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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 200933
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
533 AM EDT Sat Jul 20 2019

.SYNOPSIS...
----Dangerous heat and humidity expected through Sunday---

We will be dealing with hazy, hot and very humid conditions
until early next week when a cold front will pass and bring some
relief.

&&

.NEAR TERM /THROUGH TONIGHT/...
Nocturnal convection finally seems to be starting to diminish
over my NWRN zones, even as new storms are forming upstream
over SRN Ontario and Lake Erie. The NW PA storms formed over
Lake Erie and propagated east and southeast and have been
remarkably persistent despite the presence of some very warm air
aloft.

The potential for future convective developments will be the
biggest forecast challenge today. At this hour we have a
beautiful MCS/MCV moving over Lake Michigan. The outflow around
the system looks almost hurricane-like. Tops have begun to show
signs of warming over the last hour, even while radars show new
convection firing from Cleveland west into NRN IN, and even up
over southern Ontario. Disturbingly, the latest HRRR doesn`t
see all the current storminess, and has a very dry-optimistic
forecast as we move into the day today. I have a feeling we may
be playing catch up in the near term as a result. RAP still
shows a fair amount of CAPE for the time of night, along with
respectable mid level lapse rates of 6-8C/KM. Mid level temps in
excess of 10C have done little to dissuade developments so far.

Climatology would suggest that we will yet see a lull in the
convection as the sun comes up. The movement of the upstream
MCV will have to be watched for developments later in the day.
SPC confines its Slight Risk to the lower lakes, only bringing
the Marginal threat into far NWRN PA.

Other than the convection, it will be another hot and very humid
day, making for dangerous heat indices over most of the region.
We kept the alignment of the Heat Advisories and Warnings today
which has the entire CWA in some sort of heat headline.

&&

.SHORT TERM /SUNDAY/...
Heat concerns will continue Sunday. We expanded the Heat Warning
to include the entire SE of the forecast area, as well as
expanding the Advisory west into the CTRL Mountains.

With a cold front sagging into SRN NY/NRN PA, and upper heights
slowly falling, the highest chances for rain will be over the
NR half of the CWA. CAPEs in excess of 2000J are cooked up by
all the 00Z guidance as well as the latest GEFS/SREF. The 00Z
GFS showed surface based CAPEs going nuclear, surging to over
6000J over the SUSQ Valley! With a very humid airmass in place,
it seems likely the instability will be enough to overcome the
warm air aloft making showers possible even over the SE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Our anomalous ridge and the accompanying heat wave will break
down rapidly early next week, to be replaced by an anomalous
trough and a much welcome break in the heat and humidity.

A cold front will drop into the region later Sunday and Monday.
With a deepening upper trough to the west, models slow the front
and bring a series of waves along it Monday and Monday night.
This will have the potential to bring widespread soaking rains
and possibly flooding to the region to start the new work week,
before we ultimately cool off and dry out for the Tuesday
through Friday timeframe.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
Still a few showers and storms over the northwest part of the
keystone state of 530 AM.

A few minor updates to the TAFS.

Overall think these areas of showers and storms will slowly
weaken, given that the dewpoints and temperatures inland from
the Lakes not all that high, compared to the MDT area. The
southeast is too warm aloft for anything prior to late aft.

For now, only have VCSH in BFD.

Any morning low cigs or fog should lift by late morning, with
widespread VFR conditions a near certainty later today. An
isolated afternoon/evening thunderstorm can`t be ruled out, but
the odds are too low to mention in the forecast at this point.

.Outlook...

Sun...AM low cigs possible W Mtns. Scattered PM tsra impacts
possible.

Mon...Widespread showers and tsra impacts possible.

Tue-Wed...No sig wx expected.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ004>006-
010>012-017-018-024-033-037-041-042.
Excessive Heat Warning until 8 PM EDT this evening for PAZ028-
036-046-049>053-056>058-063>065.
Excessive Heat Warning from noon to 8 PM EDT Sunday for PAZ036-
056>058-063>065.
Heat Advisory from 8 PM this evening to noon EDT Sunday for
PAZ036-056>058-063>065.
Excessive Heat Warning from noon today to 8 PM EDT this
evening for PAZ019-025>027-034-035-045.
Heat Advisory until noon EDT today for PAZ019-025>027-034-035-
045.
Heat Advisory from noon to 8 PM EDT Sunday for PAZ019-025>027-
034-035-045.
Heat Advisory from 8 PM this evening to 8 PM EDT Sunday for
PAZ028-046-049>053.
Excessive Heat Warning until 8 PM EDT Sunday for PAZ059-066.

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...La Corte
AVIATION...Martin