Meiszberg - Boston

...Forecast Discussion...

Current Analysis

Recent visible satellite imagery depicts mostly sunny skies for the Boston area along with a surface temperature of 77 degrees in Boston as of 1743 UTC. Meanwhile temperatures in the mid-80's are being reported elsewhere in the New England area. These conditions are a result of the positioning of a surface low located over northern Michigan with a 996 mb pressure center. This is creating a setup of strong southwesterly flow for much of the east coast being in the path of this progressing low. Composite radar remains clear at this time, however a slight risk for severe weather has been issued by the Storm Prediction Center for parts of New York and Pennsylvania.

Short Term (Tonight - Thursday)

This mornings 12Z NAM indicates the continued development of strong 850mb flow which is due to an increasing pressure gradient as the low center moves closer to the area. The combination of strong southwesterly flow and clear skies will warm temperatures today into the mid-80's. Both NAM and GFS 12Z runs are in agreement for a northeast track of this low and show the associated cold front moving through Boston in the morning hours tomorrow. Precipitation along this front however is not expected once reaching Boston as the models keep the precipitation off to the northwest, this could be due in part to orographic effects. Temperatures will not begin to drop significantly until Wednesday however, when high temperatures will drop to the low 60's. Conditions are expected to be dry overall through this period as upper level flow becomes more zonal after front passage.

Long Term

In the long term outlook, the primary concern is for the next system that is currently being shown in the GFS affecting New England by Saturday night. The GFS shows the development of a large trough at 500mb by 00Z Saturday with the base of the trough and vorticity maximum located over the Tennessee Valley. This system is being forecasted to have significant precipitation with the associated surface low. Quasi-geostrophic dynamics are expected to be favorable ahead of this surface low as it beings to move to the northeast through Sunday. By 18Z Sunday, a large band of heavy precipitation is expected within this favorable region.

Verification

Boston, MA NWS Climate Reports

April 16th

High: 87 (broke record of 84)

Low: 59

QPF: Trace

April 17th:

High: 84

Low: 57

QPF: 0.00 inches

April 18th:

High: 62

Low: 49

QPF: 0.00 inches

Surface observations from April 16 21Z

The daily climate report from NOAA for April 16th reported a record setting high temperature of 87 degrees. Surface observations around the time of maximum temperatures (above) show that several station were reporting temperatures as high as 91 degrees. These record breaking events were due to a combination of strong southerly flow at the surface and low levels and clear skies for much of the day out ahead of a low pressure system that was moving off to the northeast. Forecast soundings indicated a sufficient mixing out of the boundary layer by the early afternoon, allowing for the downward movement of warm air around the 850 mb level.

NAM40 April 17 00Z PMSL/1000-500mb thicknesses

NAM40 April 17 00Z 850mb temps/temp advection by full wind

The track of the associated low pressure center did verify well, as it did track towards the northeast into Canada bringing along with it a large temperature gradient along the cold front. This cold front began to move into the northeast by Monday evening and was associated with a region of cold air advection, up to -3 degrees Celcius per hour. As indicated in the climate reports from the short-term, the Boston area did not experience this cool down until Wednesday (Apr 18) when the colder air began to fully reach the area. This change in air mass is clearly seen in the plots of 1000-500mb thicknesses produced from the NAM40 analysis hour (Apr 17 12Z).

NAM40 April 17 12Z PMSL/1000-500mb thicknesses