 the peak
occurred on 4/11. The latest peak bloom (since 1921) was in 1958 -
Radar shows light snsh over west.V. In asso west/ a vorticity in the long WV
pattern. Short range models show this dissipating as it moves east of the
While we have chance SW/rain shower in the forecast for Sat morning through middle afternoon this
is the time of yr where low level instability coupled west/ a cold pool
aloft can produce graupel.
Hipres builds during the middle-lt afternoon...which will allow for skies
to begin clearing. Thus dont have any probability of precipitation for the latter half of the
afternoon. Winds will be gusty all day...and that will continue to nightfall.
Top of mixed layer contains 25 knots...which gives a reasonable idea of
the gust potl.
Temperature guidance fairly well clustered and consistent west/ going forecast. As
such...have taken a blend to Iron out any consistencies that may
reside. That means min-T middle teens-20s mountains and 30-35f coastal plain.
Maxt middle 30s-middle 40s. Shaded temperatures across the north and west down by a
degf or two to acct for impact of cold air advection.
Short term /Saturday night through Sunday night/...
After a day in which it may feel like winter is still here - on
Sat...Sunday will be a slight rebound back toward more average
conditions. Ultimately we'll miss the mark in temperatures of average highs on
sun by a solid 10f degree of so...but light winds and mostly clear
skies will at least supplement the cooler temperatures. A weak upper ridge
will be responsible for our quiet weather conditions on sun...but with a
still very active jet stream - multiple upper disturbances remain in
the queue for passage over the coming week.
Fast on the heels of the upper ridge will be relatively large but
fairly moisture-starved upper wave from the Great Lakes region.
Overnight lows will again drop down into the M-u30s but west/ a light
southerly wind out ahead of the approaching disturbance...these conditions
will be moderated and prevent most areas from reaching the freezing
mark. A weak cold front will arrive early Monday morning...quickly passing
across the region and mainly just switching the surface wind direction
from southerly to westerly...also efficiently mixing down some gusty winds for
the daytime hours. West winds of 20-30mph expected west/ locally higher
gusts...creating some downsloping and a supplemental temperature increase
in the Lee of the Appalachians/Blue Ridge. Highs over the western half of the
area will likely jump into the M-u50s...though Nova the Piedmont may
see some M-u60s by late afternoon west/ clearing skies after the early morning
Long term /Monday through Friday/...
there may be enough moisture available out of low pressure system
over Great Lakes for weak positive vorticity advection to triggers a light rain shower or
two Tuesday. Great Lakes low will pass to our north. Temperature
profile supports mixed precipitation if any occurs late Tuesday
and early Wednesday. Weak positive vorticity advection in zonal flow will support rain ahead
of a weak frontal boundary during the latter half of the week.
Thightning gradient between approach front and offshore ridge will
produce S-SW winds 10-15 kts Thursday.
Aviation /00z Saturday through Wednesday/...
VFR conds through Sat. Rain shower/SW/ip possible during morning hours Sat alng west/ brief
Winds should be gusty bhd trough...from the northwest around 20-25 knots.
Sustained winds likely in the teens...not providing enough separation
to explicitly include gusts in taf.
No hazardous weather conds expected from late Sat into Monday...outside of
some breezy conds on Monday afternoon behind a cold front. Boundary layer
winds in the 30-40kt range west/ some 20-25kt gusts at the surface during
the daytime hours.
winds picking up tonight...although better mixing may not reach the
narrower waters until sunrise tmrw. Have made appropriate adjustments
to the database. Once it begins...top of mixed layer contains 25
knots...which gives a reasonable idea of the gust potl. Small Craft Advisory for all
Breezy northwest winds will continue over much of the waters Sat
night...espec the main Stem of the Maryland ches Bay. A slow steady wind
drop off on sun as high pressure makes a brief appearance before
another cold front on Monday morning. Behind the front...west winds will
again pick up into solid Small Craft Advisory ranges for the daytime hours Monday.
our area is in the midst of a large swing in temperatures. Ahead of
a cold front on Thursday afternoon (march 26th)...the region saw the
warmest temperatures observed since late October 2014.
Site...3/26/15 maximum T...warmest since.....
Dca.......77 f.......10/28/2014 (80 f)...
BWI.......74 f.......10/28/2014 (80 f)...
iad.......74 f.......10/28/2014 (82 f)...
Sunday morning (march 29th)...low temperatures may approach record
minimum values for the date.
Site...3/29 record min T...
District of Columbia...none.
Marine...Small Craft Advisory until 6 am EDT Sunday for anz530>534-
Small Craft Advisory from 8 am to 6 PM EDT Saturday for anz535-