Technical Discussion

Synopsis:

Ahead of an evolving and approaching disturbance, expect the chance for scattered showers as Monday progresses.  The low pressure system itself will pass to the northeast of the state, dropping a strong cold front into the region late Tuesday into Wednesday.  Showers and even a thunderstorm are possible in association with the passage of this front during this period.  Expect above-normal temperatures in the earlier portion of the week, before colder air builds in after the cold front passes through.   

Short Term:

We forecasted the chance for scattered showers as Monday progresses, earlier in the western portions of the state and later in the eastern portions.  The SREF precipitation ensemble 1200 UTC run, as well as the SREF 900 UTC 3-hour precipitation plumes, show precipitation 'peaks' (in a relative sense) later Monday into mid-day Tuesday, with, with the exception of a few outlying members, 3-hour precipitation totals not exceeding a tenth of an inch.  Therefore, we were somewhat conservative in our estimates, using phrases such as 'scattered showers', etc. rather than 'heavy rain.'

We were also somewhat conservative in our forecasting of thunderstorms with the passage of the strong cold front later on Tuesday, as the1500 UTC SREF CAPE probability projections were rather weak for Tuesday.  However, the precipitable water projections for Tuesday, as shown by NCEP model comparisons, were relatively high over the state.  That, in combination with the potential lift associated with the right entrance region of the jet overhead by then, led us to forecast the possibility of thunderstorms as Tuesday progresses, but we were not too dramatic about it.

Model temperature projections were in good agreement for Monday and Tuesday, with above-normal temperatures across essentially the whole state.

Long Term:

The SREF 900 UTC 3-hour precipitation plumes, as well as the GFS and WRF 12 UTC runs, both show a second wave of precipitation passing through the state late Tuesday night into Wednesday in association with the passage of the cold front.  More model members went on the higher end for precipitation totals during this time period (anywhere between one tenth and four tenths of an inch over the interval), so we forecasted accordingly.  The associated relatively strong low pressure system will pass well to our northeast.  Showers linger in eastern portions of the state into early Thursday.  We forecasted more seasonable temperatures behind the passage of the cold front, as the colder air builds in.