Area forecast discussion
National Weather Service State College PA
139 am EDT Tuesday Jun 18 2013
Synopsis...
a few weak surface cold fronts will drop southeast across the
commonwealth tonight and Tuesday...bringing generally scattered
showers and thunderstorms tonight and Tuesday. Generally dry
weather will follow for the second half of the week as a large
area of high pressure builds into the region. Above normal
temperatures with increasing humidity are expected for next
weekend as warm air from the central states moves to the east.
&&
Near term /until 6 am this morning/...
fair weather will continue across much of the region until well
after midnight. Within the next several hours...we/ll see an
increase in showers and thunderstorms and rain across the northwest mountains...then the ncent
mountains as a distinct wave of low pressure /currently over Lake Erie/
moves east along a stalled out frontal boundary across the
southern tier of New York state.
This low will be supported by a well defined jet entrance region
100 knots wind maximum at 300 mb over Lake Ontario at 02z/ that will be
sliding east toward the I-81 corridor of nepa and southern New
York toward daybreak.
Rainfall amounts of a tenth to quarter of an inch appear likely
across the northwest mountains tonight...with lesser amounts further southeast toward
the i99/Route 220 corridor.
Elsewhere...variable amounts of high clouds...will stream east
tonight...followed by some Alto cumulus very late tonight.
Low temperatures tonight will be near 50f across the northern mountains...and
upper 50s to lower 60s across the south.
&&
Short term /6 am this morning through 6 PM Wednesday/...
this main/third front should continue to trek through the region on
Tuesday and will make the probability of precipitation much more widespread/higher. Precipitable waters
reach near an inch and a half on Tuesday...which could combine with
slowly moving cells to make a brief heavy downpour. But ffg very
high and threat for flooding very low. This front...too...may wash
out as it reaches the southern border.
&&
Long term /Wednesday night through Monday/...
broad trough over northeast U.S. Will bring unsettled weather
early in the week...then building ridge will bring generally dry
weather for middle/late week. Humidity and temperatures increase
noticeably for next weekend along with daily thunderstorm chances.
As one frontal boundary washes out over Middle Atlantic States...
another front is pushed southward across County Warning Area Tuesday into Tuesday night as
shortwave rotates through broad trough overhead. This will keep
mention of scattered thunderstorms in forecast at least through Tuesday evening.
That frontal boundary will signal the beginnings of a pattern
change. Behind it for Wednesday...winds turn northerly as surface high
pressure builds in across the Great Lakes...with west-East Ridge axis
settling over PA on Thursday. We/ll see a few chillier
nights...especially across the north /the coldest being Wednesday night with
readings dipping into the 40s north of I-80/. Temperatures milder across
the south where higher dewpoints will be tougher to scour out.
As ridge continues to slip to the southeast...light southwesterly flow
develops Thursday. Moisture will be slow to increase Thursday and Friday...but
weakening cap will lead to increasing chances for isolated late
day thunderstorms over southern half.
Larger ridge over central U.S. Builds eastward into Ohio Valley
this weekend. Higher temperatures and dewpoints will advect eastward
around top of the ridge...arriving in PA on Sat and persisting for
several days...kicking off daily scattered thunderstorms /mainly northwest half/. We/ll
also likely see decaying mesoscale convective system/S trying to slide eastward into PA
Sunday and Monday morning. This pattern will persist until next
front comes through midweek next week.
&&
Aviation /06z Tuesday through Saturday/...
regional radar loop this evening shows rain showers/thunderstorms and rain across the lower
Great Lakes in association with a slow-moving cold front. As this
front works southeast...a late night rain showers is possible over northern PA.
However...the biggest aviation concern tonight is the possibility
of fog at bfd...MDT and lns...especially at the MDT and lns where
rain has fallen. Couple this with mclear skies...a light wind and wet
ground all favor development of fog overnight.
Current Sat shot shows cirrus moving over the region...this will
reduce the development and the severity of any fog/mist. The
clearing skies over bfd have allowed for IFR conditions to
develop...out ahead of the approaching front. MVFR continues at
lns and MVFR should develop at MDT. IFR remains possible at
MDT...lns and ipt. A thick layer of middle clouds has developed over
the central taf sites and should negate any fog formation.
Any fog that manages to form overnight should burn off within a
couple hours after sunrise. Focus will then shift toward scattered
rain showers/thunderstorms and rain developing Tuesday afternoon...as cold front works south across
the state. Although VFR conds will predominate...a brief visibility
reduction is possible with any shra/tsra. Current models show any
precipitation could linger along the Mason Dixon line...and at
lns...MDT and jst through 06z Wednesday. IFR ceilings and visibilities will
again be a possibility tomorrow night.
Outlook...
Wednesday...early am light rain/low ceilings possible jst/aoo.
Thursday...no sig weather expected.
Fri-Sat...isolated PM thunderstorms and rain impacts possible.
&&
Ctp watches/warnings/advisories...
none.
&&
$$
Synopsis...dangelo/Lambert
near term...Lambert
short term...dangelo/Lambert
long term...rxr
aviation...Fitzgerald/ceru
