http://weather.cod.edu/forecast/ECMWF/e ... spd_48.gif
Synoptically, at 500H our attention is drawn to a few critical features, the FIRST of which is a strong double contour closed upper low centered over NRN CA at 0z WED, the resultant effect of which is contributing to rising heights and strong ridging across the eastern part of the country. The pattern Doesn't change much by THU, however heights lower and the ridge is beaten down somewhat across the EUS as upper trough centered Over Hudson Bay on WED develops closed low at 500H and slides over toward Newfoundland on THU as Blocking develops over Greenland (-NAO)
http://weather.cod.edu/forecast/ECMWF/e ... spd_72.gif
At the Surface, a cold front will push through the Northeast and New England Overnight THU night and eventually clear the Northern Mid Atlantic region Friday before stalling out and eventually retreating back to the NE as a warm front over the GL and Ohio valley region SAT and SUN
http://weather.cod.edu/forecast/ECMWF/e ... emp_72.gif
http://weather.cod.edu/forecast/ECMWF/e ... mp_120.gif
http://weather.cod.edu/forecast/ECMWF/e ... mp_144.gif
IF we take a second to examine whats going on in the source region, where this warm air is originating (over the Midwest), highs today were in the 90s across MUCH of SRN MN, and even over 100F across western KS/SW NB, underneath 850H temps (based on 21z RUC analysis) over +22 C over MN, and as high as +30-34 C over WRN KS/SW NB, where the aforementioned SFC temps over 100F were observed at the same time. This air is being transported Northeastward by a strong South and SW flow in the lowest 5K feet.
The 90s across MN were also well correlated w/ an area of Low level thicknesses > 1440m.
http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_000s.gif
Across the Northeast and Mid Atlantic region, the flow around the high will bring in probably the warmest air of the season yet for the region on WED and THU, before the cold front puts and end to it on THU night and FRI.
At 18z WED the ETA has 850H temps of +15-18C, and the GFS has relatively the same thing:
We must ALSO account for:
1. Warm Advection
2. Downsloping Westerly/WSW flow
3. Near Full Sun.
That would translate to Highs of 91-96F for H850 temps of 15-18C during JUN w/ full sun, warm advection and downsloping. Or roughly the Lower to Mid 90s.
Now, lets check that against model generated guidance numbers in BWI, PHL, NYC, and BOS on WED:
http://www.nws.noaa.gov/cgi-bin/mos/get ... C&sta=KPHL
MAV guidance (based on the GFS) suggests highs in the lower 90s across the Major cities on WED, which would agree w/ the lower end of the range which we established using 850H temps, expected sky conditions, warm advection and downsloping, thus these numbers MAY be underdone by a degree or two, but by no means out of touch.
So in general, one may expect to see highs of 90-95F (if we take a blend of the 850H temp method and use of MAV numbers) in BWI, PHL, NYC, and BOS on WED.
For THU, things become complicated since the cold front will be on the doorstep of BOS at 18z THU, and Just N of the PHL and NYC areas also, thus w/ plenty of clouds and precip around, SFC heating will be limited. However even w/ that in mind, the GFS has 850H temps at 18z at NYC right around 15C, (actually the 15C isotherm runs almost right over the city its self at 18z), PHL, likely between 15-16C, and 15-17C at BWI. Highs at BOS may very well be reached EARLIER in the afternoon before the passage of the front.
The ETA is actually somewhat cooler, likely as a result of the further south placement of the cold front, which has it through the BOS area, into NYC and on the PHL doorstep at 18z. Thus for that reason highs will likely be reached earlier on, and surface heating will be significantly limited by clouds and precip.
MEX numbers at BWI, PHL, NYC and BOS outline this pretty well, which have highs THU at BOX and NYC only in the 70s, while PHL and BWI make it into the Low and mid 80s.
http://www.nws.noaa.gov/cgi-bin/mos/get ... C&sta=KPHL
These also seem pretty reasonable given convection and overcast. So in summary, WED will be the warmest day of the two which we have discussed, this is also the most likely day to crack the lower or mid 90s in the I-95 corridor. It should also be noted that the Westley flow may pin the sea breeze along the coast on WED helping eastern and coastal sections away from the immediate ocean to really bake.
