-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 221835
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
235 PM EDT Mon Apr 22 2024

.SYNOPSIS...
Another round of Frost for Late tonight/early Tuesday.

A ridge of high pressure at the surface and aloft will build
over the region today supplying abundant sunshine and milder
daytime temperatures.

Low humidity this afternoon will create excellent visibility.

Mainly clear skies and light wind will lead to areas of frost
again tonight across the Central Ridge and Valley Region with
the frost possibly being more patchy over the Lower Susquehanna
Valley, depending on how fast high clouds move in from the west
late tonight.

Light rain along and ahead of a cold front arrives late Tuesday
and lasts into Wednesday morning with scattered showers
lingering on Wednesday.

A frost/freeze risk will return for both Thursday and Friday
morning

&&

.NEAR TERM /THROUGH TONIGHT/...
* Coordinated one more Frost Advisory (Day 3 in a row) with
  Neighboring WFOs - PHI and LWX for all of the Central Ridge
  and Valley Region and Mid/Lower Susq Valley for 06-12Z
  Tuesday. Next round of Frost/Freeze products likely Wed night
  and Thursday night.

Previous...

It`s been a chilly and frosty start to the day with daybreak
low temperature readings ranging from the mid 20s in the
normally colder northern valleys to the low and mid 30s across
the Lower Susq Valley. The Freeze Warning and Frost Advisory has
recently expired (at 8AM EDT) for the Ridge/Valley Region and
Middle to Lower Susquehanna Valley.

Essentially cloud-free skies and unlimited visibility will
occur for the rest of today with ridging at the sfc and aloft.

Temps will climb quickly in the anomalously dry (low
dewpoint/PWAT) air this morning with noticeably warmer readings
this afternoon in the mid 50s to low 60s.

Deep mixing heights 6-8kft combined with a northwest breeze and
very dry air above a weak inversion supports undercutting NBM
dewpoints resulting in low humidity this afternoon (see fire wx
section for more info).

Conditions remain favorable for radiational cooling particularly
early tonight in the decoupled central and southeastern valleys.
Expect areas of frost to form with low temps in the low to mid
30s. We will let the current frost/freeze headline expire and
allow the dayshift to post the next headline for tonight. High
clouds increase after midnight and could offset the diurnal
cooling a bit, but probably not enough to prevent another frosty
morning Tuesday.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Return southwest flow on the backside of high pressure sliding
off the Eastern Seaboard will result in a breezy and warmer day
on Tuesday. There are still some fire wx concerns especially
given an increase in wind speeds (see fire wx section). Tuesday
should be the warmest day of the week with maxT 60-70F.

All guidance then points to light rain and a subsequent cool
down associated with a cold front passage Tuesday night into
Wednesday. The moisture return ahead of the front is rather
unimpressive (pw <1 inch), but strong forcing ahead of a potent
upper level shortwave supports a measurable rainfall. The
latest multi model ensemble blend produces most likely rainfall
amounts ranging from around 0.05 inches over the Lower Susq
Valley, to 0.25 to 0.50 inches over the NW Alleghenies.

Potential frost/freeze conditions for late Wednesday night into
early Thursday morning as skies clear and abnormally dry air
arrives beneath seasonably strong sfc high. The renewed
frost/freeze risk will continue to be highlighted in the HWO.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
-- Changed Discussion --
It appears there will be another chance of a frost/freeze Thu
and Fri AM, as Canadian High Pressure builds over the region.
Thursday morning temperatures are likely to be the coldest of
the week with lows ranging from the upper 20s in the north to
mid 30s across the southeast. Those with agricultural interests
should keep an eye on the forecast for the end of this week.

The next chance of rain will come Friday night into Saturday
associated with low pressure lifting into the Grt Lks and the
associated warm front approaching PA. Both the EPS and GEFS
indicate the warm front will lift north of the region by Sunday,
resulting in markedly warmer and more humid conditions with
scattered PM convection possible. Mean progged 850mb temps south
of the warm front are around 12C, supportive of highs in the
75-80F range.
-- End Changed Discussion --

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
VFR conds will prevail through 12Z Tuesday with high (> 90%)
confidence. Winds will increase slightly towards 5-10kts
sustained with gusts up to 15kts late this afternoon into the
evening hours, blowing from 300-320 deg.

Outlook...

Tue...Slight chance of evening showers/cig reductions NW Mtns.

Wed...Showers move in west-to-east from rain early, continues
throughout the day. TSRA possible SW late PM.

Thu...Clearing as high pressure builds into the area.

Fri...Mainly dry, but increasing clouds late.

&&

.FIRE WEATHER...
Marginal fire wx conditions to start the week. MinRH 15-25%
across most of the area this afternoon with wind gusts from the
northwest gusting 15-20 mph at times. The wind will increase
Tuesday with gusts 20-30 mph from the south/southwest. MinRH
should increase by 5-10%, but still bottom near or below 30%
over particularly over south central PA. The low humidity and
breezy conditions Monday & Tuesday could result in an elevated
risk of wildfire spread.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM EDT Tuesday for PAZ019-
025>028-034>036-045-046-049>053-056-057-059-063>066.

&&

$$

SYNOPSIS...Lambert/Steinbugl
NEAR TERM...Lambert/Steinbugl
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Fitzgerald/Banghoff
AVIATION...Lambert/Gartner
FIRE WEATHER...Steinbugl